Organic carbon induced mobilization of iron and manganese in a West Bengal aquifer and the muted response of groundwater arsenic concentrations

Distribution and hosts of arsenic in a sediment core from the Chianan Plain in SW Taiwan: Implications on arsenic primary source and release mechanisms

“…Moreover, the Hsin-Sheng core sediments have arsenic hosted by sulfides (Table 2), invoking the possibility of pyrite oxidation contributing arsenic to groundwater. The Hsin-Sheng core sediments also differ from the West Bengal sediments (Neidhardt et al, 2014) for having 3-35% (a) and (b) are regression lines through all but the two samples with arsenic N100 mg/kg. The thin lines indicate regressions through the samples from 0 to 225 m with those having arsenic N30 mg/kg excluded.…”

“…This procedure differentiates the following arsenic fractions: loosely and strongly adsorbed arsenic (respectively extracted by 1 M MgCl 2 and 1 M NaH 2 PO 4 ), arsenic co-precipitated with amorphous iron oxyhydroxide (extracted by 1 N HCl and 0.2 M ammonium oxalate), arsenic co-precipitated with crystalline iron oxyhydroxide (extracted by 0.05 M Ti 3+ -EDTA-bicarbonate), arsenic co-precipitated with silicates (extracted by 10 M HF), arsenic co-precipitated with sulfides (extracted by 16 N HNO 3 ), and arsenic associated with organic matter (extracted by hot 16 N HNO 3 and 30% H 2 O 2 ). Neidhardt et al (2014) also used a similar procedure to analyze the sediments from West Bengal. The extracted solutions were dried and then dissolved in nitric acid to be analyzed for arsenic concentration using the ICP-MS at NCKU.…”

“…Accumulation of arsenic in a human body can cause renal, gastrointestinal, neurological, hematological, cardiovascular, and respiratory symptoms, and skin diseases including pigmentation disorders, hyperkeratosis and skin cancer (e.g., Wu et al, 1989;Chen and Wang, 1990;Lai et al, 1994;Biswas et al, 1998;Karim, 2000;Smith et al, 2000;Ayotte et al, 2006;Maity et al, 2012;Chung et al, 2013;Samal et al, 2013). It has been estimated that~35 million people in the Ganges-Brahmaputra Delta (GBD) in Bangladesh and West Bengal, India are exposed to groundwater with arsenic concentration exceeding 50 μg/L (BGS and DPHE, 2001;Edmunds et al, 2015), which had led to intensive investigations into the compositions of the arsenic-contaminated groundwater and associated sediments to address the mechanisms of transferring arsenic between the groundwater and sediments (e.g., Nickson et al, 1998Nickson et al, , 2000Acharyya et al, 1999;Fazal et al, 2001;McArthur et al, 2001;Anawar et al, 2003;Nath et al, 2008aNath et al, , 2008bNeidhardt et al, 2014;Sailo and Mahanta, 2014). In addition, studies on arsenic distribution among the constituents of sediments have traced the primary sources of arsenic in the GBD sediments to the Himalayan litho-tectonic belts (e.g., Shamsudduha et al, 2008;Uddin et al, 2011).…”

Spatial and seasonal dynamics of organic carbon in physically fractioned sediments associated with dam construction in the middle Lancang-Mekong River

“…The organic matterrepresented by total organic carbon (TOC) and total nitrogen (TN)-buried in the sediments of aquatic systems, can induce the mobilization of iron and manganese and affect environmental quality (Baldock et al 2004;Luo et al 2009;Wu et al 2012;Neidhardt et al 2014). Labile organic carbon (LOC), such as glucose and cellulose, is known to alter sedimentary carbon dynamics by modifying the rate of mineralization of TOC (Guenet et al 2010).…”

Seasonal changes of the manganese content in the Amur River at different hydrological conditions

“…Manganese has a positive redox potential and, therefore, forms few compounds [30]. Manganese migration in surface waters may be controlled by physicochemical processes with the par ticipation of different groups of manganese reducingoxidizing microorganizms, as well as in the presence of organic matter [36,38,40]. The rate of the biogenic oxidation of this element is many times higher than that of its chemical oxidation [33].…”