Colloid-associated export of arsenic in stream water during stormflow events

摘要: Significant correlations between arsenic concentrations and those of iron natural organic matter (NOM) have been found in run-off from wetlands. This has suggested to be a result mobilization arsenic-NOM colloids. The aim this study was therefore elucidate the possible association with colloids surface water small, forested catchment area. impacts that groundwater levels prior stormflow events chemistry hydraulically active soil layers on release formation colloids, such as NOM (oxy)hydroxide were also investigated. At baseflow, NOM, iron, stream relatively low (< 650 μmol∙L− 1, < 5.5 μmol∙L− 1, 8–16 nmol∙L− 1, respectively), pH close deep (4.6–5.5). At events, discharging fed by anoxic deeper peat, deep, oxic groundwater. iron/DOC ratio high, present iron-NOM precipitated Arsenic dissolved associated conditional distribution coefficients binding (logKD values) high (around 3 L∙mol− 1). When initial table before shallow peat rich during event. ratios most water. lower under these conditions, logKD values As-NOM associations accordingly (< 3 L∙mol− 1). Large quantities (< 1000 g∙mol− 1) exported conditions. Our data reveal decreased increasing discharge consequence decreasing pH. for are higher than reported elsewhere published literature, which had derived laboratory tests arsenic. ternary complexes ferric may enhanced within studied stream.