UNSW Water Research Centre, School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
Chemosphere. 2011 Feb;82(6):879-87. doi: 10.1016/j.chemosphere.2010.10.056. Epub 2010 Nov 20.
Factors controlling the transport of geogenically-derived arsenic from a coastal acid sulfate soil into downstream sediments are identified in this study with both solid-phase associations and aqueous speciation clearly critical to the mobility and toxicity of arsenic. The data from both sequential extractions and X-ray adsorption spectroscopy indicate that arsenic in the unoxidised Holocene acid sulfate soils is essentially non-labile in the absence of prolonged oxidation, existing primarily as arsenopyrite or as an arsenopyrite-like species, likely arsenian pyrite. Anthropogenically-accelerated pedogenic processes, which have oxidised this material over time, have greatly enhanced the potential bioavailability of arsenic, with solid-phase arsenic almost solely present as As(V) associated with secondary Fe(III) minerals present. Analyses of downstream sediments reveal that a portion of the arsenic is retained as a mixed As(III)/As(V) solid-phase, though not at levels considered to be environmentally deleterious. Determination of arsenic speciation in pore waters using high performance liquid chromatography/Inductively Coupled Plasma-Mass Spectrometry shows a dominance of As(III) in upstream pore waters whilst an unidentified As species reaches comparative levels within the downstream, estuarine locations. Pore water As(V) was detected at trace concentrations only. The results demonstrate the importance of landscape processes to arsenic transport and availability within acid sulfate soil environments.
本研究确定了控制从沿海酸性硫酸盐土壤中向下游沉积物迁移的地质成因砷的因素，其中固相结合物和水相形态显然对砷的迁移性和毒性至关重要。来自连续提取和 X 射线吸收光谱的数据表明，在没有长时间氧化的情况下，全新世酸性硫酸盐土壤中的砷基本上是不可移动的，主要以毒砂或类似毒砂的物种存在，可能是砷铁矿。随着时间的推移，人为加速的成土过程氧化了这些物质，极大地提高了砷的潜在生物利用度，固相砷几乎仅以与次生 Fe(III)矿物结合的 As(V)形式存在。对下游沉积物的分析表明，一部分砷作为混合的 As(III)/As(V)固相保留下来，但没有达到被认为对环境有害的水平。使用高效液相色谱/电感耦合等离子体质谱法在孔隙水中测定砷的形态表明，上游孔隙水中以 As(III)为主，而在下游河口处则存在一种未识别的 As 物种，其浓度相当。仅在痕量浓度下检测到 As(V)。研究结果表明，景观过程对酸性硫酸盐土壤环境中砷的迁移和可利用性具有重要意义。
