Arsenic sequestration by nitrate respiring microbial communities in urban lake sediments. Chemosphere, 70(2), 329-336
ABSTRACT Changes in microbial community composition and activity were related to geochemical conditions favoring arsenic sequestration in sediments collected from the urban, arsenic-contaminated Upper Mystic Lake. After amendment with nitrate, >94% total soluble arsenic is sequestered by Fe(III)-(oxy)hydroxides generated in live sediments. Of this sequestered arsenic, >75% existed as As(III), indicating As redox state alone is not responsible for changes in mobility. Arsenic sequestration was concurrent with the microbial respiration of nitrate as indicated by steady state hydrogen concentration and the presence of organisms similar to nitrate-reducing, iron-oxidizing bacteria belonging to the genus Dechloromonas in 16S rDNA clone libraries.
- SourceAvailable from: Huaming Guo
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- "Meanwhile, in oxic conditions , adsorption of As on aquifer sediments occurs in the alluvial fans, which leads to low As concentrations in Cluster III (Fig. 6c), although the grains are coarse in the alluvial fans with low adsorption capacity for As (Stumm, 1992). Other researchers have also indicated that the reductive dissolution of Fe (hydr)oxides is largely suppressed because that NO 3 strongly buffers the redox potential and As would be adsorbed on Fe minerals in the NO 3 reduction environment (Guo et al., 2011; Kim et al., 2009; Nickson et al., 2000; Senn and Hemond, 2002; Gibney and Nüsslein, 2007). As free oxygen is consumed along the flow path, NO 3 becomes the first to be electron acceptor in the process of organic matter oxidation by microorganisms, which leads to the decrease in NO 3 concentration (Guo et al., 2011). "
ABSTRACT: Although high As groundwater has been observed in shallow groundwater of the Hetao basin, little is known about As distribution in deep groundwater. Quantitative investigations into relationships among chemical properties and among samples in different areas were carried out. Ninety groundwater samples were collected from deep aquifers of the northwest of the basin. Twenty-two physicochemical parameters were obtained for each sample. Statistical methods, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were used to analyze those data. Results show that As species were highly correlated with Fe species, NH4-N and pH. Furthermore, result of PCA indicates that high As groundwater was controlled by geological, reducing and oxic factors. The samples are classified into three clusters in HCA, which corresponded to the alluvial fans, the distal zone and the flat plain. Moreover, the combination of PCA with HCA shows the different dominant factors in different areas. In the alluvial fans, groundwater is influenced by oxic factors, and low As concentrations are observed. In the distal zone, groundwater is under suboxic conditions, which is dominated by reducing and geological factors. In the flat plain, groundwater is characterized by reducing conditions and high As concentrations, which is dominated by the reducing factor. This investigations indicate that deep groundwater in the alluvial fans mostly contains low As concentrations but high NO3 and U concentrations, and needs to be carefully checked prior to being used for drinking water sources.Chemie der Erde - Geochemistry 02/2015; 75(2). DOI:10.1016/j.chemer.2014.12.002 · 1.27 Impact Factor
- Geochmica et Cosmochimica Acta 06/2009;
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ABSTRACT: The arsenic (As) concentrations in the groundwater of alluvial plains generally show high spatial variability. We geochemically explore the factors causing the spatial variability in an alluvial plain that is mainly used for rice cultivation, the commonest land-use pattern in alluvial plains of Asia. We investigate the chemical processes, sources of chemicals that affect the behavior of As, and their relationships with the geologic conditions at seven multilevel sampler sites. All sites showed As concentrations that increased with depth at shallow levels and decreased at greater depths, which is the typical vertical pattern in alluvial aquifers where Fe-(hydr)oxide reduction is the major As release mechanism. Data show that NO(3) and SO(4) originating from the land surface play important roles in suppressing the increase in As concentration by buffering the redox potential at shallow depths and by precipitating As with sulfide minerals at deep depths, respectively. The As concentration in the intermediate depth range was also low in the presence of SO(4), because its reduction can occur together with Fe-(hydr)oxide reduction in a wide range of redox potentials. As a result, the maximum As concentrations at the sites where the land was covered with a thick silt layer (approximately 5m) were 3- to 5-times higher than those at other sites due to the supply of NO(3) and SO(4) from land surface being largely limited by the silt layer. This indicates that the surface geology could be an important indicator for the As concentration in alluvial groundwater.Chemosphere 09/2009; 77(4):478-84. DOI:10.1016/j.chemosphere.2009.07.053 · 3.34 Impact Factor