Journal articles on the topic 'TOC variability'
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1
Al-Salihi, Ali M., and Zehraa M. Hassan. "Temporal and Spatial Variability and Trend Investigation of Total Ozone Column over Iraq Employing Remote Sensing Data: 1979-2012." International Letters of Chemistry, Physics and Astronomy 53 (July 2015): 1–18. http://dx.doi.org/10.18052/www.scipress.com/ilcpa.53.1.
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The objective of this paper is to analyze the temporal and spatial variability of the total ozone column (TOC) distributions and trends over Iraq, during the last 30 years (1979–2012) using remote sensing-derived TOC data. Due to shortage of ground-based TOC measurements. TOC data derived from the Total Ozone Mapping Spectrometer (TOMS) for the period 1979–2004 and Ozone Monitoring Instrument (OMI) for the period 2005–2012 with spatial resolution (1o×1o) were used in present study. The spatial, long-term, monthly variations of TOC over Iraq were analysed. For the spatial variability, the latitudinal variability has a large range between (45 to 55) DU in winter and spring whereas during summer and autumn months ranged between (6 to 10) DU. Also represents an annual cycle with maximum in March and minimum in October. In contrast, the longitudinal variability is not significant. The long-term variability represented a notable decline for the period 1979–2012. The ozone negative trend was observed significantly during 1979–2004, for all months with trend ranged between (− 0.3 to 2) DU/year whereas the ozone positive trend was appear clearly during 2005–2007, for all months (0.1 to 2.3) DU/year ,except February and September which presented negative trends. The results can provide comprehensive descriptions of the TOC variations in Iraq and benefit climate change research in this region.
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Al-Salihi, Ali M., and Zehraa M. Hassan. "Temporal and Spatial Variability and Trend Investigation of Total Ozone Column over Iraq Employing Remote Sensing Data: 1979-2012." International Letters of Chemistry, Physics and Astronomy 53 (July 1, 2015): 1–18. http://dx.doi.org/10.56431/p-d2kryx.
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The objective of this paper is to analyze the temporal and spatial variability of the total ozone column (TOC) distributions and trends over Iraq, during the last 30 years (1979–2012) using remote sensing-derived TOC data. Due to shortage of ground-based TOC measurements. TOC data derived from the Total Ozone Mapping Spectrometer (TOMS) for the period 1979–2004 and Ozone Monitoring Instrument (OMI) for the period 2005–2012 with spatial resolution (1o×1o) were used in present study. The spatial, long-term, monthly variations of TOC over Iraq were analysed. For the spatial variability, the latitudinal variability has a large range between (45 to 55) DU in winter and spring whereas during summer and autumn months ranged between (6 to 10) DU. Also represents an annual cycle with maximum in March and minimum in October. In contrast, the longitudinal variability is not significant. The long-term variability represented a notable decline for the period 1979–2012. The ozone negative trend was observed significantly during 1979–2004, for all months with trend ranged between (− 0.3 to 2) DU/year whereas the ozone positive trend was appear clearly during 2005–2007, for all months (0.1 to 2.3) DU/year ,except February and September which presented negative trends. The results can provide comprehensive descriptions of the TOC variations in Iraq and benefit climate change research in this region.
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Chapagain, Narayan P. "Investigating Temporal Variability of Total Ozone Column over Kathmandu Using Omi Satellite Observations." Journal of Institute of Science and Technology 21, no. 1 (November 24, 2016): 140–47. http://dx.doi.org/10.3126/jist.v21i1.16066.
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The objective of this work was to analyze the trend of temporal variability of the atmospheric Total ozone column (TOC) over Kathmandu, during the last 13 years of observations using remote sensing-derived data. For this study, long-term TOC data derived from the Ozone Monitoring Instrument (OMI) for the period of October 2004–April 2016 were used. The daily, monthly, seasonal, and annual variations of TOC were analyzed. During the whole study period, the highest value of TOC is found to be 344 DU in March and the lowest value of TOC is 219 DU in December. The average TOC calculated during the whole study period over Kathmandu is found to be 268 DU. The trend of TOC shows a distinct seasonal pattern, with maximum in summer and minimum in winter season, specifically high value in April or May and lower value in December and January. The long-term variability also represents a notable increase in TOC for the period from 2004 to 2015 illustrating the significant recovery atmospheric ozone over Kathmandu. The ozone recovery during the recent years may be due to the reduction of the ozone depletory agents.Journal of Institute of Science and TechnologyVolume 21, Issue 1, August 2016, Page: 140-147
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Grabs, T., K. Bishop, H. Laudon, S. W. Lyon, and J. Seibert. "Riparian zone hydrology and soil water total organic carbon (TOC): implications for spatial variability and upscaling of lateral riparian TOC exports." Biogeosciences 9, no. 10 (October 10, 2012): 3901–16. http://dx.doi.org/10.5194/bg-9-3901-2012.
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Abstract. Groundwater flowing from hillslopes through riparian (near-stream) soils often undergoes chemical transformations that can substantially influence stream water chemistry. We used landscape analysis to predict total organic carbon (TOC) concentration profiles and groundwater levels measured in the riparian zone (RZ) of a 67 km2 catchment in Sweden. TOC exported laterally from 13 riparian soil profiles was then estimated based on the riparian flow–concentration integration model (RIM). Much of the observed spatial variability of riparian TOC concentrations in this system could be predicted from groundwater levels and the topographic wetness index (TWI). Organic riparian peat soils in forested areas emerged as hotspots exporting large amounts of TOC. These TOC fluxes were subject to considerable temporal variations caused by a combination of variable flow conditions and changing soil water TOC concentrations. Mineral riparian gley soils, on the other hand, were related to rather small TOC export rates and were characterized by relatively time-invariant TOC concentration profiles. Organic and mineral soils in RZs constitute a heterogeneous landscape mosaic that potentially controls much of the spatial variability of stream water TOC. We developed an empirical regression model based on the TWI to move beyond the plot scale and to predict spatially variable riparian TOC concentration profiles for RZs underlain by glacial till.
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Shrestha, P. M., N. P. Chapagain, I. B. Karki, and K. N. Poudyal. "Study of Variability of Atmospheric Ozone over Jumla in Half Period of 24 Solar Cycle." Journal of Nepal Physical Society 7, no. 1 (May 7, 2021): 31–38. http://dx.doi.org/10.3126/jnphyssoc.v7i1.36972.
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This paper reports the variation of total ozone column (TOC) over Jumla (Lat.:-29.28° N, Long.:-82.16° E and Alt.:- 2300 m above sea level) from 2008 to 2014 derived from Total Ozone Mapping Spectrometer (TOMS) satellite observations. The monthly, seasonal, annual variations of TOC, solar insolation and clearness index have been analyzed. The result exemplifies that during the whole study period, the maximum value of monthly average TOC is 289.21 DU ± 10.75 DU in April, while the minimum value is 257.23 DU ± 11.25 DU in December. The results also show that TOC is highly seasonal dependent with larger TOC in spring 273.68 DU ± 14.92 DU and lower in the winter season (260.68 DU ± 15.25 DU). The average annual value of TOC exhibits slightly variable with a maximum in 2010 (277.52 DU ± 40.64 DU) and minimum in 2008 (267.19 DU ± 11.11 DU). The average values of solar insolation and clearness index for whole study the period are 5.10 86 kWh/m2/day ± 0.86 kWh/m2/day and 0.59 ± 0.12 respectively. The average value of TOC during the whole study period is 271.84 DU ± 14.19 DU, which indicates a good amount of stratospheric ozone content over Jumla.
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ORUE IRASUEGI, AITOR, AITOR LIZARRALDE AIASTUI, ALVARO GARCIA SANCHEZ, and UNAI APAOLAZA PEREZ DE EULATE. "THE IMPACT OF PROTECTIVE CAPACITY IN IMPLEMENTING DRUM-BUFFER-ROPE METHODOLOGY IN MAKE-TO-ORDER ENVIRONMENTS: AN ASSESSMENT BY SIMULATION." DYNA MANAGEMENT 10, no. 1 (October 17, 2022): [13P.]. http://dx.doi.org/10.6036/mn10619.
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This study uses simulation to analyse the impact of protective capacity in the implementation of the step 3 of the theory of constraints (TOC) methodology in make-to-order (MTO) environments. The results suggest that at different levels of variability, different levels of protective capacity are needed to keep a system stable and meet the bottleneck (BN) schedule. The higher the variability is, the higher the level of protection needed. The definition of the level of protective capacity required is a strategic decision for the organisation, as it must be emphasised that with high levels of variability in a system, the protective capacity must be very high, which contradicts the efficient use of resources. However, for managers to know and control how much protection is needed without needing additional capacity, it is advisable to monitor the use of protective capacity. This concept of protection monitoring and control is relatively new in the TOC–drum-buffer-rope (TOC-DBR) methodology, but it is applied in the demand-driven adaptive business model, and therefore, should be integrated into the TOC-DBR methodology.
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Grabs, T., K. H. Bishop, H. Laudon, S. W. Lyon, and J. Seibert. "Riparian zone processes and soil water total organic carbon (TOC): implications for spatial variability, upscaling and carbon exports." Biogeosciences Discussions 9, no. 3 (March 14, 2012): 3031–69. http://dx.doi.org/10.5194/bgd-9-3031-2012.
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Abstract. Groundwater flowing from hillslopes through riparian (near stream) soils often undergoes chemical transformations that can substantially influence stream water chemistry. We used landscape analysis to predict total organic carbon (TOC) concentrations profiles and groundwater levels measured in the riparian zone (RZ) of a 67 km2 catchment in Sweden. TOC exported from 13 riparian soil profiles was then estimated based on the riparian flow-concentration integration model (RIM). Much of the observed spatial variability of riparian TOC concentrations in this system could be predicted from groundwater levels and the topographic wetness index (TWI). Organic riparian peat soils in forested areas emerged as hotspots exporting large amounts of TOC. Exports were subject to considerable temporal variations caused by a combination of variable flow conditions and changing soil water TOC concentrations. From more mineral riparian gley soils, on the other hand, only small amounts with relatively time-invariant concentrations were exported. Organic and mineral soils in RZs constitute a heterogeneous landscape mosaic that controls much of the spatial variability of stream water TOC. We developed an empirical regression-model based on the TWI to move beyond the plot scale to predict spatially variable riparian TOC concentration profiles for RZs underlain by glacial till.
8
Vaz Peres, Lucas, Hassan Bencherif, Nkanyiso Mbatha, André Passaglia Schuch, Abdoulwahab Mohamed Toihir, Nelson Bègue, Thierry Portafaix, et al. "Measurements of the total ozone column using a Brewer spectrophotometer and TOMS and OMI satellite instruments over the Southern Space Observatory in Brazil." Annales Geophysicae 35, no. 1 (January 3, 2017): 25–37. http://dx.doi.org/10.5194/angeo-35-25-2017.
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Abstract. This paper presents 23 years (1992–2014) of quasi-continuous measurements of the total ozone column (TOC) over the Southern Space Observatory (SSO) in São Martinho da Serra, Brazil (29.26° S, 53.48° and 488 m altitude). The TOC was measured by a Brewer spectrometer, and the results are also compared to daily and monthly observations from the TOMS (Total Ozone Mapping Spectrometer) and OMI (Ozone Monitoring Instrument) satellite instruments. Analyses of the main interannual modes of variability computed using the wavelet transform method were performed. A favorable agreement between the Brewer spectrophotometer and satellite datasets was found. The seasonal TOC variation is dominated by an annual cycle, with a minimum of approximately 260 DU in April and a maximum of approximately 295 DU in September. The wavelet analysis applied in the SSO TOC anomaly time series revealed that the Quasi-Biennial Oscillation (QBO) modulation was the main mode of interannual variability. The comparison between the SSO TOC anomaly time series with the QBO index revealed that the two are in opposite phases.
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Atar, Elizabeth, Christian März, Andrew C. Aplin, Olaf Dellwig, Liam G. Herringshaw, Violaine Lamoureux-Var, Melanie J. Leng, Bernhard Schnetger, and Thomas Wagner. "Dynamic climate-driven controls on the deposition of the Kimmeridge Clay Formation in the Cleveland Basin, Yorkshire, UK." Climate of the Past 15, no. 4 (August 13, 2019): 1581–601. http://dx.doi.org/10.5194/cp-15-1581-2019.
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Abstract. The Kimmeridge Clay Formation (KCF) is a laterally extensive, total-organic-carbon-rich succession deposited throughout northwest Europe during the Kimmeridgian–Tithonian (Late Jurassic). It has recently been postulated that an expanded Hadley cell, with an intensified but alternating hydrological cycle, heavily influenced sedimentation and total organic carbon (TOC) enrichment by promoting primary productivity and organic matter burial in the UK sectors of the Boreal Seaway. Consistent with such climate boundary conditions, petrographic observations, total organic carbon and carbonate contents, and major and trace element data presented here indicate that the KCF of the Cleveland Basin was deposited in the Laurasian Seaway under the influence of these conditions. Depositional conditions alternated between three states that produced a distinct cyclicity in the lithological and geochemical records: lower-variability mudstone intervals (LVMIs) which comprise clay-rich mudstone and higher-variability mudstone intervals (HVMIs) which comprise TOC-rich sedimentation and carbonate-rich sedimentation. The lower-variability mudstone intervals dominate the studied interval but are punctuated by three ∼ 2–4 m thick intervals of alternating TOC-rich and carbonate-rich sedimentation (HVMIs). During the lower-variability mudstone intervals, conditions were quiescent with oxic to suboxic bottom water conditions. During the higher-variability mudstone intervals, highly dynamic conditions resulted in repeated switching of the redox system in a way similar to the modern deep basins of the Baltic Sea. During carbonate-rich sedimentation, oxic conditions prevailed, most likely due to elevated depositional energies at the seafloor by current–wave action. During TOC-rich sedimentation, intermittent anoxic–euxinic conditions led to an enrichment of redox-sensitive and sulfide-forming trace metals at the seafloor and a preservation of organic matter, and an active Mn–Fe particulate shuttle delivered redox-sensitive and sulfide-forming trace metals to the seafloor. In addition, based on TOC–S–Fe relationships, organic matter sulfurization appears to have increased organic material preservation in about half of the analysed samples throughout the core, while the remaining samples were either dominated by excess Fe input into the system or experienced pyrite oxidation and sulfur loss during oxygenation events. New Hg∕TOC data do not provide evidence of increased volcanism during this time, consistent with previous work. Set in the context of recent climate modelling, our study provides a comprehensive example of the dynamic climate-driven depositional and redox conditions that can control TOC and metal accumulations in a shallow epicontinental sea, and it is therefore key to understanding the formation of similar deposits throughout Earth's history.
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Ayassou, Koffi, Andrea Pazmiño, Kokou Sabi, Ariane Bazureau, and Sophie Godin-Beekmann. "Evolution of Ozone above Togo during the 1979–2020 Period." Atmosphere 13, no. 12 (December 8, 2022): 2066. http://dx.doi.org/10.3390/atmos13122066.
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The objective of this paper is to estimate the trend of the Total Ozone Column (TOC) over Togo. A Multi-Sensor Reanalysis-2 (MSR-2) of the TOC over the entire territory of Togo was used. A Multiple Linear Regression (MLR) method has been applied to retrieve the interannual contributions of different forcings and the long-term variability. It was found that the Annual Oscillation (AnO), the Quasi Biennial Oscillation at 30 mb (QBO30), the Solar Flux (SF), and the El Niño–Southern Oscillation (ENSO) has a statistically significant influence on the interannual variability of the TOC. The strongest contribution (22 ± 1.4 DU) is allocated to the AnO while the weakest (<1 DU) is attributed to the Semi-Annual Oscillations (SAnO). Before the peak year of the Equivalent Effective Stratospheric Chlorine (EESC) in the tropics in 1997, the trend is negative (−0.3% ± 0.9% per decade) and is not statistically significant. After the peak year, a statistically significant positive trend is observed. The trend of the TOC is 0.6% ± 0.2% per decade. The monthly TOC trend over Togo is positive and statistically significant during the rainy season (particularly during the monsoon period) except in April, unlike during the harmattan period (DJF), where the trend is not significant.
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Yu, Z. T., X. J. Wang, E. L. Zhang, C. Y. Zhao, and X. Q. Liu. "Spatial distribution and sources of organic carbon in the surface sediment of Bosten Lake, China." Biogeosciences 12, no. 22 (November 19, 2015): 6605–15. http://dx.doi.org/10.5194/bg-12-6605-2015.
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Abstract. Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg), and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ 13Corg value (−26.77 to −23.98 ‰). Using a three-end-member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.
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Yu, Z. T., X. J. Wang, E. L. Zhang, C. Y. Zhao, and H. Y. Lan. "Spatial distribution and sources of organic carbon in the surface sediment of the Bosten Lake, China." Biogeosciences Discussions 12, no. 16 (August 25, 2015): 13793–817. http://dx.doi.org/10.5194/bgd-12-13793-2015.
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Abstract. Lake sediment is an important carbon reservoir. However, little is known on the dynamics and sources of sediment organic carbon in the Bosten Lake. We collected 13 surface (0–2 cm) sediment samples in the Bosten Lake and analyzed total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition in TOC (δ13Corg) and grain size. We found a large spatial variability in TOC content (1.8–4.4 %) and δ13Corg value (−26.77 to −23.98 ‰). Using a three end member mixing model with measured TOC : TN ratio and δ13Corg, we estimated that 54–90 % of TOC was from autochthonous sources. Higher TOC content (> 3.7 %) was found in the east and central-north sections and near the mouth of the Kaidu River, which was attributable to allochthonous, autochthonous plus allochthonous, and autochthonous sources, respectively. The lowest TOC content was found in the mid-west section, which might be a result of high kinetic energy levels. Our study indicated that the spatial distribution of sediment TOC in the Bosten Lake was influenced by multiple and complex processes.
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Agosta, Eduardo Andrés, and Pablo Osvaldo Canziani. "Austral Spring Stratospheric and Tropospheric Circulation Interannual Variability." Journal of Climate 24, no. 11 (June 1, 2011): 2629–47. http://dx.doi.org/10.1175/2010jcli3418.1.
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Abstract The relationship between the October (spring) total ozone column (TOC) midlatitude zonal asymmetry over the Southern Hemisphere (SH) and the stratospheric quasi-stationary wave 1 (QSW1) interannual phase variability is analyzed. Once contributions to the TOC from known global predictors, estimated with a multiregression model, are removed, the residual TOC interannual variability is observed to be dynamically coupled to the stratospheric QSW1 phase behavior. The stratospheric QSW1 interannual phase variability, when classified according to specifically designed indices, yields different circulation patterns in the troposphere and stratosphere. High (upper quartile) index values correspond to a westward rotation of the midlatitude ozone trough and the stratospheric QSW1 phase, while low (lower quartile) index values represent their eastward-rotated state. These values can be associated with statistically different tropospheric circulation patterns: a predominantly single poleward tropospheric jet structure for high index values and a predominantly double-jet structure for low index values. For the latter, there is a higher daily probability of double-jet occurrence in the troposphere and a stronger stratospheric jet. These jet structures and their daily behavior are supported by significant synoptic-scale activity anomalies over SH mid- to high latitudes as well as changes in tropospheric quasi-stationary waves 1–3. The wave activity flux (W flux) diagnosis shows the contribution of active quasi-stationary waves in the observed tropospheric anomalies associated with high and low index values. With low index values, the quasi-stationary waves lead to a self-sustaining state of the stratospheric–tropospheric coupled system. With high index values, the overall mid- to high latitude circulation is associated with wave energy propagation from the tropical central Pacific into higher latitudes. Thus, during the austral spring, there are interactions between the troposphere and stratosphere, leading to the locally well-defined upward and downward propagation of wave anomalies, that is, significant upper troposphere (UT)–lower stratosphere (LS) interactions can occur within a spring month itself.
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Cabezas, A., M. Angulo-Martínez, M. Gonzalez-Sanchís, J. J. Jimenez, and F. A. Comín. "Spatial variability in floodplain sedimentation: the use of generalized linear mixed-effects models." Hydrology and Earth System Sciences Discussions 7, no. 1 (February 26, 2010): 1589–619. http://dx.doi.org/10.5194/hessd-7-1589-2010.
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Abstract. Sediment, Total Organic Carbon (TOC) and total nitrogen (TN) accumulation during one overbank flood (1.15 y) were examined at one reach of the Middle Ebro River (NE Spain) for elucidating spatial patterns. To achieve this goal, four areas with different geomorphological features and located within the study reach were examined by using artificial grass mats. Within each area, 1 m2 study plots consisting on three pseudo-replicates were placed in a semi-regular grid oriented perpendicular to the main channel. TOC, TN and Particle-Size composition of deposited sediments were examined and accumulation rates estimated. Generalized linear mixed-effects models were used to analyze sedimentation patterns in order to handle clustered sampling units, specific-site effects and spatial self-correlation between observations. Our results confirm the importance of channel-floodplain morphology and site micro-topography in explaining sediment, TOC and TN deposition patterns, although the importance of another factors as vegetation morphology should be included in further studies to explain small scale variability. Generalized linear mixed-effect models provide a good framework to deal with the high spatial heterogeneity of this phenomenon at different spatial scales, and should be further investigated in order to explore its validity when examining the importance of factors such as flood magnitude or suspended sediment solid concentration.
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Cabezas, A., M. Angulo-Martínez, M. Gonzalez-Sanchís, J. J. Jimenez, and F. A. Comín. "Spatial variability in floodplain sedimentation: the use of generalized linear mixed-effects models." Hydrology and Earth System Sciences 14, no. 8 (August 25, 2010): 1655–68. http://dx.doi.org/10.5194/hess-14-1655-2010.
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Abstract. Sediment, Total Organic Carbon (TOC) and total nitrogen (TN) accumulation during one overbank flood (1.15 y return interval) were examined at one reach of the Middle Ebro River (NE Spain) for elucidating spatial patterns. To achieve this goal, four areas with different geomorphological features and located within the study reach were examined by using artificial grass mats. Within each area, 1 m2 study plots consisting of three pseudo-replicates were placed in a semi-regular grid oriented perpendicular to the main channel. TOC, TN and Particle-Size composition of deposited sediments were examined and accumulation rates estimated. Generalized linear mixed-effects models were used to analyze sedimentation patterns in order to handle clustered sampling units, specific-site effects and spatial self-correlation between observations. Our results confirm the importance of channel-floodplain morphology and site micro-topography in explaining sediment, TOC and TN deposition patterns, although the importance of other factors as vegetation pattern should be included in further studies to explain small-scale variability. Generalized linear mixed-effect models provide a good framework to deal with the high spatial heterogeneity of this phenomenon at different spatial scales, and should be further investigated in order to explore its validity when examining the importance of factors such as flood magnitude or suspended sediment concentration.
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Yang, Mingxi, and Zoë L. Fleming. "Estimation of atmospheric total organic carbon (TOC) – paving the path towards carbon budget closure." Atmospheric Chemistry and Physics 19, no. 1 (January 14, 2019): 459–71. http://dx.doi.org/10.5194/acp-19-459-2019.
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Abstract. The atmosphere contains a rich variety of reactive organic compounds, including gaseous volatile organic carbon (VOCs), carbonaceous aerosols, and other organic compounds at varying volatility. Here we present a novel and simple approach to measure atmospheric non-methane total organic carbon (TOC) based on catalytic oxidation of organics in bulk air to carbon dioxide. This method shows little sensitivity towards humidity and near 100 % oxidation efficiencies for all VOCs tested. We estimate a best-case hourly precision of 8 ppb C during times of low ambient variability in carbon dioxide, methane, and carbon monoxide (CO). As proof of concept of this approach, we show measurements of TOC+CO during August–September 2016 from a coastal city in the southwest United Kingdom. TOC+CO was substantially elevated during the day on weekdays (occasionally over 2 ppm C) as a result of local anthropogenic activity. On weekends and holidays, with a mean (standard error) of 102 (8) ppb C, TOC+CO was lower and showed much less diurnal variability. TOC+CO was significantly lower when winds were coming off the Atlantic Ocean than when winds were coming off land if we exclude the weekday daytime. By subtracting the estimated CO from TOC+CO, we constrain the mean (uncertainty) TOC in Atlantic-dominated air masses to be around 23 (±≥8) ppb C during this period. A proton-transfer-reaction mass spectrometer (PTR-MS) was deployed at the same time, detecting a large range of organic compounds (oxygenated VOCs, biogenic VOCs, aromatics, dimethyl sulfide). The total speciated VOCs from the PTR-MS, denoted here as Sum(VOC), amounted to a mean (uncertainty) of 12 (±≤3) ppb C in marine air. Possible contributions from a number of known organic compounds present in marine air that were not detected by the PTR-MS are assessed within the context of the TOC budget. Finally, we note that the use of a short, heated sample tube can improve the transmission of organics to the analyzer, while operating our system alternately with and without a particle filter should enable a better separation of semi-volatile and particulate organics from the VOCs within the TOC budget. Future concurrent measurements of TOC, CO, and a more comprehensive range of speciated VOCs would enable a better characterization and understanding of the atmospheric organic carbon budget.
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Rella, S. F., and M. Uchida. "Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr." Biogeosciences 8, no. 12 (December 6, 2011): 3545–53. http://dx.doi.org/10.5194/bg-8-3545-2011.
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Abstract. Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), CaCO3, benthic foraminiferal δ18O and the coarse grain size fraction from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on oxygen stratigraphy, radiocarbon dating and lithological constraints suggests that the piston core records paleoenvironmental changes of the last 155 kyr. TOC shows orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC might correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 45 ka before present (BP) indicating a possible response to abrupt northern hemispheric temperature changes. Between 70 and 45 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC variability. CaCO3 content tends to anti-correlate with TOC on both orbital and millennial time scales, which we interpret in terms of enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.
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Sacramento, José A. A. S. do, Jorge A. G. Santos, Diego C. Loureiro, Oldair V. Costa, and Alide M. W. Cova. "Spatial variability and changes in carbon stocks of a Regosols (Psamments) cultivated with sisal." Revista Brasileira de Engenharia Agrícola e Ambiental 22, no. 11 (November 2018): 764–69. http://dx.doi.org/10.1590/1807-1929/agriambi.v22n11p764-769.
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ABSTRACT Information on spatial variability and soil carbon stocks after the conversion of Caatinga vegetation to different cropping systems is scarce. This study aimed to characterize the spatial variability and to evaluate the changes in carbon stocks and the emission of greenhouse gases after the conversion of Caatinga vegetation with different sisal cultivation systems. The study was carried out in three areas in the city of Valente, Bahia, two areas that had been cultivated for 20 years with sisal in either a traditional (TSC) or alternative (ASC) system, and the third area containing natural Caatinga vegetation. The cultivated soils were sampled at 40 soil sampling points with 15 × 10 m spacing at depths of 0-0.20 and 0.20-0.40 m. Total organic carbon (TOC) stocks had spatial dependence and the isoline maps allowed the variability in the studied depths to be analyzed. The conversion of Caatinga vegetation to sisal cultivation using traditional farming systems caused a 30% decrease in soil TOC stocks. Moreover, the alternative culture system caused an 11% increase in soil TOC stocks. The emission factor or carbon absorption due to changes in land use after 20 years was 0.66 t ha-1 yr-1 of carbon in the traditional farming system and -0.25 t ha-1 yr-1 of carbon in the alternative culture system.
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Gbolo, P., and P. Gerla. "Statistical analysis to characterize transport of nutrients in groundwater near an abandoned feedlot." Hydrology and Earth System Sciences 17, no. 12 (December 6, 2013): 4897–906. http://dx.doi.org/10.5194/hess-17-4897-2013.
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Abstract. Surface water from a lagoon and groundwater samples from 17 wells within and near an abandoned feedlot in northwestern Minnesota, USA, were analyzed for carbon, nutrients, and field parameters. The feedlot is surrounded by wetlands that act as receptors of nutrients from the feedlot. Q- and R-mode multivariate analyses performed on total carbon (TC), inorganic carbon (IC), total organic carbon (TOC), nitrite-nitrogen (NO2-N), nitrate-nitrogen (NO3-N), ammonium-nitrogen (NH4-N), soluble or dissolved reactive phosphorus (DRP), and total phosphorus (TP) indicated three groups of the chemical species, which reflected variability in groundwater chemistry. Factor analysis indicated approximately 82% of the variability in factor 1 was caused by TC, IC, TOC, and DRP, while in factor 2 approximately 79% of the variability was caused by NO2-N, NO3-N, and TP. In factor 3, only NH4-N contributed 31% of the variability. Groundwater isotope and spatial distribution analysis indicated reduced nitrate concentration from the source to the wetlands, with variation in NO2-N, NO3-N, and NH4-N concentrations attributed to the plant nutrient uptake, high rate of denitrification and/or the dissimilatory nitrate reduction to ammonium. This study indicated the value of multivariate analyses in characterizing variability in groundwater quality.
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Sharma, Choudhurimayum Pankaj, Suman Lata Rawat, Pradeep Srivastava, Narendra K. Meena, Rajesh Agnihotri, Anil Kumar, Poonam Chahal, SKS Gahlaud, and UK Shukla. "High-resolution climatic (monsoonal) variability reconstructed from a continuous ~2700-year sediment record from Northwest Himalaya (Ladakh)." Holocene 30, no. 3 (November 18, 2019): 441–57. http://dx.doi.org/10.1177/0959683619887426.
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A chronologically well-constrained sedimentary archive from Upshi (Ladakh) was studied using a multi-proxy approach namely palynology, environmental magnetism, total organic carbon (TOC), total nitrogen (TN), stable isotopes of carbon and nitrogen providing a continuous vegetation, and paleoenvironmental history spanning the last ~2700 years with a temporal resolution of ~43 years. Pollen assemblage shows non-arboreal pollen (NAP) and non-pollen palynomorph (NPP) were dominant around the Upshi from ~2646 to 2431 cal. yr BP, indicating warmer conditions. Arboreal pollen (AP) and NAP gradually increased from 2431 to 1860 cal. yr BP in the study area, under warm and wet conditions, corresponding to the Roman Warm Period (RWP). This phase also witnessed enhanced sediment δ15N and χlf values. From ~1860 to ~1154 cal. yr BP increased Chenopodiaceae/Amaranthaceae and substantial spread of NPP suggest decreased temperature and prevalence of cold-dry climate. This period also records declining trends of χlf, δ15N, δ13Corg, TOC, and TN contents. From ~1154 to 293 cal. yr BP, the vegetation type reversed to mixed conifer and broad-leaved forest with significant increase in herbaceous taxa, rising δ15N, δ13Corg, TOC, and TN suggesting warm and wet conditions in the study area. This period broadly corresponds to the ‘Medieval Warm Period’ (MWP). Among all the proxies employed, depth profiles of TOC and TN (wt%) appear to respond best against external climate forcing showing remarkable correlation(s) with residual Δ14C in atmosphere, indicating dominance of intrinsic solar variability on regional climate/environment. The reconstructed recorded is well connected with established historical events and cultural activities of the Eurasian region.
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Zbinden, R. M., J. P. Cammas, V. Thouret, P. Nedelec, F. Karcher, and P. Simon. "Mid-latitude Tropospheric Ozone Columns from the MOZAIC program: climatology and interannual variability." Atmospheric Chemistry and Physics Discussions 5, no. 4 (July 29, 2005): 5489–540. http://dx.doi.org/10.5194/acpd-5-5489-2005.
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Abstract. Several thousands ozone vertical profiles collected in the course of the MOZAIC program (Measurements of Ozone, Water Vapour, Carbon Monoxide and Nitrogen Oxides by In-Service Airbus Aircraft) from August 1994 to February 2002 are investigated to bring out climatological and interannual variability aspects. The study is centred on the most frequently visited MOZAIC airports, i.e. Frankfurt (Germany), Paris (France), New York (USA) and the cluster of Tokyo, Nagoya and Osaka (Japan). The analysis focuses on the vertical integration of ozone from the ground to the dynamical tropopause and the vertical integration of stratospheric-origin ozone throughout the troposphere. The characteristics of the MOZAIC profiles, frequency of flights, accuracy, precision, and depth of the troposphere observed, are presented. The climatological analysis shows that the Tropospheric Ozone Column (TOC) seasonal cycle ranges from a minimum wintertime at all four stations to a spring-summer maximum in Frankfurt, Paris, and New York. Over Japan, the maximum occurs in spring because of the earlier springtime sun. The invasion of monsoon air masses in the boundary layer and in the mid-troposphere then steeply diminishes the summertime value. Boundary layer contributions to the TOC are 10% higher in New York compare to Frankfurt and Paris during spring and summer, and are 10% higher in Japan compare to New York, Frankfurt and Paris during autumn and early spring. Local and remote anthropogenic emissions as well as biomass burning over upstream regions of Asia may be responsible of larger low- and mid-tropospheric contributions to the tropospheric ozone column over Japan throughout the year except during the summer-monsoon season. A simple Lagrangian analysis has shown that a minimum range of 10% of the TOC is of stratospheric-origin throughout the year. The investigation on the short-term trends of the TOC over the period 1995–2001 shows a linear increase of 0.7%/year in Frankfurt, 0.8%/year in Japan, 0.9%/year in Paris, and 1.1%/year in New York. Essential ingredients to these positive short-term trends are the continuous increase of wintertime tropospheric ozone columns from 1996 to 1999 and the positive contributions of the mid-troposphere whatever the season.
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Zbinden, R. M., J. P. Cammas, V. Thouret, P. Nédélec, F. Karcher, and P. Simon. "Mid-latitude tropospheric ozone columns from the MOZAIC program: climatology and interannual variability." Atmospheric Chemistry and Physics 6, no. 4 (March 31, 2006): 1053–73. http://dx.doi.org/10.5194/acp-6-1053-2006.
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Abstract. Several thousands of ozone vertical profiles collected in the course of the MOZAIC programme (Measurements of Ozone, Water Vapour, Carbon Monoxide and Nitrogen Oxides by In-Service Airbus Aircraft) from August 1994 to February 2002 are investigated to bring out climatological and interannual variability aspects. The study is centred on the most frequently visited MOZAIC airports, i.e. Frankfurt (Germany), Paris (France), New York (USA) and the cluster of Tokyo, Nagoya and Osaka (Japan). The analysis focuses on the vertical integration of ozone from the ground to the dynamical tropopause and the vertical integration of stratospheric-origin ozone throughout the troposphere. The characteristics of the MOZAIC profiles: frequency of flights, accuracy, precision, and depth of the troposphere observed, are presented. The climatological analysis shows that the Tropospheric Ozone Column (TOC) seasonal cycle ranges from a wintertime minimum at all four stations to a spring-summer maximum in Frankfurt, Paris, and New York. Over Japan, the maximum occurs in spring presumably because of the earlier springtime sun. The incursion of monsoon air masses into the boundary layer and into the mid troposphere then steeply diminishes the summertime value. Boundary layer contributions to the TOC are 10% higher in New York than in Frankfurt and Paris during spring and summer, and are 10% higher in Japan than in New York, Frankfurt and Paris during autumn and early spring. Local and remote anthropogenic emissions, and biomass burning over upstream regions of Asia may be responsible for the larger low- and mid-tropospheric contributions to the tropospheric ozone column over Japan throughout the year except during the summer-monsoon season. A simple Lagrangian analysis has shown that a minimum of 10% of the TOC is of stratospheric-origin throughout the year. Investigation of the short-term trends of the TOC over the period 1995–2001 shows a linear increase 0.7%/year in Frankfurt, 0.8%/year in Japan, 1.1%/year in New York and 1.6%/year in Paris for the reduced 1995–1999 period. Dominant ingredients of these positive short-term trends are the continuous increase of wintertime tropospheric ozone columns from 1996 to 1999 and the positive contributions of the mid troposphere whatever the season.
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Rella, S. F., and M. Uchida. "Sedimentary organic matter variations in the Chukchi Borderland over the last 155 kyr." Biogeosciences Discussions 8, no. 2 (March 4, 2011): 2259–80. http://dx.doi.org/10.5194/bgd-8-2259-2011.
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Abstract. Knowledge on past variability of sedimentary organic carbon in the Arctic Ocean is important to assess natural carbon cycling and transport processes related to global climate changes. However, the late Pleistocene oceanographic history of the Arctic is still poorly understood. In the present study we show sedimentary records of total organic carbon (TOC), C/N and CaCO3 from a piston core recovered from the northern Northwind Ridge in the far western Arctic Ocean, a region potentially sensitively responding to past variability in surface current regimes and sedimentary processes such as coastal erosion. An age model based on correlation of our CaCO3 record with the benthic δ18O stack, supplemented by lithological constraints, suggests that the piston core records paleoenvironmental changes of the last 155 kyr. According to this age model, TOC and C/N show orbital-scale increases and decreases that can be respectively correlated to the waxing and waning of large ice sheets dominating the Eurasian Arctic, suggesting advection of fine suspended matter derived from glacial erosion to the Northwind Ridge by eastward flowing intermediate water and/or surface water and sea ice during cold episodes of the last two glacial-interglacial cycles. At millennial scales, increases in TOC and C/N appear to correlate to a suite of Dansgaard-Oeschger Stadials between 120 and 40 ka before present (BP) and thus seem to respond to abrupt northern hemispheric temperature changes. Between 65 and 40 ka BP, closures and openings of the Bering Strait could have additionally influenced TOC and C/N variability. CaCO3 content tends to anti-correlate with TOC and C/N on both orbital and millennial time scales, which we interpret as enhanced sediment advection from the carbonate-rich Canadian Arctic via an extended Beaufort Gyre during warm periods of the last two glacial-interglacial cycles and increased terrestrial organic carbon advection from the Siberian Arctic during cold periods when the Beaufort Gyre contracted. We propose that this pattern may be related to orbital- and millennial-scale variations of dominant atmospheric surface pressure systems expressed in mode shifts of the Arctic Oscillation.
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Chen, Mei, Klas Ohman, Jason Sinclair, Darcy Petkau, Raymond Yau, Jian Fu Deng, Thien Tran, Chris Huston, and Tom Elford. "Disinfection by-products in drinking water – a case study on Calgary, Alberta, Canada." Water Quality Research Journal 46, no. 3 (August 1, 2011): 200–210. http://dx.doi.org/10.2166/wqrjc.2011.021.
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Disinfection by-products (DBPs) have been monitored in Calgary's drinking water for approximately 15 years. The variability of the DBPs has typically exhibited similar patterns over the period of monitoring. Due to the nature of the surface waters supplying the water treatment plants, the level of DBPs was largely influenced by surface runoff events where the level of natural organic matter (NOM) increased, which was characterized by a relatively high total organic carbon (TOC) content. Principal component analysis (PCA) was utilized for this study to quickly identify the key underlying correlations present within the very large, complex multivariate data matrix. Apart from TOC, chlorine demand, chlorine residual and temperature were observed to correlate with the formation of DBPs in the finished drinking water. In addition to TOC, PCA also indicates that pH and temperature in the distribution system could have an influence on the variability of DBPs in Calgary's drinking water. It was apparent that upgrades to the water treatment systems in Calgary have resulted in an improved removal of DBP precursors such as NOM prior to chlorination, which is a key factor in reducing the DBP levels in the drinking water, thereby providing an enhanced level of public health protection.
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Vyšná, V., F. Dyer, W. Maher, and R. Norris. "Organic carbon reservoirs in five small rivers across a land-use gradient." Marine and Freshwater Research 66, no. 3 (2015): 233. http://dx.doi.org/10.1071/mf13142.
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Organic carbon (OC) inputs, stores and processing underpin river functioning. We examined patterns in OC reservoirs (total organic carbon, TOC), suspended OC, drifting coarse particulate OC (drift OC), organic debris and the biomass of in-stream primary producers in five geographically proximate small rivers in south-eastern Australia during base-flow conditions. Despite differences in the extent of land-use conversion (native forest-to-pasture) and geomorphology among all sites, we found greater within-river than ‘within-land-use’ similarities in OC reservoirs. Our predictions regarding the relationships between distant v. proximate land-use and the OC reservoirs were mostly not confirmed. Riparian canopy cover was correlated with the mass of organic debris but not with other OC reservoirs. Our predictions regarding longitudinal patterns in rivers were also not confirmed. Rivers draining catchments with conservation land-use only did not show consistent patterns that were different from rivers draining a combination of conservation and grazing land. Variability in the extent of land converted to other uses was not necessarily associated with greater longitudinal variability in OC reservoirs. Our results suggest: (1) strong within-catchment controls of TOC concentration that are maintained despite a certain level of catchment impairment and (2) between-river differences in TOC at a local scale as great as continental scale differences.
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Ghimire, Deepak, Bandhu Raj Baral, and Dinesh Panday. "Assessment of Spatial Variability of Soil Chemical Properties under Small-holder Farmers’ Field: a Case Study from Kavrepalanchowk District of Nepal." Current Agriculture Research Journal 6, no. 3 (December 25, 2018): 337–43. http://dx.doi.org/10.12944/carj.6.3.12.
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A proper understanding of variability of soil chemical properties over an area is important for identifying the soil nutrients related production constraints. The suggestions for remedial measures and execution of appropriate nutrient management strategies are also based on the good knowledge of variation in soil nutrients. A case study was undertaken with an objective of assessing spatial variability of selected soil chemical properties of agricultural land. Soil samples from the surface (0 to 15 cm) were collected from farmers’ field in the central part of Kavrepalanchowk district of Nepal in February 2018. Soil samples were analyzed for soil pH, total organic carbon (TOC), total nitrogen (N), phosphorous (P), and potassium (K). Descriptive statistics revealed that the soil in the study area was slightly acidic and contained the low status of TOC, P, and K, while the N content was medium. Coefficient of variation (CV) indicated that soil pH was the least variable (CV= 9.37% with values ranging from 5.3 to 7.7) among the investigated soil samples while N was the most variable (CV= 98.81% with content values ranging from 0.03% to 0.67%). Other selected properties (TOC, P, and K) were found to be highly variable (CV= 49.94%, 94.89%, and 57.53% respectively). These variations in soil chemical properties were mostly related to the different cropping systems and soil management practices, including nutrient management carried out in the study area. Owing to the higher variability of nutrients, the results suggested to take into account various soil and nutrient management practices for sustained soil fertility and enhanced productivity.
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Kumar, Kamlesh, Shailesh Agrawal, Anupam Sharma, and Shilpa Pandey. "Indian summer monsoon variability and vegetation changes in the core monsoon zone, India, during the Holocene: A multiproxy study." Holocene 29, no. 1 (October 12, 2018): 110–19. http://dx.doi.org/10.1177/0959683618804641.
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We present the results of sediment texture, δ13C values, TOC, TN, TOC/TN, and magnetic susceptibility (χlf) of a 1.54-m deep sediment trench recovered from the core monsoon zone (CMZ) of central India, to understand the paleovegetational history and Indian summer monsoon (ISM) variability during the Holocene. The lower δ13C values, TOC/TN ratio, and magnetic susceptibility (χlf) from ~11.4 to 9.5 ka BP suggest enhanced ISM intensity, which is well correlated with other available ISM records from both terrestrial as well as marine archives. A gradual stepwise expansion of C4 plants during ~8.1 and 6.3 ka BP, ~6.3 to 4.7 ka BP, and ~3.0 to 2.0 ka BP suggests a gradual weakening of ISM. The highest δ13C values (–18.7‰) recorded at ~2.0 ka BP indicate the dominance of C4 plants suggesting the weakest phase of ISM in the study area. The expansion of C3 plants from ~2.0 to 1.6 ka BP indicates a sudden increase in ISM intensity. Subsequently, three stages of enhanced ISM have been recorded between ~1.6 and 0.93 ka BP, ~0.76 and 0.42 ka BP, and ~0.28 ka BP to present.
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Wang, Xiyang, Liang Li, Zaijun Xin, Xiaohui Li, Shifu He, and Xiaoyan Sun. "Spatial Variations in Organic Carbon Pools and Their Responses to Different Annual Straw Return Rates in Surface Paddy Soils in South China." Sustainability 14, no. 24 (December 15, 2022): 16875. http://dx.doi.org/10.3390/su142416875.
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To identify the effects of straw return on different organic carbon pools in surface paddy soils (0–20 cm), a total of 33 soil samples under different annual straw return rates (SRr) was collected, and then the samples were analyzed based on a 100-day incubation. The data from acid hydrolysis-incubation experiments were fitted to a three-pool first-order kinetics model that divided soil organic carbon (SOC) into active (Ca), slow (Cs) and resistant (Cr) pools. The results showed that the mean pool sizes of Ca, Cs, and Cr were 0.27, 10.26, and 13.46 g·kg−1, representing a mean of 1.35%, 41.91%, and 56.74% of the total SOC (TOC), respectively. The SOC pools in the surface paddy soils in Dongxiang had a small Ca pool but had longer mean residence times of the Ca and Cs pools than those in other regions in China. The three carbon pools were less affected by the paddy soil type but showed obvious spatial variations. The SRr contributed a strong positive effect on the variability of Cs and Cr, especially on Cs variability, while it had very little effect on Ca variability. Soil available nitrogen dominated the variability in TOC and Cr compared to the other soil properties. Therefore, the Cs pool is more sensitive than the other carbon pools to long-term straw return.
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Sibir, E. E., and V. F. Radionov. "Total ozone variations at russian antarctic stations. Results of long-term observations." Arctic and Antarctic Research 64, no. 3 (September 30, 2018): 250–61. http://dx.doi.org/10.30758/0555-2648-2018-64-3-250-261.
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The results of observations of total ozone content (TOC) at the Russian Antarctic stations Mirny (66° 34′ N, 93° 01′ E), Novolazarevskaya (70° 46′ S, 11° 50′ E) and Vostok (78° 38′ S, 106° 52′ E) from 1975 to 2017 are presented. Measurements were carried out by filters ozonemeters M-83/M-124. Throughout this period, there have been steady decreases in TOC in spring time. Early 1990s, the average TOC in September and October at Mirny decreased by 70–75 % of its average values for 1975–1980. The effect of the ozone hole and its intensity depend on ozone-depleting substance (ODS) levels, the dynamical processes and variations of temperature in the stratosphere. Considering the slow rate of decrease ODSs concentration, changes in size and depth of ozone hole have been mainly controlled by variations in temperature and dynamical processes. The destruction of the stratospheric circumpolar vortex early spring of 1988 was the reason that the spring negative anomaly of the TOC was not formed at all. A sharp increase of temperature in the stratosphere in the spring of 2002 was accompanied by an increase in the TOC. It led to reduction in the size of the “ozone hole” and even its dividing into two parts at the end of September. Since the early 2000s, there has been a tendency to return the TOC to the values observed in 1970s and to increase its interannual variability in comparison to 1990s.
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Siddaway, J. M., S. V. Petelina, D. Karoly, A. R. Klekociuk, and R. J. Dargaville. "Future Antarctic ozone recovery rates in September–December predicted by CCMVal-2 model simulations." Atmospheric Chemistry and Physics Discussions 12, no. 8 (August 1, 2012): 18959–91. http://dx.doi.org/10.5194/acpd-12-18959-2012.
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Abstract. Chemistry-climate model validation phase 2 (CCMVal-2) model simulations are used to analyze Antarctic ozone recovery rates in 2000–2100 during local spring and early summer, both vertically integrated and at several pressure levels in the lower stratosphere. Multi-model median trends of monthly zonal mean total ozone column (TOC), ozone volume mixing ratio (VMR), wind speed and temperature poleward of 60° S are investigated. Median values are used to account for large variability in models, and the associated uncertainty is calculated using a bootstrapping technique. According to the selected ten CCMVal-2 models, Antarctic TOC will return to its pre-ozone hole level, taken as an average of 1970–1979 values, between 2065 and 2075 in September–November, and around 2050 in December. In 2000–2020, an increase in TOC is much smaller than in later years, and this is especially evident for December. Although the December TOC recovers to its pre-ozone hole levels earlier compared to all spring months (as the December ozone depletion was much lower), the rate of December TOC increase, is slower than that for all spring months. Projected trends in ozone VMR, temperature and winds at several pressure levels are analyzed in order to attribute the projected rate of December TOC recovery, as well as to investigate future changes in the Antarctic atmosphere in general, including some aspects of the polar vortex breakup.
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Timofeyev, Yury M., Sergei P. Smyshlyaev, Yana A. Virolainen, Alexander S. Garkusha, Alexander V. Polyakov, Maxim A. Motsakov, and Ole Kirner. "Case study of ozone anomalies over northern Russia in the 2015/2016 winter: measurements and numerical modelling." Annales Geophysicae 36, no. 6 (November 5, 2018): 1495–505. http://dx.doi.org/10.5194/angeo-36-1495-2018.
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Abstract. Episodes of extremely low ozone columns were observed over the territory of Russia in the Arctic winter of 2015/2016 and the beginning of spring 2016. We compare total ozone columns (TOCs) from different remote sensing techniques (satellite and ground-based observations) with results of numerical modelling over the territory of the Urals and Siberia for this period. We demonstrate that the provided monitoring systems (including the new Russian Infrared Fourier Spectrometer IKFS-2) and modern three-dimensional atmospheric models can capture the observed TOC anomalies. However, the results of observations and modelling show differences of up to 20 %–30 % in TOC measurements. Analysis of the role of chemical and dynamical processes demonstrates that the observed short-term TOC variability is not a result of local photochemical loss initiated by heterogeneous halogen activation on particles of polar stratospheric clouds that formed under low temperatures in the mid-winter.
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Del Moro, Yoryenys, Venkatesh Anantharamu, Lev Vernik, Alfonso Quaglia, and Eduardo Carrillo. "Seismic petrophysics workflow applied to Delaware Basin." Interpretation 8, no. 2 (May 1, 2020): T349—T363. http://dx.doi.org/10.1190/int-2019-0157.1.
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Petrophysical analysis of unconventional plays that are comprised of organic mudrock needs detailed data QC and preparation to optimize the results of quantitative interpretation. This includes accurate computation of mineral volumes, total organic carbon (TOC), porosity, and saturations. We used TOC estimation to aid the process of determining the best pay zones for development of such reservoirs. TOC was calculated as a weighted average of Passey’s (empirical) and the bulk density-based (theoretical) methods. In organic mudrock reservoirs, the computed TOC log was used as an input to compute porosity and calibrate rock-physics models (RPMs), which are needed for understanding the potential of source rocks or finding sweet spots and their contribution to the amplitude variation with offset (AVO) changes in the seismic data. Using calibrated RPM templates, we found that TOC is driving the elastic property variations in the Avalon Formation. We determined the layering and rock fabric anisotropy using empirical relationships or modeled in the rock property characterization process because reflectivity effects are often seen in the observed seismic used for well tie and wavelet estimation. A Class IV AVO response was seen at the top of the Avalon Formation, which is typical of an unconventional reservoir. We then performed solid organic matter (TOC) substitution to account for variability of elastic properties and their contrasts as expressed in seismic amplitudes. To complete the characterization of the intervals of interest, we used conventional seismic petrophysical methods in the workflow and found that the main driver modifying the elastic properties for the Avalon shales was TOC; this conclusion serves as a foundation in integrated seismic inversion that may target lithofacies, TOC, and geomechanical properties. Seismic reservoir characterization results are critical in constraining landing zones and trajectories of the horizontal wells. The final interpretation may be used to rank targets, optimize drilling campaigns, and ultimately improve production.
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Moran, Nicholas P., George G. Ganf, Todd A. Wallace, and Justin D. Brookes. "Flow variability and longitudinal characteristics of organic carbon in the Lachlan River, Australia." Marine and Freshwater Research 65, no. 1 (2014): 50. http://dx.doi.org/10.1071/mf12297.
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Heterotrophic organic-carbon cycling is a major source of energy to aquatic food webs, yet there are few studies into patterns of heterotrophic productivity in large lowland rivers. The Lachlan River experienced a period of extreme flow variability from September 2010 to February 2011; for example, daily discharge (ML day–1) at one site reached >22 times its 10-year average. Heterotrophic cycling of dissolved organic carbon (DOC) and particulate organic carbon (POC) were assessed over this period at six sites on the Lachlan River. Concentrations of total organic carbon (TOC) ranged from 7 to 30 mg L–1, of which the majority was in dissolved form. Concentration of DOC was positively correlated with daily discharge. Biochemical oxygen demand of TOC over 5 days (BOD5) showed significant variability, ranging from 0.6 to 6.6 mg O2 L–1. BOD5 did not appear related to discharge, but instead to a range of other factors, including regulation via weirs, lateral and longitudinal factors. Partitioning of DOC and POC showed that POC had an influence on BOD5 comparable to DOC. This is relevant to environmental-flow management in the Lachlan River, the Murray–Darling Basin and rivers generally, by showing that flow variability influences a fundamental ecosystem characteristic, namely organic carbon.
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Fountoulakis, Ilias, Alkiviadis F. Bais, Konstantinos Fragkos, Charickleia Meleti, Kleareti Tourpali, and Melina Maria Zempila. "Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds." Atmospheric Chemistry and Physics 16, no. 4 (March 1, 2016): 2493–505. http://dx.doi.org/10.5194/acp-16-2493-2016.
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Abstract. In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece, using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association with changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear-skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.
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Francke, A., B. Wagner, M. J. Leng, and J. Rethemeyer. "A Late Glacial to Holocene record of environmental change from Lake Dojran (Macedonia, Greece)." Climate of the Past 9, no. 1 (February 28, 2013): 481–98. http://dx.doi.org/10.5194/cp-9-481-2013.
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Abstract. A Late Glacial to Holocene sediment sequence (Co1260, 717 cm) from Lake Dojran, located at the boarder of the F.Y.R. of Macedonia and Greece, has been investigated to provide information on climate variability in the Balkan region. A robust age-model was established from 13 radiocarbon ages, and indicates that the base of the sequence was deposited at ca. 12 500 cal yr BP, when the lake-level was low. Variations in sedimentological (H2O, TOC, CaCO3, TS, TOC/TN, TOC/TS, grain-size, XRF, δ18Ocarb, δ13Ccarb, δ13Corg) data were linked to hydro-acoustic data and indicate that warmer and more humid climate conditions characterised the remaining period of the Younger Dryas until the beginning of the Holocene. The Holocene exhibits significant environmental variations, including the 8.2 and 4.2 ka cooling events, the Medieval Warm Period and the Little Ice Age. Human induced erosion processes in the catchment of Lake Dojran intensified after 2800 cal yr BP.
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Barret, B., E. Le Flochmoen, B. Sauvage, E. Pavelin, M. Matricardi, and J. P. Cammas. "The detection of post-monsoon tropospheric ozone variability over south Asia using IASI data." Atmospheric Chemistry and Physics 11, no. 18 (September 16, 2011): 9533–48. http://dx.doi.org/10.5194/acp-11-9533-2011.
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Abstract. The ozone (O3) variability over south Asia during the 2008 post-monsoon season has been assessed using measurements from the MetOP-A/IASI instrument and O3 profiles retrieved with the SOftware for a Fast Retrieval of IASI Data (SOFRID). The information content study and error analyses carried out in this paper show that IASI Level 1 data can be used to retrieve tropospheric O3 columns (TOC, surface-225 hPa) and UTLS columns (225–70 hPa) with errors smaller than 20%. Validation with global radiosonde O3 profiles obtained during a period of 6 months show the excellent agreement between IASI and radiosonde for the UTLS with correlation coefficient R > 0.91 and good agreement in the troposphere with correlation coefficient R > 0.74. For both the UTLS and the troposphere Relative Standard Deviations (RSD) are lower than 23%. Comparison with in-situ measurements from the MOZAIC program around Hyderabad demonstrates that IASI is able to capture the TOC inter and intra-seasonal variability in central India. Nevertheless, the agreement is mitigated by the fact that the smoothing of the true O3 profiles by the retrieval results in a reduction of the TOC variability detected by IASI relative to the variability observed by in situ instruments. The post-monsoon temporal variability of the vertical profile of O3 around Hyderabad has been investigated with MOZAIC observations. These observations from airborne instruments show that tropospheric O3 is steadily elevated during most of the studied period with the exception of two sharp drops following the crossing of tropical storms over India. Lagrangian simulations with the FLEXPART model indicate that elevated O3 concentrations in the middle troposphere near Hyderabad are associated with the transport of UTLS air-masses that have followed the Subtropical Westerly Jet (SWJ) and subsided over northern India together with boundary layer polluted air-masses transported from the Indo-gangetic plain by the north-easterly trades. Low O3 concentrations result from the uplift and westward transport of pristine air-masses from the marine boundary layer of the Bay of Bengal by tropical storms. In order to extend the analysis of tropospheric O3 variability to the whole of south Asia, we have used IASI-SOFRID O3 data. We show that IASI O3 data around Hyderabad were able to capture the fast variability revealed by MOZAIC. Furthermore, their spatio-temporal coverage demonstrates that the behaviour of tropospheric O3 observed near Hyderabad extended over most of central and south India and part of the Bay of Bengal. This result highlights the ability of the IASI sensor to capture fast changes in chemical composition related to dramatic tropical weather conditions.
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Wang, Aijun, and Jian Chen. "Variability of TOC and TN along the coastal salt marshes, Quanzhou Bay, China." Chinese Journal of Geochemistry 25, S1 (March 2006): 11. http://dx.doi.org/10.1007/bf02839752.
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Bragée, P., F. Mazier, A. B. Nielsen, P. Rosén, D. Fredh, A. Broström, W. Granéli, and D. Hammarlund. "Historical TOC concentration minima during peak sulfur deposition in two Swedish lakes." Biogeosciences 12, no. 2 (January 19, 2015): 307–22. http://dx.doi.org/10.5194/bg-12-307-2015.
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Abstract. Decadal-scale variations in total organic carbon (TOC) concentration in lake water since AD 1200 in two small lakes in southern Sweden were reconstructed based on visible–near-infrared spectroscopy (VNIRS) of their recent sediment successions. In order to assess the impacts of local land-use changes, regional variations in sulfur, and nitrogen deposition and climate variations on the inferred changes in TOC concentration, the same sediment records were subjected to multi-proxy palaeolimnological analyses. Changes in lake-water pH were inferred from diatom analysis, whereas pollen-based land-use reconstructions (Landscape Reconstruction Algorithm) together with geochemical records provided information on catchment-scale environmental changes, and comparisons were made with available records of climate and population density. Our long-term reconstructions reveal that inferred lake-water TOC concentrations were generally high prior to AD 1900, with additional variability coupled mainly to changes in forest cover and agricultural land-use intensity. The last century showed significant changes, and unusually low TOC concentrations were inferred at AD 1930–1990, followed by a recent increase, largely consistent with monitoring data. Variations in sulfur emissions, with an increase in the early 1900s to a peak around AD 1980 and a subsequent decrease, were identified as an important driver of these dynamics at both sites, while processes related to the introduction of modern forestry and recent increases in precipitation and temperature may have contributed, but the effects differed between the sites. The increase in lake-water TOC concentration from around AD 1980 may therefore reflect a recovery process. Given that the effects of sulfur deposition now subside and that the recovery of lake-water TOC concentrations has reached pre-industrial levels, other forcing mechanisms related to land management and climate change may become the main drivers of TOC concentration changes in boreal lake waters in the future.
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Zhang, Chenning, Asen Grytsai, Oleksandr Evtushevsky, Gennadi Milinevsky, Yulia Andrienko, Valery Shulga, Andrew Klekociuk, Yuriy Rapoport, and Wei Han. "Rossby Waves in Total Ozone over the Arctic in 2000–2021." Remote Sensing 14, no. 9 (May 4, 2022): 2192. http://dx.doi.org/10.3390/rs14092192.
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The purpose of this work is to study Rossby wave parameters in total ozone over the Arctic in 2000–2021. We consider the averages in the January–March period, when stratospheric trace gases (including ozone) in sudden stratospheric warming events are strongly disturbed by planetary waves. To characterize the wave parameters, we analyzed ozone data at the latitudes of 50°N (the sub-vortex area), 60°N (the polar vortex edge) and 70°N (inner region of the polar vortex). Total ozone column (TOC) measurements over a 22-year time interval were used from the Total Ozone Mapping Spectrometer/Earth Probe and Ozone Mapping Instrument/Aura satellite observations. The TOC zonal distribution and variations in the Fourier spectral components with zonal wave numbers m = 1–5 are presented. The daily and interannual variations in TOC, amplitudes and phases of the spectral wave components, as well as linear trends in the amplitudes of the dominant quasi-stationary wave 1 (QSW1), are discussed. The positive TOC peaks inside the vortex in 2010 and 2018 alternate with negative ones in 2011 and 2020. The extremely low TOC at 70°N in 2020 corresponds to severe depletion of stratospheric ozone over the Arctic in strong vortex conditions due to anomalously low planetary wave activity and a high positive phase of the Arctic Oscillation. Interannual TOC variations in the sub-vortex region at 50°N are accompanied by a negative trend of −4.8 Dobson Units per decade in the QSW1 amplitude, statistically significant at 90% confidence level, while the trend is statistically insignificant in the vortex edge region and inside the vortex due to the increased variability in TOC and QSW1. The processes associated with quasi-circumpolar migration and quasi-stationary oscillation of the wave-1 phase depending on the polar vortex strength in 2020 and 2021 are discussed.
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Wolter, Juliane, Hugues Lantuit, Ulrike Herzschuh, Samuel Stettner, and Michael Fritz. "Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries." Holocene 27, no. 12 (June 1, 2017): 1846–58. http://dx.doi.org/10.1177/0959683617708441.
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Palaeoclimatic reconstructions of the northern Yukon show cooler conditions before AD 1850 followed by gradual warming, and 20th-century temperature measurements indicate decadal-scale temperature fluctuations. The impact of climate on regional vegetation and lake systems has seldom been observed on this scale, however. With this study, we provide a sub-decadal reconstruction of regional vegetation and lake-basin development for the past 300 years, covering the ‘Little Ice Age’ and the period of recent warming, in low Arctic tundra. We analysed a short lake sediment core from the Yukon Coastal Plain. The age–depth relationship of the core is based on 210Pb/137Cs validated by AMS radiocarbon dating. We analysed terrestrial pollen abundances as proxies for regional vegetation development, and we used grain size and biogeochemical analyses (TOC, TN, TOC/TN, δ13C) and the analysis of semiaquatic pollen to describe the lake development. Stable abundances of regional pollen taxa between AD 1730 and AD 2012 accompanied by climatic warming indicated that the regional vegetation was not sensitive to climate change. Based on changes in TOC/TN, δ13C and pollen of shallow-water taxa, we reconstructed an increase in lake water depth after AD 1910 that likely followed climatic warming. We attributed this development to climate-driven thaw subsidence in the lake basin. The impact of widespread permafrost thaw on regional vegetation needs to be better constrained in order to predict the limits of vegetation stability and drivers of lake changes in the region.
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MacGregor, Kelly R., Catherine A. Riihimaki, Amy Myrbo, Mark D. Shapley, and Krista Jankowski. "Geomorphic and climatic change over the past 12,900 yr at Swiftcurrent Lake, Glacier National Park, Montana, USA." Quaternary Research 75, no. 1 (January 2011): 80–90. http://dx.doi.org/10.1016/j.yqres.2010.08.005.
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AbstractGlaciated alpine landscapes are sensitive to changes in climate. Shifts in temperature and precipitation can cause significant changes to glacier size and terminus position, the production and delivery of organic mass, and in the hydrologic energy related to the transport of water and sediment through proglacial environments. A sediment core representing a 12,900-yr record collected from Swiftcurrent Lake, located on the eastern side of Glacier National Park, Montana, was analyzed to assess variability in Holocene and latest Pleistocene environment. The spectral signature of total organic carbon content (%TOC) since ~ 7.6 ka matches that of solar forcing over 70–500 yr timescales. Periodic inputs of dolomite to the lake reflect an increased footprint of Grinnell Glacier, and occur during periods when sediment sinks are reduced, glacial erosion is increased, and hydrologic energy is increased. Grain size, carbon/nitrogen (C/N) ratios, and %TOC broadly define the termination of the Younger Dryas chronozone at Swiftcurrent Lake, as well as major Holocene climate transitions. Variability in core parameters is linked to other records of temperature and aridity in the northern Rocky Mountains over the late Pleistocene and Holocene.
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González, Eduardo, Etienne Muller, Belinda Gallardo, Francisco Antonio Comín, and María González-Sanchis. "Factors controlling litter production in a large Mediterranean river floodplain forest." Canadian Journal of Forest Research 40, no. 9 (September 2010): 1698–709. http://dx.doi.org/10.1139/x10-102.
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Although litter production is an essential floodplain forest function, the drivers and their relative importance remain largely unknown, especially in semi-arid rivers. The influence of forest structure, flooding regime, soil conditions, and litterfall chemistry (a total of 17 variables) on spatial variability of litter production within the Middle Ebro River floodplain forests (northeastern Spain) was examined by monitoring litterfall in 12 forest plots in 2007. Linear mixed effects (LME) models, using stem density (SD), river distance (RD) (or soil total organic C (TOC)), and soil total P (TP) as independent predictors, explained 51% of the variance in litter production, while an alternative LME model using SD and P use efficiency (P-NUE) explained 40%. In particular, litter increased with SD and TP and decreased with RD, P-NUE, and TOC. Based on these results, P limitation appears to be controlling litter production in a rather dry hydrological regime. We hypothesized that a deficient sediment input at the plot scale (especially in the outer floodplain), with flood quality (overbank flooding, ground-water seepage, ponding) being a greater determinant than quantity (flood duration, water table levels), might ultimately be responsible for the spatial variability observed in litter production.
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Fountoulakis, I., A. F. Bais, K. Fragkos, C. Meleti, K. Tourpali, and M. M. Zempila. "Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds." Atmospheric Chemistry and Physics Discussions 15, no. 24 (December 18, 2015): 35753–85. http://dx.doi.org/10.5194/acpd-15-35753-2015.
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Abstract. In this study, we discuss the short- and the long-term variability of spectral UV irradiance at Thessaloniki, Greece using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994–2014 are presented for different solar zenith angles and discussed in association to changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear- and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7–9 % per decade for 64° solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. Trends in irradiance during the two sub-periods are not discussed, because the length of the two datasets is too short for deriving statistically significant estimates. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anti-correlation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.
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Hutami, Harnanti Y., Tiara Larasati Priniarti, Ign Sonny Winardhi, and Handoyo . "ROCK PHYSICS TEMPLATE TO ESTIMATE THE EFFECTS OF TOTAL ORGANIC CARBON (TOC) AND MINERALOGY ON THE SEISMIC ELASTIC PROPERTIES OF IMMATURE SHALE RESERVOIR." Scientific Contributions Oil and Gas 42, no. 2 (August 20, 2019): 43–49. http://dx.doi.org/10.29017/scog.42.2.374.
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The low porosity and permeability shale are nowadays known as self-resourcing reservoirs. In the unique organic shales, TOC has a signifi cant contribution to the elastic properties of rocks. TOC behaves like porosity to a density log and effects in decreasing density. To reduce the uncertainty due to TOC and mineral variability effect, a quantitative interpretation of shale reservoirs should be done properly to obtain the best image of shale systems. In this study, we built rock-physics templates (RPT) to esti mate seismic response by defi ning the relationship between total organic carbon (TOC) and effective elastic properties of shale reservoirs of a data set from South Sumatera Basin, Indonesia. RPT is carried out by incorporating the amount of organic matter into shale pore space as a solid-fi lling inclusion. Moreover, shale porosity is assumed to be fully water-saturated determined by the in-situ conditions. We have estimated the general distribution of pore geometry by investigating aspect ratio from the dataset. A solid background of shale from several different minerals is estimated by using effective medium theory. Properties of porous rocks for solid pore infi ll are estimated from a generalization of Brown-Korringa Equation. Effective elastic properties of bulk rock frame fi lled with a fl uid are obtained from Gassmann equations. Results show that increasing the TOC volumes generally reduces both P-wave and S-wave velocities, acoustic impedance, and density. On the contrary, the vp/vs ratio increased as the impact of immature organic matter which will be more affecting shale rigidity than its compressibility.
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Sha, Longbin, Xianfu Li, Jiabing Tang, Junwu Shu, Weiming Wang, and Dongling Li. "Early to Mid-Holocene Palaeoenvironment Change and Sedimentary Evolution in the Xianghu Area, Zhejiang." International Journal of Environmental Research and Public Health 17, no. 19 (September 28, 2020): 7099. http://dx.doi.org/10.3390/ijerph17197099.
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A 2.5 m long sediment core (XH-2) obtained from Xianghu area, near the Kuahuqiao site, were analyzed for grain size, diatom index, and geochemistry of organic carbon. The results of the total organic carbon (TOC) and stable organic carbon isotope (δ13C) in sediment samples from core XH-2 in the Xianghu area in Zhejiang Province have revealed the evolution history of sedimentary environmental and climatic changes during the breeding–prosperity–decline period of the Kuahuqiao culture. During 9300–8200 cal a BP, TOC contents were relatively high and stable, whereas δ13C values tended to be negative. This condition indicated that the climate was humid, and the sedimentary environment in the Xianghu area was stable. During 8200–7500 cal a BP, TOC contents presented a fluctuating declining trend, and δ13C values were significantly high, implying that the climate was arid, and the Xianghu area was gradually reduced to land. Thus, conducive conditions were provided for the development of the Kuohuqiao culture (7700–7400 cal a BP). From 7500 cal a BP, TOC contents obviously declined, and δ13C values were partially low, suggesting strengthened hydrodynamic force and wet conditions in the Xianghu area. This condition was related to the rise in sea level at approximately 7400 cal a BP, and the Kuahuqiao site became obsolete due to the transgression event. The TOC contents in core XH-2 were remarkably influenced by grain size, whereas no significant correlation existed between the δ13C variability and grain size. Sedimentary environment changes in the Xianghu area from 9300 to 6600 cal a BP, which was reflected by the TOC and δ13C records in core XH-2, accorded with the diatom results in this core and those in the Baima Lake area.
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Martinez-Portilla, Raigam J., Jose R. Villafan-Bernal, Diana L. Lip-Sosa, Eva Meler, Jordi Clotet, Francisco J. Serna-Vela, Sergio Velazquez-Garcia, Leopoldo C. Serrano-Diaz, and Francesc Figueras. "Osteocalcin Serum Levels in Gestational Diabetes Mellitus and Their Intrinsic and Extrinsic Determinants: Systematic Review and Meta-Analysis." Journal of Diabetes Research 2018 (December 30, 2018): 1–15. http://dx.doi.org/10.1155/2018/4986735.
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Background. Undercarboxylated osteocalcin (ucOC) increases insulin release and insulin resistance in mice. In humans, evidence is scarce but a correlation of ucOC and total osteocalcin (tOC) with glycemic status markers has been demonstrated. The relationship of ucOC and tOC with gestational diabetes mellitus (GDM) has been even less characterized. Objective. To assess the mean difference of tOC and ucOC serum concentrations among nondiabetic pregnant women and women diagnosed as GDM in the second trimester of pregnancy and to determine the possible intrinsic and extrinsic contributors to this difference. Methods. A systematic search was performed to identify relevant studies published in English and Spanish using PubMed, SCOPUS, ISI Web of Knowledge, and PROSPERO database for meta-analysis. Observational studies measuring mean serum levels of osteocalcin among GDM, with at least 10 subjects analyzed in each group were selected. Mean difference (MD) by random effects model was used. Heterogeneity between studies was assessed using Cochran’s Q, H, and I2 statistics. Results. From 38 selected studies, 5 were retained for analysis for a total of 1119 pregnant women. Serum concentrations of tOC were not significantly different among women with GDM and nondiabetic pregnant controls (MD: 1.56; 95% CI: −0.70 to 3.82; p=0.175). Meanwhile, ucOC serum levels were significantly higher among women with GDM (MD: 1.17; 95% CI: 0.24 to 2.11; p=0.013). The only factor influencing tOC was the UV index, showing a reduction in mean difference between GDM and controls when exposed to higher concentrations of UV rays. Conclusions. This meta-analysis provides evidence to support the use of ucOC as a potential marker for GDM rather than tOC, yielding very little variability among studies and no difference among methods or brands used for its analysis.
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Hocke, K., M. Lainer, and A. Schanz. "Composite analysis of a major sudden stratospheric warming." Annales Geophysicae 33, no. 6 (June 25, 2015): 783–88. http://dx.doi.org/10.5194/angeo-33-783-2015.
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Abstract. We present the characteristics of a major sudden stratospheric warming (SSW) by using the composite analysis method and ERA Interim reanalysis data from 1979 to 2014. The anomalies of the parameters total ozone column density (TOC), temperature (T), potential vorticity (PV), eastward wind (u), northward wind (v), vertical wind (w), and geopotential height (z) are derived with respect to the ERA Interim climatology (mean seasonal behaviour 1979 to 2014). The composites are calculated by using the time series of the anomalies and the central dates of 20 major SSWs. Increases of up to 90 Dobson units are found for polar TOC after the SSW. Polar TOC remains enhanced until the summer after the major SSW. Precursors of the SSW are a negative TOC anomaly 3 months before the SSW and enhanced temperature at 10 hPa at mid-latitudes about 1 month before the SSW. Eastward wind at 1 hPa is decreased at mid-latitudes about 1 month before the SSW. The 1 hPa geopotential height level is increased by about 500 m during the month before the SSW. These features are significant at the 2σ level for the mean behaviour of the ensemble of the major SSWs. However, knowledge of these precursors may not lead to a reliable prediction of an individual SSW since the variability of the individual SSWs and the polar winter stratosphere is large.
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SILVA, EUDOCIO RAFAEL OTAVIO DA, MURILO MACHADO DE BARROS, MARCOS GERVASIO PEREIRA, JOÃO HENRIQUE GAIA GOMES, and STEPHANY DA COSTA SOARES. "EFFECTS OF SPATIAL VARIABILITY OF SOIL CHEMICAL PARAMETERS ON TIFTON 85 GRASS YIELD1." Revista Caatinga 33, no. 1 (March 2020): 236–45. http://dx.doi.org/10.1590/1983-21252020v33n125rc.
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ABSTRACT Studies on spatial variability of soil attributes of tropical pastures gather information that can assist in decision making about managements of these soils. The objective of the present study was to evaluate the spatial variability of soil chemical attributes and their effects on grass yield of Tifton 85. The experiment was carried out in an area of 3.91 ha at the Feno Rio Farm of the Federal Rural University of Rio de Janeiro, Seropédica, RJ, Brazil. Soils of the 0-0.20 and 0.20-0.40 m layers were sampled considering an irregular sampling mesh, making a total of 50 georeferenced points. The parameters evaluated were: the soil chemical attributes pH, Al+3, Ca+2, Mg+2, Na+, K+, P, H+Al, and total organic carbon (TOC); and the Tifton 85 dry matter yield (DMY). The results of these parameters were subjected to descriptive statistics, linear correlation, and geostatistics, and maps were developed for the analyses. Regions with grass yields different from the general mean were found in the area, which presented mean grass yield of 2248 kg ha-1. The soil chemical parameters Na+, Ca+2, TOC, and H+Al were significantly correlated with DMY, confirming that they are important and affect the Tifton 85 grass yield. The mapping of the Tifton 85 cycle is important for understanding the variability of DMY. The investigation of areas with different productive potentials should be followed by development of maps of soil chemical attributes to correlate and understand the ratios that may be involved with these variations.
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Krull, Evelyn G., and Steven S. Bray. "Assessment of vegetation change and landscape variability by using stable carbon isotopes of soil organic matter." Australian Journal of Botany 53, no. 7 (2005): 651. http://dx.doi.org/10.1071/bt04124.
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Stable carbon isotopic (δ13C) analyses of soil organic matter (SOM) have been used in the past to characterise C3–C4 vegetation changes. However, the temporal and spatial resolution of these isotopic data are not well established. Here, we present data from δ13C analyses of whole and size-separated SOM, which are discussed in conjunction with organic (total organic carbon (TOC) content) and inorganic (%clay) soil data. These data are put into context with the current vegetation state (assessed from tree size-class distribution) and the 50-year vegetation history (assessed from aerial photographs). By linking below- and above-ground datasets, we show that δ13C analyses of SOM can accurately record vegetation-change histories over short- (10 and 50years) and longer-term (hundreds of years) time scales. Our data also show that spatial variability was relatively small for the clay TOC content but was much larger for δ13C data, indicating that the number of soil cores required for statistical significance is highly dependent on the kind of measurements intended. Finally, interpretation of δ13C data from SOM to assess the history of C3–C4 vegetation change is complicated by the inherent 13C-enrichment of SOM, owing to decomposition processes, which occurs regardless of vegetation change. We suggest a method for distinguishing 13C-enrichment of SOM that is due to soil-inherent (decomposition-related) processes from 13C-enrichment that is due to increased inputs of C4 organic matter.
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Sharma, R. R., B. Kjeldstad, and P. J. Espy. "UV Index and Total Ozone Column Climatology of Nepal Himalaya Using TOMS and OMI Data." Journal of Hydrology and Meteorology 9, no. 1 (August 30, 2016): 45–59. http://dx.doi.org/10.3126/jhm.v9i1.15581.
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Ultraviolet index (UVI) and Total Ozone Column (TOC) climatology of six stations of Nepal Himalaya using ground measurement, and OMI / TOMS satellite data is presented. The positive bias found in the OMI UV index from previous study is corrected empirically using a ratio factor using the clear sky coincident data of OMI and ground measurement from NILU UV multi-band filter radiometer (MBFR). UV index >3 in the winter months (e.g. December) and more than 9 during the summer months (May-August) are common in most of the stations. High altitude stations even have more extreme values (>11) during the summer months. Under some meteorological conditions, UV index often found more than 16 at the high altitude station (latitude 28o, altitude 2850m) during a clear sky day in the monsoon season. Diurnal and altitudinal variability is also highlighted. Monthly average TOC climatology from November 1978 to March 2012 using TOMS (Nimbus 7, Meteor3 and Earth Probe) and OMI is also presented. The ozone column data follows the annual cycle, minimum in November/December and maximum in April/May. In addition, slight negative trend of TOC is found in the data from 1978 to 2012.Journal of Hydrology and Meteorology, Vol. 9(1) 2015, p.45-59