Based on the quantitative analyses of abundance of planktonic foraminifera, benthic foraminifera, calcareous nannofossils, the ratios of calcareous to siliceous microfossils, and the determination of carbonate content...Based on the quantitative analyses of abundance of planktonic foraminifera, benthic foraminifera, calcareous nannofossils, the ratios of calcareous to siliceous microfossils, and the determination of carbonate contents in the surface sediments of the northeastern South China Sea, it has been found that the carbonate contents, the abundance of planktonic foraminifera and calcareous nannoplankton, and the ratio of calcareous microfossils decrease rapidly while the ratio of the benthic foraminifera to the total foraminiferal fauna, specific value of siliceous microfossils, and the percentage of the agglutinated tests in the benthic foraminiferal fauna increase with the water depth. The results indicate that the microfossils abundance and ratio, and the carbonate content are closely related to the carbonate lysocline and carbonate compensation depth (CCD) in the study area. In addition, the carbonate lysocline and the CCD are different between the southern and northern parts of the South China Sea. Both the lysocline and the CCD are deeper in the south with 2 600 and 3 600 m than in the north with 2 200 and 3 400 m, respectively.展开更多
This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms...This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.展开更多
The presence of submerged vegetation on river beds can change the water flow structure and alter the state of sediment motion. In this study, the incipient motion of sediment in the presence of submerged flexible vege...The presence of submerged vegetation on river beds can change the water flow structure and alter the state of sediment motion. In this study, the incipient motion of sediment in the presence of submerged flexible vegetation in open channels was investigated in a laboratory experiment. The vegetation was simulated with flexible rubber cylinders arranged in parallel arrays. The effect of the vegetation density, water depth, and sediment grain size on the incipient motion was investigated. The experimental results indicate that the incipient motion velocity of sediment increases as the vegetation density decreases and the water depth and sediment grain size increase. With flexible plants, the incipient motion velocity of sediment is lower than it is without vegetation, and is larger than it is with rigid vegetation. A general incipient motion velocity equation was derived, which can be applied to both flexible and rigid vegetation conditions.展开更多
Populations of culturable microbes and activities of dehydrogenase & ?-D glucosidase were found maximum in surface soil and decreased with increase in depth in Sundarban mangrove environment.The maximum (13.529 X ...Populations of culturable microbes and activities of dehydrogenase & ?-D glucosidase were found maximum in surface soil and decreased with increase in depth in Sundarban mangrove environment.The maximum (13.529 X 106 C.F.U g-1 dry weight of soil) and minimum (11.547 X 106 C.F.U g-1 dry weight of soil) total microbial popu- lations in surface soil were recorded during po- st-monsoon and monsoon respectively. At 60 cm depth, the lower (6.396 X 106 C.F.U g-1 dry weight of soil) and higher (8.003 X 106 C.F.U g-1 dry weight of soil) numbers of total microbial populations were observed during monsoon and post-monsoon respectively. A decreasing trend of total microbial load, enzyme activities and nutrient status with organic carbon were found with increase in depth throughout the year. Present study revealed the relationship among depth integrated variations of physico-chemical compo- nents (viz. soil temperature, pH, moisture, orga- nic-C, .nitrogen, and available-P) and microbial populations as well as activity of dehydrogenase and ?-D glucosidase enzymes.展开更多
Missouri is a state with rich karst terrain. Geotechnical evaluation of foundation design for bridges and dams requires an understanding of the characteristics of subsurface geological environment, including sediments...Missouri is a state with rich karst terrain. Geotechnical evaluation of foundation design for bridges and dams requires an understanding of the characteristics of subsurface geological environment, including sediments, bedrock and benthic habitat. It is crucial that the community empowers itself with the knowledge of the karst system’s characteristics in order to potentially use it as a source of water and drainage, but also to avoid the disaster of building constructions too close to vulnerable land on top of massive karst caverns. Electrical resistivity tomography profiling (underwater cables), and continuous resistivity profiling (towed cable) surveys were conducted to characterize the lake sediments (rock and soil) beneath the man-made Little Prairie Lake, in Central of Missouri State, United States. Electrical resistivity (with marine cables and towed cable) was used to determine variability in the lithology and thickness of sediments (soil and rock) beneath the lake with conjunction of echo sounder in order to calculate water depth. Side scan sonar was used to map the variations in the lithology/nature of exposed lakebed sediments and to locate the potential hazard of trees. On land, electrical resistivity tomography was used with multi-channel analysis of surface wave method to determine sediments, joints, and the depth of bedrock. Analyses of the acquired data revealed the location and orientation of the original stream channels (prior to the construction of the earth fill dam). Underwater electrical resistivity tomography and continuous resistivity profiling determined joints, sediments, and bedrock underneath water bodies. Integrated marine geophysical tools help to evaluate the subsurface prior to any construction project (dam or bridge), are useful in determining the characteristics of lithology (fractured rock, intact rock and soil), and make it possible to map benthic habitat and the submerged potential hazards of trees on the lakebed as well as accurately measuring water depth.展开更多
Temporal and spatial variations in accommodation (i.e., paleo-water depth) and sediment accumulation (amount of deposition) in the intra-arc Osaka Basin, Japan, were reconstructed from the post-glacial transgression t...Temporal and spatial variations in accommodation (i.e., paleo-water depth) and sediment accumulation (amount of deposition) in the intra-arc Osaka Basin, Japan, were reconstructed from the post-glacial transgression through the sea-level highstand, a total of 9000 years. At the beginning of the marine transgressive stage (about 11,000 cal y BP), paleo-water depths were shallow and the sediment accumulation was large. The area occupied by Osaka Bay gradually extended and sediment deposition decreased from 11,000 to 6000 cal y BP. During the period of maximum transgression (6000 - 5000 cal y BP), an inner bay, Kawachi Bay with a water depth of 5 - 10 m, was expanded in the inland eastern Osaka area, and paleo-water depths reached a maximum and depositional rates reached a minimum. During the subsequent highstand and small regression (about 5000 cal y BP to the present), however, deposition increased rapidly as a result of river delta and shoreline progradations. Regional differences were observed in accommodation and accumulation between the outer bay area and the inner bay area. During both the transgressive and regressive stages, deposition decreased in the inner bay area. In contrast, in the outer bay area and in the basin overall, deposition was high during the first part of the transgressive stage but it decreased during the maximum transgression, before reaching a maximum during the subsequent highstand and regression. During the regressive stage, fluvial delta progradation led to the formation of a thick sequence of delta body sediments. Sediment accumulation was 30% - 40% higher during the regressive stage than that during the transgressive stage.展开更多
This paper assesses the sediment load of the glacier fed Langtang River, Nepal from April 2014 to March 2015. Water samples were collected from the centre of the river with a frequency of two samples per each sampling...This paper assesses the sediment load of the glacier fed Langtang River, Nepal from April 2014 to March 2015. Water samples were collected from the centre of the river with a frequency of two samples per each sampling day using the Depth Integration Technique (DIT) on daily basis in the monsoon season, weekly in the pre- and post-monsoon seasons and bi-monthly in the winter season. Suspended sediment concentration (SSC) is calculated from the water samples using filtration followed by oven-drying, and a rating curve is used to calculate daily discharge of the Langtang River. The annual sediment yield is 109,276.75 tons and 37.69, 11.52 and 5.54 tons of sediment is transported per day in the pre-monsoon, post-monsoon and winter seasons, respectively. There is a very high value of 872.86 tons per day in the monsoon season, which contributes the highest sediment load among all of the seasons comprising 83% of the total sediment transport. Diurnal cycle of sediment discharge is clearly seen with higher sediment discharge during the evening than the morning and reaching maximum values of 41.1 kg·s<sup>-1</sup> and 61.5 kg·s<sup>-1</sup>, respectively. A clock-wise hysteresis loop has been obtained for discharge and sediment discharge where sediment flux is higher in the early monsoon than in the late monsoon for a corresponding discharge.展开更多
<span style="font-family:Verdana;">Land-use change has been</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">...<span style="font-family:Verdana;">Land-use change has been</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">a factor that alters the hydrologic response of the watersheds leading to influencing on sediment yield changes. This study is mainly focusing on the assessment of the impacts of the land-use changes on sediment load and lake depth reduction on Lake Ziway, Ethiopia using an integrated approach of Remote Sensing (RS), GIS and SWAT model. ERDAS IMAGINE 14 model was used to generate land-use maps from Landsat TM, ETM+, and Ls8 acquired, in 1988, 2002 and 2015 as representative for the periods of (1988</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">1998), (1998</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2008) and (2008</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">2018), respectively. The maximum likelihood algorithm of supervised classification applied to classify the </span><span style="font-family:Verdana;">basin land-use into seven land-use classes. The SWAT hydrological model</span><span style="font-family:Verdana;"> with ArcGIS interface setup for the basin to evaluate the flow and sediment load with calibration and validation performance of the model range R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (0.71 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 0.89) and NSE (0.57 </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 0.87). As a result, the total average annual sediment yield from the sub-basins estimated as 3.59</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr, 4.36</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr, and 4.89</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr for three consecutive decadal periods 1988</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">1998, 1998</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2008, and</span><span style="font-family:Verdana;"> 2008</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">2018 respectively. The increasing trend of sediment yield in the Lake Ziway watershed through one period to another justified as due to land-use. Similarly, the net sediment volume deposited in the lake also showed incremental </span><span style="font-family:Verdana;">trained with the land-use changes as 1.5</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mcm/yr, 1.81 mcm/yr, and 2.033</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mcm/yr for the period of 1988-1998, 1999-2008, and 2009-2018, respectively. The depth and water holding capacity of the lake reduced by 4.3</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">m and 25.76</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mcm, respectively, from the depth and capacity recorded on the 2006 bathy</span><span style="font-family:Verdana;">metric survey, which was the effect of deposited sediment over the last 12</span><span style="font-family:Verdana;"> years.</span></span>展开更多
Nitrite-and nitrate-coupled anaerobic oxidation of methane(AOM),mediated by Candidatus Methylomirabilis-like bacteria and Methanoperedens-like archaea,respectively,are two recent additions of freshwater carbon and nit...Nitrite-and nitrate-coupled anaerobic oxidation of methane(AOM),mediated by Candidatus Methylomirabilis-like bacteria and Methanoperedens-like archaea,respectively,are two recent additions of freshwater carbon and nitrogen cycles.However,the quantitative roles of the two AOM processes in CH_(4)emission reduction in lakes have not yet been characterized.Here,we explored vertical(0–10,10–20,and 20–30 cm)variation in nitrite-and nitrate-coupled AOM activity,as well as the abundance and community structure of Methylomirabilis-and Methanoperedens-like methanotrophs in freshwater lake sediment.The potential rates of nitrite-and nitrate-coupled AOM quantified via^(13)CH_(4)isotopic experiments were 0.41–3.84 and 0.32–3.88 nmol CH_(4)/(g·d),respectively.The rates of AOM exhibited significant and consistent depth-related variation across different sampling sites,with both peaking in the 10–20 cm layer.The abundance of Methylomirabilis-like bacteria and Methanoperedens-like archaea quantified via quantitative PCR was 3.34×10^(5)–9.17×10^(6)and 1.27×10^(6)–9.46×10^(6)copies/g,respectively.There was no consistent depth-related variation in the abundance of bacteria or archaea.The community composition of both Methylomirabilis-and Methanoperedens-like methanotrophs remained relatively stable along the sediment profile,while the composition significantly changed across sampling sites.Sediment pH and the content of NH4+and organic carbon were key variables influencing the community structure of Methylomirabilis-and Methanoperedens-like methanotrophs.Overall,we characterized vertical variation in nitrite-and nitrate-coupled AOM processes in lake sediment,which helps quantify their role in CH_(4)consumption in freshwater aquatic ecosystems.展开更多
文摘Based on the quantitative analyses of abundance of planktonic foraminifera, benthic foraminifera, calcareous nannofossils, the ratios of calcareous to siliceous microfossils, and the determination of carbonate contents in the surface sediments of the northeastern South China Sea, it has been found that the carbonate contents, the abundance of planktonic foraminifera and calcareous nannoplankton, and the ratio of calcareous microfossils decrease rapidly while the ratio of the benthic foraminifera to the total foraminiferal fauna, specific value of siliceous microfossils, and the percentage of the agglutinated tests in the benthic foraminiferal fauna increase with the water depth. The results indicate that the microfossils abundance and ratio, and the carbonate content are closely related to the carbonate lysocline and carbonate compensation depth (CCD) in the study area. In addition, the carbonate lysocline and the CCD are different between the southern and northern parts of the South China Sea. Both the lysocline and the CCD are deeper in the south with 2 600 and 3 600 m than in the north with 2 200 and 3 400 m, respectively.
文摘This paper presents numerical simulations of dam-break flow over a movable bed. Two different mathematical models were compared: a fully coupled formulation of shallow water equations with erosion and deposition terms(a depth-averaged concentration flux model), and shallow water equations with a fully coupled Exner equation(a bed load flux model). Both models were discretized using the cell-centered finite volume method, and a second-order Godunov-type scheme was used to solve the equations. The numerical flux was calculated using a Harten, Lax, and van Leer approximate Riemann solver with the contact wave restored(HLLC). A novel slope source term treatment that considers the density change was introduced to the depth-averaged concentration flux model to obtain higher-order accuracy. A source term that accounts for the sediment flux was added to the bed load flux model to reflect the influence of sediment movement on the momentum of the water. In a onedimensional test case, a sensitivity study on different model parameters was carried out. For the depth-averaged concentration flux model,Manning's coefficient and sediment porosity values showed an almost linear relationship with the bottom change, and for the bed load flux model, the sediment porosity was identified as the most sensitive parameter. The capabilities and limitations of both model concepts are demonstrated in a benchmark experimental test case dealing with dam-break flow over variable bed topography.
基金supported by the China National Funds for Distinguished Young Scientists(Grant No.51125034)the State Key Program of the Nationa Natural Science Foundation of China(Grant No.51239003)the Nationa Natural Science Foundation of China(Grants No.51109066 and 51109065)
文摘The presence of submerged vegetation on river beds can change the water flow structure and alter the state of sediment motion. In this study, the incipient motion of sediment in the presence of submerged flexible vegetation in open channels was investigated in a laboratory experiment. The vegetation was simulated with flexible rubber cylinders arranged in parallel arrays. The effect of the vegetation density, water depth, and sediment grain size on the incipient motion was investigated. The experimental results indicate that the incipient motion velocity of sediment increases as the vegetation density decreases and the water depth and sediment grain size increase. With flexible plants, the incipient motion velocity of sediment is lower than it is without vegetation, and is larger than it is with rigid vegetation. A general incipient motion velocity equation was derived, which can be applied to both flexible and rigid vegetation conditions.
文摘Populations of culturable microbes and activities of dehydrogenase & ?-D glucosidase were found maximum in surface soil and decreased with increase in depth in Sundarban mangrove environment.The maximum (13.529 X 106 C.F.U g-1 dry weight of soil) and minimum (11.547 X 106 C.F.U g-1 dry weight of soil) total microbial popu- lations in surface soil were recorded during po- st-monsoon and monsoon respectively. At 60 cm depth, the lower (6.396 X 106 C.F.U g-1 dry weight of soil) and higher (8.003 X 106 C.F.U g-1 dry weight of soil) numbers of total microbial populations were observed during monsoon and post-monsoon respectively. A decreasing trend of total microbial load, enzyme activities and nutrient status with organic carbon were found with increase in depth throughout the year. Present study revealed the relationship among depth integrated variations of physico-chemical compo- nents (viz. soil temperature, pH, moisture, orga- nic-C, .nitrogen, and available-P) and microbial populations as well as activity of dehydrogenase and ?-D glucosidase enzymes.
文摘Missouri is a state with rich karst terrain. Geotechnical evaluation of foundation design for bridges and dams requires an understanding of the characteristics of subsurface geological environment, including sediments, bedrock and benthic habitat. It is crucial that the community empowers itself with the knowledge of the karst system’s characteristics in order to potentially use it as a source of water and drainage, but also to avoid the disaster of building constructions too close to vulnerable land on top of massive karst caverns. Electrical resistivity tomography profiling (underwater cables), and continuous resistivity profiling (towed cable) surveys were conducted to characterize the lake sediments (rock and soil) beneath the man-made Little Prairie Lake, in Central of Missouri State, United States. Electrical resistivity (with marine cables and towed cable) was used to determine variability in the lithology and thickness of sediments (soil and rock) beneath the lake with conjunction of echo sounder in order to calculate water depth. Side scan sonar was used to map the variations in the lithology/nature of exposed lakebed sediments and to locate the potential hazard of trees. On land, electrical resistivity tomography was used with multi-channel analysis of surface wave method to determine sediments, joints, and the depth of bedrock. Analyses of the acquired data revealed the location and orientation of the original stream channels (prior to the construction of the earth fill dam). Underwater electrical resistivity tomography and continuous resistivity profiling determined joints, sediments, and bedrock underneath water bodies. Integrated marine geophysical tools help to evaluate the subsurface prior to any construction project (dam or bridge), are useful in determining the characteristics of lithology (fractured rock, intact rock and soil), and make it possible to map benthic habitat and the submerged potential hazards of trees on the lakebed as well as accurately measuring water depth.
文摘Temporal and spatial variations in accommodation (i.e., paleo-water depth) and sediment accumulation (amount of deposition) in the intra-arc Osaka Basin, Japan, were reconstructed from the post-glacial transgression through the sea-level highstand, a total of 9000 years. At the beginning of the marine transgressive stage (about 11,000 cal y BP), paleo-water depths were shallow and the sediment accumulation was large. The area occupied by Osaka Bay gradually extended and sediment deposition decreased from 11,000 to 6000 cal y BP. During the period of maximum transgression (6000 - 5000 cal y BP), an inner bay, Kawachi Bay with a water depth of 5 - 10 m, was expanded in the inland eastern Osaka area, and paleo-water depths reached a maximum and depositional rates reached a minimum. During the subsequent highstand and small regression (about 5000 cal y BP to the present), however, deposition increased rapidly as a result of river delta and shoreline progradations. Regional differences were observed in accommodation and accumulation between the outer bay area and the inner bay area. During both the transgressive and regressive stages, deposition decreased in the inner bay area. In contrast, in the outer bay area and in the basin overall, deposition was high during the first part of the transgressive stage but it decreased during the maximum transgression, before reaching a maximum during the subsequent highstand and regression. During the regressive stage, fluvial delta progradation led to the formation of a thick sequence of delta body sediments. Sediment accumulation was 30% - 40% higher during the regressive stage than that during the transgressive stage.
文摘This paper assesses the sediment load of the glacier fed Langtang River, Nepal from April 2014 to March 2015. Water samples were collected from the centre of the river with a frequency of two samples per each sampling day using the Depth Integration Technique (DIT) on daily basis in the monsoon season, weekly in the pre- and post-monsoon seasons and bi-monthly in the winter season. Suspended sediment concentration (SSC) is calculated from the water samples using filtration followed by oven-drying, and a rating curve is used to calculate daily discharge of the Langtang River. The annual sediment yield is 109,276.75 tons and 37.69, 11.52 and 5.54 tons of sediment is transported per day in the pre-monsoon, post-monsoon and winter seasons, respectively. There is a very high value of 872.86 tons per day in the monsoon season, which contributes the highest sediment load among all of the seasons comprising 83% of the total sediment transport. Diurnal cycle of sediment discharge is clearly seen with higher sediment discharge during the evening than the morning and reaching maximum values of 41.1 kg·s<sup>-1</sup> and 61.5 kg·s<sup>-1</sup>, respectively. A clock-wise hysteresis loop has been obtained for discharge and sediment discharge where sediment flux is higher in the early monsoon than in the late monsoon for a corresponding discharge.
文摘<span style="font-family:Verdana;">Land-use change has been</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">a factor that alters the hydrologic response of the watersheds leading to influencing on sediment yield changes. This study is mainly focusing on the assessment of the impacts of the land-use changes on sediment load and lake depth reduction on Lake Ziway, Ethiopia using an integrated approach of Remote Sensing (RS), GIS and SWAT model. ERDAS IMAGINE 14 model was used to generate land-use maps from Landsat TM, ETM+, and Ls8 acquired, in 1988, 2002 and 2015 as representative for the periods of (1988</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">1998), (1998</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2008) and (2008</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">2018), respectively. The maximum likelihood algorithm of supervised classification applied to classify the </span><span style="font-family:Verdana;">basin land-use into seven land-use classes. The SWAT hydrological model</span><span style="font-family:Verdana;"> with ArcGIS interface setup for the basin to evaluate the flow and sediment load with calibration and validation performance of the model range R</span><sup><span style="font-family:Verdana;">2</span></sup><span style="font-family:Verdana;"> (0.71 </span></span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 0.89) and NSE (0.57 </span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;"> 0.87). As a result, the total average annual sediment yield from the sub-basins estimated as 3.59</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr, 4.36</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr, and 4.89</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">t/ha/yr for three consecutive decadal periods 1988</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">1998, 1998</span><span style="font-family:Verdana;">-</span><span style="font-family:Verdana;">2008, and</span><span style="font-family:Verdana;"> 2008</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">2018 respectively. The increasing trend of sediment yield in the Lake Ziway watershed through one period to another justified as due to land-use. Similarly, the net sediment volume deposited in the lake also showed incremental </span><span style="font-family:Verdana;">trained with the land-use changes as 1.5</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mcm/yr, 1.81 mcm/yr, and 2.033</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">mcm/yr for the period of 1988-1998, 1999-2008, and 2009-2018, respectively. The depth and water holding capacity of the lake reduced by 4.3</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">m and 25.76</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mcm, respectively, from the depth and capacity recorded on the 2006 bathy</span><span style="font-family:Verdana;">metric survey, which was the effect of deposited sediment over the last 12</span><span style="font-family:Verdana;"> years.</span></span>
基金supported by the National Natural Science Foundation of China(No.42377116)the R&D Foundation of Jiangsu Province,China(No.BK20220021)the 333 High-Level Talents Training Project of Jiangsu Province,China(No.BRA2022023).
文摘Nitrite-and nitrate-coupled anaerobic oxidation of methane(AOM),mediated by Candidatus Methylomirabilis-like bacteria and Methanoperedens-like archaea,respectively,are two recent additions of freshwater carbon and nitrogen cycles.However,the quantitative roles of the two AOM processes in CH_(4)emission reduction in lakes have not yet been characterized.Here,we explored vertical(0–10,10–20,and 20–30 cm)variation in nitrite-and nitrate-coupled AOM activity,as well as the abundance and community structure of Methylomirabilis-and Methanoperedens-like methanotrophs in freshwater lake sediment.The potential rates of nitrite-and nitrate-coupled AOM quantified via^(13)CH_(4)isotopic experiments were 0.41–3.84 and 0.32–3.88 nmol CH_(4)/(g·d),respectively.The rates of AOM exhibited significant and consistent depth-related variation across different sampling sites,with both peaking in the 10–20 cm layer.The abundance of Methylomirabilis-like bacteria and Methanoperedens-like archaea quantified via quantitative PCR was 3.34×10^(5)–9.17×10^(6)and 1.27×10^(6)–9.46×10^(6)copies/g,respectively.There was no consistent depth-related variation in the abundance of bacteria or archaea.The community composition of both Methylomirabilis-and Methanoperedens-like methanotrophs remained relatively stable along the sediment profile,while the composition significantly changed across sampling sites.Sediment pH and the content of NH4+and organic carbon were key variables influencing the community structure of Methylomirabilis-and Methanoperedens-like methanotrophs.Overall,we characterized vertical variation in nitrite-and nitrate-coupled AOM processes in lake sediment,which helps quantify their role in CH_(4)consumption in freshwater aquatic ecosystems.
