薄膜扩散梯度技术测定水体中砷及其影响因素研究

薄膜扩散梯度技术（Diffusive Gradientsin Thin Films Technique,DGT）是近年来应用于水体、沉积物和土壤中的铜镉等重金属生物有效性研究的一种新技术。采用标准溶液培养方法研究了以氧化铁作为吸附剂的DGT测定水环境中无机砷含量的可行性,并探讨了待测介质的pH和As价态对DGT测定结果的影响。结果表明,研究所用DGT装置中的吸附凝胶对砷吸附的最大容量≤42μg,其有效容量≤13μg,为确保DGT测定值的准确性,需要对DGT装置的放置时间加以控制;当水体中砷浓度为0.1～11.0mg·L-1时,DGT测定的溶液中无机砷浓度与直接用HG-AFS测定待测水体中无机砷浓度之间有较好的响应关系,DGT测定水体中无机砷的浓度能较好反应水体中无机砷的真实浓度;当溶液的pH值为2.95～8.18时,不同pH下吸附凝胶对砷的吸附量间差异不显著,溶液pH值在一定范围不影响DGT的测定结果;As（V）、As（Ⅲ）在进行DGT试验时不存在竞争吸附关系,砷离子的价态对DGT测定水体中的无机砷的浓度没有显著影响。总之,在各种环境相关的条件下,DGT是一种可以用于测定水体中总无机砷的有效方法。

Study on Measurement and Influencing Factors of Inorganic Arsenic with use of Diffusive Gradients in Thin Films Technique in Waters

The performance of Diffusive Gradients in Thin Films Technique（DGT） for the in situ accumulation of bioavailable metals such as copper and cadmium in nature waters,sediments,and soils has been investigated in recent years.To evaluate the feasibility of using DGT for the measurement of inorganic arsenic（As） under natural conditions,hydroponic experiments were conducted.They enabled the study of the ability of As to adsorption to the iron-hydroxide gel in the DGT device.Various factors that may affect the adsorption of the As species to the iron-hydroxide adsorbent were investigated.The results indicated that the maximum and effective As adsorption capacities of iron-hydroxide gel were limited to ≤42 μg and ≤13 μg As,respectively.The implication for practical measurements is that the deployment time used should be carefully considered to ensure the accuracy of the measured value.Under laboratory conditions,pH and As species in solutions were demonstrated not to affect the concentration measured by using DGT.For each sample,the concentration was obtained using DGT and additionally by direct measurement using hydride generation atomic fluorescence spectrometry（HG-AFS）.Good agreement was obtained between the two measurements.We can conclude that for the conditions used in this study,DGT was a reliable and efficient method for pre-concentration of total dissolved As,enabling its measurement at environmentally relevant concentrations.