Environmental Engineering Program, University of Connecticut , 261 Glenbrook Road, Storrs, Connecticut 06269-3037, United States.
Environ Sci Technol. 2014 Jan 21;48(2):920-9. doi: 10.1021/es402552u. Epub 2013 Dec 30.
Seasonal changes in arsenic and iron accumulation rates were examined in the sediments of a brook that receives groundwater discharges of arsenic and reduced iron. Clean glass bead columns were deployed in sediments for known periods over the annual hydrologic cycle to monitor changes in arsenic and iron concentrations in bead coatings. The highest accumulation rates occurred during the dry summer period (July-October) when groundwater discharges were likely greatest at the sample locations. The intermediate flow period (October-March), with higher surface water levels, was associated with losses of arsenic and iron from bead column coatings at depths below 2-6 cm. Batch incubations indicated iron releases from solids to be induced by biological reduction of iron (oxy)hydroxide solids. Congruent arsenic releases during incubation were limited by the high arsenic sorption capacity (0.536 mg(As)/mg(Fe)) of unreacted iron oxide solids. The flooded spring (March-June) with high surface water flows showed the lowest arsenic and iron accumulation rates in the sediments. Comparisons of accumulation rates across a shoreline transect were consistent with greater rates at regions exposed above surface water levels for longer times and greater losses at locations submerged below surface water. Iron (oxy)hydroxide solids in the shallowest sediments likely serve as a passive barrier to sorb arsenic released to pore water at depth by biological iron reduction.
对接受地下水砷和还原铁排放的小溪沉积物中砷和铁的积累速率的季节性变化进行了研究。在每年的水文循环中，将干净的玻璃珠柱部署在沉积物中已知时间段内，以监测珠涂层中砷和铁浓度的变化。最高的积累速率发生在干燥的夏季（7 月至 10 月），此时地下水排放可能在采样点最大。中等流量期（10 月至 3 月），由于地表水水位较高，在 2-6 厘米以下深度，从珠柱涂层中损失了砷和铁。批式培养表明，生物还原铁（氢）氧化物固体诱导了从固体中释放铁。在培养过程中，砷的释放受未反应氧化铁固体高砷吸附容量（0.536 mg(As)/mg(Fe)）的限制。高地表水流量的春洪（3 月至 6 月）显示出沉积物中砷和铁积累率最低。沿岸线的积累率比较表明，在长时间暴露于地表水以上的区域的积累率较高，而在被地表水淹没的区域的积累率较高。浅层沉积物中的铁（氢）氧化物固体可能作为一种被动的屏障，吸附生物还原在深部释放到孔隙水中的砷。
