刁江底泥砷形态的化学分级法与XANES方法比较

采用XANES(X射线近边分析)方法和化学分级法,研究了刁江污染源区尾砂及刁江底泥的砷形态组成特征. XANES方法结果表明,尾砂中砷的形态主要以毒砂(FeAsS)存在,其相对百分含量为63%~99%；而刁江底泥中的砷形态主要是毒砂、砷酸盐和亚砷酸盐,其中毒砂的比例较高,表现出典型的尾砂污染特征. 化学分级法结果表明,尾砂中砷形态主要是残渣态砷(Res-As),而底泥中的砷主要以铁合态、钙合态及残渣态形式存在. 刁江底泥中毒砂相对百分含量和残渣态砷随着与污染源区距离的增大而减小,砷酸盐和亚砷酸盐则呈相反的趋势. 化学分级法和XANES方法所反映的刁江底泥和污染源的砷形态组成和变化趋势总体上较为一致,但这2种方法所获得的定量数据存在一定的差异. 

Comparative Analysis of Arsenic Speciation in Sediments of the Diaojiang River Using X-Ray Absorption Near Edge Structure Spectra and Sequential Chemical Extraction

Sequential chemical extraction method and X-Ray absorption near edge structure(XANES) spectra were used to investigate arsenic speciation in sediments of the Diaojiang River and tailings from a pollution source area.XANES spectra showed that arsenic was mainly present as arsenopyrite(FeAsS) in the tailings,with range from 63% to 99%.Arsenic fractions in the sediments were mainly present as arsenite,arsenate and arsenopyrite.A high proportion of FeAsS in the sediments showed the typical character of a mining tailing contaminated river.The relative percentage contents of FeAsS and Res-As in the sediments gradually decreased with the increase of distance to the pollution sources,while arsenite and arsenate showed the opposite pattern.The results from sequential chemical extraction method and XANES spectra showed that the composition and trend of arsenic speciation in pollution sources and sediments of the Diaojiang River were generally in good agreement,although the quantitative data from the two methods showed some differences.