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1
Nau, Amy, Vanessa Lucieer, Yoann Ladroit, Haris Kunnath und Tara Martin. „Multibeam sonar water column data simulation for improved and automated detection of gas seeps“. Journal of the Acoustical Society of America 154, Nr. 4_supplement (01.10.2023): A92—A93. http://dx.doi.org/10.1121/10.0022905.
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Water column data (WCD) collected by multibeam echosounders (MBES) provide valuable datasets for the detection of gas bubbles. However, the presence of noise patterns, primarily caused by sidelobe interference from seafloor reverberation, limits the usability of WCD. We present a method for simulating characteristic noise patterns in WCD, particularly in Mills Cross configurations, by simulating predicted seafloor reverberation and transducer artefacts. The simulation is based on a reference pattern created from a subset of data and then applied as a correction based on the depth and seafloor backscatter of each ping within the dataset. Noise patterns can be removed by subtracting the simulated data from the original data, allowing for improved analysis of near-benthic water column features such as gas seeps. This method requires no prior knowledge of specific transducer characteristics, making it applicable to a wide range of MBES systems and acoustic targets. This method was applied to two MBES datasets collected simultaneously over a seep field in the Bay of Plenty, New Zealand, as part of the Quantitative Ocean-Column Imaging (QUOI) voyage in July 2018. We demonstrate the utility of applying a reference pattern for detecting the spatial extent of gas seep bases mapped using two different frequencies.
2
Ghannami, Mohamed Ali, Sylvie Daniel, Guillaume Sicot und Isabelle Quidu. „A Likelihood-Based Triangulation Method for Uncertainties in Through-Water Depth Mapping“. Remote Sensing 16, Nr. 21 (02.11.2024): 4098. http://dx.doi.org/10.3390/rs16214098.
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Coastal environments, which are crucial for economic and strategic reasons, heavily rely on accurate bathymetry for safe navigation and resource monitoring. Recent advancements in through-water photogrammetry have shown promise in mapping shallow waters efficiently. However, robust uncertainty modeling methods for these techniques, especially in challenging coastal environments, are lacking. This study introduces a novel likelihood-based approach for through-water photogrammetry, focusing on uncertainties associated with camera pose—a key factor affecting depth mapping accuracy. Our methodology incorporates probabilistic modeling and stereo-photogrammetric triangulation to provide realistic estimates of uncertainty in Water Column Depth (WCD) and Water–Air Interface (WAI) height. Using simulated scenarios for both drone and airborne surveys, we demonstrate that viewing geometry and camera pose quality significantly influence resulting uncertainties, often overshadowing the impact of depth itself. Our results reveal the superior performance of the likelihood ratio statistic in scenarios involving high attitude noise, high flight altitude, and complex viewing geometries. Notably, drone-based applications show particular promise, achieving decimeter-level WCD precision and WAI height estimations comparable to high-quality GNSS measurements when using large samples. These findings highlight the potential of drone-based surveys in producing more accurate bathymetric charts for shallow coastal waters. This research contributes to the refinement of uncertainty quantification in bathymetric charting and sets a foundation for future advancements in through-water surveying methodologies.
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Lu, Yanhong, Xiaomin Xia, Shunyan Cheung, Hongmei Jing und Hongbin Liu. „Differential Distribution and Determinants of Ammonia Oxidizing Archaea Sublineages in the Oxygen Minimum Zone off Costa Rica“. Microorganisms 7, Nr. 10 (15.10.2019): 453. http://dx.doi.org/10.3390/microorganisms7100453.
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Ammonia oxidizing archaea (AOA) are microbes that are widely distributed in the ocean that convert ammonia to nitrite for energy acquisition in the presence of oxygen. Recent study has unraveled highly diverse sublineages within the previously defined AOA ecotypes (i.e., water column A (WCA) and water column B (WCB)), although the eco-physiology and environmental determinants of WCB subclades remain largely unclear. In this study, we examined the AOA communities along the water columns (40–3000 m depth) in the Costa Rica Dome (CRD) upwelling region in the eastern tropical North Pacific Ocean. Highly diverse AOA communities that were significantly different from those in oxygenated water layers were observed in the core layer of the oxygen minimum zone (OMZ), where the dissolved oxygen (DO) concentration was < 2μM. Moreover, a number of AOA phylotypes were found to be enriched in the OMZ core. Most of them were negatively correlated with DO and were also detected in other OMZs in the Arabian Sea and Gulf of California, which suggests low oxygen adaptation. This study provided the first insight into the differential niche partitioning and environmental determinants of various subclades within the ecotype WCB. Our results indicated that the ecotype WCB did indeed consist of various sublineages with different eco-physiologies, which should be further explored.
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Vahtmäe, Ele, Tiit Kutser und Birgot Paavel. „Performance and Applicability of Water Column Correction Models in Optically Complex Coastal Waters“. Remote Sensing 12, Nr. 11 (08.06.2020): 1861. http://dx.doi.org/10.3390/rs12111861.
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Maps of submerged aquatic vegetation (SAV) are of primary importance for the sustainable management of coastal areas and serve as a basis for fundamental ecological studies. Various water column correction (WCC) models are successfully applied in clear Case-1 waters to compensate for the variable water depth effect. The performance of the WCC in less clear Case-2 waters is rarely assessed. In this study, the performance and applicability of model-based WCC algorithms in the complex Baltic Sea were analyzed. The bottom reflectance was retrieved from the Compact Airborne Spectrographic Imager (CASI) water surface reflectance by applying the Maritorena and Lee WCC algorithms. The Maritorena model retrieved bottom spectra that showed large variations in reflectance magnitudes. The Lee model was more successful in retrieving reasonable spectral magnitudes, although only in a rather narrow wavelength region (550–600 nm). Shorter and longer spectral regions were significantly overcorrected, resulting in unrealistic spectral shapes. Sensitivity analysis indicated that slight under- or overestimation of water depth and water column constituents affect retrieval of correct bottom spectra in Case-2 waters. To assess the performance of WCC models in improving the SAV quantification, the surface reflectance, as well as the retrieved bottom reflectance, were correlated with the corresponding in situ estimated SAV percent cover (%SAV). Although the quality of the Lee WCC model was not considered high, the spectral region least affected by the input parameters variations (550–600 nm) can be used for the SAV quantification. Application of the Lee model provided better results in %SAV assessment than not performing the WCC correction.
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Mazouz, Radia, Naima Filali, Zhour Hattab und Kamel Guerfi. „Valorization of granulated slag of Arcelor-Mittal (Algeria) in cationic dye adsorption from aqueous solution: column studies“. Journal of Water Reuse and Desalination 6, Nr. 1 (14.09.2015): 204–13. http://dx.doi.org/10.2166/wrd.2015.049.
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A continuous adsorption study in a fixed-bed column was carried out using granulated slag (GS) as an adsorbent for the removal of methylene blue (MB) from aqueous solution. The effects of various parameters, such as initial dye concentration, flow rate, bed depth, and pH were investigated. Obtained results confirmed that the breakthrough time and exhaustion time were dependent on these factors. The adsorption capacity of GS was calculated at the 50% breakthrough point for different conditions. The highest breakthrough capacity (q,exp = 0.296 mg.g–1) was obtained with a 15 cm bed height and a 2 mL.min–1 rate by using a 10 mg.L–1 initial MB concentration at pH 7.5. Bohart–Adams, Bed Depth Service Time (BDST), and Thomas models were applied to experimental data to determine the characteristic parameters of the column. The Thomas model was found suitable for the description of the whole breakthrough curve, while the Bohart–Adams model was only used to predict the initial part of the dynamic process. The data were in good agreement with the BDST model. Thus, the granulated slag can be used as an adsorbent in the treatment of wastewater. Desorption was carried out with a deionized water as the desorbing agent, and reuse study was investigated.
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Khélifi, N., und M. Frank. „A major change in North Atlantic deep water circulation 1.6 million years ago“. Climate of the Past 10, Nr. 4 (29.07.2014): 1441–51. http://dx.doi.org/10.5194/cp-10-1441-2014.
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Abstract. The global ocean–climate system has been highly sensitive to the formation and advection of deep overflow water from the Nordic Seas as integral part of the Atlantic Meridional Overturning Circulation (AMOC) but its evolution over the Pliocene–Pleistocene global cooling is not fully understood. In particular, changes in the sources and mixing of prevailing deep waters that were involved in driving overturning throughout the Pliocene–Pleistocene climate transitions are not well constrained. Here we investigate the evolution of a substantial deep southward return overflow of the AMOC over the last 4 million years. We present new records of the bottom-water radiogenic neodymium isotope (&varepsilon;Nd) variability obtained from three sediment cores (DSDP site 610 and ODP sites 980/981 and 900) at water depths between 2170 and 5050 m in the northeast Atlantic. We find that prior to the onset of major Northern Hemisphere glaciation (NHG) ∼3 million years ago (Ma), &varepsilon;Nd values primarily oscillated between −9 and −11 at all sites, consistent with enhanced vertical mixing and weak stratification of the water masses during the warmer-than-today Pliocene period. From 2.7 Ma to ∼2.0 Ma, the &varepsilon;Nd signatures of the water masses gradually became more distinct, which documents a significant advection of Nordic Seas overflow deep water coincident with the intensification of NHG. Most markedly, however, at ∼1.6 Ma the interglacial &varepsilon;Nd signatures at sites 610 (2420 m water depth (w.d.)) and 980/981 (2170 m w.d.) synchronously and permanently shifted by 2 to 3 &varepsilon;Nd units to less radiogenic values, respectively. Since then the difference between glacial and interglacial &varepsilon;Nd values has been similar to the Late Quaternary at each site. A decrease of ∼2&varepsilon;Nd units at 1.6 Ma was also recorded for the deepest water masses by site 900 (∼5050 m w.d.), which thereafter, however, evolved to more radiogenic values again until the present. This major &varepsilon;Nd change across the 1.6 Ma transition reflects a significant reorganization of the overturning circulation in the northeast Atlantic paving the way for the more stratified water column with distinct water masses prevailing thereafter.
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Pan, Tianshi, Shibo Wang, Lijun Zuo und Qiang Liu. „Influence of Grain on Green Patterns and Their Underlying Surface Characteristics on Water Conservation: A Case Study in a Semiarid Area“. Forests 14, Nr. 10 (09.10.2023): 2020. http://dx.doi.org/10.3390/f14102020.
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Water-conservation enhancement is a crucial objective of regional ecological restoration projects in arid and semiarid areas, and it is significantly influenced by land use/cover change (LUCC). The Grain for Green Project (GFGP) is a common strategy for ecological restoration. However, insufficient attention has been paid to the impact of reforestation patterns and the underlying surface characteristics on the effectiveness of GFGP in enhancing water conservation. In this study, a Soil and Water Assessment Tool (SWAT) scenario-based simulation was conducted to assess changes in water-conservation depth (WCD) in the Zhangjiakou section of the Guanting Reservoir basin. Redundancy analysis (RDA) and a mixed linear model were employed to determine the effects of different reforestation patterns and their underlying slope gradient and soil-type characteristics on WCD variation. The results showed that there were differences in the effect characteristics of reforestation patterns and different vegetation types on WCD changes; the effectiveness of increased water conservation is associated with the adaptation of reforestation plants to underlying characteristics. Returning farmland to evergreen forests was the most effective approach, leading to a relative increase in WCD that was 2.6 times greater than the relative increase in total WCD. WCD decreased with the slope gradient, with WCD decreasing by 0.2 mm for every 1° increase in slope. Converting grassland to evergreen forests on slopes greater than 16.19° and converting deciduous forests to grassland on slopes less than 16.19° would further increase WCD, promoting the synergistic development of ecosystem services. This study provides insights into the development of more efficient reforestation strategies to enhance water conservation in a complex terrain area.
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Kao, S. J., K. K. Liu, S. C. Hsu, Y. P. Chang und M. H. Dai. „North Pacific-wide spreading of isotopically heavy nitrogen during the last deglaciation: Evidence from the western Pacific“. Biogeosciences 5, Nr. 6 (06.12.2008): 1641–50. http://dx.doi.org/10.5194/bg-5-1641-2008.
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Abstract. Sedimentary δ15 N records in two IMAGES cores (MD012404 and MD012403) retrieved from the Okinawa Trough (OT) in the western North Pacific reveal deglacial increases with two peaks occurring during the Bølling/Allerød and the Preboreal/early Holocene periods. These peaks are synchronous with previously reported δ15 N peaks in the Eastern Tropical North Pacific, although the amplitudes (from 3.8 to 5.8‰) are much smaller in the OT. Similar δ15 N values for the last glacial maximum and the late-Holocene observed by us at a site far from the present-day zones of water-column denitrification (WCD) indicate that the mean 15 N/14 N of nitrate in the upper ocean did not differ much between the two climate states. The accumulation rate of organic carbon and total sulfur content are used as indices of the local WCD potential. The results suggest that enhancement of global WCD rather than local denitrification should be responsible for the deglacial maxima of sedimentary δ15 N in the Okinawa Trough. Our data could provide additional constraints to better understand changes in nitrogen budget during the glacial to interglacial transition.
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Somes, C. J., A. Oschlies und A. Schmittner. „Isotopic constraints on the pre-industrial oceanic nitrogen budget“. Biogeosciences 10, Nr. 9 (06.09.2013): 5889–910. http://dx.doi.org/10.5194/bg-10-5889-2013.
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Abstract. The size of the bioavailable (i.e., "fixed") nitrogen inventory in the ocean influences global marine productivity and the biological carbon pump. Despite its importance, the pre-industrial rates for the major source and sink terms of the oceanic fixed nitrogen budget, N2 fixation and denitrification, respectively, are not well known. These processes leave distinguishable imprints on the ratio of stable nitrogen isotopes, δ15N, which can therefore help to infer their patterns and rates. Here we use δ15N observations from the water column and a new database of seafloor measurements to constrain rates of N2 fixation and denitrification predicted by a global three-dimensional Model of Ocean Biogeochemistry and Isotopes (MOBI). Sensitivity experiments were performed to quantify uncertainties associated with the isotope effect of denitrification in the water column and sediments. They show that the level of nitrate utilization in suboxic zones, that is the balance between nitrate consumption by denitrification and nitrate replenishment by circulation and mixing (dilution effect), significantly affects the isotope effect of water column denitrification and thus global mean δ15NO3–. Experiments with lower levels of nitrate utilization within the suboxic zone (i.e., higher residual water column nitrate concentrations, ranging from 20 to 32 μM) require higher ratios of benthic to water column denitrification, BD : WCD = 0.75–1.4, to satisfy the global mean NO3– and δ15NO3– constraints in the modern ocean. This suggests that nitrate utilization in suboxic zones plays an important role in global nitrogen isotope cycling. Increasing the net fractionation factor &varepsilon;BD for benthic denitrification (&varepsilon;BD = 0–4‰) requires even higher ratios, BD : WCD = 1.4–3.5. The model experiments that best reproduce observed seafloor δ15N support the middle to high-end estimates for the net fractionation factor of benthic denitrification (&varepsilon;BD = 2–4‰). Assuming a balanced fixed nitrogen budget, we estimate that pre-industrial rates of N2 fixation, water column denitrification, and benthic denitrification were between 195–350 (225), 65–80 (76), and 130–270 (149) Tg N yr−1, respectively, with our best model estimate (&varepsilon;BD = 2‰) in parentheses. Although uncertainties still exist, these results suggest that marine N2 fixation is occurring at much greater rates than previously estimated and the residence time for oceanic fixed nitrogen is between ~ 1500 and 3000 yr.
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Wang, Jiarui, Junju Zhou, Dongfeng Ma, Xi Zhao, Wei Wei, Chunfang Liu, Dongxia Zhang und Chunli Wang. „Impact of Ecological Restoration Project on Water Conservation Function of Qilian Mountains Based on InVEST Model—A Case Study of the Upper Reaches of Shiyang River Basin“. Land 12, Nr. 10 (28.09.2023): 1850. http://dx.doi.org/10.3390/land12101850.
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Scientifically evaluating the influence of ecological restoration projects on the water conservation function (WCF) of regional ecosystems is the foundation for formulating regional ecological restoration policies and optimizing and adjusting ecological restoration projects. In this paper, we considered fully the runoff generation and confluence process in the Qilian Mountains with the actual situation of the basin and re-rated the parameter Z to improve the simulation accuracy of InVEST model. On this basis, the impact of ecological restoration project on the WCF in the upper reaches of Shiyang River Basin (SRB) in the eastern part of Qilian Mountains was quantified. The results showed that, on the whole, the water conservation depth (WCD) of forest land was the largest (138.5 mm) and that of cultivated land was the smallest (24.78 mm), while the water conservation coefficient of forest land was also the largest (93.36%) and that of unused land was the smallest (16.67%). From 1986 to 2018, the WCD showed an increasing trend in the upper reaches of SRB, among them, the WCD in the western tributaries increased faster than that in the eastern tributaries from 1986 to 2000. The significantly increased areas were mainly distributed in the middle reaches of the western tributaries and the river source areas of the eastern tributaries, while the significantly decreased areas were mainly distributed in the river source areas of the western tributaries and the cultivated land expansion area in the middle reaches of the eastern tributaries. From 2000 to 2018, the WCD of the eastern tributaries increased more than that of the western tributaries. The significantly increased areas were mainly distributed in the four eastern tributaries, and the significantly decreased areas were scattered in the middle and lower reaches of each tributary. From 1986 to 2000, the overall influence of land use change on the increase in WCD was negative, while the influence of climate and land use change on the increase in water conservation were both positive from 2000 to 2018. The influence of land use change on WCD was different in different tributaries. Among them, that of the western tributaries (except the Dongda River) was positive in two different periods, while that of the eastern tributaries (except the Xiying River) was changed from negative to positive. The implementation of ecological restoration project was one of the main reasons for the improvement of WCF in Qilian Mountains from 2000 to 2018, with a contribution of 9.04%. In the future, the protection and restoration of decreased areas of WCF should be strengthened, and the Z value determined in this paper is expected to be applied in the arid inland river basins of northwest China.
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Jasron, Jahirwan Ut, Sudjito Soeparmani, Lilis Yuliati und Djarot B. Darmadi. „Comparison of the performance of oscillating water column devices based on arrangements of water columns“. Journal of Mechanical Engineering and Sciences 14, Nr. 3 (28.09.2020): 7082–93. http://dx.doi.org/10.15282/jmes.14.3.2020.10.0555.
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The hydrodynamic performance of oscillating water column (OWC) depends on the depth of the water, the size of the water column and its arrangement, which affects the oscillation of the water surface in the column. An experimental method was conducted by testing 4 water depths with wave periods of 1-3 s. All data recorded by the sensor is then processed and presented in graphical form. The research focused on analyzing the difference in wave power absorption capabilities of the three geometric types of OWC based on arrangements of water columns. The OWC devices designed as single water column, the double water column in a series arrangement which was perpendicular to the direction of wave propagation, and double water column in which the arrangement of columns was parallel to the direction of wave propagation. This paper discussed several factors affecting the amount of power absorbed by the device. The factors are the ratio of water depth in its relation to wavelength (kh) and the inlet openings ratio (c/h) of the devices. The test results show that if the water depth increases in the range of kh 0.7 to 0.9, then the performance of the double chamber oscillating water column (DCOWC) device is better than the single chamber oscillating water column (SCOWC) device with maximum efficiency for the parallel arrangement 22,4%, series arrangement 20.8% and single column 20.7%. However, when referring to c/h, the maximum energy absorption efficiency for a single column is 27.7%, double column series arrangement is 23.2%, and double column parallel arrangement is 29.5%. Based on the results of the analysis, DCOWC devices in parallel arrangement showed the ability to absorb better wave power in a broader range of wave frequencies. The best wave of power absorption in the three testing models occurred in the wave period T = 1.3 seconds.
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Li, Jie, Sida Li, Junfeng Zhang, Yupeng Geng und Dayu Yang. „Influence of pier-water interaction on natural vibration characteristics of bridge with complex piers in water“. Bridge Structures 19, Nr. 1-2 (11.07.2023): 15–29. http://dx.doi.org/10.3233/brs-230204.
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In order to clarify the influence of water on the natural vibration of bridge with complex piers, based on a continuous beam with 4-column pier, the numerical analysis model is established. Single column circular pier is taken to discuss the range of waters. Then the influences of water on the natural vibration are analyzed. The research shows that waters reduce the natural frequency. When waters area width is less than 10 m, the natural frequency of the pier decreases. And the first-order longitudinal bending frequency is reduced by 3.36%. When waters area width is more than 10 m, the vibration frequencies tend to be stable gradually. Therefore, the waters 10 m can be regarded as an infinite boundary. The natural frequencies of single column pier and 4-column pier decrease with the increase of water depth. When the water depth is less than 10 m, the changes of natural frequency of the first four orders of single column pier are relatively small, and the changes of 5–10 order natural frequency are large. The maximum effect of the first ten orders is 14.84%. The natural vibration frequency of the bridge decreases gradually with the increase of water depth. The maximum effect of the first five orders is 3.33%.
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Landrø, M. „Attenuation of seismic water-column noise, tested on seismic data from the Grane field“. GEOPHYSICS 72, Nr. 4 (Juli 2007): V87—V95. http://dx.doi.org/10.1190/1.2740020.
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Seismic analysis of long-offset data is gaining increased attention for several purposes: constraining three-parameter amplitude variation with offset (AVO) methods, 4D analysis, and imaging below salt and basalt. A major challenge for exploiting long-offset seismic data is that the water-column noise mixes with and distorts the reflected seismic signal from interfaces at the target level. Traditional processing methods such as [Formula: see text] filtering often reduce this distortion problem. This article offers an alternative to conventional processing methods. The alternative exploits the difference in water depth and reservoir depth to subtract water-column noise. The proposed subtraction method works well where water depth is constant. The method was tested on a multicomponent seismic data set from the Grane field (North Sea). In this location, the water depth is fairly constant over the field. The fieldwise similarity level of water-column noise is high. A comparison of the water-column noise from various locations shows that the similarity is 10%, measured in normalized root mean squared error. The fact that the water-column noise is highly repeatable is a strong indication that the major part of it is harmonic waves that propagate in the water layer.
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Toller, Simone, Beatrice M. S. Giambastiani, Nicolas Greggio, Marco Antonellini, Ivo Vasumini und Enrico Dinelli. „Assessment of Seasonal Changes in Water Chemistry of the Ridracoli Water Reservoir (Italy): Implications for Water Management“. Water 12, Nr. 2 (20.02.2020): 581. http://dx.doi.org/10.3390/w12020581.
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The Ridracoli artificial basin is the main water reservoir of the Emilia-Romagna region (Northeast Italy). The reservoir was made by construction of a dam on the Bidente River in 1982. It is used as the main drinking water supply of the region and for hydropower production. The physical and chemical parameterseters (temperature, pH, electrical conductivity, and dissolved oxygen) of shallow water are continuously monitored whereas vertical depth profiles of water chemical data (major anions and cations, as well as heavy metals) are available on a bimonthly base. The dataset used in this research is related to the years 2015 and 2016. Data show that the reservoir is affected by an alternation of water stratification and mixing processes due to seasonal change in water temperature, density, and the reservoir water level. In late summer and winter months, the water column is stratified with anoxic conditions at the bottom. During the spring, on the other hand, when storage is at its maximum, water recirculation and mixing occur. The reservoir is characterized by a dynamic system in which precipitation, dissolution, and adsorption processes at the bottom affect water quality along the reservoir depth column. The temperature stratification and anoxic conditions at the reservoir bottom influence the concentration and mobility of some heavy metals (i.e., Fe and Mn) and, consequently, the quality of water that reaches the treatment and purification plant. This study is relevant for water resource management of the reservoir. Assessing the seasonal changes in water quality along the reservoir water column depth is fundamental to plan water treatment operations and optimize their costs. The reservoir assessment allows one to identify countermeasures to avoid or overcome the high concentrations of heavy metals and the stratification problem (i.e., artificial mixing of the water column, new water intakes at different depths operating at different times of the year, blowers, etc.).
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Tsuboi, Tatsuya, Hiroshi Iwata, Hideki Wada, Hiroyuki Matsuzaki, Rumi Sohrin, Yutaka Hiroe, Tadafumi Ichikawa, Kiyotaka Hidaka und Tomoo Watanabe. „Water Column Profiles of Dissolved Inorganic Radiocarbon for the Kuroshio Region, Offshore of the Southern Japanese Coast“. Radiocarbon 53, Nr. 4 (2011): 679–90. http://dx.doi.org/10.1017/s0033822200039138.
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We present the water column profiles (surface to 2000 m depth) for dissolved inorganic radiocarbon (14CDIC) from 2 stations in the Kuroshio region including the Kuroshio large meander (LM) of 2004–2005. Surprisingly, the Δ14CDIC value varied up to 125‰ in the intermediate layer, especially near 600 m depth. In addition, the Δ14CDIC value was approximately − 150‰ at 200 m depth at the northern station of Kuroshio in August 2005. This value is ∼100‰ less than other Δ14CDIC values for the same depth. In comparison, the Δ14CDIC water column profiles for the southern station of Kuroshio and GEOSECS station 224 decrease down to 600 m depth and were similar below 600 m depth. Our results suggest that strong upwelling associated with the Kuroshio LM has a powerful influence on the Δ14CDIC water column profiles in the study region.
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Baskar, S., K. R. Aswin Sidhaarth und L. Mangaleshwaran. „Utilisation of Clamshell Waste for Removing Mercury From Water: Fixed Bed Adsorption and Modelling Studies“. Asian Journal of Water, Environment and Pollution 20, Nr. 6 (27.11.2023): 77–85. http://dx.doi.org/10.3233/ajw230082.
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The present communication investigated the sustainable utilization of the clamshell waste powder (CSP) for eliminating mercury through fixed bed adsorption. This CSP is freshly prepared and packed in a stable multi-port column. Their breakthrough performance in the column is evaluated by varying its bed depth (5, 10, 15, 20 and 25 min) and flow rate (8, 10 and 12 mL/min). The CSP column’s design parameters and kinetic behavior are estimated from its breakthrough curve and validated using column models. The results revealed that slow saturation of the CSP bed and maximum adsorption capacity (2.8 mg/g) occurred at lower column depth (5 cm) and elevated influent flow rates (12 mL/min). Moreover, the mass transfer zone exhibited fluctuations with elevated column depth, indicating the presence of non-ideal conditions. The YN model showed superior fitness for mercury removal using CSP. The dynamic studies showed that CSP is a cost-effective, eco-friendly, biocompatible and sustainable adsorbent that can be successfully employed for treating industrial effluent.
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Swartzman, Gordon, Emily Silverman und Neal Williamson. „Relating trends in walleye pollock (Theragra chalcogramma) abundance in the Bering Sea to environmental factors“. Canadian Journal of Fisheries and Aquatic Sciences 52, Nr. 2 (01.02.1995): 369–80. http://dx.doi.org/10.1139/f95-039.
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Generalized additive models (GAM), a nonparametric regression method with less restrictive statistical assumptions than traditional regression methods, were used to model the trend in mean abundance of Bering Sea walleye pollock (Theragra chalcogramma) as a function of ocean environmental conditions including water column depth, temperature at 50 m, and depth of the thermocline. Acoustic survey data collected in the summers of 1988 and 1991 were used to test these relationships. In both surveys, mean walleye pollock abundance was highest in areas having a 70–130 m depth range and where the 50-m temperature was close to 2.5 °C. Thermocline depth, while not itself significant, had a significant effect on walleye pollock abundance through interactions with both bottom depth and temperature at 50 m. Walleye pollock in the top 50 m of the water column (mostly juveniles) were influenced differently by temperature and thermocline depth than the adult walleye pollock, which were generally deeper in the water column. The depth, temperature, and thermocline preferences of walleye pollock are hypothesized to be linked to food availability which is, in turn, related to temperature regimes or fronts along the Bering Sea shelf slope.
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Lardies, Marco Antonio, Elena Clasing, Jorge M. Navarro und R. A. Stead. „Effects of environmental variables on burial depth of two infaunal bivalves inhabiting a tidal flat in southern Chile“. Journal of the Marine Biological Association of the United Kingdom 81, Nr. 5 (Oktober 2001): 809–16. http://dx.doi.org/10.1017/s0025315401004635.
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The annual pattern of burial depth in natural populations of the infaunal bivalves Tagelus dombeii (Tellinacea) and Venus antiqua (Veneracea) is described in relation to annual food availability in both the water column and the sediment and abiotic factors (temperature and salinity) at Coihuín tidal flat, in southern Chile. A field experiment in which burial depth was measured in situ each month (over 14 months), with the aid of a fixed-length nylon thread attached to the shell. For T. dombeii the results showed a significant increase in burial depth with increasing bivalve size and syphon weight. Tagelus dombeii had a mean burial depth of 17·5 cm, which was three times more than in V. antiqua (5·30 cm). The burial depth dynamics for both species displayed a strong correlation with food availability in the water column. Approximately 60% of the variability in burial depth in T. dombeii and V. antiqua was explained by concentration of chlorophyll-a in the water column. Food concentration on the sediment surface did not effect burial depth, i.e. deposit feeding seems to be of minor significance in either species.
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Ding, Jiawei, Shujiao Pang und Zhenmu Chen. „Hydrodynamic performance study of shore-based oscillating water column wave energy conversion device“. Journal of Physics: Conference Series 2707, Nr. 1 (01.02.2024): 012099. http://dx.doi.org/10.1088/1742-6596/2707/1/012099.
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Abstract To cope with the increasing energy demand, countries have started to actively develop renewable energy. Therefore, the study of wave energy generation devices is an important issue. In this paper, we investigate the performance and characteristics of shore-based oscillating water column wave energy generators concerning structural dimensions such as front wall draft and water depth variation. The results show that the front wall draft have significant effects on the internal flow characteristics of the oscillating water column wave energy generator. When the draft of the front wall changes, the reflection coefficient of the air chamber changes accordingly and the performance changes significantly. The variation of water depth has less effect on the performance of the low-frequency region of the oscillating water column wave energy generation device.
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Andersen, D. T., C. P. Mckay und R. A. Wharton. „Dissolved gases in perennially ice-covered lakes of the McMurdo Dry Valleys, Antarctica“. Antarctic Science 10, Nr. 2 (Juni 1998): 124–33. http://dx.doi.org/10.1017/s0954102098000170.
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Measurements of dissolved N2, O2, Ar, CO2, and CH4 were made in perennially ice-covered Lake Hoare. Results confirm previous reports that O2 concentrations in the upper water column exceed atmospheric equilibrium and that N2 and Ar are supersaturated throughout the water column. The mean supersaturation of N2 was found to be 2.0 (±0.37) and Ar was 3.8 (±1.1). The ratios of N2/Ar (20.3 ±3.8), and O2/Ar (22.5 ±4.0) at the ice-water interface are consistent with those previously measured, suggesting that bubble formation is the main process for removing gas from the lake. However, the saturations of N2 and Ar greatly exceed those previously predicted for degassing by bubble formation only at the ice-water interface. The data support the hypothesis that removal of gas by bubbles occurs in the water column to a depth of 11 m in Lake Hoare. CO2 concentration increases from near zero at the ice-water interface to 80–100 times saturation at and below the chemocline at c. 28 m. There is considerable variability in the gas concentrations throughout the water column; samples separated in depth by one metre may vary by more than 50% in gas content. It is likely that this phenomenon results from the lack of turbulent mixing in the water column. Methane (c. 2 μg 1−1) was detected below the chemocline and immediately above the sediment/water interface at a depth of 30 m. Samples from lakes Vanda, Joyce, and Miers, also show supersaturations of O2, N2, and Ar at levels similar to levels found in Lake Hoare.
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Zhang, Dong, Meng Wang, Xiao-kang Li und A.-qiang Liu. „Experimental Study on the Effect of Initial Water Content and Temperature Gradient on Soil Column Segregation Frost Heave“. Geofluids 2022 (08.10.2022): 1–14. http://dx.doi.org/10.1155/2022/4679547.
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A series of freezing experiments were carried out on the Qinghai silty clay using a one-dimensional soil column particle image velocimetry (PIV) system. The effects of the initial water content and temperature gradient on the frost heave of the soil column were analysed. The experimental results show that the total volumetric water content after the Qinghai silty clay freezing is much greater than the initial water content before freezing, and the total volumetric water content at the segregated layer reaches the maximum value. The average unfrozen water content firstly increases sharply with time and then decreases slowly. The obvious horizontal layered segregation cracks filled with unsaturated needle-columnar ice lenses have occurred above the soil column frozen fringe. The thickness of segregated ice is about 43% of the total frost heave. There is a small frost heave in the frozen fringe and a small compression deformation amount in the unfrozen zone. Under the same temperature gradient conditions, the soil column with the low initial water content has a smaller frozen depth, larger total volumetric water content, more water intake, smaller segregated ice thickness, and less total frost heave amount than that of the soil column with the high initial water content. Under the same initial water content conditions, the soil column with a large temperature gradient has a greater frozen depth, consistent total volumetric water content, larger segregated ice thickness, and greater total frost heave amount than that of the soil column with a small temperature gradient.
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Saputra, L. R., I. M. Radjawane, H. Park und H. Gularso. „Effect of Turbidity, Temperature and Salinity of Waters on Depth Data from Airborne LiDAR Bathymetry“. IOP Conference Series: Earth and Environmental Science 925, Nr. 1 (01.11.2021): 012056. http://dx.doi.org/10.1088/1755-1315/925/1/012056.
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Abstract The influence of seawater parameters cannot be ignored when conducting bathymetric LiDAR (Laser Induced Detection and Ranging or Light Detection and Ranging) surveys such as turbidity, temperature, and salinity. Turbidity affects the attenuation diffusion coefficient of the green laser is penetrating the air column. The comparison of LiDAR bathymetric depth with Secchi disk depth is used as a reference in determining the effect of turbidity. The results are in locations with primarily clear water the ability of LiDAR can penetrate up to 7m, while in turbid waters up to 3m. On average, the ability of the green laser LiDAR bathymetry can penetrate the waters of 1.5-2 times the depth at the location of this study around the bay of Lampung Indonesia. Other water parameters are temperature and salinity. These parameters are used to calculate the refractive index value of water. The Different temperature and salinity values in a water column can result in differences in the accuracy of the bathymetry LiDAR depth of 4-6mm. The influence of water column parameters can be a concern in planning and processing airborne LiDAR altimetry (ALB) surveys.
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Pados, T., R. F. Spielhagen, D. Bauch, H. Meyer und M. Segl. „Oxygen and carbon isotope composition of modern planktic foraminifera and near-surface waters in the Fram Strait (Arctic Ocean) – a case study“. Biogeosciences 12, Nr. 6 (17.03.2015): 1733–52. http://dx.doi.org/10.5194/bg-12-1733-2015.
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Abstract. The upper 500 m of the water column and the sediment surface along an E–W transect in the Fram Strait were sampled for recent planktic foraminifera. The δ18O and δ13C values of the tests are compared to the stable isotope composition of the water samples taken from the same depths, and related to the characteristics of the water column. The polar species Neogloboquadrina pachyderma clearly dominates the species assemblage in the Fram Strait in the early summer, while the subpolar Turborotalita quinqueloba accounts only for 5–23%. In this area the average depth of calcification of N. pachyderma lies between 70–150 m water depth, T. quinqueloba shows a similar range with 50–120 m water depth. The δ18O values of N. pachyderma show an average vital effect of about −1.5‰ compared to calculated equilibrium calcite values. Except for the upper ∼75 m, the vertical profiles of δ13C of the net-sampled shells are nearly parallel to the values measured in the water column with an average offset of −1.6‰ and −3.6‰ for N. pachyderma and T. quinqueloba, respectively. The discrepancy found in the upper ~75 m might indicate an influence of the "carbonate ion effect" on the carbon isotope incorporation in the tests. Oxygen and carbon isotopes from the sediment surface yield higher values than those from the water column for both species. This may be because specimens from the water column reflect a modern snapshot only, while tests from surface sediments record environmental parameters from the past ~1000 years.
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Pados, T., R. F. Spielhagen, D. Bauch, H. Meyer und M. Segl. „Oxygen and carbon isotope composition of modern planktic foraminifera and near-surface waters in the Fram Strait (Arctic Ocean) – a case-study“. Biogeosciences Discussions 11, Nr. 6 (11.06.2014): 8635–72. http://dx.doi.org/10.5194/bgd-11-8635-2014.
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Abstract. The upper 500 m of the water column and the sediment surface along an E–W transect in the Fram Strait were sampled for recent planktic foraminifera. The δ18O and δ13C values of the tests are compared to the stable isotope composition of water samples taken from the same depths, and related to the characteristics of the water column. The polar species Neogloboquadrina pachyderma (sin.) clearly dominates the species assemblage in the Fram Strait in the early summer, while the subpolar Turborotalita quinqueloba accounts only for 5–23%. In this area the average depth of calcification of N. pachyderma (sin.) lies between 70–150m water depth, T. quinqueloba shows a similar range with 50–120 m water depth. The δ18O values of N. pachyderma (sin.) show an average vital effect of about −1.5‰ compared to calculated equilibrium calcite values. Except for the upper ~ 75 m, the vertical profiles of δ13C of the net-sampled shells are nearly parallel to the values measured in the water column with an average offset of −1.6‰ and −3.6‰ for N. pachyderma (sin.) and T. quinqueloba, respectively. The discrepancy found in the upper ~ 75 m might indicate the influence of the "carbonate ion effect" on the carbon isotope incorporation in the tests. Oxygen and carbon isotopes from the sediment surface yield higher values than those from the water column for both species. This may be because specimens from the water column reflect a modern snapshot only, while tests from surface sediments record environmental parameters from the past ~ 1000 years.
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Singh, Tej Pratap, Sanjoy Ghosh und Majumder Cb. „TREATMENT OF FLUORIDE BEARING CONTAMINATED WATER USING SIMULTANEOUS ADSORPTION AND BIODEGRADATION IN A LABORATORY SCALE UP: FLOW BIO-COLUMN REACTOR BY JAVA PLUM SEED“. Asian Journal of Pharmaceutical and Clinical Research 9, Nr. 9 (01.12.2016): 331. http://dx.doi.org/10.22159/ajpcr.2016.v9s3.14136.
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ABSTRACTObjective: Here, we aimed for the treatment of fluoride bearing contaminated water using simultaneous adsorption and biodegradation in a biocolumnreactor by using java plum seed.Methods: We immobilized Acinetobacter baumannii bacteria on the java plum seed in the bio-column reactor. The water used contained a sample offluoride with concentration of 20 mg/L. The bed depth service time design model and empty bed residence time were used to analyze the performance thebio-column. We examined and observed closely the effect of different operating parameters such as flow rate of bed depth and initial concentration on thissimplified bio-column reactor design model. Desorption experiment was conducted to evaluate the possibilities of regeneration and to reutilize of media.Results: We observed that the bio-column reactor is capable to reduce the concentration of the pollutants in the effluent water below their permissiblelimit. Reduction in DO along the bed height of the reactor was also observed, which supports the aerobic nature of the bacteria.Conclusion: The experimental results were encouraging and indicate that java plum (Syzygium cumini) seed is a feasible option to use as a biosorbentto remove fluoride in the bio-column reactor.Keywords: Bio-reactor, Simultaneous adsorption and biodegradation, Flow rate, Acinetobacter baumannii MTCC 11451, Physicochemical adsorption,Bed depth service time, Empty bed residence time.
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Jiang, Jing Bo, Zuo Tao Ni, Si Ren Li und De Jun Gong. „A Wave-Powered Technique for Water Column Profiling“. Applied Mechanics and Materials 284-287 (Januar 2013): 1739–43. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.1739.
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A technique using surface wave energy to move a sensor platform up and down a mooring wire is introduced in this paper. It permits a complete vertical profile to be obtained with a single sensor, eliminating the need for multiple sensors on the mooring line. The sensor platform can be pre-programmed to dwell at depth for set periods of time. The platform can be configured to carry a variety of payloads including CTD, optical and acoustic sensors.
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Rasheed, Sajida, Luiza C. Campos, Jong K. Kim, Qizhi Zhou und Imran Hashmi. „Optimization of total trihalomethanes' (TTHMs) and their precursors' removal by granulated activated carbon (GAC) and sand dual media by response surface methodology (RSM)“. Water Supply 16, Nr. 3 (30.12.2015): 783–93. http://dx.doi.org/10.2166/ws.2015.175.
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A response surface methodology (RSM) applying central composite design with rotatable full factorial (14 non-center and six center points) was used to discern the effect of granular activated carbon (GAC), sand and pH on total trihalomethanes (TTHMs) and humic acid (HA) removal from drinking water. Results showed efficient TTHMs and HA removal by GAC while a sand column showed little effect for TTHMs but was significant for total organic carbon (TOC) removal. With GAC and a sand column of 4 cm, a pH increase from 6 to 8 caused an increase in TTHM removal from 79.8 to 83.6% while a decrease in HA removal from 26.6 to 6.6% was observed. An increase in GAC column depth from 10 to 20 cm caused a slight increase in TTHM removal from 99.4 to 99.7%, while TOC removal was increased from an average of 38.85% to 57.4% removal. The developed quadratic model for TTHM removal (p = 0.048) and linear model for TOC removal (p = 0.039) were significant. GAC column depth (p < 0.0117) and column depth2 (p < 0.039) were the most significant factors. A 98% TTHMs, 30%TOC and 51% residual chlorine removal were optimized at 9 cm GAC and 4 cm sand column depth at pH 8 with desirability factor (D) 0.64.
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Kingsford, M. J., und R. G. Cole. „Vertical distribution patterns of ichthyoplankton in temperate waters of New Zealand“. Marine and Freshwater Research 73, Nr. 4 (31.01.2022): 503–19. http://dx.doi.org/10.1071/mf21282.
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Multifactorial sampling designs were used to determine the vertical distribution of ichthyoplankton at multiple temporal and spatial scales in New Zealand. Hypotheses concerning the vertical distribution of fish larvae were tested in the following: depth strata, surface, near-surface, mid-depth and deep, and near the substratum. The consistency of abundance patterns was examined at three sites separated by 2–20 km over 2 months. We also tested for differences in shallow water columns of two depths (20 and 40 m) and both day and night. Although peak abundance of total larval fish was found at upper and lower strata, regardless of total depth of the water column, consistent taxa specific patterns of vertical distribution were also found. Some taxa were most abundant at the surface (e.g. mullids, hemiramphids, and kyphosids), whereas others were found at multiple depths below the surface and throughout the water column, regardless of site, time or depth of water column (e.g. carangids, engraulids, clupeids, scombrids, sparids and pleuronectids). Some taxa were most abundant in shallow water columns (e.g. mullids, tripterygiids and gobiids). Rank abundance by depth stratum for non-surface dwelling species varied among sites and times. Diel vertical movements were detected, some taxa (e.g. clupeids, scombrids and bothids) that were most abundant at the surface at night whereas for other taxa this pattern was more variable (e.g. carangids). We conclude that diel depth-related patterns in shallow water columns will influence interactions among taxa and the importance of different transport mechanisms for larval transport.
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Jarwinda, A. Badhurahman, G. J. Kusuma und R. S. Gautama. „1-Dimensional numerical modelling of unsaturated water flow and oxygen diffusion in overburden material column using hydrus 1-D“. IOP Conference Series: Earth and Environmental Science 882, Nr. 1 (01.11.2021): 012064. http://dx.doi.org/10.1088/1755-1315/882/1/012064.
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Abstract Coal mining activities, especially overburden material dumping can cause a negative impact into the environment, i.e., acid mine drainage, Acid mine drainage is characterized as low pH water with high sulphate and metal content produced from sulphidic-bearing overburden material with oxygen and water. In unsaturated condition, both of gaseous and water phases exist, acid mine drainage is generated. This study aims to characterize and model the water content in unsaturated condition and diffusion of oxygen of overburden material using the Hydrus 1-D software in a laboratory-scaled column. Laboratory-scaled column is initially filled with 75-cm height of dry overburden material and subjected into 5-cm constant head water level at the top of the column with free-flow condition at the bottom of column. The modelling result shows the water content of overburden material varies within depth and time elapsed and is saturated between 32400 minutes and 36000 minutes after initial wetting. Diffusivity of oxygen is linearly correlated with the water content of the overburden material at any given time and depth that varies between 1.34 × 10−7 m2/s and 8.80 × 10−12 m2/s. Water content and diffusivity of oxygen is expected to affect the generation of acid mine drainage in the overburden material.
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Fediuk, Annika, Tina Wunderlich, Dennis Wilken und Wolfgang Rabbel. „Ground Penetrating Radar Measurements in Shallow Water Environments—A Case Study“. Remote Sensing 14, Nr. 15 (30.07.2022): 3659. http://dx.doi.org/10.3390/rs14153659.
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In this study, we investigate GPR measurements in freshwater of less than 5 m at four different locations to derive rules of thumb in terms of depth penetration, resolution, and material contrasts of the method for 200 and 400 MHz antennas under field conditions. The objective is to improve the attractiveness of the method for archaeological issues in water, as there are hardly any studies on this subject so far. The depth penetration of 2–4 m is negligibly influenced by the choice of the 200 or 400 MHz antenna. Organic material in the water column also does not affect the water depth but offers new fields of applications for mapping and volume estimation of biomass in lakes with GPR. The horizontal resolution in the cm range in the direction of the profile and in the dm range across the profile could not be improved by the narrow antenna radiation pattern of <30° at the 3 dB level. In the crossline direction, the use of an antenna array would be necessary here. Still, the narrow antenna pattern reduces side reflections. Most common archaeological material contrasts can be resolved with the method. The method shows reflection coefficients >0.1 for materials of <80% porosity to the water column and for materials of <25% porosity and of >45% porosity to water-saturated sand. Large reflection coefficients also show, for example, granite to sand and gyttja to wood. The water column has a considerable effect on the data quality of the 400 MHz antenna from a depth of 2 m due to the antenna ringing. Furthermore, multiples must be expected in a water column <0.5 m. The method can especially complement the common geophysical methods of seismics and geoelectrics to exclude material ambiguities. The major advantage is the simple setting of the land equipment in the water.
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Chu, Peter C., und Chenwu Fan. „Prediction of Falling Cylinder Through Air-Water-Sediment Columns“. Journal of Applied Mechanics 73, Nr. 2 (04.08.2005): 300–314. http://dx.doi.org/10.1115/1.2125975.
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A falling rigid body through air, water, and sediment is investigated experimentally and theoretically. Two experiments were conducted to drop rigid cylinders with density ratio around 1.8 into shallow water (around 13 m deep) in the Monterey Bay (Exp-1) and into the Naval Postgraduate School’s swimming pool (Exp-2). During the experiments, we carefully observe cylinder track and burial depth while simultaneously taking gravity cores (in Exp-1). After analyzing the gravity cores, we obtain the bottom sediment density and shear strength profiles. The theoretical work includes the development of a 3D rigid body impact burial prediction model (IMPACT35) that contains three components: triple coordinate transform and hydrodynamics of a falling rigid object in a single medium (air, water, or sediment) and in multiple media (air-water and water-sediment interfaces). The model predicts the rigid body’s trajectory in the water column and burial depth and orientation in the sediment. The experimental data (burial depth, sediment density, and shear strength) show the capability of IMPACT35 in predicting the cylinder’s trajectory and orientation in a water column and burial depth and orientation in sediment.
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Sæbø, Torstein O., Roy E. Hansen, Stig A. Synnes und Ole E. Lorentzen. „Depth estimation of water column objects using interferometric synthetic aperture sonar“. Journal of the Acoustical Society of America 141, Nr. 5 (Mai 2017): 4042. http://dx.doi.org/10.1121/1.4989341.
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Kovač, Žarko, Trevor Platt, Živana Ninčević Gladan, Mira Morović, Shubha Sathyendranath, Dionysios Raitsos, Branka Grbec, Frano Matić und Jere Veža. „A 55-Year Time Series Station for Primary Production in the Adriatic Sea: Data Correction, Extraction of Photosynthesis Parameters and Regime Shifts“. Remote Sensing 10, Nr. 9 (12.09.2018): 1460. http://dx.doi.org/10.3390/rs10091460.
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In 1962, a series of in situ primary production measurements began in the Adriatic Sea, at a station near the island of Vis. To this day, over 55 years of monthly measurements through the photic zone have been accumulated, including close to 3000 production measurements at different depths. The measurements are conducted over a six-hour period around noon, and the average production rate extrapolated linearly over day length to calculate daily production. Here, a non-linear primary production model is used to correct these estimates for potential overestimation of daily production due to linear extrapolation. The assimilation numbers are recovered from the measured production profiles and subsequently used to model production at depth. Using the recovered parameters, the model explained 87% of variability in measured normalized production at depth. The model is then used to calculate daily production at depth, and it is observed to give on average 20% lower daily production at depth than the estimates based on linear extrapolation. Subsequently, water column production is calculated, and here, the model predicted on average 26% lower water column production. With the recovered parameters and the known magnitude of the overestimation, the time-series of water column production is then re-established with the non-linearly-corrected data. During this 55-year period, distinct regimes were observed, which were classified with a regime shift detection method. It is then demonstrated how the recovered parameters can be used in a remote sensing application. A seasonal cycle of the recovered assimilation number is constructed along with the seasonal cycle of remotely-sensed chlorophyll. The two are then used to model the seasonal cycle of water column production. An upper and a lower bound on the seasonal cycle of water column production based on remotely-sensed chlorophyll data are then presented. Measured water column production was found to be well within the range of remotely-sensed estimates. With this work, the utility of in situ measurements as a means of providing information on the assimilation number is presented and its application as a reference for remote sensing models highlighted.
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Li, Xuemei, Zihao Meng, Kang Chen, Feifei Hu, Lu Liu, Tingbing Zhu und Deguo Yang. „Comparing diversity patterns and processes of microbial community assembly in water column and sediment in Lake Wuchang, China“. PeerJ 11 (05.01.2023): e14592. http://dx.doi.org/10.7717/peerj.14592.
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The study compare the diversity patterns and processes of microbial community assembly in the water and sediment of Lake Wuchang (China) using high-throughput sequencing of 16S rRNA gene amplicons. A higher microbial α-diversity in the sediment was revealed (P < 0.01), and the most common bacterial phyla in water column were Proteobacteria, Cyanobacteria and Actinobacteria, while Proteobacteria, Acidobacteria, Chloroflexi and Nitrospirae were dominant in sediment. Functions related to phototrophy and nitrogen metabolism primarily occurred in the water column and sediment, respectively. The microbial communities in water column from different seasons were divided into three groups, while no such dispersion in sediment based on PCoA and ANOSIM. According to Pearson correlation analysis, water temperature, dissolved oxygen, water depth, total nitrogen, ammonium, and nitrite were key factors in determining microbial community structure in water column, while TN in sediment, conductivity, and organic matter were key factors in sediment. However, the stochastic processes (|βNTI| < 2) dominated community assembly in both the water column and sediment of Lake Wuchang. These data will provide a foundation for microbial development and utilization in lake water column and sediment under the circumstances of increasing tendency of lake ecological fishery in China.
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di Sarra, A., D. Fuà und D. Meloni. „Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth“. Atmospheric Chemistry and Physics Discussions 13, Nr. 1 (08.01.2013): 527–48. http://dx.doi.org/10.5194/acpd-13-527-2013.
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Abstract. Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer. The wave occurred during an event of Saharan dust at Lampedusa. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation to the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e. the radiative perturbation to the net surface irradiance produced by a unit optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at 60° solar zenith angle is −(181 ± 17) W m−2 in the shortwave, and −(83 ± 7) W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively.
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Cai, Jinlong, Min Tu und Wensong Xu. „Failure Depth of a Floor of a Fully Mechanized Working Face When Passing a Collapse Column“. Advances in Civil Engineering 2018 (16.09.2018): 1–9. http://dx.doi.org/10.1155/2018/9406839.
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The stress change law of a collapse column and the failure depth of a coal seam floor before and after mining when the fully mechanized coal mining face passes through the collapse column are investigated. Here, we present the constructed program in FISH language, render the damage variable in FLAC3D to establish the numerical model, and complete the numerical calculation. The 10–115 working faces that pass the collapse column at a coal mine in Tuanbai are identified as the research object. The floor failure is numerically simulated to assess the damage. The following results were obtained: the failure depth of the full floor is stabilized at 14.6 m; the maximum failure depth of the floor near the collapse column is 18.2 m; and the stress concentration coefficient is 1.27 times greater than that of normal mining. The calculated depth failure of the floor of the working face without structural defects is 14.6–14.7 m based on the Hoek–Brown criterion. With the collapse column, the failure depth of the floor is 16.8–17.8 m. According to the water injection test, the maximum failure depth of the floor is 18 m. The three derived values agree well with one another.
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Reiter, Edmund C., M. Nafi Toksöz, Timothy H. Keho und G. M. Purdy. „Imaging with deep‐water multiples“. GEOPHYSICS 56, Nr. 7 (Juli 1991): 1081–86. http://dx.doi.org/10.1190/1.1443119.
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Acquisition of on‐bottom hydrophone data recording of a near‐surface source provides an opportunity to treat water column multiples as useful signal. A ray‐equation based Kirchhoff depth migration is used to image primary reflections and deep‐water multiples recorded on an Ocean Bottom Hydrophone (OBH). The image of the subbottom sediments is shown to be improved by inclusion of the deep‐water multiple in the imaging process. Field data, jointly acquired by Woods Hole Oceanographic Institute and University of Texas Institute for Geophysics at Austin and consisting of an OBH (2300 m depth) recording a 10 800 cubic inch air gun array, are used to illustrate the feasibility of the technique. Images are obtained from both the primary reflections and from energy that has undergone an additional passage through the water column. Comparison of these images reveals an excellent correlation of reflectors with the predicted polarity reversal observed in the multiple’s image. Synthetic data are used to examine the difficulties in identifying the true path of the water column multiple. For flat‐layered media there are two different multiple paths — one that reflects beneath the source and one that reflects over the receiver — which have identical traveltimes. They do not, however, have the same amplitude, and it can be shown that their amplitudes differ sufficiently to allow a reliable image to be extracted from the energy that reflects over the receiver. As a final step, the image obtained from the multiple is corrected for the π phase shift from the free surface and added to the image from the primary reflection. This approach is limited to areas where water depths allow reliable separation of primary reflections from water column multiples. Application of this technique allows the utilization of coherent deep water multiples and results in both extended lateral coverage and an increased signal‐to‐noise ratio in the final image.
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Chow, Aaron C., Ishita Shrivastava, E. Eric Adams, Fahed Al-Rabaie und Bader Al-Anzi. „Unconfined Dense Plunging Jets Used for Brine Disposal from Desalination Plants“. Processes 8, Nr. 6 (15.06.2020): 696. http://dx.doi.org/10.3390/pr8060696.
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Laboratory experiments were conducted to measure entrained air bubble penetration depth and dilution of a dense vertical unconfined plunging jet to evaluate its performance as an outfall to dilute brine from desalination plants as well as a means to aerate water column. Experiments involved neutrally buoyant or dense plunging jets discharging in quiescent receiving water. The density difference between effluent and receiving water, the plunging jet length (height above water surface), and the receiving water salinity were varied in the experiments. Observed penetration depth for neutrally buoyant jets was somewhat greater than previously reported, and increased modestly with jet density. Increasing density also resulted in an increasing number of fine bubbles descending together with the dense plume. These observations can help guide the design of plunging jets to mitigate anoxic conditions in the water column when brine is introduced to a receiving water body, as with seawater desalination.
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Bonelli, Ana G., Paulina Martin, Phillip Noel und Gregory P. Asner. „Global Chlorophyll Concentration Distribution and Effects on Bottom Reflectance of Coral Reefs“. Oceans 5, Nr. 2 (10.04.2024): 210–26. http://dx.doi.org/10.3390/oceans5020013.
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Despite the limited coverage of coral reefs in the world’s oceans, they play a crucial role in global marine biodiversity and providing essential ecosystem services. This study explores the influence of chlorophyll-a (Chl-a) concentration in the water column on the estimation of bottom reflectance (rb) in coral reefs monitored by the Allen Coral Atlas coral reef monitoring system, using satellite imagery from a Sentinel-2 MSI sensor. We conducted a comprehensive analysis, considering Chl-a global distribution and variability, and its combined effect with water column depth over rb calculation. Our results demonstrated that the impact of Chl-a on rb estimation becomes significant when the water column depth exceeds 3 m. While suggesting the optionality of using regional Chl-a values, our study highlights potential overestimations of Chl-a in optically complex environments, such as along the Brazilian coast. This research contributes to refining coral reef monitoring systems and underscores the importance of accurate Chl-a assessments for robust environmental evaluations.
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Ciuffardi, Tiziana, Zoi Kokkini, Maristella Berta, Marina Locritani, Andrea Bordone, Ivana Delbono, Mireno Borghini et al. „Deep-water hydrodynamic observations around a cold-water coral habitat in a submarine canyon in the eastern Ligurian Sea (Mediterranean Sea)“. Earth System Science Data 15, Nr. 5 (09.05.2023): 1933–46. http://dx.doi.org/10.5194/essd-15-1933-2023.
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Abstract. A 2-year dataset of a stand-alone mooring, deployed in November 2020 down the Levante Canyon in the eastern Ligurian Sea, is presented. The Levante Canyon Mooring (LCM) is a deep submarine multidisciplinary observatory positioned at 608 m depth in a key ecosystem area. The Levante Canyon hosts a valuable and vulnerable ecosystem of deep-living cold-water corals (CWCs), studied and monitored since 2013 through integrated mapping of the seabed and water column. The 2-year dataset, acquired on the mooring and presented here (data from November 2020 to October 2022), includes measurements conducted with both current meters and conductivity–temperature–depth (CTD) probes and provides information about the hydrodynamics and thermohaline properties across almost the entire water column. The observatory is still ongoing, and the dataset is regularly updated. All the described data are publicly available from https://doi.org/10.17882/92236 (Borghini et al., 2022). They must therefore be preserved and are of considerable scientific interest.
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Knobles, David P., Tracianne B. Neilsen, William Hodgkiss, Preston S. Wilson und James H. Miller. „Mid-frequency sound propagation over a mud seabed with a compressional sound speed depth gradient“. Journal of the Acoustical Society of America 153, Nr. 3_supplement (01.03.2023): A86. http://dx.doi.org/10.1121/10.0018260.
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During Seabed Characterization Experiment 2017 in the New England Mudpatch under near isospeed conditions of the water column, observations were made of well-defined intensity striations in time-frequency spectrograms in the 1.5–4.0 kHz band. These observations provided the basis for the hypothesis that the compressional sound speed profile for a homogenous fine-grained sediment possessed a gradient in the upper portions of the seabed. This hypothesis was tested with a statistical inference method that extracts probability density functions for parameter values representing an empirical-based nonlinear profile whose origins go back to Hamilton. Inferred was a surface sound speed that is less than the sound speed of the water at the seafloor and a surface sound speed gradient of about 6 1/s. In 2022 the experiment was repeated during non-isospeed conditions of the water column. The results for 2017 and 2022 are compared with the intent of understanding the response of the geoacoustic properties of the upper portions of a fine-grained sediment to changes in the bottom water temperature and salinity of the water column. [Work supported by Office of Naval Research.]
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Zhang, Yu Guo, Ya Dong Bian und Kang He Xie. „Consolidation Theory for Composite Ground with Granular Columns Based on Different Calculation Models“. Advanced Materials Research 261-263 (Mai 2011): 1534–38. http://dx.doi.org/10.4028/www.scientific.net/amr.261-263.1534.
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The consolidation of the composite ground under non-uniformly distributed initial excess pore water pressure along depth was studied in two models which respectively considering both the radial and vertical flows in granular column and the vertical flow only in granular column, and the corresponding analytical solutions of the two models were presented and compared with each other. It shows that the distribution of initial excess pore water pressure has obvious influence on the consolidation of the composite ground with single drainage boundary, and the rate of consolidation considering the radial-vertical flow in granular column is faster than that considering the vertical flow only in granular column.
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Xu, Bin Bin, Kentaro Nakai und Toshihiro Noda. „Seismic Stability Analysis of Light-Weight Column Considering Depth of Liquefiable Layer“. Applied Mechanics and Materials 638-640 (September 2014): 1956–60. http://dx.doi.org/10.4028/www.scientific.net/amm.638-640.1956.
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A series of light-weight column for receiving the wireless signals to control the stoppage of gas supply are built on the liquefiable ground and their seismic stability should be precisely investigated to prevent the second accident. For the conventional judgment of liquefiable ground, if the soil type of the ground surface is the same, the potential liquefaction of the ground is also the same. In this paper, based on the soil-water coupled finite element method the influence of the depth of the liquefiable layer is taken into consideration and it is found that the seismic stability of the column varies significantly depending on the depth of liquefiable layer even though the embedment depth of the column is the same. Therefore, it is necessary to con-sider the depth of liquefiable layer for the high accuracy analysis.
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Niroumand-Jadidi, Milad, Nima Pahlevan und Alfonso Vitti. „Mapping Substrate Types and Compositions in Shallow Streams“. Remote Sensing 11, Nr. 3 (29.01.2019): 262. http://dx.doi.org/10.3390/rs11030262.
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Remote sensing of riverbed compositions could enable advances in hydro-morphological and habitat modeling. Substrate mapping in fluvial systems has not received as much attention as in nearshore, optically shallow inland, and coastal waters. As finer spatial-resolution image data become more available, a need emerges to expand research on the remote sensing of riverbed composition. For instance, research to date has primarily been based on spectral reflectance data from above the water surface without accounting for attenuation by the water-column. This study analyzes the impacts of water-column correction for substrate mapping in shallow fluvial systems (depth < 1 m). To do so, we performed three different experiments: (a) analyzing spectroscopic measurements in a hydraulic laboratory setting, (b) simulating water-leaving radiances under various optical scenarios, and (c) evaluating the potential to map bottom composition from a WorldView-3 (WV3) image of a river in Northern Italy. Following the retrieval of depth and diffuse attenuation coefficient ( K d ), bottom reflectances were estimated using a water-column correction method. The results indicated significant enhancements in streambed maps based on bottom reflectances relative to maps produced from above-water spectra. Accounting for deep-water reflectance, embedded in the water-column correction, was demonstrated to have the greatest impact on the retrieval of bottom reflectance in NIR bands, when the water column is relatively thick (>0.5 m) and/or when the water is turbid. We also found that the WV3’s red-edge band (i.e., 724 nm) considerably improved the characterization of submerged aquatic vegetation (SAV) densities from either above-water or retrieved bottom spectra. This study further demonstrated the feasibility of mapping SAV density classes from a WV3 image of the Sarca River in Italy by retrieving the bottom reflectances.
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di Sarra, A., D. Fuà und D. Meloni. „Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth“. Atmospheric Chemistry and Physics 13, Nr. 11 (10.06.2013): 5647–54. http://dx.doi.org/10.5194/acp-13-5647-2013.
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Abstract. Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi-periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer, as also confirmed by satellite images. The wave occurred during a Saharan dust event. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation of the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e., the radiative perturbation of the net surface irradiance produced by a unit of optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at about 60° solar zenith angle is −(181 ± 17) W m−2 in the shortwave, and −(83 ± 7) W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively.
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Lawrence, Jade P., Peter T. Doran, Luke A. Winslow und John C. Priscu. „Subglacial brine flow and wind-induced internal waves in Lake Bonney, Antarctica“. Antarctic Science 32, Nr. 3 (13.02.2020): 223–37. http://dx.doi.org/10.1017/s0954102020000036.
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AbstractBrine beneath Taylor Glacier has been proposed to enter the proglacial west lobe of Lake Bonney (WLB) as well as from Blood Falls, a surface discharge point at the Taylor Glacier terminus. The brine strongly influences the geochemistry of the water column of WLB. Year-round measurements from this study are the first to definitively identify brine intrusions from a subglacial entry point into WLB. Furthermore, we excluded input from Blood Falls by focusing on winter dynamics when the absence of an open water moat prevents surface brine entry. Due to the extremely high salinities below the chemocline in WLB, density stratification is dominated by salinity, and temperature can be used as a passive tracer. Cold brine intrusions enter WLB at the glacier face and intrude into the water column at the depth of neutral buoyancy, where they can be identified by anomalously cold temperatures at that depth. High-resolution measurements also reveal under-ice internal waves associated with katabatic wind events, a novel finding that challenges long-held assumptions about the stability of the WLB water column.
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Mueller, Benjamin, Erik H. Meesters und Fleur C. van Duyl. „DOC concentrations across a depth-dependent light gradient on a Caribbean coral reef“. PeerJ 5 (12.06.2017): e3456. http://dx.doi.org/10.7717/peerj.3456.
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Photosynthates released by benthic primary producers (BPP), such as reef algae and scleractinian corals, fuel the dissolved organic carbon (DOC) production on tropical coral reefs. DOC concentrations near BPP have repeatedly been observed to be elevated compared to those in the surrounding water column. As the DOC release of BPP increases with increasing light availability, elevated DOC concentrations near them will, in part, also depend on light availability. Consequently, DOC concentrations are likely to be higher on the shallow, well-lit reef terrace than in deeper sections on the fore reef slope. We measured in situ DOC concentrations and light intensity in close proximity to the reef alga Dictyota sp. and the scleractinian coral Orbicella faveolata along a depth-dependent light gradient from 5 to 20 m depth and compared these to background concentrations in the water column. At 10 m (intermediate light), DOC concentrations near Dictyota sp. were elevated by 15 µmol C L−1 compared to background concentrations in the water column, but not at 5 and 20 m (high and low light, respectively), or near O. faveolata at any of the tested depths. DOC concentrations did not differ between depths and thereby light environments for any of the tested water types. However, water type and depth appear to jointly affect in situ DOC concentrations across the tested depth-dependent light gradient. Corroborative ex situ measurements of excitation pressure on photosystem II suggest that photoinhibition in Dictyota sp. is likely to occur at light intensities that are commonly present on Curaçaoan coral reefs under high light levels at 5 m depth during midday. Photoinhibition may have thereby reduced the DOC release of Dictyota sp. and DOC concentrations in its close proximity. Our results indicate that the occurrence of elevated DOC concentrations did not follow a natural light gradient across depth. Instead, a combination of multiple factors, such as water type, light availability (including the restriction by photoinhibition), and water movement are proposed to interactively determine the DOC concentrations in the close vicinity of BPP.
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Schmale, O., M. Blumenberg, K. Kießlich, G. Jakobs, C. Berndmeyer, M. Labrenz, V. Thiel und G. Rehder. „Microbial methane oxidation at the redoxcline of the Gotland Deep (Central Baltic Sea)“. Biogeosciences Discussions 9, Nr. 7 (20.07.2012): 8783–805. http://dx.doi.org/10.5194/bgd-9-8783-2012.
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Abstract. Methane concentrations in the stratified water column of the Gotland Deep (Central Baltic Sea) show a strong gradient from high values in the saline deep water (max. 504nM) to low concentrations in the less dense, brackish surface water (about 4 nM). The steepest gradient is present within the redoxcline (between 115 and 135 m water depth) that separates the anoxic deep part from the oxygenated surface water, implying a methane consumption rate of 0.28 nM d−1. The process of microbial methane oxidation within the redoxcline is mirrored by a shift of the stable carbon isotope ratio of methane between the bottom water (δ13C CH4 = −82.4‰) and the suboxic depth interval (δ13C CH4 = −38.7‰). A water column sample from 100 m water depth was studied to identify the microorganisms responsible for the methane turnover at the redoxcline. Notably, methane monoxygenase gene expression analyses for the specific water depth demonstrated that accordant methanotrophic activity was due to only one microbial phylotype. An imprint of these organisms on the particular organic matter was revealed by distinctive lipid biomarkers showing bacteriohopanepolyols and lipid fatty acids characteristic for aerobic type I methanotrophic bacteria (e.g. 35-aminobacteriohopane-30,31,32,33,34-pentol). In conjunction with earlier findings, our results support the idea that biogeochemical cycles in Central Baltic Sea redoxclines are mainly driven by only a few microbial key species.
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Wells, Mathew, und Parthiban Nadarajah. „The Intrusion Depth of Density Currents Flowing into Stratified Water Bodies“. Journal of Physical Oceanography 39, Nr. 8 (01.08.2009): 1935–47. http://dx.doi.org/10.1175/2009jpo4022.1.
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Abstract Theory and laboratory experiments are presented describing the depth at which a density current intrudes into a linearly stratified water column, as a function of the entrainment ratio E, the buoyancy flux in the dense current B, and the magnitude of the stratification N. The main result is that Z ∼ E−1/3B1/3/N. It is shown that the depth of the intrusion scales as Z ∼ (3 ± 1)B1/3/N for laboratory experiments, and as for oceanic density currents. The velocity of a large-scale density current is controlled by a geostrophic balance defined as Ugeo = 0.25g′s/f, where s is the slope and f is the Coriolis parameter. The geostrophic buoyancy flux is then defined by Bgeo = g′Ugeoh, with g′ the reduced gravity and h the thickness of the current. The scaling herein implies that the depth of an oceanic intrusion is relatively insensitive to changes in source water properties but is very sensitive to changes in the stratification of the water column, consistent with the previous scaling of Price and Baringer. For example, if the buoyancy flux of a dense current were to double while the stratification remained constant, then there would only be a 25% increase in the intrusion depth, whereas doubling the stratification would result in a 50% decrease of the intrusion depth.
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Khan, U. T., C. Valeo, A. Chu und B. van Duin. „Bioretention cell efficacy in cold climates: Part 2 — water quality performance“. Canadian Journal of Civil Engineering 39, Nr. 11 (November 2012): 1222–33. http://dx.doi.org/10.1139/l2012-111.
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Field and column experiments were conducted to test the ability of bioretention cells to improve urban runoff quality. The effects of cold climate conditions, media depth, long-term operation, and extreme loading were analyzed. Field experiments demonstrated significant decrease in contaminant mass, which was a function of the large runoff volume capture. Significant decreases in concentration for sediment (96%), biochemical oxygen demand (BOD, 8%), and total phosphorus (0.6%) were noted. Long-term simulation experiments demonstrated a decrease in effluent concentration over time, suggesting a dependence on media chemistry. Sediment and BOD capture remained high throughout the testing period. Media depth did not impact performance in laboratory experiments. Extreme loading experiments proved that the effluent concentration of contaminants was independent of the influent concentration. Cold climate conditions did not have a significant impact on performance in both field and column experiments.