scholarly journals Spatial–temporal variation of nitrogen and diffusion flux across the water–sediment interface at the hydro-fluctuation belt of Danjiangkou reservoir in China

2020 ◽  
Vol 20 (4) ◽  
pp. 1241-1252
Author(s):  
Han Wang ◽  
Yuping Han ◽  
Lide Pan
Keyword(s):  
Diffusion Flux ◽  
Sample Collection ◽  
Sediment Pore Water ◽  
Overlying Water ◽  
Danjiangkou Reservoir ◽  
Water And Sediment ◽  
Water Quality Deterioration ◽  
Nitrogen Contents ◽  
And Diffusion ◽  
Sediment Interface

Abstract Based on overlying water and sediment sample collection from 15 sites during July, September, November 2018 and January 2019 in the hydro-fluctuation belt of Danjiangkou reservoir China, the variation of nitrogen (N) was studied. And the concentrations of NH4+-N, NO3−-N and NO2−-N in the sediment, pore water and overlying water were determined to evaluate the diffusion flux across the water–sediment interface. The results showed that the lowest sediment N concentration was 36.54 mg/L in July, and the highest one was 145.93 mg/L in November. Spatially, the sediment N concentrations were higher in tidal soil and loam than in sandy soil. According to the diffusion fluxes of NH4+, NO3− and NO2−, sediments at all sites tend to release N to the overlying water except in the sampling month of November, when the sediment acts as a sink of NO3−. The highest release rates of NH4+-N and NO3−-N were 17.66 mg m−2·d−1 and 80.15 mg m−2·d−1, respectively, which are much higher than the release rate of NO2−-N (0.29 mg m−2·d−1). The findings indicate that hydro-fluctuation belt sediment contributes a lot to the nitrogen contents in the overlying water, and internal pollution is a main reason for the water quality deterioration and even eutrophication.

scholarly journals Changes in mobility and solubility of the redox sensitive metals Fe, Mn and Co at the seawater-sediment interface following CO<sub>2</sub> seepage

2009 ◽  
Vol 6 (3) ◽  
pp. 5623-5659 ◽  
Author(s):  
M. V. Ardelan ◽  
E. Steinnes
Keyword(s):  
Second Phase ◽  
Total Acid ◽  
Sediment Pore Water ◽  
Overlying Water ◽  
Control Chamber ◽  
Water And Sediment ◽  
Iron Manganese ◽  
The Impact ◽  
Diffusive Gradients ◽  
Sediment Interface

Abstract. The impact of CO2 seepage on the solubility and distribution of the redox-sensitive metals iron, manganese, and cobalt in seawater and sediment pore water has been studied in experiments in laboratory-scale 0.6 m3 chambers. The mobility and solubility of Fe, Mn and Co were investigated in seawater, membrane filtered seawater, and DGT samplers deployed in water and sediment during a 26 day CO2 seepage study. During the first phase of the experiment of CO2 seepage (0–16 days), total acid-leachable (pH≈1) and "dissolved" (<0.2 μm) concentrations of Fe, Mn and Co (DFe, DMn and DCo) in the seawater increased significantly; the ratios of concentrations of DFe, DMn and DCo in the CO2 chamber to the corresponding values in the control chamber (RDFe, RDMn and RDCo) were as high as 6, 65 and 58, respectively. The second phase of experiment consisted of an additional 10 days of incubation, where the concentrations of all the metals studied still increased but at reduced rates for DMn and DCo. The highest values of RDFe, RDMn and RDCo were about 3 for all metals during this part of the experiment. DGT (diffusive gradients in thin film) labile fractions denoted FeDGT, MnDGT and CoDGT were, respectively 50, 25 and 22 times higher in the CO2 seepage chamber than in the control chamber in the first phase of the experiment. During the second phase, all DGT labile metal concentrations still increased considerably, most notably for Fe. The ratio of FeDGT in the CO2 chamber to that in the control (RDGT-Fe) was still high, about 5, in the second phase of the experiment, whereas the increase in MnDGT and CoDGT slowed down. Our results indicate that acidification following CO2 seepage enhances the mobility and solubility of Fe Mn and Co in sediment and overlying water with contribution of changing in redox conditions and seepage related re-suspension.

scholarly journals Changes in mobility and solubility of the redox sensitive metals Fe, Mn and Co at the seawater-sediment interface following CO<sub>2</sub> seepage

2010 ◽  
Vol 7 (2) ◽  
pp. 569-583 ◽  
Author(s):  
M. V. Ardelan ◽  
E. Steinnes
Keyword(s):  
Second Phase ◽  
Total Acid ◽  
Sediment Pore Water ◽  
Overlying Water ◽  
Control Chamber ◽  
Water And Sediment ◽  
Iron Manganese ◽  
The Impact ◽  
Diffusive Gradients ◽  
Sediment Interface

Abstract. The impact of CO2 seepage on the solubility and distribution of the redox-sensitive metals iron, manganese, and cobalt in seawater and sediment pore water has been studied in experiments in laboratory-scale 0.6 m3 chambers. The mobility and solubility of Fe, Mn and Co were investigated in seawater, membrane filtered seawater, and DGT samplers deployed in water and sediment during a 26 day CO2 seepage study. During the first phase of the experiment of CO2 seepage (0–16 days), total acid-leachable (pH 1) and "dissolved" (<0.2 μm) concentrations of Fe, Mn and Co (DFe, DMn and DCo) in the seawater increased significantly; the ratios of concentrations of DFe, DMn and DCo in the CO2 chamber to the corresponding values in the control chamber (RDFe, RDMn and RDCo) were as high as 6, 65 and 58, respectively. The second phase of experiment consisted of an additional 10 days of incubation, where the concentrations of all the metals studied still increased but at reduced rates for DMn and DCo. The highest values of RDFe, RDMn and RDCo were about 3 for all metals during this part of the experiment. DGT (diffusive gradients in thin film) labile fractions denoted FeDGT, MnDGT and CoDGT were, respectively 50, 25 and 22 times higher in the CO2 seepage chamber than in the control chamber in the first phase of the experiment. During the second phase, all DGT labile metal concentrations still increased considerably, most notably for Fe. The ratio of FeDGT in the CO2 chamber to that in the control (RDGT-Fe) was still high, about 5, in the second phase of the experiment, whereas the increase in MnDGT and CoDGT slowed down. Our results indicate that acidification following CO2 seepage enhances the mobility and solubility of Fe Mn and Co in sediment and overlying water with contribution of changing in redox conditions and seepage related re-suspension.

scholarly journals Diffusion flux of phosphorus nutrients at the sediment–water interface of the Ulansuhai Lake in northern China

2017 ◽  
Vol 75 (6) ◽  
pp. 1455-1465 ◽  
Author(s):  
Shengnan Zhao ◽  
Xiaohong Shi ◽  
Changyou Li ◽  
Sheng Zhang ◽  
Biao Sun ◽  
...  
Keyword(s):  
Interstitial Water ◽  
Diffusion Flux ◽  
Northern China ◽  
Inorganic Phosphorus ◽  
Exchange Capacity ◽  
Internal Source ◽  
Water Interface ◽  
Overlying Water ◽  
Water And Sediment ◽  
Exchange Flux

Overlying water and sediment samples were collected from 11 locations in Ulansuhai Lake in June of 2012 to determine the concentration of dissolved inorganic phosphorus (DIP) in the interstitial water, overlying water and sediment and to estimate the diffusion flux of DIP at the sediment–water interface. The DIP levels in overlying water were 0.004–0.185 mg/L (average = 0.062 mg/L), while they were 0.05–0.25 mg/L (average = 0.124 mg/L) in the interstitial water in the 0–2 cm surface sediment. Moreover, the annual mean exchange flux of DIP in the sediment was between −0.092 mg/m2·d and 0.053 mg/m2·d, and this occurred via internal source action in most areas. After area weighting, it is estimated that the exchange capacity of DIP at the sediment–water interface of the Ulansuhai Lake is 1.30 t/a. These findings indicate internal loading of phosphorus in sediment of the Ulansuhai Lake; thus, the diffusion of DIP in the interstitial water has effects on the lake, with a degree of influence of 2.7% to 81.5%.

Benthic exchange of sedimentary metals (Cd, Cu, Fe, Mn, Ni and Zn) in the Deûle River (Northern France)

2012 ◽  
Vol 9 (5) ◽  
pp. 485 ◽  
Author(s):  
Beatriz Lourino-Cabana ◽  
Ludovic Lesven ◽  
Gabriel Billon ◽  
Lionel Denis ◽  
Baghdad Ouddane ◽  
...  
Keyword(s):  
Trace Metal ◽  
Sediment Cores ◽  
Metal Exchange ◽  
Negative Effects ◽  
Overlying Water ◽  
Colloidal Iron ◽  
Northern France ◽  
Anoxic Events ◽  
Co Precipitation ◽  
Sediment Interface

Environmental context Exchange processes at the water–sediment interface can release metals to riverine waters, having negative effects on organisms in the water column. We investigate the geochemical processes and metal exchange between the surface sediment and the overlying water under metal contamination conditions. Results suggest that the sediment can be a significant source of metal pollution in aquatic systems, particularly during anoxic events. Abstract Experiments were performed on the Deûle River (Northern France), which is strongly polluted by smelting plants, in the aim to investigate the influence of diagenetic processes and benthic macro-faunal activity on trace metal (Cd, Cu, Ni and Zn) and major metal (Fe, Mn) exchanges occurring at the water–sediment interface. Diffusive metal fluxes were determined from pore water metal concentration gradients measured in sediment cores. Benthic metal fluxes were evaluated using incubation chambers under dark conditions, and by further examining key variables (O2, CO2, redox potential and pH) affecting metal release and sequestration processes. As a whole, it was demonstrated that benthic fluxes were strongly dependent upon medium oxygenation and generation of colloidal iron oxides and hydroxides at the overlying water–sediment interface, raising the possibility of trace-metal adsorption and (co)precipitation.

Distribution of chlorophenolic compounds, from a pulp mill, in Lake Bonney, South Australia

1993 ◽  
Vol 44 (6) ◽  
pp. 825 ◽  
Author(s):  
JA Van Leeuwen ◽  
BC Nicholson ◽  
KP Hayes
Keyword(s):  
South Australia ◽  
Pulp Mill ◽  
Molecular Chlorine ◽  
Sample Collection ◽  
Sediment Samples ◽  
Discharge Point ◽  
Water And Sediment ◽  
Chlorinated Guaiacols ◽  
Effluent Discharge ◽  
Chlorinated Catechols

Water and sediment samples from Lake Bonney (south-eastern South Australia) were collected at various distances from the effluent discharge point of a sulfite-based pulp mill and analysed for chlorophenolic compounds. The period of sample collection (July 1991 to January 1992) occurred during a time when bleaching process of the mill was being converted from using molecular chlorine to using hydrogen peroxide. In water samples, the major chlorophenolic compounds detected were 2,4,6-trichlorophenol, tetrachlorocatechol and chlorinated guaiacols. In sediment samples, the major chlorophenolic compounds detected were chlorinated guaiacols and chlorinated catechols. The concentrations of these compounds in lake water generally decreased over the sampling period, corresponding to the decrease in use of molecular chlorine. Concentrations in sediment decreased with increasing distance from the discharge point. The presence of chlorinated guaiacols in water and sediment at a site 17 km from the effluent discharge point indicated that these compounds degrade slowly in the lake. The presence of the chlorinated catechols in sediments at localities where these compounds were not detected in the water suggests that de-0-methylation of adsorbed chlorinated guaiacols occurs and/or that there is preferential adsorption of chlorinated catechols to sediment.

Heat and Diffusion Fluxes in a Multicomponent Ionized Gas in a Magnetic Field

1969 ◽  
Vol 24 (6) ◽  
pp. 967-976
Author(s):  
R. S. Devoto
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Thermal Diffusion ◽  
Diffusion Flux ◽  
Momentum Equation ◽  
Ionized Gas ◽  
Burnett Method ◽  
And Diffusion ◽  
Monatomic Gas

Ordinary and thermal diffusion as well as heat flux in a dilute, ionized, multicomponent monoatomic gas in a magnetic field are considered with the Chapman-Enskog-Burnett method. It is shown how, with certain modifications, the usual expressions for the properties of an un-ionized monatomic gas may be applied to this case. The expression for the diffusion flux is compared with the momentum equation suggested by Schliiter.

scholarly journals Migration and transformation of dissolved carbon during accumulated cyanobacteria decomposition in shallow eutrophic lakes: a simulated microcosm study

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5922 ◽  
Author(s):  
Zhichun Li ◽  
Yanping Zhao ◽  
Xiaoguang Xu ◽  
Ruiming Han ◽  
Mingyue Wang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Cycling ◽  
Dissolved Inorganic Carbon ◽  
Eutrophic Lakes ◽  
Overlying Water ◽  
Dissolved Carbon ◽  
Laboratory Microcosm ◽  
Transformation Mechanisms ◽  
Diffusive Fluxes ◽  
Sediment Interface

The decomposition processes of accumulated cyanobacteria can release large amounts of organic carbon and affect the carbon cycling in shallow eutrophic lakes. However, the migration and transformation mechanisms of dissolved carbon (DC) require further study and discussion. In this study, a 73-day laboratory microcosm experiment using suction samplers (Rhizon and syringe) was conducted to understand the migration and transformation of DC during the cyanobacteria decomposition. The decomposition of cyanobacteria biomass caused anoxic and reduction conditions, and changed the acid-base environment in the water column. During the early incubation (days 0–18), a large amount of cyanobacteria-derived particulate organic matter (POM) was decomposed into dissolved organic carbon (DOC) in the overlying water, reaching the highest peak value of 1.82 g L−1 in the treatment added the high cyanobacteria biomass (470 g). After 18 days of incubation, the mineralization of increased DOC to dissolved inorganic carbon (DIC) maintained a high DIC level of overlying water in treatments added cyanobacteria biomass. The treatment added the medium cyanobacteria biomass (235 g) presented the lower DOC/total dissolved carbon ratio than the high cyanobacteria biomass associated with the lower mineralization from DOC to DIC. Due to the concentration differences of DIC at water-sediment interface, the main migration of DIC from pore water to overlying water occurred in the treatment without added cyanobacteria biomass. However, the treatments added the cyanobacteria biomass presented the obvious diffusion of DOC and the low migration of DIC at the water-sediment interface. The diffusive fluxes of DOC at the water-sediment interface increased with the cyanobacteria biomass added, reaching the maximum value of 411.01 mg/(m2·d) in the treatment added the high cyanobacteria biomass. In the overlying water, the group added the sediment and medium cyanobacteria biomass presented a faster degradation of cyanobacteria-derived POM to DOC and a higher mineralization level of DOC to DIC than added the medium cyanobacteria biomass without sediment. Therefore, during accumulated cyanobacteria decomposition, the biomass of accumulated cyanobacteria and sediment property can influence the migration and transformation of DC, playing an important role in carbon cycling in shallow eutrophic lakes.

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