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Pujate, Agnese, Karina Stankevica, Laimdota Kalnina, Maris Klavins, Aija Cerina, Anda Drucka e Kristaps Kiziks. "Records of the anthropogenic influence on different origin lake sediments of Latvia". Baltica 28, n. 2 (11 dicembre 2015): 135–50. http://dx.doi.org/10.5200/baltica.2015.28.12.
Testo completoAbstract (sommario):
Sediments in lakes have formed under the conditions of sensitive ecosystem functions as archives of micro- and macrocomponents. Besides others, lake sediments preserve palaeobotanical and chemical evidence reflecting environmental changes. During the last centuries, sediment composition has been influenced also by inconsistent urban and industrial developments. This paper represents the results of chemical and palaeobotanical signatures in the sediments from four lakes of different origin: Lake Lilaste, Lake Velnezers, Lake Engure, and Lake Vevers. The data were compared with the results from sediment composition analysis obtained by Loss on Ignition and chemical methods taking into account changes in plant macroremains. The studies of lake sediments revealed that human impact is recognisable in the upper sediment layer of all investigated sites, but at different depth from sediment surface. The most recognisable traces of anthropogenic influence can be attributed to the sharp increase of the amount of lead (Pb) and number of plant macroremains in analysed lake sediments.
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Wu, Chao, Xiaodong Wu, Xuguang Ge, Lian Feng, Ya Tan, Jiuyun Yang, Weixiang Ren e Min Zou. "Characteristics of Dissolved Organic Matter in Sediments of Typical Lakes in Southeastern Hubei Province, China". International Journal of Environmental Research and Public Health 19, n. 12 (16 giugno 2022): 7402. http://dx.doi.org/10.3390/ijerph19127402.
Testo completoAbstract (sommario):
This study aimed to reveal the distribution characteristics and sources of dissolved organic matter (DOM) in sediments of typical lakes in the southeastern of the Hubei province and provide a reference for pollution control of eutrophic lakes. The sediments of four typical lakes (Liangzi, Baoan, Daye, and Qingshan) in the southeastern of the Hubei Province were investigated in May 2019. Ultraviolet-visible (UV-Vis) absorption spectroscopy and excitation-emission matrixes characteristics of DOM were obtained by UV-Vis spectrophotometry and three-dimensional fluorescence spectroscopy. Moreover, the DOM fluorescence components were resolved by parallel factor analysis (PARAFAC). The results showed that: (1) The absorption coefficient a350 in surface sediments followed the order: Baoan Lake (16.99 ± 3.82 m−1) > Qingshan Lake (15.37 ± 3.8 m−1) > Liangzi Lake (12.54 ± 5.58 m−1) > Daye Lake (12.43 ± 1.43 m−1). Specifically, with increasing depth in the sediment cores, a350 increased and then gradually decreased in Daye Lake and Baoan Lake, but fluctuated in Liangzi Lake and Qingshan Lake with a roughly decreasing trend. (2) Two humic-like components (C1, C2) and one protein-like component (C3) were identified via PARAFAC. This analysis also showed that the surface sediment fluorescent dissolved organic matter (FDOM) was dominated by protein-like, while the sediment core FDOM was dominated by humic-like in Liangzi Lake. The proportion of humic-like in FDOM was higher than protein-like in surface sediments and sediment cores of Baoan, Daye, and Qingshan Lakes. (3) The DOM of surface sediments in the Liangzi Lake comprised mostly autochthonous components, mainly produced by the vital activities of aquatic organisms. The DOM of surface sediments in Baoan Lake and Qingshan Lake showed weak humic and moderate autochthonous characteristics. The humification of DOM in sediment cores of Liangzi, Baoan, and Qingshan Lakes gradually decreased from depth to the surface. The DOM in surface sediments of Daye Lake had strong humic and moderate autochthonous characteristics. (4) In general, the DOM of lake sediments in southeastern Hubei Province has dual-contribution characteristics representing terrigenous and endogenous sources. In the restoration and treatment of lake ecology, both internal and terrestrial pollution should be considered. At the same time, it is noteworthy that cyanobacteria depletion and aquatic residues caused potential internal pollution.
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Luo, Wenguang, Yan Pan, Yangzhen Fan, Jing Lu e Senlin Zhu. "Distribution Patterns of Sediment Organic Carbon Stocks in Shallow Lakes and the Significance for Sustainable Lake Management: Chaohu Lake in Eastern China as a Case Study". Land 13, n. 4 (12 aprile 2024): 507. http://dx.doi.org/10.3390/land13040507.
Testo completoAbstract (sommario):
Shallow lake sediments have huge potential for carbon storage, but they are vulnerable to various environmental changes and are highly susceptible to becoming a source of carbon emissions. Understanding the amount of sediment carbon storage can provide information about the potential of shallow lakes in mitigating climate change. In this study, sediment sampling was conducted at 12 study sites in Chaohu Lake, China, and sediment water content, grain size, bulk density, and sediments organic carbon (SOC) content were examined in five layers along the vertical direction, respectively, and the distribution and storage of SOC were estimated. The results showed that the surface sediments in the west lake area of Chaohu Lake would release 66,300 tons of SOC to the overlying water body in the future. The sediments in the middle lake area and the east lake area will absorb another 15,900 t and 17,300 t of TOC from the water body in the future, respectively. Overall, the lake-wide sediments will release 33,100 t of SOC into the water body in the future. In addition, the results of the study also indicate that human activities are another major influence on the change in organic carbon stocks in lake sediments, and therefore, proactive measures for the restoration and protection of lake sediments are essential because increasing the SOC stocks in the sediments and maintaining the lakes in a sustainable manner can contribute to the crucial role they play in mitigating climate change.
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Nik Daud, Nik Norsyahariati, Nur Safrah Anuar, Zainuddin Yusoff e Amimul Ahsan. "Assessment of Lake Sediments Properties and Contaminations Level". Advanced Materials Research 610-613 (dicembre 2012): 2100–2103. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.2100.
Testo completoAbstract (sommario):
Sediments are principal carriers of the trace elements in the hydrosphere. Properties of the sediment (such as grain size, specific surface area and pore volume) decide the concentration level of the pollutant contain in water. The properties of sediment differed in each lake according to the normal geological phenomenon and source of discharge wastewater. The purpose of this study is to investigate the properties and contamination level of the sediment collected from lakes in Universiti Putra Malaysia (UPM). Sediment samples are taken from three different lakes; Lake IT, Lake ENG and Lake PK. These locations are selected due to the type of wastewater has been discharged into the lakes which are from colleges and academic buildings. The sediments were tested in terms of physical, chemical properties and contaminant concentration (Pb, P and Cu). Using the contaminant concentration results; the sediment concentration level of the pollutant of each lakes were referred to the Consensus- Based Sediment Quality Guidelines (CBSQG-2003). The dominant grain sizes of the sediments were found in the range of silt/clay; with the size fraction in the range 12.74% to 12.83%. The specific surface areas of sediments were in the range of 16.3 to 22.5 m2/g with a pore size distribution in the range of 20 to 29 mm3/g. The chemical properties show that the pH values are in normal range; pH 7, TOC values in the range of 10.84 to 12.39% and salinity values in the range of 0.05 to 0.06 dS/m. The contaminant concentrations show that the main heavy metal presents in Lake IT, Lake ENG and Lake PK as Lead (Pb) with 0.033 mg/l, 0.036 mg/L and 0.038 mg/L, respectively. According to the CBSQG-2003, due to the concentration of Lead presents in lakes sediment in UPM area, the sediments were categorised as non-polluted.
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Gyulai, István, János Korponai, Sheila Mumbi A. Wamugi, Jázmin Jakab, Umar Abba Kawu, Andor G. Soltész, Tamás Karches e Uyanga Tumurtogoo. "Cladocera and Geochemical Variables from Core Sediments Show Different Conditions of Hungarian Lakes". Water 16, n. 9 (5 maggio 2024): 1310. http://dx.doi.org/10.3390/w16091310.
Testo completoAbstract (sommario):
Studies on the sediments of lakes with varying trophic status are of particular importance when considering changes in the natural environment. In this study, our objective was to examine subfossil remains of Cladocera species and the relationship between the sedimental Cladocera assemblages and geochemical variables during 11 years of sediment records from northern Hungarian lakes. To achieve this, we compared sedimental cladoceran communities and the geochemistry of the sediment layers among lakes. Among the studied lakes, one was an intermittent lake (KMT: the Kis-Morotva Lake) which dried out in 2012 but was subsequently naturally refilled in 2013 by groundwater affected by the high-water level of the River Tisza. The other type consisted of permanent lakes (SZA: the Szabolcs oxbow lake, TI: the Timár Morotva Lake) that never dried out. The results of the beta diversity analysis show that the deposition of Cladocera communities was similar among the sediment layers of lakes, while the abundance differences contributed significantly to replacement. Subsequently, core sediment samples of the three lakes were compared based on the remains of Cladocera communities and geochemical variables using Adonis (PERMANOVA). The core sediment samples indicate variations in Cladocera communities alongside disparities in geochemical variables across the same lakes. In conclusion, the significance of sediment cores containing the remains of the Cladocera community has grown significantly in the reconstruction of historical ecological and climatic changes.
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Syrykh, Liudmila S. "SEDIMENTATION AS A CLASSIFICATION CRITERION FOR LAKES ON THE EAST EUROPEAN PLAIN". Географический вестник = Geographical bulletin, n. 3 (2023): 19–26. http://dx.doi.org/10.17072/2079-7877-2023-3-19-26.
Testo completoAbstract (sommario):
The article studies lake sedimentation on the East European Plain and adjacent areas. Lake sediment formation is researched in detail in paleolimnology. The main aim of the present study is to describe the features of lake sedimentogenesis on the East European Plain and to identify classes of lakes in accordance with the types of sedimentogenesis. PaleoLake Database, created for the analysis, contains paleolimnological information about the bottom sediments of lakes of the East European Plain and nearby territories. We analyzed 216 lakes located in different climatic and geological zones, for which the most complete information had been collected: lithostratigraphy, age and thickness of bottom sediments, lake coordinates, water depth etc. Claster analysis of the collected data identified three main types of lake sedimentation for the East European Plain. (1) Sedimentation of large deep-water lakes (minerogenic sedimentogenesis of the Pleistocene). The bottom sediments are represented by minerogenic sediments, mainly clays and silts. (2) Sedimentation of isolated lake basins (mineragenic-organogenic sedimentogenesis of the Pleistocene and Holocene). The main feature of the lithostratigraphy is the presence of three main sediment sequences: minerogenic sediments formed in a large reservoir, transitional deposits formed during the isolation, organic deposits of a shallow basin. (3) Sedimentation of lakes located outside maritime transgressions and regressions (organogenic sedimentogenesis of the Holocene). The bottom sediments of such lakes are mainly represented by gyttja.
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Tretjakova, Rasma, e Andris Karpovičs. "MINERAL COMPOSITION OF SOME LATGALE LAKE SEDIMENTS". ENVIRONMENT. TECHNOLOGIES. RESOURCES. Proceedings of the International Scientific and Practical Conference 1 (20 giugno 2019): 304. http://dx.doi.org/10.17770/etr2019vol1.4146.
Testo completoAbstract (sommario):
Our research is focused on sedimentological conditions and postdepositional changes of recent fine grained lake sediments. We used bulk sediment mineralogical composition and grain size distribution as indicators to identify sediment source areas and possible changes during Holocene. We analysed fine grained (clayey) sediments from three Latgale lakes - Zeili, Pauguļi and Plusons, situated in Latgale upland. Lake sediments cover Late Pleistocene glacial deposits – loam and sandy loam. Bulk mineral composition of 6 sediment samples was determined by X-ray diffraction (XRD). Sediments contained typical minerals found in surrounding glacial sediments: rock-forming minerals as quartz, plagioclase, albite, enstatite, dolomite, calcite, and clay minerals - illite, kaolinite. To identify postdepositional changes in lake sediments of Holocene age clay minerals in clay fraction (<2 mkm) should be analysed. Particularly illite, smectite mixed layered minerals - illite/smectite (I/Sm) and chlorite. Additionally, grain size distribution of studied lake sediments was analysed. Accordingly, our studied sediments are clays, silty clays and clayey silts with bimodal particle distribution, except two samples from Zeiļi and Plusons with unimodal distribution.
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Woszczyk, Michał, Wojciech Tylmann, Jan Jędrasik, Tomasz Szarafin, Alfred Stach, Joanna Skrzypczak e Monika Lutyńska. "Recent sedimentation dynamics in a shallow coastal lake (Lake Sarbsko, northern Poland): driving factors, processes and effects". Marine and Freshwater Research 65, n. 12 (2014): 1102. http://dx.doi.org/10.1071/mf13336.
Testo completoAbstract (sommario):
Despite the fact that sediment dynamics in shallow coastal lakes strongly influences lake water quality and is crucial for preserving good quality paleo-records from coastal zones, the depositional processes in coastal lakes have not been thoroughly recognised so far. The present study aims at investigating the relationship between lake water circulation and the distribution of surface sediments, identifying the postdepositional physical mechanisms affecting lake deposits, and estimating the intensity of sediment mixing in a coastal lake on the Baltic coast. Our approach includes analyses of sediment grain size and chemical composition, hydrodynamic modelling and measurements of 210Pb activity in sediment short-cores from various sections of the lake. We showed that the distribution of lithofacies in the lake is explained by hydrodynamic conditions. Enhanced water dynamics reduces spatial extent of organic-rich lacustrine deposits and results in the exposure of relic marine-lagoonal sediments. A major part of the lake sediments is prone to vertical mixing by wind waves to a depth of ≥ 40 cm. Hydrodynamic modelling and 210Pb displayed overall agreement in predicting the depth of sediment mixing. At the same time the limitations of 210Pb as a geochronologic marker in shallow coastal lakes are revealed. It appears that even exponential depth-wise 210Pb distributions may be produced by storm redeposition.
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Nzekwe, Obinna P., Pierre Francus, Guillaume St-Onge, Patrick Lajeunesse, David Fortin, Antoine Gagnon-Poiré, Édouard G. H. Philippe e Alexandre Normandeau. "Recent sedimentation in three adjacent fjord-lakes on the Québec North Shore (eastern Canada): facies analysis, laminae preservation, and potential for varve formation". Canadian Journal of Earth Sciences 55, n. 2 (febbraio 2018): 138–53. http://dx.doi.org/10.1139/cjes-2017-0070.
Testo completoAbstract (sommario):
This paper analyzes short gravity cores sampled along transects in three adjacent deep fjord-lakes (lakes Pentecôte, Walker, and Pasteur) on the Québec North Shore, eastern Canada, to evaluate the distribution of laminated sediments and potential for varve formation. Facies analysis based on lithological description, digital photos, CT-scan images, and bathymetric data allowed for the identification of four main sediment facies, namely laminated sediments, partially laminated sediments, bioturbated sediments, and massive sediments. Direct evidence that Lake Walker undergoes thermal stratification was monitored from 2014 to 2016. Mean sedimentation rates and sedimentation fluxes of postglacial sediments in the distal basin of the three studied lakes are ≤0.12 cm a−1 and 0.03–0.16 g cm−2 a−1, respectively, based on 210Pb, 137Cs, and AMS radiocarbon dating. On the basis of thin section image analysis and 210Pb (CIC) chronology model, Lake Pentecôte contains mainly massive, partially laminated sediments, while Lake Pasteur contains partially laminated sediments and non-annual varve-like sediments. However, Lake Walker contains laminated sediments that are likely varves. The increased potential for laminae preservation observed in Lake Walker compared to lakes Pentecôte and Pasteur is associated with more favourable morphological characteristics including higher relative depth, mean depth, maximum depth, and topographic exposure.
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Tylmann, Wojciech, Paulina Głowacka e Agnieszka Szczerba. "Tracking climate signals in varved lake sediments: research strategy and key sites for comprehensive process studies in the Masurian Lakeland". Limnological Review 17, n. 3 (1 settembre 2017): 159–66. http://dx.doi.org/10.1515/limre-2017-0015.
Testo completoAbstract (sommario):
AbstractLake sediments are excellent archives of environmental and climate change. Especially important are varved sediments which can provide high-resolution (annual) records of those changes. Process studies including limnological measurements, particle flux monitoring and analyses of sediment structures give an opportunity to explain relationships between meteorological conditions, in-lake processes and varve formation. In our study, three lakes were selected in the Masurian Lakeland: Lake Żabińskie, Łazduny and Rzęśniki. These relatively small and deep lakes contain well preserved biogenic varves. The lakes are influenced by the same meteorological conditions but differ in terms of their catchment size, land use, hydrology, lake basin morphology and trophic status. To explore the relationships between different parameters and preservation/transformation of climate signals in the sediments we started systematic limnological measurements in the water column of these lakes, water sampling for hydrochemical analyses, monitoring of modern sedimentation using sediment traps and analysis of topmost varves from short sediment cores. With this comprehensive and high-resolution monitoring program scheduled for at least four years we are going to verify the potential of varves to track short-term meteorological phenomena in lake sediments.
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Young, Thomas C., Joseph V. DePinto, James R. Rhea e Richard D. Scheffe. "Calcite Dose Selection, Treatment Efficiency, and Residual Calcite Fate after Whole-Lake Neutralization". Canadian Journal of Fisheries and Aquatic Sciences 46, n. 2 (1 febbraio 1989): 315–22. http://dx.doi.org/10.1139/f89-042.
Testo completoAbstract (sommario):
A modeling approach guided whole-lake neutralization treatments of two acidic Adirondack lakes and aided examination of treatment efficiency as measured by initial water column dissolution and calcite delivery to sediments, prediction of posttreatment water chemistry, and assessment of the fate of calcite deposited on sediments. The lake model incorporated both dissolution and sedimentation of calcite in a vertically segmented lake assumed to behave as a closed system. Observed short-term calcite dissolution exceeded predictions (75 versus 45%) because (1) dispersion and thermocline presence slowed calcite particle settling; and, (2) CO2 influx altered the chemical environment of the particles. Prior to calcite treatment, the two lakes had sediments with similar base neutralizing capacities (BNC). Quantitatively, minor sediment neutralization resulted from the treatment; however, sediment pH gradients changed from positive to negative downward, and Caτ in surficial sediments increased as sediment BNC decreased. During the subsequent 16 mo of reacidification, sediment chemical characteristics partially returned to pretreatment conditions by contributing alkalinity to the overlying water.
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Vyse, Stuart A., Ulrike Herzschuh, Gregor Pfalz, Lyudmila A. Pestryakova, Bernhard Diekmann, Norbert Nowaczyk e Boris K. Biskaborn. "Sediment and carbon accumulation in a glacial lake in Chukotka (Arctic Siberia) during the Late Pleistocene and Holocene: combining hydroacoustic profiling and down-core analyses". Biogeosciences 18, n. 16 (24 agosto 2021): 4791–816. http://dx.doi.org/10.5194/bg-18-4791-2021.
Testo completoAbstract (sommario):
Abstract. Lakes act as important sinks for inorganic and organic sediment components. However, investigations of sedimentary carbon budgets within glacial lakes are currently absent from Arctic Siberia. The aim of this paper is to provide the first reconstruction of accumulation rates, sediment and carbon budgets from a lacustrine sediment core from Lake Rauchuagytgyn, Chukotka (Arctic Siberia). We combined multiple sediment biogeochemical and sedimentological parameters from a radiocarbon-dated 6.5 m sediment core with lake basin hydroacoustic data to derive sediment stratigraphy, sediment volumes and infill budgets. Our results distinguished three principal sediment and carbon accumulation regimes that could be identified across all measured environmental proxies including early Marine Isotope Stage 2 (MIS2) (ca. 29–23.4 ka cal BP), mid-MIS2–early MIS1 (ca. 23.4–11.69 ka cal BP) and the Holocene (ca. 11.69–present). Estimated organic carbon accumulation rates (OCARs) were higher within Holocene sediments (average 3.53 g OC m−2 a−1) than Pleistocene sediments (average 1.08 g OC m−2 a−1) and are similar to those calculated for boreal lakes from Quebec and Finland and Lake Baikal but significantly lower than Siberian thermokarst lakes and Alberta glacial lakes. Using a bootstrapping approach, we estimated the total organic carbon pool to be 0.26 ± 0.02 Mt and a total sediment pool of 25.7 ± 1.71 Mt within a hydroacoustically derived sediment volume of ca. 32 990 557 m3. The total organic carbon pool is substantially smaller than Alaskan yedoma, thermokarst lake sediments and Alberta glacial lakes but shares similarities with Finnish boreal lakes. Temporal variability in sediment and carbon accumulation dynamics at Lake Rauchuagytgyn is controlled predominantly by palaeoclimate variation that regulates lake ice-cover dynamics and catchment glacial, fluvial and permafrost processes through time. These processes, in turn, affect catchment and within-lake primary productivity as well as catchment soil development. Spatial differences compared to other lake systems at a trans-regional scale likely relate to the high-latitude, mountainous location of Lake Rauchuagytgyn.
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Kļaviņš, Māris, Ilga Kokorīte, Valērijs Rodinovs e Maruta Jankevica. "Past human impact and pollutant loading reconstruction in Lake Engure as a tool for lake basin management". Proceedings of the Latvian Academy of Sciences. Section B. Natural, Exact, and Applied Sciences. 68, n. 1-2 (1 aprile 2014): 31–37. http://dx.doi.org/10.2478/prolas-2014-0003.
Testo completoAbstract (sommario):
Abstract Environmental pollution of lakes and rivers is considered as one of the most important environmental problems. Analysis of nutrient and trace element accumulation in sedimentary phases of lakes can reflect the overall regional pollution level, and the observed accumulation patterns of pollutants in sediment profiles can be used to reconstruct the history of anthropogenic impacts. As pollutants in sediments are associated with other substances, it is important not only to study total concentrations of pollutants, but also their speciation forms. The aim of this study was to describe phosphorus (including speciation forms) and trace element concentrations in sediment profiles of Lake Engure and to evaluate human impact on organic matter accumulation and properties in lake sediments. The concentrations of the studied elements in sediments of Lake Engure are at background levels, which is clearly evident when compared with metal concentrations in lake sediments in West European countries. The analysis of element concentration changes in sedimentary profiles provided information about trends in recent accumulation (within the last 100 years) and on the balance between natural and human-induced accumulation processes. Analysis of nutrient concentrations in sediments aided in identifying background values as targets for lake management activities.
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Moreton, Steven G., Gunhild C. Rosqvist, Sarah J. Davies e Michael J. Bentley. "Radiocarbon Reservoir Ages from Freshwater Lakes, South Georgia, Sub-Antarctic: Modern Analogues from Particulate Organic Matter and Surface Sediments". Radiocarbon 46, n. 2 (2004): 621–26. http://dx.doi.org/10.1017/s0033822200035669.
Testo completoAbstract (sommario):
Lake sediments have the potential to preserve proxy records of past climate change. Organic material suitable for radiocarbon dating often provides age control of such proxy records. Six shallow freshwater lakes on the sub-Antarctic island of South Georgia were investigated for carbon reservoir effects that may influence age-depth profiles from lake sediment records in this important region. Paired samples of particulate organic matter (POM) from the water column and surface sediment (bulk organic carbon) were analyzed by accelerator mass spectrometry 14C. POM in 4 lakes was found to be in equilibrium with the atmosphere (~107% modern), whereas 2 lakes showed significant depletion of 14C. In each lake, the surface sediment ages were older than the paired POM age. Surface sediment ages showed a much greater range of ages compared to the equivalent POM ages, even for lakes located in close proximity. We conclude that sediment disturbance during coring, bioturbation, and periodic resuspension of sediments are likely factors causing the difference in the apparent age of surface sediments.
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Leidonald, R., Z. A. Harahap e A. Muhtadi. "The distribution of Siombak lake sediments, a tropical tidal lake in Indonesia". IOP Conference Series: Earth and Environmental Science 977, n. 1 (1 giugno 2022): 012117. http://dx.doi.org/10.1088/1755-1315/977/1/012117.
Testo completoAbstract (sommario):
Abstract Siombak Lake is one of Indonesia’s tropical tidal lakes located in Medan City, North Sumatra Province. This lake is very dynamic because the lake water level is fluctuating according to the Belawan waters’ tidal (Malacca Strait). This study aims to determine the distribution of sediments in Siombak Lake. The research was conducted from December 2018 - August 2019. The observation locations were taken at 8 points representing all depth layers. The technique used was the filtering analysis using the wet sieve method with stratified sediment filters in different diameters (4.75 mm, 1.7 mm, 250 μm, 850 μm, 150 μm). The data analyzed were weight percentage, texture type, C-organic, the content of nitrogen and phosphorus. The results of the analysis of sediment samples show that there are 3 sediment textures, namely loam, silt loam, and sandy loam. The C- Organic content in the sediments of Siombak Lake ranges from 1.73 - 5.10% at high tide and 1.91-4.40% at low tide. Nitrogen levels in the sediments range from 0.15 - 2.40% at high tide and 0.14-2.35% at low tide. Meanwhile, phosphorus levels in the sediments range between 5.95 - 19.86 ppm at high tide and 1.27-16.35 ppm at low tide.
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Tu, Luyao, Paul Zander, Sönke Szidat, Ronald Lloren e Martin Grosjean. "The influences of historic lake trophy and mixing regime changes on long-term phosphorus fraction retention in sediments of deep eutrophic lakes: a case study from Lake Burgäschi, Switzerland". Biogeosciences 17, n. 10 (20 maggio 2020): 2715–29. http://dx.doi.org/10.5194/bg-17-2715-2020.
Testo completoAbstract (sommario):
Abstract. Hypolimnetic anoxia in eutrophic lakes can delay lake recovery to lower trophic states via the release of sediment phosphorus (P) to surface waters on short timescales in shallow lakes. However, the long-term effects of hypolimnetic redox conditions and trophic state on sedimentary P fraction retention in deep lakes are not clear yet. Hypolimnetic withdrawal of P-rich water is predicted to diminish sedimentary P and seasonal P recycling from the lake hypolimnion. Nevertheless, there is a lack of evidence from well-dated sediment cores, in particular from deep lakes, about the long-term impact of hypolimnetic withdrawal on sedimentary P retention. In this study, long-term sedimentary P fraction data since the early 1900s from Lake Burgäschi provide information on benthic P retention under the influence of increasing lake primary productivity (sedimentary green-pigment proxy), variable hypolimnion oxygenation regimes (Fe∕Mn ratio proxy), and hypolimnetic withdrawal since 1977. Results show that before hypolimnetic withdrawal (during the early 1900s to 1977), the redox-sensitive Fe∕Mn-P fraction comprised ∼50 % of total P (TP) in the sediment profile. Meanwhile, long-term retention of total P and labile P fractions in sediments was predominantly affected by past hypolimnetic redox conditions, and P retention increased in sedimentary Fe- and Mn-enriched layers when the sediment-overlaying water was seasonally oxic. However, from 1977 to 2017, due to eutrophication-induced persistent anoxic conditions in the hypolimnion and to hypolimnetic water withdrawal increasing the P export out of the lake, net burial rates of total and labile P fractions decreased considerably in surface sediments. By contrast, refractory Ca–P fraction retention was primarily related to lake primary production. Due to lake restoration since 1977, the Ca–P fraction became the primary P fraction in sediments (representing ∼39 % of total P), indicating a lower P bioavailability of surface sediments. Our study implies that in seasonally stratified eutrophic deep lakes (like Lake Burgäschi), hypolimnetic withdrawal can effectively reduce P retention in sediments and potential for sediment P release (internal P loads). However, after more than 40 years of hypolimnetic syphoning, the lake trophic state has not improved nor has lake productivity decreased. Furthermore, this restoration has not enhanced water column mixing and oxygenation in hypolimnetic waters. The findings of this study are relevant regarding the management of deep eutrophic lakes with mixing regimes typical for temperate zones.
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Yang, Yuyin, Ningning Li, Wei Wang, Bingxin Li, Shuguang Xie e Yong Liu. "Vertical profiles of sediment methanogenic potential and communities in two plateau freshwater lakes". Biogeosciences 14, n. 2 (24 gennaio 2017): 341–51. http://dx.doi.org/10.5194/bg-14-341-2017.
Testo completoAbstract (sommario):
Abstract. Microbial methanogenesis in sediment plays a crucial role in CH4 emission from freshwater lake ecosystems. However, knowledge of the layer-depth-related changes of methanogen community structure and activities in freshwater lake sediment is still limited. The present study was conducted to characterize the methanogenesis potential in different sediment-layer depths and the vertical distribution of microbial communities in two freshwater lakes of different trophic status on the Yunnan Plateau (China). Incubation experiments and inhibitor studies were carried out to determine the methanogenesis potential and pathways. 16S rRNA and mcrA genes were used to investigate the abundance and structure of methanogen and archaeal communities, respectively. Hydrogenotrophic methanogenesis was mainly responsible for methane production in sediments of both freshwater lakes. The layer-depth-related changes of methanogenesis potential and the abundance and community structure of methanogens were observed in both Dianchi Lake and Erhai Lake. Archaeal 16S rRNA and mcrA genes displayed a similar abundance change pattern in both lakes, and the relative abundance of methanogens decreased with increasing sediment-layer depth. Archaeal communities differed considerably in Dianchi Lake and Erhai Lake, but methanogen communities showed a slight difference between these two lakes. However, methanogen communities illustrated a remarkable layer-depth-related change. Order Methanomicrobiales was the dominant methanogen group in all sediments, while Methanobacteriales showed a high proportion only in upper layer sediments. The trophic status of the lake might have a notable influence on the depth-related change pattern of methanogenesis activity, while the methanogen community structure was mainly influenced by sediment depth.
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Amano, Koji, e Takehiko Fukushima. "On the Longitudinal and Vertical Changes in Lake Estuarine Sediments". Water Science and Technology 20, n. 6-7 (1 giugno 1988): 143–53. http://dx.doi.org/10.2166/wst.1988.0198.
Testo completoAbstract (sommario):
In order to obtain environmental information about lake water and watersheds, the vertical and longitudinal distributions of physical and chemical properties in lake sediments were investigated. The concentrations of several substances (e.g., nutrients, metals, and chemicals) in the sediments were determined at fifty sampling sites in sixteen shallow lakes in Japan. The vertical profiles of particle size, particle organic carbon, particle organic nitrogen, total phosphorus, some metals (Ti, Mn, Fe, Zn, and Cu), and LAS were analysed. Various sediment properties, such as the sedimentation conditions and the redox conditions, were related to the vertical profiles observed, and traces of historical changes in the water and watersheds were found in the sediments. Longitudinal changes in the sediments between the mouths of the rivers and the deepest points of the lakes were clearly observed, and it was expected that these changes would correlate with one of the estuarine characteristics since they reflect the spatial variation in average composition of the particulate matter and in the average water quality. Some significant relationships between the lake sediments and the lake or watershed type were observed, indicating the possibility that lake sediments may be one of the most important indices for understanding lake environments.
19
Huang, Wei, Xing Chen, Kun Wang e Xia Jiang. "Seasonal characteristics of phosphorus sorption by sediments from plain lakes with different trophic statuses". Royal Society Open Science 5, n. 8 (agosto 2018): 172237. http://dx.doi.org/10.1098/rsos.172237.
Testo completoAbstract (sommario):
Phosphorus (P) sorption in sediments plays a significant role in trophic status of a lake. This study investigated the characteristics of P sorption in sediments from three lakes with different trophic statuses (moderately eutrophic, lightly eutrophic and moderately trophic) through kinetic, batch equilibrium and thermodynamic experiments. Results show that pseudo-second-order kinetics best describe P sorption in sediments from the three lakes. Fitting by modified Langmuir and Freundlich isotherms indicates that the moderately trophic lake sediment has higher sorption capacity (maximum of 0.848 mg g −1 at 35°C) than the sediments of the other two lakes at different temperatures (5, 15, 25 and 35°C). Thermodynamic results indicate that the processes of P sorption of the three sediments are spontaneous, entropy-driven and endothermic reactions. The risk of P release in sediments was analysed according to the calculated results of isotherms combined with the change in P fraction. Sediments from the moderately eutrophic lake act as a source in summer. The lightly eutrophic and moderately trophic lakes act as sources in spring and winter, and a pool in summer and autumn, respectively. Furthermore, the amounts of reductant-soluble P, calcium-bound P and iron-bound P are significantly related to the sorption capacity of sediments from the three lakes ( p < 0.05). The different sediments have different P release risk, and P fraction in sediment is one of the significant factors of P sorption.
20
Jiao, Li Ping, Xia Sun e Yang Luo. "Chinese Arctic Yellow River Station Research Monitoring Program. 1. Polycyclic Aromatic Hydrocarbons in Sediment from Svalbard". Applied Mechanics and Materials 522-524 (febbraio 2014): 25–33. http://dx.doi.org/10.4028/www.scientific.net/amm.522-524.25.
Testo completoAbstract (sommario):
Surface sediments of the west coast of Svalbard near Ny-Ålesund Spitsbergen were collected. PAHs of lake sediments (mean: 260, range: 11 - 1100 ng/g dry wt) were higher than previously report of surface lake sediment in Svalbard 1995, suggesting significant PAH contamination is occurring due to long-term atmospheric transport and local coal mining and fossil fuel sources, pointing to the role of Arctic lakes as potential reservoirs of semi-volatile organic compounds, including PAHs. Compound-specific analysis revealed different PAH patterns between Svalbard lakes and European high mountain lakes, showing higher proportions of low molecular weight compounds and lower levels of high molecular weight PAHs in Svalbard lakes. PAH indicator ratios suggest that the majority of PAHs in lake sediments have pyrogenic origins (coal mining, fossil fuel and biomass combustion), while coastal marine sediments were mainly contaminated by petroleum-derived PAHs (shipping activities in coastal areas, and perhaps as a result of an oil spill in 1986). Sediment fluxes of PAHs were estimated to be 0.2 - 22 ng cm-2yr-1. The current PAH levels exceeded Canadian sediment quality guidelines, suggesting the presence of possible risks for aquatic organisms and the need for further studies.
21
Astles, Brittany C., John Chételat, Michael J. Palmer e Jesse C. Vermaire. "Experimental investigation of short-term warming on arsenic flux from contaminated sediments of two well-oxygenated subarctic lakes". PLOS ONE 17, n. 12 (21 dicembre 2022): e0279412. http://dx.doi.org/10.1371/journal.pone.0279412.
Testo completoAbstract (sommario):
Legacy arsenic (As) contamination from past mining operations remains an environmental concern in lakes of the Yellowknife area (Northwest Territories, Canada) due to its post-depositional mobility in sediment and potential for continued remobilization to surface waters. Warmer temperatures associated with climate change in this subarctic region may impact As internal loading from lake sediments either by a direct effect on sediment porewater diffusion rate or indirect effects on microbial metabolism and sediment redox conditions. This study assessed the influence of warmer temperatures on As diffusion from contaminated sediment of two lakes with contrasting sediment characteristics using an experimental incubation approach. Sediments from Yellowknife Bay (on Great Slave Lake) contained predominately clay and silt with low organic matter (10%) and high As content (1675 μg/g) while sediments of Lower Martin Lake had high organic matter content (~70%) and approximately half the As (822 μg/g). Duplicate sediment batches from each lake were incubated in a temperature-controlled chamber, and overlying water was kept well-oxygenated while As flux from sediment was measured during four weekly temperature treatments (7°C to 21°C, at ~5°C intervals). During the experiment, As diffused from sediment to overlying water in all cores and temperature treatments, with As fluxes ranging from 48–956 μg/m2/day. Arsenic fluxes were greater from Yellowknife Bay sediments, which had higher solid-phase As concentrations, compared to those of Lower Martin Lake. Short-term warming did not stimulate As flux from duplicate cores of either sediment type, in contrast with reported temperature enhancement in other published studies. We conclude that warmer temperatures were insufficient to strongly enhance sediment As diffusion into overlying oxic waters. These observations are relevant for evaluating climate-warming effects on sediment As mobility in subarctic lakes with little or no thermal stratification and a well-oxygenated water column.
22
Harasimiuk, Andrzej, Bogumił Wicik e Tomasz Grabowski. "The lake deposits in Płock Basin (case studies of Lakes Rakutowskie and Żłoby)". Limnological Review 10, n. 1 (1 gennaio 2010): 23–28. http://dx.doi.org/10.2478/v10194-011-0003-7.
Testo completoAbstract (sommario):
The lake deposits in Płock Basin (case studies of Lakes Rakutowskie and Żłoby)Reconstruction of development of Lakes Rakutowskie and Żłoby in the late Pleistocene and Holocene was the aim of this research. Analysis of content of calcium carbonate, organic matter and C14 datings (7 samples) were done for two cores of sediments of 750 cm long. An average rate of accumulation was counted. Sediments of Lake Rakutowskie show homogeneity along the core which indicates similarity of sedimentation conditions. Sediments of Lake Żłoby were diversified and show variety related to cyclic changes. A common feature is a thick layer of fine sand without carbonate deposited during the older dryas, shown in both cores. The difference in sediment features of both lakes (which have similar depths) indicates that the Lake Żłoby is the more dynamic, filtering element, preceding Lake Rakutowskie in system of water catchment.
23
Rowan, D. J., J. Kalff e J. B. Rasmussen. "Profundal Sediment Organic Content and Physical Character Do Not Reflect Lake Trophic Status, but Rather Reflect Inorganic Sedimentation and Exposure". Canadian Journal of Fisheries and Aquatic Sciences 49, n. 7 (1 luglio 1992): 1431–38. http://dx.doi.org/10.1139/f92-158.
Testo completoAbstract (sommario):
An analysis of profundal sediment data from 83 north-temperate lakes shows that increasing inorganic sedimentation and exposure (or lake surface area) results in lower organic content and water content, and greater bulk density. Because sedimentation rates are unavailable for most lakes, we estimate sedimentation rates from readily available catchment sediment loads using a mass-balance model. The mass-balance estimate of sediment retention (per square metre of depositional zone) is an excellent predictor of measured inorganic sedimentation rates for a data set covering 19 lakes (R2 = 0.92). Multiple regressions are used to predict organic content, water content, and bulk density of profundal sediment from inorganic sedimentation rates and either exposure or lake surface area, which are surrogates for the energy of the depositional environment. These analyses explain 76, 74, and 66% of the between-lake variation in the three sediment parameters, respectively. Sediment organic content is not related to lake trophic status (chlorophyll a) and is negatively correlated with net organic matter sedimentation rates. The common occurrence of organic-rich sediments in oligotrophic shield lakes is, therefore, not a reflection of high organic matter inputs, but rather the extremely low inputs of mineral sediments to these lakes.
24
Srdoč, Dušan, Bogomil Obelić, Nada Horvatinčić, Ines Krajcar-Bronić, Elena Marčenko, Joseph Merkt, How Kin Wong e Adela Sliepčević. "Radiocarbon Dating of Lake Sediment from Two Karst Lakes in Yugoslavia". Radiocarbon 28, n. 2A (1986): 495–502. http://dx.doi.org/10.1017/s0033822200007633.
Testo completoAbstract (sommario):
Samples of sediment cores from two lakes in the karst area of northwest Yugoslavia were analyzed. Both Lakes Kozjak and Prošće are in the Plitvice National Park, Central Croatia. 14C dating, sedimentologic, seismic, and isotopic studies, and distribution of diatoms are presented.14C dating of lake marl revealed a uniforn sedimentation rate in Lake Prošće as opposed to Lake Kozjak. Both lake sediments belong to the Holocene period. 14C dating of lake sediment is in agreement with seismic profiles, sedimentologic analysis, and diatom frequency measurements both in an undisturbed as well as in a disturbed lake sediment.
25
Gonsiorczyk, Thomas, Peter Casper e Rainer Koschel. "Phosphorus-binding forms in the sediment of an oligotrophic and an eutrophic hardwater lake of the Baltic Lake District (Germany)". Water Science and Technology 37, n. 3 (1 febbraio 1998): 51–58. http://dx.doi.org/10.2166/wst.1998.0173.
Testo completoAbstract (sommario):
The vertical distribution of various phosphorus (P)-binding forms, associated potential P-binding partners and the composition of dry material were investigated in the bottom sediments of the dimictic oligotrophic Lake Stechlin and the dimictic eutrophic Lake Feldberger Haussee. Reductant soluble P (Fe- and Mn-bound) at the sediment surface (0−1 cm) was considerably higher in the oligotrophic Lake Stechlin (1.29 g kg−1) than in the eutrophic Lake Haussee (0.32 g kg−1). The amounts of dissolved, loosely adsorbed, metal oxide- and calcium carbonate bound P were higher in the eutrophic lake. The depth profiles of the investigated P species indicated that the mobilization of Fe- and Mn-bound P is the most important mechanism of P-release in oligotrophic lakes, whereas the mobilization of recently sedimented labile organic bound P seems to be the driving force of P-release in eutrophic lakes. In both lakes autochthonous calcite precipitations occurs during the summer months. The coprecipitation of P with calcite is an important self-cleaning mechanism in eutrophic hardwater lakes and contributes to the permanent burial of P in the sediments. Although, the precipitation of calcite is inhibited by the presence of high concentrations of soluble reactive P, the coprecipitation of P with calcite seems to be enhanced.
26
Potakhin, M. S., N. A. Belkina e D. A. Subetto. "The Lake Onego watershed: morphology of lakes and classification of the bottom sediments". Limnology and Freshwater Biology, n. 4 (2022): 1526–28. http://dx.doi.org/10.31951/2658-3518-2022-a-4-1526.
Testo completoAbstract (sommario):
Abstract. The data on the lake morphometry and sediment lithostratigraphy of the Lake Onego watershed were collected. The classification of lakes was carried out according to the genetic features of relief. Four types of the lakes have been identified for the catchment area. The structural features of lake basins and bottom sediments were determined for each type of lakes.
27
Wang, W. W., X. Jiang, B. H. Zheng, J. Y. Chen, L. Zhao, B. Zhang e S. H. Wang. "Composition, mineralization potential and release risk of nitrogen in the sediments of Keluke Lake, a Tibetan Plateau freshwater lake in China". Royal Society Open Science 5, n. 9 (settembre 2018): 180612. http://dx.doi.org/10.1098/rsos.180612.
Testo completoAbstract (sommario):
The lakes distributed in the Tibetan Plateau constitute a lake group with the highest altitude, largest lakes and largest area in the world and are important in global climate and environmental effects. Freshwater lakes in the Tibetan Plateau possess high ecological values and high vulnerability. The migration and transformation of nitrogen in sediments are critical to lake ecosystems, but information on sedimentary nitrogen in the freshwater lakes in the Tibetan Plateau is limited. A case study was conducted in Keluke Lake, China, to reveal the effects of sedimentary nitrogen on water quality in plateau freshwater lakes. Nitrogen speciation, mineralization potential and release flux were analysed through a sequential extraction method, waterlogged incubation experiment and Fick's first diffusion law, respectively. The content of total nitrogen (TN) was 1295.75–6151.69 mg kg −1 , and 94.2% of TN was organic nitrogen (ON). The contents of three nitrogen fractions were in the order of hydrolysable nitrogen > residual nitrogen > exchangeable nitrogen. Ammonia nitrogen ( N H 4 + − N ) was the main mineralization product, and hydrolysable ON was the most significant contributor. The sediments showed a great mineralization potential, with a potentially mineralizable nitrogen value of 408.76 mg N kg −1 of sediment, that was mainly affected by hydrolysable ammonium nitrogen. The N H 4 + − N diffusion flux ranged from 24.14 to 148.75 mg m −2 d −1 , and the sediments served as an internal nitrogen source. Nitrogen release from sediments was considerably influenced by exchangeable ammonia nitrogen. The sediments in Keluke Lake pose a potential nitrogen release risk and threaten the water quality of the lake. The total content, speciation, mineralization of ON and the release flux at sediment–water interface should be considered comprehensively to evaluate the effects of nitrogen in sediments to water quality.
28
Baranov, Viktor, Jörg Lewandowski e Stefan Krause. "Bioturbation enhances the aerobic respiration of lake sediments in warming lakes". Biology Letters 12, n. 8 (agosto 2016): 20160448. http://dx.doi.org/10.1098/rsbl.2016.0448.
Testo completoAbstract (sommario):
While lakes occupy less than 2% of the total surface of the Earth, they play a substantial role in global biogeochemical cycles. For instance, shallow lakes are important sites of carbon metabolism. Aerobic respiration is one of the important drivers of the carbon metabolism in lakes. In this context, bioturbation impacts of benthic animals (biological reworking of sediment matrix and ventilation of the sediment) on sediment aerobic respiration have previously been underestimated. Biological activity is likely to change over the course of a year due to seasonal changes of water temperatures. This study uses microcosm experiments to investigate how the impact of bioturbation (by Diptera, Chironomidae larvae) on lake sediment respiration changes when temperatures increase. While at 5°C, respiration in sediments with and without chironomids did not differ, at 30°C sediment respiration in microcosms with 2000 chironomids per m 2 was 4.9 times higher than in uninhabited sediments. Our results indicate that lake water temperature increases could significantly enhance lake sediment respiration, which allows us to better understand seasonal changes in lake respiration and carbon metabolism as well as the potential impacts of global warming.
29
Rao, S. S., M. D. Dickman e H. G. Thode. "Isotopic and Diatom Evidence of Bacterial Sulphate Reduction in Sediments". Water Quality Research Journal 24, n. 2 (1 maggio 1989): 215–32. http://dx.doi.org/10.2166/wqrj.1989.013.
Testo completoAbstract (sommario):
Abstract Sulphur contents and sulphur isotope ratios (δ34 So/00 values) in deep sediments (10–12 cms; circa 50–100 years before the present) and surface sediments (0–2 cm; circa 0–10 years before the present) from eight lakes located north of Lake Superior, Canada indicated that surface sediments had a significantly higher sulphur content (largely organic sulphur) per gram dry weight and a lower sulphur isotope ratio than the deeper layers. The increased sulphur content and decreased sulphur isotope ratios (δ34 S0/00 values) in the surficial sediments were much greater for the lakes near and downwind from the Wawa sintering plant than for more remote lakes reflecting the impact of the sintering plant emissions on the lake environment. A significant relationship was observed between the sulphate reducing bacterial populations and the magnitude of the isotope shift in the study lakes. It was evident from the data that the greater the abundance of sulphate reducers the greater was the surface sediment sulphate content and the degree of isotope fractionation in the anaerobic and organic rich sediments. The surface sediments of the eight study lakes revealed isotopic evidence of bacterial sulphate reduction. The deeper sediments, however, did not reveal such a condition due to the absence of sulphate reducers. The rate of lake acidification as inferred from the downcore diatom inferred pH profile for each of the study lakes was not significantly correlated with the amount of sulphur in the lake sediments, nor was it correlated with the density of sulphate reducing bacteria or shifts in the sulphur isotope ratios (δ34S).
30
Pazdur, Anna, M. F. Pazdur, Tomasz Goslar, Bogumił Wicik e Maurice Arnold. "Radiocarbon Chronology of Late Glacial and Holocene Sedimentation and Water-Level Changes in the Area of the Gościąż Lake Basin". Radiocarbon 36, n. 2 (1994): 187–202. http://dx.doi.org/10.1017/s0033822200040492.
Testo completoAbstract (sommario):
We obtained 14C ages on samples of lake marl and other sediments from cores taken in Gościąż Lake and its environs. Comparison of 14C dates of bulk samples of laminated sediment with varve chronology and available AMS dates of terrestrial macrofossils indicates a reservoir correction of 2000 ± 120 yr for the basal series of lake sediments. 14C dates obtained on peat layers underlying the oldest lacustrine sediments in Gościąż and other lakes consistently locate the beginning of organogenic sedimentation in this area at ca. 13 ka bp. We distinguished three periods of lacustrine gyttja sedimentation in cores taken in Gościąż and adjacent lakes: 11.8–10.2 ka, 8–7 ka and 2.7–2.1 ka bp. From the 14C dates of lithological boundaries in these cores, we reconstruct a pattern of lake-level changes during the last 12 ka, remarkably similar to Swedish lakes and generally agreeing with available records from European and American lakes. The behavior of Gościąż Lake during the last 12 ka fairly well reflects global climate changes in the temperate zone during the Late Glacial and Holocene periods.
31
Shin, I. Chan, Tetsuji Akatsuka, Hisayuki Azumi, Lan Ao, Nozomi Amahashi, Maki Oyagi, Noriko Ishida et al. "Grain size distribution and chemistry of the brackish Lake sediment in Korea". Environmental Engineering Research 26, n. 5 (5 ottobre 2020): 200365–0. http://dx.doi.org/10.4491/eer.2020.365.
Testo completoAbstract (sommario):
To determine the grain size distribution and chemical characteristics of bottom surface sediments in shallow brackish lagoons, we studied sediment samples collected from the entire horizontal lake area and in vertical profiles from three stations in Lakes Youngrang and Hwajinpo, on the eastern coast of Korea. Vertical and horizontal grain size distributions of the bottom sediments indicated predominantly sand- and silt in both lakes. The vertical distribution of C/N ratios ranged from 6.14 to 11.92 in Lake Youngrang, and 6.74 to 12.34 in Lake Hwajinpo. The horizontal distribution of C/N ratios in Lake Youngrang ranged from 6.1 to 17.6, whereas they ranged from 4.4 to 12.1 in Lake Hwajinpo. C/N ratios showed locally different responses to the origin of allochthonous (partial region) and autochthonous (entire region) organic materials. Horizontally, bottom sediment with low δ<sup>13</sup>C and high δ<sup>15</sup>N in Lake Youngrang were likely to be influenced by autochthonous organic material derived from primary production, and would be affected by N inputs from sources. In contrast, high δ<sup>13</sup>C and low δ<sup>15</sup>N sediments in Lake Hwajinpo were likely to be influenced by cyanobacteria.
32
Belzile, Nelson, Helen A. Joly e Hongbo Li. "Characterization of humic substances extracted from Canadian lake sediments". Canadian Journal of Chemistry 75, n. 1 (1 gennaio 1997): 14–27. http://dx.doi.org/10.1139/v97-003.
Testo completoAbstract (sommario):
Humic substances (HS) were extracted from the sediments of four Sudbury area lakes, namely, Tilton, Clearwater, Silver, and Ramsey Lakes, with the aid of 0.1 M Na4P2O7 and 0.5 M NaOH solutions. The HS (humic and fulvic acids) were purified and characterized using the methods of elemental analysis, visible spectroscopy (E4/E6 ratio), FTIR, and solid-state 13C CPMAS NMR. A substantial amount of information with regard to the composition and chemical nature of lake sediment HS was obtained. The results obtained for the Sudbury area lake sediments were compared with one another and with HS from other sources, such as soils. The elemental composition, atomic ratios, E4/E6 ratios, and FTIR and NMR features of the samples from the above lakes were found to be nearly identical, suggesting that HS formed in the Sudbury area have similar chemical properties. Compared with soil HS, the Sudbury lake sediments HS have undergone a low degree of aromatic condensation and are considerably more aliphatic in nature. Keywords: humic substances, characterization, lake sediments, extraction, 13C NMR.
33
Rada, Ronald G., David E. Powell e James G. Wiener. "Whole-Lake Burdens and Spatial Distribution of Mercury in Surficial Sediments in Wisconsin Seepage Lakes". Canadian Journal of Fisheries and Aquatic Sciences 50, n. 4 (1 aprile 1993): 865–73. http://dx.doi.org/10.1139/f93-099.
Testo completoAbstract (sommario):
We quantified total mercury in surficial sediments (uppermost 5 cm) of six small seepage lakes. Fifty cores were taken from each lake, based on a random sampling design stratified by water depth. Volumetric concentrations (mass per volume of wet sediment) more accurately portrayed the depth distribution of mercury in the lakes than did dry-weight concentrations, which underrepresented the significance of the shallow-water sediments as a reservoir of potentially available mercury. Estimates of whole-lake burdens (masses) of mercury in the surficial sediment, which represent the maximum amount of sedimentary mercury available for methylation, ranged from 45 to 149 g. These sedimentary pools of mercury greatly exceeded the inventories of the metal in water, seston, and fish, and the release of mercury from the sediments could significantly increase its bioaccumulation. Areal burdens of mercury (mass per unit of lake area) varied fivefold among lakes (1.65–7.84 g/ha) and were strongly correlated with lake pH, but were not correlated with dissolved organic carbon, conductance, or chlorophyll a of lakes. We hypothesize that the observed variation in areal burdens of mercury was partly due to variation among lakes in the pH-related efflux of gaseous mercury (Hg0) from the lakes to the atmosphere.
34
Wu, Dun, Hai Liu, Jian Wu e Xia Gao. "Spatial Distribution, Ecological Risk Assessment and Source Analysis of Heavy Metals Pollution in Urban Lake Sediments of Huaihe River Basin". International Journal of Environmental Research and Public Health 19, n. 22 (8 novembre 2022): 14653. http://dx.doi.org/10.3390/ijerph192214653.
Testo completoAbstract (sommario):
Heavy metals in freshwater lake sediments often exist in various chemical forms. However, the investigation and evaluation of heavy-metal elements in the sediments of the study area have not been reported, and there is a lack of objective understanding of the concentration level of heavy-metal elements. Therefore, this study is the first to report the concentrations, sources, and potential ecological risks of heavy metals in the sediments of Chengdong Lake and Chengxi Lake in Huoqiu County, Anhui Province, China. The spatial distribution, pollution characteristics, potential pollution sources, and ecological risks of heavy metals in the sediments of Chengxi Lake and Chengdong Lake of Huoqiu City in the middle section of Huaihe River in Anhui Province, China have not been reported. In this study, the sediment samples of the two Lakes were collected systematically, and the concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were determined. The potential sources of heavy-metal elements in sediments were quantitatively analyzed according to the principal component analysis–absolute principal component fraction–multiple linear regression (PCA–APCS–MLR) receptor model. Descriptive statistics data showed that the enrichment degree of heavy metals in Chengxi Lake was higher than that in Chengdong Lake. The geo-accumulation index (Igeo) and pollution load index (PLI) indicated that there was moderate pollution for Cu, As, Hg, Ni, and Zn. The calculation results of the potential ecological risk index (Er) of the two lakes indicated that Cd (Er,max = 92.22, n = 60) and Hg (Er,max = 64.39, n = 60) showed a certain potential ecological risk in a small amount of sediment, while other heavy metals were classified as low risk. The mean sediment quality guideline quotient indicated that there was a moderate degree of potential adverse biological toxicity in lake sediments. Spatially, the seriously polluted contamination zones were the central position of Chengxi Lake and the northeast end of Chengdong Lake. The PCA–APCS–MLR receptor model revealed that Cr, Ni, Cu, and Zn were mainly from natural sources while Cd, As, Hg, and Pb elements were mainly from industrial sources and pesticide sources.
35
Vincent, S. G. T., J. H. Salahudeen, P. S. Godson, S. R. Abhijith, A. V. Nath, K. A. Krishnan, N. S. Magesh, S. K. Kumar e S. A. Moses. "Environmental factors influencing methanogenic activity in two contrasting tropical lake sediments". Journal of Environmental Biology 42, n. 2 (1 marzo 2021): 211–19. http://dx.doi.org/10.22438/jeb/42/2/mrn-1413.
Testo completoAbstract (sommario):
Aim: To investigate the influence of environmental variables on the abundance and activity of methanogenic archaea (MA) in Akkulam-Veli and Vellayani Lake sediments. Methodology: Sediment and overlying water samples (n=5 each) were collected from Veli and Vellayani lakes of Thiruvananthapuram, Kerala. Samples were analysed for environmental variables using standard protocols. Multivariate analysis was done to study the influence of environmental variables on abundance and activity of MA. Results: Environmental variables of overlying water and sediment showed significant variation between the two lakes. Salinity and sulphate were more in Akkulam-Veli than Vellayani, as Akkulam-Veli is a brackish lake and temporarily connected with Arabian Sea. Highly reduced sediments of Akkulam-Veli favoured more population of methylotrophic and acetoclastic MA than Vellayani. A distributional difference of MA with depth was observed in both lakes, which is attributed to availability of more labile organic matter. The methylotrophic MA activity was not significantly different between the two lakes; however, their abundance was significantly different. Nevertheless, methane production was higher in Vellayani than in Akkulam-Veli Lake. PCA revealed that Corg and labile organic matter (LOM) were the important environmental variables influencing methane production potential. Interpretation: Anthropogenic activities like sewage and waste disposal results in increased input of organic matter in lake sediments. The labile organic matter fraction in the sediments favours methanogenic activity thereby resulting in methane production and release from the lakes. Key words: Labile organic matter, Methanogenic archaea, Methane production, Sulphate reduction, Tropical lakes
36
Kolpakova, Marina. "Heavy metal contamination in bottom sediments of saline endorheic lakes of Kulunda and Barabinsk steppes (Western Siberia, Russia)". E3S Web of Conferences 80 (2019): 03009. http://dx.doi.org/10.1051/e3sconf/20198003009.
Testo completoAbstract (sommario):
The article presents the results of assessment of heavy metals contamination in bottom sediments of saline lakes located on the territory of Kulunda and Barabinsk steppes of Western Siberia, Russia. The territory is characterized by large amount of lakes (more than 5000), including the Chany lake, which is the biggest lake of south of Western Siberia. By calculation the geochemical parameters, such as Enrichment factor, Contamination factor, Geoaccumulation index, Pollution load index, the common level of bottom sediments was classified as unpolluted. However, in comparison with average level of bottom sediment on that territory the lake sediments are enriched with the following elements: Sr> Rb> Zn> V> Cr> Ni> Cu> As> Pb> Th> U> Mn> Fe> K> Ti.
37
Yuan, Xu Yin, Quan Liu, Ji Zhou Li, Jun Feng Ji e Chang Ping Mao. "Risk Assessment of Organochlorine Compounds in Water and Surface Sediments from Taihu Lake and Nanjing Section of Changjiang, China". Advanced Materials Research 356-360 (ottobre 2011): 624–29. http://dx.doi.org/10.4028/www.scientific.net/amr.356-360.624.
Testo completoAbstract (sommario):
Samples of surface water and sediment were collected in Taihu Lake and Nanjing section of Changjiang. Organochlorine compounds(OCCs) of samples were detected to investigate the characteristics and ecological risk of them in the lake and river. The concentrations of OCCs in water of Nanjing section of Changjiang were higher than those in Taihu Lake, but the concentrations of OCCs in sediments were higher in Taihu Lake. HCHs of Taihu sediments were relatively enriched, indicating the agricultural source of compounds. PCBs of Changjiang sediments were higher compared to Taihu sediments, denoting a obvious industrial source. Comparing with other compartments in China, HCHs of the study area were higher than most sediment of Chinese rivers, DDTs didn’t show high contents in sediments, PCBs was in relatively low levels. By contrast with the relevant sediment quality guidelines of these compounds, the ecological risk of OCCs in sediments were evaluated. The OCCs of sediments in Taihu Lake and Nanjing section of Changjiang didn’t show high ecological risk.
38
Shaw, J. F. H., e E. E. Prepas. "Temporal and Spatial Patterns of Porewater Phosphorus in Shallow Sediments, and its Potential Transport into Narrow Lake, Alberta". Canadian Journal of Fisheries and Aquatic Sciences 46, n. 6 (1 giugno 1989): 981–88. http://dx.doi.org/10.1139/f89-127.
Testo completoAbstract (sommario):
During 1985 and 1986, summer and spatial patterns of porewater soluble reactive phosphorus (SRP) from sediments ≤ 15-m depth were examined at Narrow Lake, a deep, mesoeutrophic Albertan lake. At three sites (different in depth and macrophyte colonization), trends in porewater SRP concentrations ([SRP]) in the top 5 cm of the sediment from May to August varied, possibly due to root uptake of SRP by macrophytes. At a depth of 5 m, mean (in the top 5 cm of the sediment) and variance of porewater [SRP] at one site (<0.15 m2) were the same as over the entire lake. Excluding data from macrophyte sites, porewater [SRP] were positively related to depth of the water column (P < 0.0001). Molecular diffusion of SRP from sediments with and without macrophytes located in the trophogenic zone was calculated. During summer, molecular diffusion from shallow sediments to the trophogenic zone was 0.05 mg∙m−2 d−1, or 29% of atmospheric deposition of phosphorus (P) (the major external source of P to the lake). A sampling strategy is discussed to enable the calculation of whole-lake P transport from shallow sediments to the trophogenic zone in lakes with similar morphometry and trophic status to Narrow Lake.
39
Liu, Bo, Xiaofei Zhang, Yi Tong, Wen Ao, Zenglong Wang, Senlin Zhu e Yanping Wang. "Quantification of Nutrient Fluxes from Sediments of Lake Hulun, China: Implications for Plateau Lake Management". Sustainability 15, n. 11 (26 maggio 2023): 8680. http://dx.doi.org/10.3390/su15118680.
Testo completoAbstract (sommario):
Dramatic changes in lake water conditions may induce sensitive feedback in sediments, such as the release of phosphate and ammonia. There is a lack of the understanding of sediment nutrient release fluxes and their responses to various environmental factors in plateau lakes. In this study, nutrient contents in the water and sediment, sediment nutrient release rates, and their responses to various influential factors in a steppe shallow plateau lake, Lake Hulun, China, were investigated. Sediment is a large store of nutrients, with bioavailable phosphorus of 555 mg kg−1 in surface lake sediments. If water became anoxic, sediments will release appreciable amounts of phosphate (2.1 mg P m−2 d−1) and ammonia (40.0 mg N m−2 d−1), three times greater than those in oxic conditions. Raised temperatures greatly increased sediment phosphate release rates, while the highest temperature (23 °C) slightly decreased ammonia release rates due to strong nitrification. Assuming a whole year of internal loading, ammonia and dissolved reactive phosphorus concentrations in water column would increase by an estimated 0.22 mg N L−1 and 0.01 mg P L−1, respectively, which is equal to 2 and 0.5 times of their ambient concentrations. A pH increase from 8.4 to 9.4 significantly decreased internal nitrogen and phosphorus release rates by around three times. Overall, dissolved oxygen (DO) and pH had a greater impact on sediment nutrient release from lake sediments compared to temperature, and further increased the eutrophic status in the overlying water when these three parameters varied within the normal seasonal range (temperature: 1.9–23.1 °C, DO: oxic and anoxic; pH: 7.5–9.4). With the periodic low DO and frequency of drought in the future, lake management strategies that mitigate water eutrophication, such as water diversion, may need to be considered.
40
Heslop, J. K., K. M. Walter Anthony, A. Sepulveda-Jauregui, K. Martinez-Cruz, A. Bondurant, G. Grosse e M. C. Jones. "Thermokarst lake methanogenesis along a complete talik profile". Biogeosciences 12, n. 14 (24 luglio 2015): 4317–31. http://dx.doi.org/10.5194/bg-12-4317-2015.
Testo completoAbstract (sommario):
Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD: 5.95 ± 1.67 μg C–CH4 g dw−1 d−1; 125.9 ± 36.2 μg C–CH4 g C−1org d−1). High CH4 production potentials were also observed in recently thawed permafrost (1.18 ± 0.61 μg C–CH4g dw−1 d−1; 59.60± 51.5 μg C–CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawing in the talik for a longer period of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw and shore erosion of yedoma permafrost are important to lake CH4 production.
41
Heslop, J. K., K. M. Walter Anthony, A. Sepulveda-Jauregui, K. Martinez-Cruz, A. Bondurant, G. Grosse e M. C. Jones. "Thermokarst-lake methanogenesis along a complete talik profile". Biogeosciences Discussions 12, n. 6 (24 marzo 2015): 4865–905. http://dx.doi.org/10.5194/bgd-12-4865-2015.
Testo completoAbstract (sommario):
Abstract. Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD 5.95 ± 1.67 μg C-CH4 g dw−1 d−1; 125.9± 36.2 μg C-CH4 g C−1org d−1). High CH4 production potentials were also observed in recently-thawed permafrost (1.18± 0.61 μg C-CH4g dw−1 d−1; 59.60± 51.5 μg C-CH4 g C−1org d−1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawed in the talik for longer periods of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst-lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw as well as shore erosion of yedoma permafrost are important to lake CH4 production.
42
Afzal, Shahzad, Mohammad Younas e Khadim Hussain. "Selenium Speciation of Surface Sediments from Saline Lakes of the Soan-Sakesar Valley Salt-Range, Pakistan". Water Quality Research Journal 34, n. 4 (1 novembre 1999): 575–88. http://dx.doi.org/10.2166/wqrj.1999.029.
Testo completoAbstract (sommario):
Abstract The chemical species of selenium from the surface sediments from three eutroph-ic lakes of the Soan-Sakesar Valley were examined. The major objectives of the study were to examine the oxidation states of selenium in the lake sediments. The following selenium concentrations were observed from lakes Uchhali, Khabbaki and Jahlar, respectively: total selenium: 4.03, 1.55 and 1.4 mg/kg; Se+VI: 0.86, 0.39 and 0.31 mg/kg; Se+IV: 0.95, 0.27 and 0.25 mg/kg; Se-II:1.15, 0.45 and 0.33; and Se0: 1.17, 0.48 and 0.53 mg/kg. Lake sediments have higher nitrogen (0.04—0.35% of dry weight) and phosphorus (0.04—0.29% of dry weight) levels due to agriculture drainage water and sewage waste from small villages. X-ray diffraction analysis has shown that albite, calcite, chlorite, illite and quartz minerals were present in the sediments of lakes Uchhali, Khabbaki and Jahlar. Kaolinite was present only in lakes Uchhali and Khabbaki and goethite only in Lake Uchhali. Linear relationships were observed between selenium fractions, and minerals present in these lakes point out the phenomena of adsorption on the surface of these minerals. The organic C contents of 2.2, 2.8 and 3.1% dry weight in lakes Uchhali, Khabbaki and Jahlar, respectively, show linear relationships with Se-II, Se0 and total selenium. It suggests that Se in the sediments is highly associated with the sediment organic fraction. The results indicate that nutrient loads and organic C are responsible for the high microbial activity, which reduces sele-nates to more insoluble Se species in the lake sediments.
43
Schiff, Sherry L., e Robert F. Anderson. "Limnocorral Studies of Chemical and Biological Acid Neutralization in Two Freshwater Lakes". Canadian Journal of Fisheries and Aquatic Sciences 44, S1 (18 dicembre 1987): s173—s187. http://dx.doi.org/10.1139/f87-293.
Testo completoAbstract (sommario):
Twenty-nine 1 m diameter limnocorrals were installed in two Canadian Shield lakes to examine the relative importance of individual acid neutralization processes. Once the water column alkalinity was depleted, the within-lake alkalinity production processes were confined to the lake sediments. The flocculent organic-rich sediments of a shallow dystrophic lake (Lake 114) neutralized acid at a significantly greater rate than the sandy littoral sediments of an oligotrophy lake (Lake 302). Since the water column alkalinity of Lake 114 is much lower than Lake 302, ambient alkalinity is not a good predictor of acid neutralization capacity in the sediments. In both lakes, HNO3 was neutralized at a substantially higher rate than HCl or H2SO4. The rates of nitrate consumption, sulfate consumption, and abiotic acid neutralizing processes are independent of each other. Denitrification to an uncharged end-product is the primary mechanism of NO3− removal. The principal source of non-anion-specific buffering in the enclosure experiments was Ca2+ release from the sediments in Lake 302 and Ca2+ and NH4+ release in Lake 114. There is no significant difference between the organic-rich sediments of Lake 114 and the sandy sediments of Lake 302 in the concentration of exchangeable cations (μeq∙cm−3) for all cations except NH4+ and Mn2+. Alkalinity production in epilimnetic sediments is an important component of the resistance of softwater lakes to anthropogenic acidification.
44
Urban, N. R., e A. E. Monte. "Sulfur burial in and loss from the sediments of Little Rock Lake, Wisconsin". Canadian Journal of Fisheries and Aquatic Sciences 58, n. 7 (1 luglio 2001): 1347–55. http://dx.doi.org/10.1139/f01-085.
Testo completoAbstract (sommario):
Lake sediments often are regarded as accurate records of changes in climatic conditions, rates of atmospheric deposition of substances to the lake, or other processes occurring within lakes. In this study, the sedimentary record of sulfur was examined in Little Rock Lake, Wisconsin. This lake received experimental sulfate additions from 1985 through 1990, and a mass balance showed that 35% (425 kg) of experimental sulfur additions were buried in the sediments. Sediment cores collected before and after sulfur additions confirmed that burial of 180360 kg of sulfur occurred during the 6 years of experimental sulfur additions. However, cores collected in 1992 and 1996 contained less sulfur than cores taken in 1990 and suggested that sulfur incorporation in sediments is not permanent. To examine seasonal sulfur loss from sediments, sulfur inventories in the top 4 cm of sediments were measured in multiple cores before and after fall overturn. At water depths greater than 5 m, surface sediments retrieved after fall overturn had significantly less sulfur than did those collected before overturn. The small seasonal release from the sediments (25 kg S in 1996) might be caused by organic matter decomposition or sulfide oxidation.
45
Lebo, ME, e JE Reuter. "Spatial variability in sediment composition and evidence for resuspension in a large, deep lake". Marine and Freshwater Research 46, n. 1 (1995): 321. http://dx.doi.org/10.1071/mf9950321.
Testo completoAbstract (sommario):
Spatial variability in the composition of sediments in Pyramid Lake, Nevada, was assessed in June 1992 by collecting surficial samples at 32 sites. For those sites, organic fractions were highest in the centre of the lake and low near the single inflow to the system. The spatial patterns for organic C, N, and P in lake sediments indicated that small organic-rich particles are preferentially deposited in the centre of the lake. This sorting of particles by water depth was supported by a corresponding decrease in the particle size distribution of sediments with station depth and by limited sediment-trap data. Further, a comparison of sediment-trap particle flux rates with the net sediment accumulation rate for the centre of the lake based on 210Pb decay indicated that the resuspension of bottom sediments in Pyramid Lake (zmax = 102 m) must occur throughout the lake.
46
Kostka, Anna. "History of Environmental and Climatic Changes Recorded in Lacustrine Sediments—A Wigry Lake Case Study". Sustainability 15, n. 21 (5 novembre 2023): 15628. http://dx.doi.org/10.3390/su152115628.
Testo completoAbstract (sommario):
Wigry Lake represents one of the most beautiful and valuable postglacial lakes that is located in the north-eastern part of Poland. It has been an object of scientific interest for over a century, but the most intense period of research started in 1997 and resulted in the production of numerous papers of a multidisciplinary range. The lake is especially well analyzed in terms of its sediments, which were studied using geophysical methods and using traditional lake cartography based on the sampling of sediments and their geochemical characterization. Nearly two decades of research has resulted in the extraction of over 1200 sediment samples, which facilitated the analysis and the description of five main sediment types that can be found at the bottom of Wigry Lake, i.e., carbonate gyttja, lacustrine chalk, clastic sediment, fluvial-lacustrine sediment, and organic gyttja. A very thorough vertical as well as spatial examination of Wigry Lake sediments, together with paleobiological research and isotopic dating, allowed researchers to analyze the history of environmental changes in the lake and its immediate vicinity, including anthropogenic changes. Wigry Lake had been preserved as a pristine lake for a long time, and, despite the significant growth of anthropopressure, which began in the 17th century and intensified in the 20th century, it retained its natural character to a large extent. This was possible mainly due to the favorable morphometry of the lake (large depth and capacity of the reservoir) and different forms of active and passive protection, introduced mainly after the establishment of the Wigry National Park in 1989.
47
Liu, Yong, Jv Liu, Guoli Xu, Jingfu Wang, Kai Xu, Zuxue Jin e Guojia Huang. "The Recycling Characteristics of Different Silicon Forms and Biogenic Silicon in the Surface Sediments of Dianchi Lake, Southwest China". Water 16, n. 13 (26 giugno 2024): 1824. http://dx.doi.org/10.3390/w16131824.
Testo completoAbstract (sommario):
Silicon (Si) is one of the main biogenic elements in the aquatic ecosystem of lakes, significantly affecting the primary productivity of lakes. Lake sediment is an important sink of Si, which exists in different Si forms and will be released and participate in the recycling of Si when the sediment environment changes. Compared to carbon (C), nitrogen (N) and phosphorus (P), the understanding of different Si forms in sediments and their biogeochemical cycling is currently insufficient. Dianchi Lake, a typical eutrophic lake in southwest China, was selected as an example, and the contents of different Si forms and biogenic silicon (BSi), as well as their correlations with total organic carbon (TOC), total nitrogen (TN), and chlorophyll a in the surface sediments, were systematically investigated to explore Si’s recycling characteristics. The results showed that the coupling relationship of the four different Si forms in the surface sediments of Dianchi Lake was poor (p > 0.05), indicating that their sources were relatively independent. Moreover, their formation may be greatly influenced by the adsorption, fixation and redistribution of dissolved silicon by different lake substances. The contents of different Si forms in the surface sediments of Dianchi Lake were ranked as iron-manganese-oxide-bonded silicon (IMOF-Si) > organic sulfide-bonded silicon (OSF-Si) > ion-exchangeable silicon (IEF-Si) > carbonate-bound silicon (CF-Si). In particular, the contents of IMOF-Si and OSF-Si reached 2983.7~3434.7 mg/kg and 1067.6~1324.3 mg/kg, respectively, suggesting that the release and recycling of Si in surface sediments may be more sensitive to changes in redox conditions at the sediment–water interface, which become the main pathway for Si recycling, and the slow degradation of organic matter rich in OSF-Si may lead to long-term and continuous endogenous Si recycling. The low proportion (0.3~0.6%) and spatial differences of biogenic silicon (BSi) in the surface sediments of Dianchi Lake, as well as the poor correlation between BSi and TOC, TN, and chlorophyll a, indicated that the primary productivity of Dianchi Lake was still dominated by cyanobacteria and other algal blooms, while the relative abundance of siliceous organisms such as diatoms was low and closer to the central area of Dianchi Lake. Additionally, BSi may have a faster release capability relative to TOC and may participate in Si recycling.
48
Nwosu, Ebuka Canisius, Patricia Roeser, Sizhong Yang, Lars Ganzert, Olaf Dellwig, Sylvia Pinkerneil, Achim Brauer, Elke Dittmann, Dirk Wagner e Susanne Liebner. "From Water into Sediment—Tracing Freshwater Cyanobacteria via DNA Analyses". Microorganisms 9, n. 8 (21 agosto 2021): 1778. http://dx.doi.org/10.3390/microorganisms9081778.
Testo completoAbstract (sommario):
Sedimentary ancient DNA-based studies have been used to probe centuries of climate and environmental changes and how they affected cyanobacterial assemblages in temperate lakes. Due to cyanobacteria containing potential bloom-forming and toxin-producing taxa, their approximate reconstruction from sediments is crucial, especially in lakes lacking long-term monitoring data. To extend the resolution of sediment record interpretation, we used high-throughput sequencing, amplicon sequence variant (ASV) analysis, and quantitative PCR to compare pelagic cyanobacterial composition to that in sediment traps (collected monthly) and surface sediments in Lake Tiefer See. Cyanobacterial composition, species richness, and evenness was not significantly different among the pelagic depths, sediment traps and surface sediments (p > 0.05), indicating that the cyanobacteria in the sediments reflected the cyanobacterial assemblage in the water column. However, total cyanobacterial abundances (qPCR) decreased from the metalimnion down the water column. The aggregate-forming (Aphanizomenon) and colony-forming taxa (Snowella) showed pronounced sedimentation. In contrast, Planktothrix was only very poorly represented in sediment traps (meta- and hypolimnion) and surface sediments, despite its highest relative abundance at the thermocline (10 m water depth) during periods of lake stratification (May–October). We conclude that this skewed representation in taxonomic abundances reflects taphonomic processes, which should be considered in future DNA-based paleolimnological investigations.
49
Srdoč, Dušan, Nada Horvatinčić, Marijan Ahel, Walter Giger, Christian Schaffner, Ines Krajcar Bronić, Donat Petricioli, Jože Pezdič, Elena Marčenko e Anđelka Plenković-Moraj. "Anthropogenic Influence on the 14C Activity and Other Constituents of Recent Lake Sediments: A Case Study1". Radiocarbon 34, n. 3 (1992): 585–92. http://dx.doi.org/10.1017/s0033822200063864.
Testo completoAbstract (sommario):
Anthropogenic activities that introduce an excess of nutrients and other pollutants into rivers and lakes are causing significant changes in their aquatic environment. Excessive nutrients greatly accelerate eutrophication, and lake marl formed during eutrophication differs from that formed in oligotrophic water.We analyzed recent sediment cores from Prošće and Kozjak lakes located in Plitvice National Park, central Croatia. Analyses consisted of 14C activity of calcareous lake marl, the ratio of stable isotopes (δ13C, δ18O), organic compounds in the sediment and the distribution of diatoms. Previous 14C activity measurements helped to determine the sedimentation rate and thus the time period of increased input of nutrients into lakes. We determined the increased 14C activity in lake sediments caused by nuclear bomb effect in recent depth profiles. We attributed the sudden increase in diatom species, Cyclotella operculata unipuctata and Achnanthes clevei rostrata, in the uppermost 5-cm layer, to eutrophication of the lake water.We performed a molecular characterization of hydrocarbons isolated from the sediments, and applied computer-assisted high-resolution gas chromatography/mass spectrometry to estimate contributions of biogenic, fossil and pyrolytic hydrocarbons.
50
Kolpakova, E. S., e A. V. Velyamidova. "Organochlorine compounds in subarctic small lakes". Arctic and Antarctic Research 66, n. 2 (10 luglio 2020): 180–97. http://dx.doi.org/10.30758/0555-2648-2020-66-2-180-197.
Testo completoAbstract (sommario):
The article presents the results of studies of the environmental properties of organochlorines which differ in properties and origin, in the lake ecosystems of the Bolshezemelskaya tundra (Nenets Autonomous Okrug, Russia). The purpose of this study was to evaluate and assess the levels, distribution characteristics and composition of organochlorines in the bottom sediments of small lakes located in the Adzva river basin in Pymvashor natural boundary (the northernmost location of the exit of thermal-mineral springs of the continental Europe) and in the adjacent area, outside this unique subarctic hydrothermal zone.In order to meet this goal, multi-method (hydrochemical, geochemical, etc.) research was carried out using standard generally approved laboratory practices with their adaptation to the study goals. The quantitative content and composition of the target individual organochlorines were determined by gas chromatographic method with electron-capture detection.The presence of chlorophenol compounds and polychlorinated benzenes (including persistent organic pollutants) was shown in the lakes sediments. The influence of specific microclimatic conditions of subarctic hydrothermal system on the composition and distribution of chlorophenol compounds in lake sediments was considered. In the small lake sediment core in Pymvashor natural boundary a reducing trend in the levels of organochlorines with depth has been recorded (conditioned among other things by the lithological features of bottom sediments). The chlorophenol compounds were found at highest concentrations (619.3–765.5 ng/g) in the sediment upper layers, rich in organic matter; chlorophenol composition was represented mainly by chlorinated phenols, most likely of biotic origin. A lower concentration (185.0 ng/g) of chlorophenol compounds of predominantly abiogenic origin was determined in the lake sediments outside hydrothermal system. The presence and levels of persistent organochlorine pollutants (pentachlorophenol 0.1–2.4 ng/g; hexa- and pentachlorobenzenes 0.4–3.6 ng/g) in the lake sediments were associated with long-range atmospheric transport from various origin sources in nearby regions and low-latitude territories.