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Maxwell, Reed M., Julie K. Lundquist, Jeffrey D. Mirocha, Steven G. Smith, Carol S. Woodward i Andrew F. B. Tompson. "Development of a Coupled Groundwater–Atmosphere Model". Monthly Weather Review 139, nr 1 (1.01.2011): 96–116. http://dx.doi.org/10.1175/2010mwr3392.1.
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Abstract Complete models of the hydrologic cycle have gained recent attention as research has shown interdependence between the coupled land and energy balance of the subsurface, land surface, and lower atmosphere. PF.WRF is a new model that is a combination of the Weather Research and Forecasting (WRF) atmospheric model and a parallel hydrology model (ParFlow) that fully integrates three-dimensional, variably saturated subsurface flow with overland flow. These models are coupled in an explicit, operator-splitting manner via the Noah land surface model (LSM). Here, the coupled model formulation and equations are presented and a balance of water between the subsurface, land surface, and atmosphere is verified. The improvement in important physical processes afforded by the coupled model using a number of semi-idealized simulations over the Little Washita watershed in the southern Great Plains is demonstrated. These simulations are initialized with a set of offline spinups to achieve a balanced state of initial conditions. To quantify the significance of subsurface physics, compared with other physical processes calculated in WRF, these simulations are carried out with two different surface spinups and three different microphysics parameterizations in WRF. These simulations illustrate enhancements to coupled model physics for two applications: water resources and wind-energy forecasting. For the water resources example, it is demonstrated how PF.WRF simulates explicit rainfall and water storage within the basin and runoff. Then the hydrographs predicted by different microphysics schemes within WRF are compared. Because soil moisture is expected to impact boundary layer winds, the applicability of the model to wind-energy applications is demonstrated by using PF.WRF and WRF simulations to provide estimates of wind and wind shear that are useful indicators of wind-power output.
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FOX, R. J., T. R. FISHER, A. B. GUSTAFSON, T. E. JORDAN, T. M. KANA i M. W. LANG. "Searching for the missing nitrogen: biogenic nitrogen gases in groundwater and streams". Journal of Agricultural Science 152, S1 (13.03.2014): 96–106. http://dx.doi.org/10.1017/s0021859614000070.
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SUMMARYBiogenic nitrogen (N2) and nitrous oxide (N2O) accumulations were measured in groundwater, streams and the vadose zone of small agricultural watersheds in the Mid-Atlantic USA. In general, N2and N2O in excess of atmospheric equilibrium were found in groundwater virtually everywhere that was sampled. Excess N2in groundwater ranged from undetectable to 616 μmol N2-N/l, the latter representingc. 50% of background N2. The N2O-N concentrations varied from undetectable to 75 μm, and usually greatly exceeded values at atmospheric equilibrium (25–30 nM); however, N2O was generally 1–10% of excess N2. Intermediate levels of deficit and excess N2in flowing streams (−65 to +250 μmol N2-N/L) resulting from both abiotic and biotic processes were also measured. In vadose zone gases, multiple N2/Ar gas profiles were measured which exhibited seasonal variations with below atmospheric values when the soil was warming in spring/summer and above atmospheric values when groundwater was cooling in fall/winter. Both abiotic and biotic processes contributed to the excess N2and N2O that was observed. The current data indicate that large concentrations of excess N gases can accumulate within soil, groundwater, and streams of agriculturally dominated watersheds. When excess N gases are exchanged with the atmosphere, the net fluxes to the atmosphere may represent an important loss term for watershed N budgets.
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Sulis, Mauro, John L. Williams, Prabhakar Shrestha, Malte Diederich, Clemens Simmer, Stefan J. Kollet i Reed M. Maxwell. "Coupling Groundwater, Vegetation, and Atmospheric Processes: A Comparison of Two Integrated Models". Journal of Hydrometeorology 18, nr 5 (1.05.2017): 1489–511. http://dx.doi.org/10.1175/jhm-d-16-0159.1.
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Abstract This study compares two modeling platforms, ParFlow.WRF (PF.WRF) and the Terrestrial Systems Modeling Platform (TerrSysMP), with a common 3D integrated surface–groundwater model to examine the variability in simulated soil–vegetation–atmosphere interactions. Idealized and hindcast simulations over the North Rhine–Westphalia region in western Germany for clear-sky conditions and strong convective precipitation using both modeling platforms are presented. Idealized simulations highlight the strong variability introduced by the difference in land surface parameterizations (e.g., ground evaporation and canopy transpiration) and atmospheric boundary layer (ABL) schemes on the simulated land–atmosphere interactions. Results of the idealized simulations also suggest a different range of sensitivity in the two models of land surface and atmospheric parameterizations to water-table depth fluctuations. For hindcast simulations, both modeling platforms simulate net radiation and cumulative precipitation close to observed station data, while larger differences emerge between spatial patterns of soil moisture and convective rainfall due to the difference in the physical parameterization of the land surface and atmospheric component. This produces a different feedback by the hydrological model in the two platforms in terms of discharge over different catchments in the study area. Finally, an analysis of land surface and ABL heat and moisture budgets using the mixing diagram approach reveals different sensitivities of diurnal atmospheric processes to the groundwater parameterizations in both modeling platforms.
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Pavlov, S. Kh. "PROCESSES OF FORMATION OF SODIUM BICARBONATE GROUNDWATER IN THE RAINWATER – SANDSTONE SYSTEM". Geodynamics & Tectonophysics 14, nr 6 (14.12.2023): 0733. http://dx.doi.org/10.5800/gt-2023-14-6-0733.
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In modeling, a study was made of the processes of the physical-chemical interaction between rainwater and sandstone. It was stated that as a result of the interaction, already in mineralization of water equal to 55 mg/l, there emerges a pure soda solution whose sharp oxidation properties, retaining up to 200 mg/l, change to sharp restorative when exceeding this value. At the mineralization of water equal to 30 mg/l, an intensive increase in the number of hydroxide ions in a solution makes it highly alkaline. The active removal of calcium from solution is due to the formation of not only solid phase calcite, whose share does not exceed 15 %, but largely limonite, whose content is as high as 25 %. The accumulation of high concentrations of sodium in a solution is caused by the absence of its secondary mineral formations in a wide range of the rock/water ratios. Under reservoir conditions, the solution is composed of carbonate. This solution, transferred from reservoir to surface conditions, undergoes transformation in the result of interaction with the atmosphere. A decrease in pH of the solution resulted in the acquisition of sharp oxidation properties, with the cation, sulfate, fluorine and chlorine contents remained at the level corresponding to the reservoir conditions and the cardinal changes affected the carbonate system components and silicon compounds. Hydrosilicate ion was transformed into precipitated silicon oxide. Carbonate ions were transformed into hydrocarbonate, and the additional hydrocarbonate ions were formed for the solution to preserve a state of equilibrium after the removal of the representative number of hydrosilicate ions therefrom. An amount of carbon required for their formation was extracted from the atmosphere. The solution became hydrocarbonate, with hydrosilicate ions almost disappeared therefrom. Different calculation options for model solution, which is in equilibrium with the atmosphere, correlate with the representative group of soda-type groundwater. The calculation results are confirmed by field observations over the authigenic mineral formation on a large part of the Russian territory.
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Coxon, Catherine E. "Carbonate Deposition in Turloughs (Seasonal Lakes) on the Western Limestone Lowlands of Ireland - I: Present Day Processes". Irish Geography 27, nr 1 (15.01.2015): 14–27. http://dx.doi.org/10.55650/igj.1994.428.
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This paper describes an investigation of carbonate deposition in seasonal groundwater-fed lakes (turloughs) situated on the limestone lowland of south-east county Mayo. Chemical data from four turloughs suggest that present-day calcite deposition is due predominantly to supersaturation caused by the loss of excess carbon dioxide from the water to the atmosphere. This process occurs throughout the winter. Biological influences appear to play only a minor role, although investigations of turlough trophic status and algal biomass are required to confirm this.
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Richard, A., S. Galle, M. Descloitres, J. M. Cohard, J. P. Vandervaere, L. Séguis i C. Peugeot. "Riparian forest and permanent groundwater: a key coupling for balancing the hillslope water budget in Sudanian West Africa". Hydrology and Earth System Sciences Discussions 10, nr 5 (2.05.2013): 5643–86. http://dx.doi.org/10.5194/hessd-10-5643-2013.
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Abstract. Forests are thought to play an important role in the regional dynamics of the West African monsoon, through their capacity to extract water from permanent aquifers located deep in the soil and pump it into the atmosphere even during the dry season. This is especially true for riparian forests located at the bottom of the hillslopes. This coupling between the riparian forests and the permanent aquifers is investigated, looking for quantifying its contribution to the catchment water balance. To this end, use is made of the observations available from a comprehensively instrumented hillslope through the framework of the AMMA-CATCH (African Monsoon Multidisciplinary Analysis – Coupling the Tropical Atmosphere and the Hydrological Cycle) observing system. Attention is paid to measurements of actual evapotranspiration, soil moisture and deep groundwater level. A vertical 2-D approach is followed using the physically-based Hydrus 2-D model in order to simulate the hillslope hydrodynamics, the model being calibrated and evaluated through a multi-criteria approach. The model correctly simulates the hydrodynamics of the hillslope as far as soil moisture dynamics, deep groundwater fluctuation and actual evapotranspiration dynamics are concerned. In particular, the model is able to reproduce the observed hydraulic disconnection between the deep permanent groundwater table and the river. A virtual experiment shows that the riparian forest depletes the deep groundwater table level through transpiration occurring throughout the year so that the permanent aquifer and the river are not connected. Moreover the riparian forest and the deep groundwater table form a coupled transpiration system: the riparian forest transpiration is due to the water redistribution at the hillslope scale feeding the deep groundwater through lateral saturated flow. The annual cycle of the transpiration origin is also quantified. The riparian forest which covers only 5% of the hillslope generates 37% of the annual transpiration, this proportion reaching 57% during the dry season. In a region of intense anthropogenic pressure, forest clearing and its replacement by cropping could impact significantly the water balance at catchment scale with a possible feedback on the regional monsoon dynamics.
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Barenbaum, Azariy A. "On the relationship of oil and gas formation and degassing processes with groundwater decomposition". Georesursy 20, nr 4 (30.11.2018): 290–300. http://dx.doi.org/10.18599/grs.2018.4.290-300.
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The article is referred to important consequence of the biosphere oil and gas formation concept, according to which the process of hydrocarbons generation in the subsoil and degassing of the Earth are a single natural phenomenon. The main role in this phenomenon is played by geochemical circulation of carbon and water through the Earth’s surface accompanied by polycondensation synthesis of hydrocarbons by CO2+H2O reaction. This reaction is accompanied by a colossal decomposition of groundwater into hydrogen and oxygen within the sedimentary cover of the earth’s crust. Unreacted CO2, as well as H2 and most of the methane produced during the reaction are degassed into the atmosphere, while resulting C5+ hydrocarbons remain under the surface filling geological traps in the form of oil and gas. The article presents the results of model experiments, which make it possible to estimate the rate of groundwater decomposition and on this basis explain the current rate of Earth’s degassing, as well as the observed CO2, CH4 and H2 ratio in degassing products.
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Al-Najjar, Hassan, Gokmen Ceribasi, Emrah Dogan, Khalid Qahman, Mazen Abualtayef i Ahmet Iyad Ceyhunlu. "Statistical modeling of spatial and temporal vulnerability of groundwater level in the Gaza Strip (Palestine)". H2Open Journal 4, nr 1 (1.01.2021): 352–65. http://dx.doi.org/10.2166/h2oj.2021.120.
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Abstract The water supply in the Gaza Strip substantially depends on the groundwater resource of the Gaza coastal aquifer. The climate changes and the over-exploiting processes negatively impact the recovery of the groundwater balance. The climate variability is characterized by the decline in the precipitation of −5.2% and an increase in temperature of +1 °C in the timeframe of 2020–2040. The potential evaporation and the sunshine period are expected to increase by about 111 mm and 5 hours, respectively, during the next 20 years. However, the atmosphere is predicted to be drier where the relative humidity will fall by a trend of −8% in 20 years. The groundwater abstraction is predicted to increase by 55% by 2040. The response of the groundwater level to climate change and groundwater pumping was evaluated using a model of a 20-neuron ANN with a performance of the correlation coefficient (r)=0.95–0.99 and the root mean square error (RMSE)=0.09–0.21. Nowadays, the model reveals that the groundwater level ranges between −0.38 and −18.5 m and by 2040 it is expected to reach −1.13 and −28 m below MSL at the northern and southern governorates of the Gaza Strip, respectively.
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Martínez-de la Torre, Alberto, i Gonzalo Miguez-Macho. "Groundwater influence on soil moisture memory and land–atmosphere fluxes in the Iberian Peninsula". Hydrology and Earth System Sciences 23, nr 12 (2.12.2019): 4909–32. http://dx.doi.org/10.5194/hess-23-4909-2019.
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Abstract. Groundwater plays an important role in the terrestrial water cycle, interacting with the land surface via vertical fluxes through the water table and distributing water resources spatially via gravity-driven lateral transport. It is therefore essential to have a correct representation of groundwater processes in land surface models, as land–atmosphere coupling is a key factor in climate research. Here we use the LEAFHYDRO land surface and groundwater model to study the groundwater influence on soil moisture distribution and memory, and evapotranspiration (ET) fluxes in the Iberian Peninsula over a 10-year period. We validate our results with time series of observed water table depth from 623 stations covering different regions of the Iberian Peninsula, showing that the model produces a realistic water table, shallower in valleys and deeper under hilltops. We find patterns of shallow water table and strong groundwater–land surface coupling over extended interior semi-arid regions and river valleys. We show a strong seasonal and interannual persistence of the water table, which induces bimodal memory in the soil moisture fields; soil moisture “remembers” past wet conditions, buffering drought effects, and also past dry conditions, causing a delay in drought recovery. The effects on land–atmosphere fluxes are found to be significant: on average over the region, ET is 17.4 % higher when compared with a baseline simulation with LEAFHYDRO's groundwater scheme deactivated. The maximum ET increase occurs in summer (34.9 %; 0.54 mm d−1). The ET enhancement is larger over the drier southern basins, where ET is water limited (e.g. the Guadalquivir basin and the Mediterranean Segura basin), than in the northern Miño/Minho basin, where ET is more energy limited than water limited. In terms of river flow, we show how dry season baseflow is sustained by groundwater originating from accumulated recharge during the wet season, improving significantly on a free-drain approach, where baseflow comes from water draining through the top soil, resulting in rivers drying out in summer. Convective precipitation enhancement through local moisture recycling over the semi-arid interior regions and summer cooling are potential implications of these groundwater effects on climate over the Iberian Peninsula. Fully coupled land surface and climate model simulations are needed to elucidate this question.
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Alkhaier, F., G. N. Flerchinger i Z. Su. "Shallow groundwater effect on land surface temperature and surface energy balance under bare soil conditions: modeling and description". Hydrology and Earth System Sciences Discussions 8, nr 5 (23.09.2011): 8639–70. http://dx.doi.org/10.5194/hessd-8-8639-2011.
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Abstract. Appreciating when and how groundwater affects surface temperature and energy fluxes is important for utilizing remote sensing in groundwater studies and for integrating aquifers within land surface models. To explore the shallow groundwater effect, we numerically exposed two soil profiles – one having shallow groundwater – to the same meteorological forcing, and inspected their different responses regarding surface soil moisture, temperature and energy balance. We found that the two profiles differed in the absorbed and emitted amounts of energy, in portioning out the available energy and in heat fluency within the soil. We conclude that shallow groundwater areas reflect less shortwave radiation due to their lower albedo and therefore they get higher magnitude of net radiation. When potential evaporation demand is high enough, a large portion of the energy received by these areas is spent on evaporation. This makes the latent heat flux predominant, and leaves less energy to heat the soil. Consequently, this induces lower magnitudes of both sensible and ground heat fluxes. The higher soil thermal conductivity in shallow groundwater areas facilitates heat transfer between the top soil and the subsurface, i.e. soil subsurface is more thermally connected to the atmosphere. In view of remote sensors' capability of detecting shallow groundwater effect, we conclude that this effect can be sufficiently clear to be sensed if at least one of two conditions is met: high potential evaporation and big contrast in air temperature between day and night. Under these conditions, most day and night hours are suitable for shallow groundwater depth detection.
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Koschorreck, Matthias, Klaus Holger Knorr i Lelaina Teichert. "Temporal patterns and drivers of CO2 emission from dry sediments in a groyne field of a large river". Biogeosciences 19, nr 22 (18.11.2022): 5221–36. http://dx.doi.org/10.5194/bg-19-5221-2022.
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Abstract. River sediments falling dry at low water levels are sources of CO2 to the atmosphere. While the general relevance of CO2 emissions from dry sediments has been acknowledged and some regulatory mechanisms have been identified, knowledge on mechanisms and temporal dynamics is still sparse. Using a combination of high-frequency measurements and two field campaigns we thus aimed to identify processes responsible for CO2 emissions and to assess temporal dynamics of CO2 emissions from dry sediments at a large German river. CO2 emissions were largely driven by microbial respiration in the sediment. Observed CO2 fluxes could be explained by patterns and responses of sediment respiration rates measured in laboratory incubations. We exclude groundwater as a significant source of CO2 because the CO2 concentration in the groundwater was too low to explain CO2 fluxes. Furthermore, CO2 fluxes were not related to radon fluxes, which we used to trace groundwater-derived degassing of CO2. CO2 emissions were strongly regulated by temperature resulting in large diurnal fluctuations of CO2 emissions with emissions peaking during the day. The diurnal temperature–CO2 flux relation exhibited a hysteresis which highlights the effect of transport processes in the sediment and makes it difficult to identify temperature dependence from simple linear regressions. The temperature response of CO2 flux and sediment respiration rates in laboratory incubations was identical. Also deeper sediment layers apparently contributed to CO2 emissions because the CO2 flux was correlated with the thickness of the unsaturated zone, resulting in CO2 fluxes increasing with distance to the local groundwater level and with distance to the river. Rain events lowered CO2 emissions from dry river sediments probably by blocking CO2 transport from deeper sediment layers to the atmosphere. Terrestrial vegetation growing on exposed sediments greatly increased respiratory sediment CO2 emissions. We conclude that the regulation of CO2 emissions from dry river sediments is complex. Diurnal measurements are mandatory and even CO2 uptake in the dark by phototrophic micro-organisms has to be considered when assessing the impact of dry sediments on CO2 emissions from rivers.
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Vergnes, J. P., i B. Decharme. "A simple groundwater scheme in the TRIP river routing model: global off-line evaluation against GRACE terrestrial water storage estimates and observed river discharges". Hydrology and Earth System Sciences Discussions 9, nr 7 (4.07.2012): 8213–56. http://dx.doi.org/10.5194/hessd-9-8213-2012.
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Abstract. Groundwater is a non-negligible component of the global hydrological cycle, and its interaction with its overlying unsaturated zones can influence water and energy fluxes between the land surface and the atmosphere. Despite its importance, groundwater is not yet represented in most climate models. In this paper, the simple groundwater scheme implemented in the Total Runoff Integrating Pathways (TRIP) river routing model is applied in off-line mode at global scale using a 0.5° model resolution. The simulated river discharges are evaluated against a large dataset of about 3500 gauging stations compiled from the Global Data Runoff Center (GRDC) and other sources, while the Terrestrial Water Storage (TWS) variations derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission helps to evaluate the simulated TWS. The forcing fields (surface runoff and deep drainage) come from an independent simulation of the ISBA land surface model covering the period from 1950 to 2008. Results show that groundwater improves the efficiency scores for about 70% of the gauging stations and deteriorates them for 15%. The simulated TWS are also in better agreement with the GRACE estimates. These results are mainly explained by the lag introduced by the low-frequency variations of groundwater, which tend to shift and smooth the simulated river discharges and TWS. A sensitivity study on the global precipitation forcing used in ISBA to produce the forcing fields is also proposed. It shows that the groundwater scheme is not influenced by the uncertainties in precipitation data.
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Dietzel, M., A. Leis, R. Abdalla, J. Savarino, S. Morin, M. E. Böttcher i S. Köhler. "<sup>17</sup>O-excess traces atmospheric nitrate in paleo groundwater of the Saharan desert". Biogeosciences Discussions 10, nr 12 (20.12.2013): 20079–111. http://dx.doi.org/10.5194/bgd-10-20079-2013.
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Abstract. Saharan paleo groundwater from the Hasouna area of Libya contains up to 1.8 mM of nitrate, the origin of which is still disputed. Herein we show that a positive 17O-excess in NO3– (Δ17ONO3 = δ17ONO3 – 0.52 δ18ONO3) is preserved in the paleo groundwater. The 17O-excess provides an excellent tracer of atmospheric NO3–, which is caused by the interaction of ozone with NOx via photochemical reactions, coupled with a non-mass dependent isotope fractionation. Our Δ17ONO3 data from 0.4 to 5.0‰ (n = 28) indicate that up to x [NO3–]atm = 20 mol % of total dissolved NO3– originated from the Earth's atmosphere. High Δ17ONO3 values correspond to soils that are barren in dry periods, while low Δ17ONO3 values correspond to more fertile soils. Coupled high Δ17ONO3 and high x [NO3–]atm values are caused by a sudden wash out of dry deposition of atmospheric NO3– on plant or soil surfaces within humid-wet cycles. The individual isotope and chemical composition of the Hasouna groundwater can be followed by a binary mixing approach using the lowest and highest mineralized groundwater as end-members without considering evaporation. Using the δ34SSO4 and δ18OSO4 isotope signature of dissolved sulfate, no indication is found for a superimposition by denitrification, e.g. involving pyrite minerals within the aquifers. It is suggested that dissolved sulfate originates from the dissolution of calcium sulfate minerals during groundwater evolution.
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Mikhalchuk, Alexander, Yulia Kharanzhevskaya, Elena Burnashova, Evgeniya Nekhoda, Irina Gammerschmidt, Elena Akerman, Sergey Kirpotin, Viktor Nikitkin, Aldynai Khovalyg i Sergey Vorobyev. "Soil Water Regime, Air Temperature, and Precipitation as the Main Drivers of the Future Greenhouse Gas Emissions from West Siberian Peatlands". Water 15, nr 17 (26.08.2023): 3056. http://dx.doi.org/10.3390/w15173056.
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This modeling study intended to solve a part of the global scientific problem related to increased concentrations of carbon dioxide in the atmosphere via emissions from terrestrial ecosystems that, along with anthropogenic emissions, make notable contributions to the processes of climate change on the planet. The main stream of CO2 from natural terrestrial ecosystems is related to the activation of biological processes, such as the production/destruction of plant biomass. In this study, the Wetland-DNDC computer simulation model with a focus on nitrogen and carbon biogeochemical cycles was used to study the effect of hydrothermal conditions on greenhouse gas fluxes in West Siberian peatlands. The study was implemented on the site of the world’s largest pristine wetland/peatland system, the Great Vasyugan Mire (GVM). The study was carried out based on data from permanent measurements at meteo stations and our own in situ measurements of hydrological and thermal parameters on sites, which allowed for testing different scenarios of changes in environmental conditions (temperature, precipitation, groundwater level) together with a change in GHG fluxes. The study revealed the air temperature and the level of groundwater as the main drivers controlling CO2 fluxes. The study of different scenarios of change in annual air temperature revealed the threshold of change in the wetland/peatland ecosystem from carbon sink to carbon source to the atmosphere to happen with an increase in the average annual air temperature by 3 °C with reference to the average annual air temperature values in 2019. Also, we found that the wetland/peatland ecosystem turned to act as an active carbon sink with about 7 cm increase in annual groundwater level, compared with its base level of −21 cm.
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Shrestha, P., M. Sulis, M. Masbou, S. Kollet i C. Simmer. "A Scale-Consistent Terrestrial Systems Modeling Platform Based on COSMO, CLM, and ParFlow". Monthly Weather Review 142, nr 9 (wrzesień 2014): 3466–83. http://dx.doi.org/10.1175/mwr-d-14-00029.1.
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A highly modular and scale-consistent Terrestrial Systems Modeling Platform (TerrSysMP) is presented. The modeling platform consists of an atmospheric model (Consortium for Small-Scale Modeling; COSMO), a land surface model (the NCAR Community Land Model, version 3.5; CLM3.5), and a 3D variably saturated groundwater flow model (ParFlow). An external coupler (Ocean Atmosphere Sea Ice Soil, version 3.0; OASIS3) with multiple executable approaches is employed to couple the three independently developed component models, which intrinsically allows for a separation of temporal–spatial modeling scales and the coupling frequencies between the component models. Idealized TerrSysMP simulations are presented, which focus on the interaction of key hydrologic processes, like runoff production (excess rainfall and saturation) at different hydrological modeling scales and the drawdown of the water table through groundwater pumping, with processes in the atmospheric boundary layer. The results show a strong linkage between integrated surface–groundwater dynamics, biogeophysical processes, and boundary layer evolution. The use of the mosaic approach for the hydrological component model (to resolve subgrid-scale topography) impacts simulated runoff production, soil moisture redistribution, and boundary layer evolution, which demonstrates the importance of hydrological modeling scales and thus the advantages of the coupling approach used in this study. Real data simulations were carried out with TerrSysMP over the Rur catchment in Germany. The inclusion of the integrated surface–groundwater flow model results in systematic patterns in the root zone soil moisture, which influence exchange flux distributions and the ensuing atmospheric boundary layer development. In a first comparison to observations, the 3D model compared to the 1D model shows slightly improved predictions of surface fluxes and a strong sensitivity to the initial soil moisture content.
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Hornum, Mikkel Toft, Andrew Jonathan Hodson, Søren Jessen, Victor Bense i Kim Senger. "Numerical modelling of permafrost spring discharge and open-system pingo formation induced by basal permafrost aggradation". Cryosphere 14, nr 12 (21.12.2020): 4627–51. http://dx.doi.org/10.5194/tc-14-4627-2020.
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Abstract. In the high Arctic valley of Adventdalen, Svalbard, sub-permafrost groundwater feeds several pingo springs distributed along the valley axis. The driving mechanism for groundwater discharge and associated pingo formation is enigmatic because wet-based glaciers are not present in the adjacent highlands and the presence of continuous permafrost seems to preclude recharge of the sub-permafrost groundwater system by either a subglacial source or a precipitation surplus. Since the pingo springs enable methane that has accumulated underneath the permafrost to escape directly to the atmosphere, our limited understanding of the groundwater system brings significant uncertainty to predictions of how methane emissions will respond to changing climate. We address this problem with a new conceptual model for open-system pingo formation wherein pingo growth is sustained by sub-permafrost pressure effects, as related to the expansion of water upon freezing, during millennial-scale basal permafrost aggradation. We test the viability of this mechanism for generating groundwater flow with decoupled heat (one-dimensional transient) and groundwater (three-dimensional steady state) transport modelling experiments. Our results suggest that the conceptual model represents a feasible mechanism for the formation of open-system pingos in lower Adventdalen and elsewhere. We also explore the potential for additional pressurisation and find that methane production and methane clathrate formation and dissolution deserve particular attention on account of their likely effects upon the hydraulic pressure. Our model simulations also suggest that the generally low-permeability hydrogeological units cause groundwater residence times to exceed the duration of the Holocene. The likelihood of such pre-Holocene groundwater ages is supported by the geochemistry of the pingo springs which demonstrates an unexpected seaward freshening of groundwater potentially caused by a palaeo-subglacial meltwater “wedge” from the Weichselian. Whereas permafrost thickness (and age) progressively increases inland, accordingly, the sub-permafrost meltwater wedge thins, and less unfrozen freshwater is available for mixing. Our observations imply that millennial-scale permafrost aggradation deserves more attention as a possible driver of sustained flow of sub-permafrost groundwater and methane to the surface because, although the hydrological system in Adventdalen at first appears unusual, it is likely that similar systems have developed in other uplifted valleys throughout the Arctic.
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Deirmendjian, Loris, Denis Loustau, Laurent Augusto, Sébastien Lafont, Christophe Chipeaux, Dominique Poirier i Gwenaël Abril. "Hydro-ecological controls on dissolved carbon dynamics in groundwater and export to streams in a temperate pine forest". Biogeosciences 15, nr 2 (1.02.2018): 669–91. http://dx.doi.org/10.5194/bg-15-669-2018.
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Abstract. We studied the export of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) from forested shallow groundwater to first-order streams, based on groundwater and surface water sampling and hydrological data. The selected watershed was particularly convenient for such study, with a very low slope, with pine forest growing on sandy permeable podzol and with hydrology occurring exclusively through drainage of shallow groundwater (no surface runoff). A forest plot was instrumented for continuous eddy covariance measurements of precipitation, evapotranspiration, and net ecosystem exchanges of sensible and latent heat fluxes as well as CO2 fluxes. Shallow groundwater was sampled with three piezometers located in different plots, and surface waters were sampled in six first-order streams; river discharge and drainage were modeled based on four gauging stations. On a monthly basis and on the plot scale, we found a good consistency between precipitation on the one hand and the sum of evapotranspiration, shallow groundwater storage and drainage on the other hand. DOC and DIC stocks in groundwater and exports to first-order streams varied drastically during the hydrological cycle, in relation with water table depth and amplitude. In the groundwater, DOC concentrations were maximal in winter when the water table reached the superficial organic-rich layer of the soil. In contrast, DIC (in majority excess CO2) in groundwater showed maximum concentrations at low water table during late summer, concomitant with heterotrophic conditions of the forest plot. Our data also suggest that a large part of the DOC mobilized at high water table was mineralized to DIC during the following months within the groundwater itself. In first-order streams, DOC and DIC followed an opposed seasonal trend similar to groundwater but with lower concentrations. On an annual basis, leaching of carbon to streams occurred as DIC and DOC in similar proportion, but DOC export occurred in majority during short periods of the highest water table, whereas DIC export was more constant throughout the year. Leaching of forest carbon to first-order streams represented a small portion (approximately 2 %) of the net land CO2 sink at the plot. In addition, approximately 75 % of the DIC exported from groundwater was not found in streams, as it returned very fast to the atmosphere through CO2 degassing.
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Aslam, Muhammad, Ali Salem, Vijay P. Singh i Muhammad Arshad. "Estimation of Spatial and Temporal Groundwater Balance Components in Khadir Canal Sub-Division, Chaj Doab, Pakistan". Hydrology 8, nr 4 (4.12.2021): 178. http://dx.doi.org/10.3390/hydrology8040178.
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Evaluation of the spatial and temporal distribution of water balance components is required for efficient and sustainable management of groundwater resources, especially in semi-arid and data-poor areas. The Khadir canal sub-division, Chaj Doab, Pakistan, is a semi-arid area which has shallow aquifers which are being pumped by a plethora of wells with no effective monitoring. This study employed a monthly water balance model (water and energy transfer among soil, plants, and atmosphere)—WetSpass-M—to determine the groundwater balance components on annual, seasonal, and monthly time scales for a period of the last 20 years (2000–2019) in the Khadir canal sub-division. The spatial distribution of water balance components depends on soil texture, land use, groundwater level, slope, and meteorological conditions. Inputs for the model included data on topography, slope, soil, groundwater depth, slope, land use, and meteorological data (e.g., precipitation, air temperature, potential evapotranspiration, and wind speed) which were prepared using ArcGIS. The long-term average annual rainfall (455.7 mm) is distributed as 231 mm (51%) evapotranspiration, 109.1 mm (24%) surface runoff, and 115.6 mm (25%) groundwater recharge. About 51% of groundwater recharge occurs in summer, 18% in autumn, 14% in winter, and 17% in spring. Results showed that the WetSpass-M model properly simulated the water balance components of the Khadir canal sub-division. The WetSpass-M model’s findings can be used to develop a regional groundwater model for simulation of different aquifer management scenarios in the Khadir area, Pakistan.
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Decharme, B., R. Alkama, H. Douville, M. Becker i A. Cazenave. "Global Evaluation of the ISBA-TRIP Continental Hydrological System. Part II: Uncertainties in River Routing Simulation Related to Flow Velocity and Groundwater Storage". Journal of Hydrometeorology 11, nr 3 (1.06.2010): 601–17. http://dx.doi.org/10.1175/2010jhm1212.1.
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Abstract In the companion paper to this one (Part I), the Interactions between Soil, Biosphere, and Atmosphere–Total Runoff Integrating Pathways (ISBA-TRIP) continental hydrological system of the Centre National de Recherches Météorologiques is evaluated by using river discharge measurements and terrestrial water storage (TWS) variations derived from three independent datasets of the Gravity Recovery and Climate Experiment (GRACE). One of the conclusions is that the river reservoir simulated by TRIP at the global scale seems to be one of the main sources of TWS and/or discharge errors. Here, the authors study these uncertainties in river routing processes, such as flow velocity and groundwater storage. For this purpose, a simple groundwater reservoir depending on a time delay factor and a variable streamflow velocity calculated via Manning’s formula are added to TRIP following the approach of Arora and Boer. The previous and the new TRIP are then compared, and two studies of the sensitivity to the groundwater time delay factor and to the flow velocity are performed. Using the same experiment design as in Part I, the authors show that the effect of this flow velocity and of the groundwater time delay factor on the ISBA-TRIP simulation is potentially significant. Nevertheless, over tropical and temperate basins, a competition between the two processes implies a slight difference between the previous and the new TRIP compared to both the GRACE and the discharge signals. The global results underline that simulating a realistic streamflow velocity is a key process for global-scale application.
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Dietzel, M., A. Leis, R. Abdalla, J. Savarino, S. Morin, M. E. Böttcher i S. Köhler. "<sup>17</sup>O excess traces atmospheric nitrate in paleo-groundwater of the Saharan desert". Biogeosciences 11, nr 12 (17.06.2014): 3149–61. http://dx.doi.org/10.5194/bg-11-3149-2014.
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Abstract. Saharan paleo-groundwater from the Hasouna area of Libya contains up to 1.8 mM of nitrate, which exceeds the World Health Organization limit for drinking water, but the origin is still disputed. Herein we show that a positive 17O excess in NO3− (Δ17ONO3 = Δ17ONO3 − 0.52 δ18ONO3) is preserved in the paleo-groundwater. The 17O excess provides an excellent tracer of atmospheric NO3−, which is caused by the interaction of ozone with NOx via photochemical reactions, coupled with a non-mass-dependent isotope fractionation. Our Δ17ONO3 data from 0.4 to 5.0 ‰ (n = 28) indicate that up to 20 mol % of total dissolved NO3- originated from the Earth's atmosphere (x[NO3−]atm), where the remaining NO3− refers to microbially induced nitrification in soils. High Δ17ONO3 values correspond to soils that are barren in dry periods, while low Δ17ONO3 values correspond to more fertile soils. Coupled high Δ17ONO3 and high x[NO3−]atm values are caused by a sudden wash-out of accumulated disposition of atmospheric NO3− on plants, soil surfaces and in vadose zones within humid–wet cycles. The individual isotope and chemical composition of the Hasouna groundwater can be followed by a binary mixing approach using the lowest and highest mineralised groundwater as end members without considering evaporation. Using the δ34SSO4 and δ18OSO4 isotope signature of dissolved SO42−, no indication is found for a superimposition by denitrification, e.g. involving pyrite minerals within the aquifers. It is suggested that dissolved SO42− originates from the dissolution of CaSO4 minerals during groundwater evolution.
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Shevchenko, O., V. Bublyas i D. Oshurok. "COMBINATION OF GEOPHYSICAL AND HYDROGEOLOGICAL DATA TO EXPLAIN CONTRADICTIONS BETWEEN INFILTRATION AND ATMOSPHERIC PRECIPITATION". Visnyk of Taras Shevchenko National University of Kyiv. Geology, nr 1 (100) (2023): 111–23. http://dx.doi.org/10.17721/1728-2713.100.13.
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A traditional and non-standard approach to the analysis of estimated values of groundwater infiltration feeding using the charge sign of the electric field of the surface atmosphere is considered. A comparison of the results of hydrogeological calculations and observations from specific electrophysical and meteorological factors made it possible to explain the discrepancies between the values of infiltration nutrition and the amount of precipitation. The daily values of groundwater recharge were determined based on 41-year observations in wells in the city Khmelnyk. The average long-term value of infiltration recharge of groundwater from GWT 0.8–2.3 m was 145 mm, from GWT 2.7–4.5 m – 14.7 mm (fluctuations in the range from 129 mm to negative values). A significant correlation between the annual values of infiltration and precipitation at GWT0.8–2.3 m was observed only at the first stage of observations (1980–1988). However, there are also significant contradictions in the ratios of infiltration and precipitation, which could be explained only by involving the data of our own electrophysical observations. For the period from 2008 to 2017, the negative values of the "infiltration-temperature" correlation coefficients for the summer season changed to positive ones, which suggests an increase in the importance of moisture transfer mechanisms in the form of steam. Data on the charge sign of the static electric field of the surface layer of the atmosphere support this conclusion. At high values of the intensity of the static electric field (E) with a negative sign, the direction of moisture movement has an upward character, thanks to which evaporation from the aeration zone increases several times compared to what happens at zero values of E. And the intensity of the electric field with a positive sign forms a downward movement of moisture, which leads to an increase of GWT. From this, the cases when low values of infiltration nutrition were obtained with a significant amount of precipitation become more understandable. Conversely, the low amount of precipitation in 2014–2017 (average value 524 mm) was accompanied by high groundwater recharge (160 mm – 10 % above the norm), stable underground flow to the river in the range of 90–100 m3 /year/m and by the growth of GWT due to the positive values of the static electric field and the decrease in wind strength. This electrical factor has such a powerful influence that it is able to neutralize and effectively counteract the negative impact on groundwater recharge of temperature rise and air humidity deficiency. Since electrodynamic processes have a significant and sometimes decisive role not only in moisture transport in the aeration zone, but also in regional processes of groundwater feeding, the creation of artificial positively charged static fields above the soil surface can become the most effective safeguard against the depletion of groundwater reserves during hydrogeological drought.
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Maksimavičius, Edmundas, i Peter Roslev. "Methane emission and methanotrophic activity in groundwater-fed drinking water treatment plants". Water Supply 20, nr 3 (23.01.2020): 819–27. http://dx.doi.org/10.2166/ws.2020.009.
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Abstract Groundwater for drinking water production may contain dissolved methane (CH4) at variable concentrations. Most of this important greenhouse gas is often vented to the atmosphere during primary aeration and gas stripping processes at drinking water treatment plants (DWTPs). However, limited information exists regarding emission and fate of methane at many groundwater-fed DWTPs. This study estimates emission of methane from 1,004 DWTPs in Denmark and includes data from 3,068 groundwater wells. The fate of methane and occurrence of methane oxidizing bacteria in DWTPs was examined, including the potential role in ammonia removal. Methane emission from Danish DWTPs was estimated to be 1.38–2.95 × 10−4 Tg CH4/y which corresponds to 0.05–0.11% of the national anthropogenic methane emission. Trace levels of methane remained in the drinking water after primary aeration and entered the sand filters as a potential microbial substrate. Methanotrophic bacteria and active methane oxidation was always detected in the sand filters at groundwater-fed DWTPs. Methanotrophic consortia isolated from DWTP sandfilters were inoculated into laboratory-scale sand filters and the activity confirmed that methanotrophic consortia can play a role in the removal of ammonia via assimilation and co-oxidation. This suggests a potential for facilitating the removal of inorganic constituents from drinking water using methane as a co-substrate.
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Quichimbo, E. Andrés, Michael Bliss Singer, Katerina Michaelides, Daniel E. J. Hobley, Rafael Rosolem i Mark O. Cuthbert. "DRYP 1.0: a parsimonious hydrological model of DRYland Partitioning of the water balance". Geoscientific Model Development 14, nr 11 (15.11.2021): 6893–917. http://dx.doi.org/10.5194/gmd-14-6893-2021.
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Abstract. Dryland regions are characterised by water scarcity and are facing major challenges under climate change. One difficulty is anticipating how rainfall will be partitioned into evaporative losses, groundwater, soil moisture, and runoff (the water balance) in the future, which has important implications for water resources and dryland ecosystems. However, in order to effectively estimate the water balance, hydrological models in drylands need to capture the key processes at the appropriate spatio-temporal scales. These include spatially restricted and temporally brief rainfall, high evaporation rates, transmission losses, and focused groundwater recharge. Lack of available input and evaluation data and the high computational costs of explicit representation of ephemeral surface–groundwater interactions restrict the usefulness of most hydrological models in these environments. Therefore, here we have developed a parsimonious distributed hydrological model for DRYland Partitioning (DRYP). The DRYP model incorporates the key processes of water partitioning in dryland regions with limited data requirements, and we tested it in the data-rich Walnut Gulch Experimental Watershed against measurements of streamflow, soil moisture, and evapotranspiration. Overall, DRYP showed skill in quantifying the main components of the dryland water balance including monthly observations of streamflow (Nash–Sutcliffe efficiency, NSE, ∼ 0.7), evapotranspiration (NSE > 0.6), and soil moisture (NSE ∼ 0.7). The model showed that evapotranspiration consumes > 90 % of the total precipitation input to the catchment and that < 1 % leaves the catchment as streamflow. Greater than 90 % of the overland flow generated in the catchment is lost through ephemeral channels as transmission losses. However, only ∼ 35 % of the total transmission losses percolate to the groundwater aquifer as focused groundwater recharge, whereas the rest is lost to the atmosphere as riparian evapotranspiration. Overall, DRYP is a modular, versatile, and parsimonious Python-based model which can be used to anticipate and plan for climatic and anthropogenic changes to water fluxes and storage in dryland regions.
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Hain, Christopher R., Wade T. Crow, Martha C. Anderson i M. Tugrul Yilmaz. "Diagnosing Neglected Soil Moisture Source–Sink Processes via a Thermal Infrared–Based Two-Source Energy Balance Model". Journal of Hydrometeorology 16, nr 3 (27.05.2015): 1070–86. http://dx.doi.org/10.1175/jhm-d-14-0017.1.
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Abstract In recent years, increased attention has been paid to the role of previously neglected water source (e.g., irrigation, direct groundwater extraction, and inland water bodies) and sink (e.g., tile drainage) processes on the surface energy balance. However, efforts to parameterize these processes within land surface models (LSMs) have generally been hampered by a lack of appropriate observational tools for directly observing the impact(s) of such processes on surface energy fluxes. One potential strategy for quantifying these impacts are direct comparisons between bottom-up surface energy flux predictions from a one-dimensional, free-drainage LSM with top-down energy flux estimates derived via thermal infrared remote sensing. The neglect of water source (and/or sink) processes in the bottom-up LSM can be potentially diagnosed through the presence of systematic energy flux biases relative to the top-down remote sensing retrieval. Based on this concept, the authors introduce the Atmosphere–Land Exchange Inverse (ALEXI) Source–Sink for Evapotranspiration (ASSET) index derived from comparisons between ALEXI remote sensing latent heat flux retrievals and comparable estimates obtained from the Noah LSM, version 3.2. Comparisons between ASSET index values and known spatial variations of groundwater depth, irrigation extent, inland water bodies, and tile drainage density within the contiguous United States verify the ability of ASSET to identify regions where neglected soil water source–sink processes may be impacting modeled surface energy fluxes. Consequently, ASSET appears to provide valuable information for ongoing efforts to improve the parameterization of new water source–sink processes within modern LSMs.
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Shrestha, P., M. Sulis, C. Simmer i S. Kollet. "Impacts of grid resolution on surface energy fluxes simulated with an integrated surface-groundwater flow model". Hydrology and Earth System Sciences Discussions 12, nr 7 (3.07.2015): 6437–66. http://dx.doi.org/10.5194/hessd-12-6437-2015.
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Abstract. The hydrological component of the Terrestrial System Modeling Platform (TerrSysMP) which includes integrated surface-groundwater flow, was used to investigate the grid resolution dependence of simulated soil moisture, soil temperature, and surface energy fluxes over a sub-catchment of the Rur, Germany. The investigation was motivated by the recent developments of new earth system models, which include 3-D physically based groundwater models for the coupling of land–atmosphere interaction and subsurface hydrodynamics. Our findings suggest that for grid resolutions between 100 and 1000 m, the non-local controls of soil moisture are highly grid resolution dependent. Local vegetation, however, strongly modulates the scaling behavior especially for surface fluxes and soil temperature, which depends on the radiative transfer property of the canopy. This study also shows that for grid-resolutions above a few 100 m, the variation of spatial and temporal pattern of sensible and latent heat fluxes may significantly affect the resulting atmospheric mesoscale circulation and boundary layer evolution in coupled runs.
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Marotta, H., C. M. Duarte, L. Pinho i A. Enrich-Prast. "Rainfall leads to increased <i>p</i>CO<sub>2</sub> in Brazilian Coastal Lakes". Biogeosciences Discussions 6, nr 6 (15.12.2009): 11521–39. http://dx.doi.org/10.5194/bgd-6-11521-2009.
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Abstract. The variation of surface partial pressure of CO2 (pCO2), pH, salinity and dissolved organic carbon (DOC) in 12 coastal Brazilian lakes was examined following periods of contrasting rainfall. It was tested the hypothesis of a positive relationship of rainfall and the associated transport of terrestrial carbon with pCO2 in tropical lakes. High rainfall was followed by a large, almost 10 fold increase in pCO2 and a one unit decrease in pH in the lakes, whereas no consistent changes in DOC were observed. CO2 emissions to the atmosphere from the Brazilian coastal lakes studied here were enhanced, on average, almost 10 fold, from 28.5±6.0 mmol m−2 d−1 in drier periods to 245.3.1±51.5 mmol m−2 d−1 following heavy rain. Hence, precipitation and subsequent ventilation of groundwater CO2 in lakes might provide an important conduit to deliver CO2 resulting from soil respiration to the atmosphere.
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Nousu, Jari-Pekka, Kersti Leppä, Hannu Marttila, Pertti Ala-aho, Giulia Mazzotti, Terhikki Manninen, Mika Korkiakoski, Mika Aurela, Annalea Lohila i Samuli Launiainen. "Multi-scale soil moisture data and process-based modeling reveal the importance of lateral groundwater flow in a subarctic catchment". Hydrology and Earth System Sciences 28, nr 20 (24.10.2024): 4643–66. http://dx.doi.org/10.5194/hess-28-4643-2024.
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Abstract. Soil moisture plays a key role in soil nutrient and carbon cycling; plant productivity; and energy, water, and greenhouse gas exchanges between the land and the atmosphere. The knowledge on drivers of spatiotemporal soil moisture dynamics in subarctic landscapes is limited. In this study, we used the Spatial Forest Hydrology (SpaFHy) model, in situ soil moisture data, and Sentinel-1 synthetic aperture radar (SAR)-based soil moisture estimates to explore spatiotemporal controls of soil moisture in a subarctic headwater catchment in northwestern Finland. The role of groundwater dynamics and lateral flow in soil moisture was studied through three groundwater model conceptualizations: (i) omission of groundwater storage and lateral flow, (ii) conceptual TOPMODEL approach based on topographic wetness index, and (iii) explicit 2D lateral groundwater flow. The model simulations were compared against continuous point soil moisture measurements, distributed manual measurements, and novel SAR-based soil moisture estimates available at high spatial and temporal resolutions. Based on model scenarios and model–data comparisons, we assessed when and where the lateral groundwater flow shapes shallow soil moisture and under which conditions soil moisture variability is driven more by local ecohydrology, i.e., the balance of infiltration, drainage, and evapotranspiration. The choice of groundwater flow model was shown to have a strong impact on modeled soil moisture dynamics within the catchment. All model conceptualizations captured the observed soil moisture dynamics in the upland forests, but accounting for the lateral groundwater flow was necessary to reproduce the saturated conditions common in the peatlands and occasionally in lowland forest grid cells. We further highlight the potential of integrating multi-scale observations with land surface and hydrological models. The results have implications for ecohydrological and biogeochemical processes, as well as for modeling hydrology and Earth system feedbacks in subarctic and boreal environments.
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Vergnes, J. P., B. Decharme, R. Alkama, E. Martin, F. Habets i H. Douville. "A Simple Groundwater Scheme for Hydrological and Climate Applications: Description and Offline Evaluation over France". Journal of Hydrometeorology 13, nr 4 (1.08.2012): 1149–71. http://dx.doi.org/10.1175/jhm-d-11-0149.1.
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Abstract Despite their potential influences on surface water and climate, groundwater processes are generally not represented in climate models. Here, a simple groundwater scheme including two-dimensional flow dynamics and accounting for groundwater–river exchanges is introduced into the global Total Runoff Integrated Pathways (TRIP) river routing model coupled to the Météo-France climate model. This original scheme is tested in offline mode over France at high () and low (0.5°) resolution against a dense network of river discharge and water table observations over the 1970–2010 period, and is compared to the fine-tuned Système d’Analyze Fournissant des Renseignements Atmosphériques à la Neige (SAFRAN)–Interactions between Soil, Biosphere, and Atmosphere (ISBA) coupled hydrometeorological model (MODCOU). In addition, the simulated terrestrial water storage (TWS) variations are compared to the TWS estimates from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. The aquifer basins over France are defined using the World-wide Hydrogeological Mapping and Assessment Programme (WHYMAP) groundwater resources map, a simplified French lithological map, and the International Geological Map of Europe (IGME). TRIP is forced by daily runoff and drainage data derived from a preexisting simulation of the ISBA land surface scheme driven by the high-resolution SAFRAN meteorological analysis. Four simulations are carried out with or without groundwater at both resolutions. Results show that the groundwater scheme allows TRIP to better capture the spatiotemporal variability of the observed river discharges and piezometric heads. Summer base flows are particularly improved over the main rivers of France. Decreasing the horizontal resolution has a limited impact on the simulated discharges, while it slightly degrades the simulation of water table variations.
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Bublyas, Volodymyr, i Oleksii Shevchenko. "JUSTIFICATION OF THE EXTENDED COMPOSITION OF OBSERVATIONS AT WATER BALANCE STATIONS AND RESEARCH HYDROGEOPHYSICAL RANGES". Meteorology. Hydrology. Environmental monitoring 2024, nr 5 (20.10.2024): 63–88. http://dx.doi.org/10.15407/meteorology2024.05.063.
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The current level of understanding of the subordination and multifactorial dependence of the determining processes in the atmosphere, lithosphere and hydrosphere of the Earth requires a corresponding reorganization of the basic system of environmental monitoring, improvement and expansion of research on water these stations, which can become the supporting 'nodes' of the balance of this system. The appearance of fundamentally new theoretical developments, modern devices and equipment, a large number of software tools, etc., prompts a significant reorganization and strengthening of the environmental monitoring system. The article substantiates an additional set of studies, which should be included in the regulation of observations at already existing water balance stations, with their mandatory modernization. Spheres are subject to control - the atmosphere, surface and underground (subsurface) hydrospheres, which change over time at different rates and pedosphere. A certain inertia of hydrogeological processes implies the possibility of using meteorological indicators, which can be used to predict changes in the moisture regime in the aeration zone and shallow groundwater in the near future; based on the reliably predictable changes of the latter - to forecast changes in interlayer groundwater resources, etc. It is proposed to include in the monitoring regulations the following indicators of the state of the environment, which will allow to identify and analyze the causes of changes in the water situation, balance and resources, to determine the mechanisms of moisture transfer and accumulation, as well as to build models and perform predictive assessments. The results of comprehensive research at the «Lutiz» landfill demonstrate significant variability of hydrogeophysical indicators and changes in the intensity of natural signals depending on the landscape timing, the latest tectonics, the geological basis and the composition of the overlying sediments. Original devices are presented, which are used to determine indicators of electric and thermal fields, the ratio of positive and negative air ions, etc.
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De Marco, Alessandra, Maria Francesca Fornasier, Augusto Screpanti, Danilo Lombardi i Marcello Vitale. "Nitrogen Budget and Statistical Entropy Analysis of the Tiber River Catchment, a Highly Anthropized Environment". Soil Systems 6, nr 1 (2.02.2022): 17. http://dx.doi.org/10.3390/soilsystems6010017.
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Modern farming causes a decline in the recycling of the soil’s inorganic matter due to losses by leaching, runoff, or infiltration into the groundwater. The Soil System Budget approach was applied to evaluate the net N budget at the catchment and sub-catchment levels of the Tiber River (central Italy) in order to establish the causes for different N budgets among the sub-catchments. Statistical Entropy Analysis (SEA) was used to evaluate the N efficiency of the Tiber River and its sub-catchments, providing information on the dispersion of different N forms in the environment. The total N inputs exceeded the total outputs, showing a low N retention (15.8%) at the catchment level, although some sub-catchments showed higher N retention values. The Utilized Agricultural Area was important in the determination of the N balance, as it was linked to zoo- and agricultural activities, although the Random Forest analysis showed that the importance ranking changed with the land use. The low N retention of the Tiber catchment was due to the soil characteristics (Cambisols and Leptosols), loads from atmospheric deposition, biological fixation, and the livestock industry. The SEA simulations showed a reduction of the N released into the atmosphere and groundwater compartments from 34% to 6% through a reduction of the N loads by 50%.
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Smith, K., D. Jackson, G. Smith i S. Norris. "Comparison of modelled uptake to cereal crops of 14C from gaseous or groundwater mediated pathways". Mineralogical Magazine 76, nr 8 (grudzień 2012): 3241–49. http://dx.doi.org/10.1180/minmag.2012.076.8.37.
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AbstractCarbon-14 has been identified as one of the more significant radionuclides in solid radioactive wastes in a repository, due to the potential radiological impact arising if 14C were to be released and enter the biosphere. However, the assessment of radiation doses is complicated by the major role of carbon in biological processes, and this has tended to lead to the adoption of a cautious assessment approach.An international comparison of five models used to predict uptake of 14C to agricultural crops has been undertaken, within the BIOPROTA framework. Processes investigated include conversion of 14C-labelled CH4 into CO2 in soils, carbon accumulation in and release from soil carbon pools, gaseous emanation to, and dispersion from, the plant canopy atmosphere and, incorporation into plants by photosynthesis.For a unit rate of entry of 14C to soil, modelled activity concentrations in cereal crops differ by three to five orders of magnitude. This reflects, in part, differing assumptions for mixing and dispersion of air above the soil surface and within the crop canopy layer. For a unit activity concentration of 14C in air, the modelled uptake to cereal crops converges significantly. Following an assumed irrigation of crops with groundwater containing unit activity of 14C, the predicted uptake to crops varied by two to four orders of magnitude, again largely dominated by assumptions regarding the canopy atmosphere. In all cases, there is some convergence in model predictions as field size increases.A continuing programme of field research is being undertaken in parallel with the assessment work.
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Hodson, Andrew J., Aga Nowak, Mikkel T. Hornum, Kim Senger, Kelly Redeker, Hanne H. Christiansen, Søren Jessen i in. "Sub-permafrost methane seepage from open-system pingos in Svalbard". Cryosphere 14, nr 11 (9.11.2020): 3829–42. http://dx.doi.org/10.5194/tc-14-3829-2020.
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Abstract. Methane release from beneath lowland permafrost represents an important uncertainty in the Arctic greenhouse gas budget. Our current knowledge is arguably best developed in settings where permafrost is being inundated by rising sea level, which means much of the methane is oxidised in the water column before it reaches the atmosphere. Here we provide a different process perspective that is appropriate for Arctic fjord valleys where local deglaciation causes isostatic uplift to out pace rising sea level. We describe how the uplift induces permafrost aggradation in former marine sediments, whose pressurisation results in methane escape directly to the atmosphere via groundwater springs. In Adventdalen, central Spitsbergen, we show how the springs are historic features responsible for the formation of open-system pingos and capable of discharging brackish waters enriched with high concentrations of mostly biogenic methane (average 18 mg L−1). Thermodynamic calculations show that the methane concentrations sometimes marginally exceed the solubility limit for methane in water at 0 ∘C (41 mg L−1). Year-round emissions from the pingos are described. During winter, rapid methane loss to the atmosphere occurs following outburst events from beneath an ice blister. During summer, highly variable emissions occur due to complex surface processes at the seepage point and its inundation by surface runoff. In spite of this complexity, our observations confirm that sub-permafrost methane migration deserves more attention for the improved forecasting of Arctic greenhouse gas emissions.
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Poshyvailo-Strube, Liubov, Niklas Wagner, Klaus Goergen, Carina Furusho-Percot, Carl Hartick i Stefan Kollet. "Impact of groundwater representation on heat events in regional climate simulations over Europe". Earth System Dynamics 15, nr 2 (5.03.2024): 167–89. http://dx.doi.org/10.5194/esd-15-167-2024.
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Abstract. The representation of groundwater is simplified in most regional climate models (RCMs), potentially leading to biases in the simulations. This study introduces a unique dataset from the regional Terrestrial Systems Modelling Platform (TSMP) driven by the Max Planck Institute Earth System Model at Low Resolution (MPI-ESM-LR) boundary conditions in the context of dynamical downscaling of global climate models (GCMs) for climate change studies. TSMP explicitly simulates full 3D soil and groundwater dynamics together with overland flow, including complete water and energy cycles from the bedrock to the top of the atmosphere. By comparing the statistics of heat events, i.e., a series of consecutive days with a near-surface temperature exceeding the 90th percentile of the reference period, from TSMP and those from GCM–RCM simulations with simplified groundwater dynamics from the COordinated Regional Climate Downscaling EXperiment (CORDEX) for the European domain, we aim to improve the understanding of how groundwater representation affects heat events in Europe. The analysis was carried out using RCM outputs for the summer seasons of 1976–2005 relative to the reference period of 1961–1990. While our results show that TSMP simulates heat events consistently with the CORDEX ensemble, there are some systematic differences that we attribute to the more realistic representation of groundwater in TSMP. Compared to the CORDEX ensemble, TSMP simulates fewer hot days (i.e., days with a near-surface temperature exceeding the 90th percentile of the reference period) and lower interannual variability and decadal change in the number of hot days on average over Europe. TSMP systematically simulates fewer heat waves (i.e., heat events lasting 6 d or more) compared to the CORDEX ensemble; moreover, they are shorter and less intense. The Iberian Peninsula is particularly sensitive with respect to groundwater. Therefore, incorporating an explicit 3D groundwater representation in RCMs may be a key in reducing biases in simulated duration, intensity, and frequency of heat waves in Europe. The results highlight the importance of hydrological processes for the long-term regional climate simulations and provide indications of possible potential implications for climate change projections.
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Le Lay, Hugo, Zahra Thomas, François Rouault, Pascal Pichelin i Florentina Moatar. "Characterization of Diffuse Groundwater Inflows into Stream Water (Part II: Quantifying Groundwater Inflows by Coupling FO-DTS and Vertical Flow Velocities)". Water 11, nr 12 (20.11.2019): 2430. http://dx.doi.org/10.3390/w11122430.
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Temperature has been used to characterize groundwater and stream water exchanges for years. One of the many methods used analyzes propagation of the atmosphere-influenced diurnal signal in sediment to infer vertical velocities. However, despite having good accuracy, the method is usually limited by its small spatial coverage. The appearance of fiber optic distributed temperature sensing (FO-DTS) provided new possibilities due to its high spatial and temporal resolution. Methods based on the heat-balance equation, however, cannot quantify diffuse groundwater inflows that do not modify stream temperature. Our research approach consists of coupling groundwater inflow mapping from a previous article (Part I) and deconvolution of thermal profiles in the sediment to obtain vertical velocities along the entire reach. Vertical flows were calculated along a 400 m long reach, and a period of 9 months (October 2016 to June 2017), by coupling a fiber optic cable buried in thalweg sediment and a few thermal lances at the water–sediment interface. When compared to predictions of hyporheic discharge by traditional methods (differential discharge between upstream and downstream of the monitored reach and the mass-balance method), those of our method agreed only for the low-flow period and the end of the high-flow period. Our method underestimated hyporheic discharge during high flow. We hypothesized that the differential discharge and mass-balance methods included lateral inflows that were not detected by the fiber optic cable buried in thalweg sediment. Increasing spatial coverage of the cable as well as automatic and continuous calculation over the reach may improve predictions during the high-flow period. Coupling groundwater inflow mapping and vertical hyporheic flow allows flow to be quantified continuously, which is of great interest for characterizing and modeling fine hyporheic processes over long periods.
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Jahangir, M. M. R., O. Fenton, L. Gill, C. Müller, P. Johnston i K. G. Richards. "Carbon and nitrogen dynamics and greenhouse gases emissions in constructed wetlands: a review". Hydrology and Earth System Sciences Discussions 11, nr 7 (4.07.2014): 7615–57. http://dx.doi.org/10.5194/hessd-11-7615-2014.
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Abstract. The nitrogen (N) removal efficiency of constructed wetlands (CWs) is very inconsistent and does not alone explain if the removed species are reduced by physical attenuation or if they are transformed to other reactive forms (pollution swapping). There are many pathways for the removed N to remain in the system: accumulation in the sediments, leaching to groundwater (nitrate-NO3- and ammonium-NH4+), emission to atmosphere via nitrous oxide- N2O and ammonia and/or conversion to N2 gas and adsorption to sediments. The kinetics of these pathways/processes varies with CWs management and therefore needs to be studied quantitatively for the sustainable use of CWs. For example, the quality of groundwater underlying CWs with regards to the reactive N (Nr) species is largely unknown. Equally, there is a dearth of information on the extent of Nr accumulation in soils and discharge to surface waters and air. Moreover, CWs are rich in dissolved organic carbon (DOC) and produce substantial amounts of CO2 and CH4. These dissolved carbon (C) species drain out to ground and surface waters and emit to the atmosphere. The dynamics of dissolved N2O, CO2 and CH4 in CWs is a key "missing piece" in our understanding of global greenhouse gas budgets. In this review we provide an overview of the current knowledge and discussion about the dynamics of C and N in CWs and their likely impacts on aquatic and atmospheric environments. We suggest that the fate of various N species in CWs and their surface emissions and subsurface drainage fluxes need to be evaluated in a holistic way to better understand their potential for pollution swapping. Research on the process based N removal and balancing the end products into reactive and benign forms are critical to assess environmental impacts of CWs. Thus we strongly suggest that in situ N transformation and fate of the transformation products with regards to pollution swapping requires further detailed examination.
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Yevenes-Burgos, M. A., i C. M. Mannaerts. "Untangling hydrological pathways and nitrate diffusive sources by chemical appraisal in a stream network of a reservoir catchment". Hydrology and Earth System Sciences Discussions 8, nr 2 (2.03.2011): 2289–322. http://dx.doi.org/10.5194/hessd-8-2289-2011.
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Abstract. Stable water isotopes and water hydrochemistry of a catchment in the Alentejo region, south Portugal, were analysed to investigate source origins of water and nitrate flows towards a reservoir. The 353 km2 headwater catchment of Roxo river, is strongly influenced by agricultural impacts, and high variations in water and chemical inflows into an important drinking and irrigation water supply (108 m3) are observed. This leads to regular disputes on water quantity and quality amongst local authorities and population. Three sampling campaigns in different seasons were used to address the temporal and spatial variations in stream and groundwater hydrochemistry and water isotopic signatures. A total of 27 sampling points from the stream network, shallow groundwater and reservoir were used. Isotopic signatures and chemistry of precipitation were obtained from local data of the Global Network of Isotopes in Precipitation (GNIP) and the Global Atmosphere Watch (GAWSIS) network. Other meteorological, hydrological and environmental datasets were obtained from local authorities. The stable water isotopes deuterium (δ2H), oxygen-18 (δ18O) together with chloride (Cl–) and sulphate (SO42–) were used as environmental tracers in the hydrological pathways. Water pathways were then related with nitrate concentrations to elucidate potential relationships between the water and nutrient sources. Interpretation of isotope signatures showed a high degree of isotope enrichment in both surface (stream flow) and shallow groundwater. For the entire period, most of stream waters were located right of the global meteoric water line or GMWL and plotted along a local evaporation line (LEL) established for the study area. The LEL showed slopes similar to stream systems in other dry environments. Monthly stream flow and precipitation, seasonal isotope compositions and major ion chemistry data were used for an evaluation of the relative contribution of water sources using an end-member mixing analysis. An extensive PCA or principal component analysis preceded the mixing analysis. Contributions of the three water end-members in the catchment: groundwater, surface runoff and precipitation to stream flow could be identified based on their 2H, 18O and Cl– signatures. Also two hydro chemical data outliers for Cl– and NO3– from two sample points were identified by the analysis and could be related to local waste water outfalls, giving the method also diagnostic value for pollution source allocation. The shallow groundwater source could be related to stream nitrate concentrations during the wet seasons, indicating a linkage between hydrological flow paths, nitrate sources and season. Conversely, weak links between precipitation, and surprisingly also surface water runoff and nitrate levels were found. In this catchment, we found a consistent pattern of the particular groundwater end member, being main source of nitrate to the stream water and reservoir, based on conservative mixing of the different water sources.
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Schyns, J. F., A. Y. Hoekstra i M. J. Booij. "Review and classification of indicators of green water availability and scarcity". Hydrology and Earth System Sciences Discussions 12, nr 6 (11.06.2015): 5519–64. http://dx.doi.org/10.5194/hessd-12-5519-2015.
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Abstract. Research on water scarcity has mainly focused on blue water (surface- and groundwater), but green water (soil moisture directly returning to the atmosphere as evaporation) is also scarce, because its availability is limited and there are competing demands for green water. Crop production, grazing lands, forestry and terrestrial ecosystems are all sustained by green water. The implicit distribution or explicit allocation of limited green water resources over competitive demands determines which economic and environmental goods and services will be produced and may affect food security and nature conservation. We need to better understand green water scarcity to be able to measure, model, predict and handle it. This paper reviews and classifies around 80 indicators of green water availability and scarcity and discusses the way forward to develop operational green water scarcity indicators that can broaden the scope of water scarcity assessments.
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Rahlff, Janina, Helge-Ansgar Giebel, Christian Stolle, Oliver Wurl, Alexander J. Probst i Daniel P. R. Herlemann. "Overlooked Diversity of Ultramicrobacterial Minorities at the Air-Sea Interface". Atmosphere 11, nr 11 (10.11.2020): 1214. http://dx.doi.org/10.3390/atmos11111214.
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Members of the Candidate phylum Patescibacteria, also called Candidate Phyla Radiation (CPR), are described as ultramicrobacteria with limited metabolic capacities. Wide diversity and relative abundances up to 80% in anaerobic habitats, e.g., in groundwater or sediments are characteristic for Candidatus Patescibacteria. However, only few studies exist for marine surface water. Here, we report the presence of 40 patescibacterial candidate clades at air-sea interfaces, including the upper water layer, floating foams and the sea-surface microlayer (SML), a < 1 mm layer at the boundary between ocean and atmosphere. Particle-associated (>3 µm) and free-living (3–0.2 µm) samples were obtained from the Jade Bay, North Sea, and 16S rRNA (gene) amplicons were analyzed. Although the abundance of Cand. Patescibacteria representatives were relatively low (<1.3%), members of Cand. Kaiserbacteria and Cand. Gracilibacteria were found in all samples. This suggests profound aerotolerant capacities of these phylogenetic lineages at the air-sea interface. The presence of ultramicrobacteria in the >3 µm fraction implies adhesion to bigger aggregates, potentially in anoxic niches, and a symbiotic lifestyle. Due to their small sizes, Cand. Patescibacteria likely become aerosolized to the atmosphere and dispersed to land with possible implications for affecting microbial communities and associated processes in these ecosystems.
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Zhang, Quan, Huimin Lei, Dawen Yang, Lihua Xiong, Pan Liu i Beijing Fang. "Decadal variation in CO<sub>2</sub> fluxes and its budget in a wheat and maize rotation cropland over the North China Plain". Biogeosciences 17, nr 8 (22.04.2020): 2245–62. http://dx.doi.org/10.5194/bg-17-2245-2020.
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Abstract. Carbon sequestration in agroecosystems has great potential to mitigate global greenhouse gas emissions. To assess the decadal trend of CO2 fluxes of an irrigated wheat–maize rotation cropland over the North China Plain, the net ecosystem exchange (NEE) with the atmosphere was measured by using an eddy covariance system from 2005 to 2016. To evaluate the detailed CO2 budget components of this representative cropland, a comprehensive experiment was conducted in the full 2010–2011 wheat–maize rotation cycle by combining the eddy covariance NEE measurements, plant carbon storage samples, and a soil respiration experiment that differentiated between heterotrophic and below-ground autotrophic respirations. Over the past decade (from 2005 to 2016), the cropland exhibited a statistically nonsignificant decreasing carbon sequestration capacity; the average of total NEE, gross primary productivity (GPP), and ecosystem respiration (ER), respectively, were −364, 1174, and 810 gC m−2 for wheat and −136, 1008, and 872 gC m−2 for maize. The multiple regression revealed that air temperature and groundwater depth showed pronounced correlations with the CO2 fluxes for wheat. However, in the maize season, incoming shortwave radiation and groundwater depth showed pronounced correlations with CO2 fluxes. For the full 2010–2011 agricultural cycle, the CO2 fluxes for wheat and maize were as follows: for NEE they were −438 and −239 gC m−2, for GPP 1078 and 780 gC m−2, for ER 640 and 541 gC m−2, for soil heterotrophic respiration 377 and 292 gC m−2, for below-ground autotrophic respiration 136 and 115 gC m−2, and for above-ground autotrophic respiration 128 and 133 gC m−2. The net biome productivity was 59 gC m−2 for wheat and 5 gC m−2 for maize, indicating that wheat was a weak CO2 sink and maize was close to CO2 neutral to the atmosphere for this agricultural cycle. However, when considering the total CO2 loss in the fallow period, the net biome productivity was −40 gC m−2 yr−1 for the full 2010–2011 cycle, implying that the cropland was a weak CO2 source. The investigations of this study showed that taking cropland as a climate change mitigation tool is challenging and that further studies are required for the CO2 sequestration potential of croplands.
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Subašić, Mirel, Dunja Šamec, Alisa Selović i Erna Karalija. "Phytoremediation of Cadmium Polluted Soils: Current Status and Approaches for Enhancing". Soil Systems 6, nr 1 (4.01.2022): 3. http://dx.doi.org/10.3390/soilsystems6010003.
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Cadmium (Cd) is a heavy metal present in atmosphere, rocks, sediments, and soils without a known role in plants. It is relatively mobile and can easily enter from soil into groundwater and contaminate the food chain. Its presence in food in excess amounts may cause severe conditions in humans, therefore prevention of cadmium entering the food chain and its removal from contaminated soils are important steps in preserving public health. In the last several years, several approaches for Cd remediation have been proposed, such as the use of soil amendments or biological systems for reduction of Cd contamination. One of the approaches is phytoremediation, which involves the use of plants for soil clean-up. In this review we summarized current data on the use of different plants in phytoremediation of Cd as well as information about different approaches which have been used to enhance phytoremediation. This includes data on the increasing metal bioavailability in the soil, plant biomass, and plant accumulation capacity as well as seed priming as a promising novel approach for phytoremediation enhancing.
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Wu, Yali, Ying Ma, Xianfang Song, Lihu Yang i Shengtian Yang. "Responses of Water Fluxes and Water-Use Efficiency of Maize to Warming Based on Water Transformation Dynamical Processes Experimental Device (WTDPED) Experiment". Water 10, nr 11 (14.11.2018): 1660. http://dx.doi.org/10.3390/w10111660.
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Evaluating the impacts of warming on water balance components in the groundwater–soil–plant–atmosphere continuum (GSPAC) and crop growth are crucial for assessing the risk of water resources and food security under future global warming. A water transformation dynamical processes experimental device (WTDPED) was developed using a chamber coupled with a weighing lysimeter and groundwater supply system, which could simultaneously control both climatic and ground-water level conditions and accurately monitor water fluxes in the GSPAC. Two experiments with maize under increased temperature by 2 °C (T-warm) and ambient temperature (T-control) scenarios were conducted via the WTDPED. The duration of growing season decreased from 125 days under T-control to 117 days under 2 °C warming. There was little difference of total evapotranspiration (ET) (332.6 mm vs. 332.5 mm), soil water storage change (∆W) (−119.0 mm vs. −119.0 mm), drainage (D) (−13.6 mm vs. −13.5 mm) between T-control and T-warm experiments. The average daily ET for maize significantly increased by approximately 6.7% (p < 0.05) in the T-warm experiment, especially during the sixth leaf to tasseling—silking stage with an increase of 0.36 mm with respect to the T-control experiment. There were evident decreases in LAI (leaf area index), whereas non-significant decreases in mean stem diameter, crop height and leaf chlorophyll content under T-warm compared to T-control experiment. However, the chlorophyll content increased by 12% during the sixth leaf to tasseling–silking stage under 2 °C warming, which accelerated the photosynthesis and transpiration rate. The grain yield and water-use efficiency (WUE) for maize increased by 11.0% and 11.1% in the T-warm experiment, respectively, especially due to enhanced growth during the sixth leaf to tasseling–silking stage. This study provided important references for agricultural planting and water management to adapt to a warming environment.
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Hertek, S. G., i V. I. Tatarenko. "Creation of 3d model of the object for real estate cadastre purposes". Interexpo GEO-Siberia 6 (18.05.2022): 275–80. http://dx.doi.org/10.33764/2618-981x-2022-6-275-280.
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This article describes the effects of waste on the environment, the problem of environmental pollution by landfills, the amount of waste is growing every year, solid municipal waste. Under the influence of atmospheric air, water and biota, various biochemical and chemical processes occur in these soils, which emit heat and form biogas and filtrates. The need to monitor the state and pollution of the atmosphere. Sampling and analysis of filtrate, groundwater pollution, waste recycling. The results of the monitoring are used to evaluate and analyze the effectiveness of measures aimed at reducing the negative impact of waste disposal facilities on the environment, education standards, waste disposal limits. The need for container sites, the separation of garbage by types and groups, the environmental benefits of operating sites, waste recycling and recycling companies are described, the result will be a reduction in environmental pollution, the production of secondary raw materials.
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Mirel, Oana Stela, i Constantin Florescu. "Simulation of Wastewater Depolution Processes by Advanced Biological Methods". Revista de Chimie 71, nr 10 (3.11.2020): 150–60. http://dx.doi.org/10.37358/rc.20.10.8359.
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This paper presents the results from a study which simulates wastewater depollution processes using advanced biological methods. The experimental research was performed in a static biological reactor, equipped with an air compressor and an agitator / mixer. Synthetic wastewater, prepared with the addition of glucose, was fed into the reactor. The wastewater was subjected to alternating cycles of aeration and slow mixing, for consecutive 3 h intervals within the reactor to ensure the necessary conditions for the reduction of nitrogen based organic compounds within the wastewater. In the successive aeration processes, aerobic / nitrifying microorganisms which developed within the reactor, facilitated the decomposition of organic substances into nitrites and then into nitrates. By stopping aeration and starting the slow mixing cycle the anaerobic / denitrifying microorganisms growing in the reactor consume the necessary oxygen from nitrates and release free nitrogen into the atmosphere, thus completing the process of advanced depollution. Therefore, the experimental procedure highlights the existence of two distinct phases in the development of the depollution process. In the first phase, the biological process is initiated using glucose in order to promote the growth of the bacterial flora. In the second phase (the regime phase), the reduction of mineral and organic pollutants from the wastewater is ensured. The activity of microorganisms in the biological reactor can be further supported by the recirculation of activated sludge retained in the secondary decanter. The proposed technology offers a fast, safe and relatively inexpensive method for advanced wastewater depollution. Bioreactors of this type are recommended in wastewater treatment schemes in the hearth of rural localities, agro-zootechnical complexes and tourist units with seasonal activities due to their fluctuations in hourly wastewater flow rates. Similar approaches can also be considered for the elimination of ammonium compounds in groundwater polluted with animal manure.
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Thaysen, E. M., D. Jacques, S. Jessen, C. E. Andersen, E. Laloy, P. Ambus, D. Postma i I. Jakobsen. "Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms". Biogeosciences 11, nr 24 (17.12.2014): 7179–92. http://dx.doi.org/10.5194/bg-11-7179-2014.
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Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying mechanisms. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modeled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol C m−2 s−1, respectively, and grossly exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Plant biomass was high in the mesocosms as compared to a standard field situation. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one-third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Modeling suggested that increasing soil alkalinity during plant growth was due to nutrient buffering during root nitrate uptake.
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Thaysen, E. M., D. Jacques, S. Jessen, C. E. Andersen, E. Laloy, P. Ambus, D. Postma i I. Jakobsen. "Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms". Biogeosciences Discussions 11, nr 3 (17.03.2014): 4251–99. http://dx.doi.org/10.5194/bgd-11-4251-2014.
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Abstract. The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles, and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modelled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol carbon (C) m−2 s−1, respectively, and largely exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Plant biomass and soil pCO2 were high in the mesocosms as compared to a standard field situation. Our results indicate no change of the cropland C balance under elevated atmospheric CO2 in a warmer future climate, in which plant biomass and soil pCO2 are expected to increase.
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Pozdniakov, S. P., S. O. Grinevsky, E. A. Dediulina i V. N. Samartsev. "Model analysis of observed and predicted climate changes of groundwater recharge in the basin of a small river". Moscow University Bulletin. Series 4. Geology, nr 3 (28.06.2019): 78–86. http://dx.doi.org/10.33623/0579-9406-2019-3-78-86.
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The analysis of the connection of groundwater recharge in the basin of a small river with the current and expected climatic changes in the European territory of Russia is carried out using the catchment basin of Zhizdra river Kaluga region as an example. The analysis was based on the modeling of the processes of transformation of moisture on the earth surface and moisture transfer in the aeration zone. The results of global climate predictions for five models of the general circulation of the atmosphere and ocean (GCM) from the CMI5 family were applied for the forecast in the second half of the 21st century using the LARSWG5 forecast weather conditions generator. The simulation results show that despite the fact that all the GCM used predict a warming in the region at 2–6 ᵒC, the difference in the predicted recharge is still significantly large, which is associated with the difference in the predicted dryness index.
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Corapcioglu, M. Y., i A. Baehr. "Immiscible Contaminant Transport in Soils and Groundwater with an Emphasis on Petroleum Hydrocarbons: System of Differential Equations vs Single Cell Model". Water Science and Technology 17, nr 9 (1.09.1985): 23–37. http://dx.doi.org/10.2166/wst.1985.0080.
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Soil and groundwater contamination resulting from leaks of petroleum products, from faulty storage tanks and pipelines has become a recent environmental concern. A generalized mathematical model, incorporating the physical, chemical and biological processes which collectively describe the transport of a reactive and immiscible contaminant in soils and groundwater is presented. The problem is one of multiphase transport, that is, the contaminant can be transported as solutes in water, vapors in air and as unreacted constituents in an immiscible phase. Additionally, it may be adsorbed onto the soil surface. Conservation principles lead to a system of nonlinear partial differential equations governing the phenomenon. As an alternative, a single cell model as a simplified version of this generalized system is also presented. The whole system is represented by a single element. Such an approach yields conservative estimates of a single constituent contaminant as only advective solute transport is allowed. The model has been applied to study the fate and transport of individual hydrocarbon constituents in an unsaturated zone. The results predict the concentrations of each hydrocarbon in all phases in space and time allowing the user to estimate the amounts of hydrocarbons which enter the underlying aquifer or which leave the soil via volatilization into the atmosphere. Such predictions are presented for selected cases. Comparisons of the single cell model with the generalized one are also given.
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Dulinski, M., K. Rozanski, T. Kuc, Z. Gorczyca, J. Kania i M. Kapusta. "Evolution of Radiocarbon in a Sandy Aquifer Across Large Temporal and Spatial Scales: Case Study from Southern Poland". Radiocarbon 55, nr 2 (2013): 905–19. http://dx.doi.org/10.1017/s0033822200058069.
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We present the results of a comprehensive study aimed at tracing the evolution of carbon isotopic composition of the TDIC (total dissolved inorganic carbon) reservoir from the unsaturated zone down to the discharge area, in a sandy aquifer near Kraków, southern Poland. A multilevel well penetrating the unsaturated zone in the study area was equipped with horizontally mounted lysimeters with ceramic suction cups to collect samples of pore water and metal probes to collect soil air. Strong seasonal fluctuations were observed of soil pCO2 extending down to the water table, coupled with distinct, well-defined depth profiles of δ13CTDIC reaching approximately −10′ at 8 m depth and almost constant radiocarbon content in the TDIC pool, comparable to 14CO2 levels in the local atmosphere. Simple models (closed/open system) do not account for the observed depth variations of carbon isotopic composition of the TDIC pool. This suggests that the TDIC reservoir of pore waters is evolving under conditions gradually changing from an open towards a closed system. In order to explain 13C and 14C content of dissolved carbonates in groundwater in the recharge area of the studied aquifer, additional sources of carbon in the system are considered, such as organic matter decomposition accompanied by reduction of dissolved nitrates and sulfates. The piston-flow l4C ages of groundwater in the confined part of the studied system were calculated using 2 approaches: 1) the correction model proposed by Fontes and Garnier (1979) was used to calculate groundwater ages, utilizing the chemical and carbon isotopic data available for the sampled wells; and 2) inverse geochemical modeling was performed for selected pairs of wells using NETHPATH code. The calculated 14C ages of groundwater range from approximately 0.6 to 37.5 ka BP. Although both methods appeared to be in a broad agreement, NETHPATH calculations revealed that isotopic exchange processes between TDIC pool and solid carbonates present in relatively small amounts in the aquifer matrix play an important role in controlling the 13C and 14C signatures of the dissolved carbonate species in groundwater and should be taken into account when 14C ages are calculated.
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Yao, Yuan, Yongsong Huang, Jiaju Zhao, Li Wang, Youhua Ran, Weiguo Liu i Hai Cheng. "Permafrost thaw induced abrupt changes in hydrology and carbon cycling in Lake Wudalianchi, northeastern China". Geology 49, nr 9 (3.06.2021): 1117–21. http://dx.doi.org/10.1130/g48891.1.
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Abstract Lakes in the permafrost zone have been proposed to serve as key outlets for methane and carbon dioxide emissions. However, there has been no geological record of the hydrological and biogeochemical responses of lakes throughout the thawing of surrounding permafrost. We use multiple biomarker and isotopic proxies to reconstruct hydrological and biogeo-chemical changes in Lake Wudalianchi in northeastern China during regional thawing of the permafrost. We show permafrost thawing, as indicated by lignin degradation, initiated rapid lake water freshening as a result of the opening of groundwater conduits, and negative organic δ13C excursion due to increased inorganic and organic carbon fluxes. These hydro-logical changes were followed, with an ∼5–7 yr delay, by abrupt and persistent increases in microbial lake methanotrophy and methanogenesis, indicating enhanced anaerobic organic decomposition and methane emissions from lakes as permafrost thaws. Our data provide a detailed assessment of the processes involved during permafrost thaw, and highlight the importance of lakes in ventilating greenhouse gases to the atmosphere.
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Mobbs, Shelly, George Shaw, Simon Norris, Laura Marang, Trevor Sumerling, Achim Albrecht, Shulan Xu i in. "Intercomparison of Models of 14C in the Biosphere for Solid Radioactive Waste Disposal". Radiocarbon 55, nr 2 (2013): 814–25. http://dx.doi.org/10.1017/s0033822200057970.
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Radiocarbon is present in solid radioactive wastes arising from the nuclear power industry, in reactor operating wastes, and in graphite and activated metals that will arise from reactor decommissioning. Its half-life of 5730 yr, among other factors, means that 14C may be released to the biosphere from radioactive waste repositories. These releases may occur as 14C-bearing gases, especially methane, or as aqueous species, and enter the biosphere from below via natural processes or via groundwater pumped from wells. Assessment of radiation doses to humans due to such releases must take account of the major role of carbon in biological processes, requiring specific 14C assessment models to be developed. Therefore, an intercomparison of 5 14C assessment models was organized by the international collaborative forum, BIOPROTA. The intercomparison identified significantly different results for the activity concentrations in the soil, atmosphere, and plant compartments, based upon the different modeling approaches. The major source of uncertainty was related to the identification of conditions under which mixing occurs and isotopic equilibrium is established. Furthermore, while the assumed release area plays a role in determining the calculated atmospheric 14C concentrations, the openness of the plant canopy and the wind profile in and above the canopy are the key drivers. The intercomparison has aided understanding of the processes involved and helped to identify areas where further research is required to address some of the uncertainties.