海水中痕量重金属的薄膜扩散梯度技术原位富集

In situ Enrichment of Labile Heavy Metals in Seawater with Diffusive Gradients in Thin Films

研究表明对生物体有直接作用的金属并非溶解态的全部,而是其中的活性部分.薄膜扩散梯度技术（DGT）作为一种原位富集有效态金属的新技术,被广泛应用于自然水体里重金属的分析.本研究设计了一种能同时原位富集海水中的Mn、Co、Ni、Cu、Zn、Cd、Pb的DGT装置;使用自制的凝胶扩散系数测定装置获得了金属离子在扩散相凝胶中的扩散系数;考察了pH、离子强度等对富集效果的影响,当pH为5.6-8.6、离子强度在10-700mmol/L范围内,富集效果不受影响.在厦门近岸海域成功地进行为期7d的海水中重金属的原位富集,实验结果显示,DGT能够富集该海域海水中6.672%-45.33%的溶解态重金属,即获得DGT有效态.平行样测定的相对标准偏差均小于10%,该方法可用于海水中痕量有效态重金属的分析.

Heavy metals are introduced into marine environments mostly by human activities,causing adverse effects on marine ecosystems.Nowadays scientists have recognized that the bioavailability of heavy metals controls the potential of adverse effects rather than the total or filterable concentrations.Diffusive gradients in thin films（DGT）is a recently developed technique that is capable of in situ enrichment of labile metal species in aqueous systems for quantitative measurements.In this study,DGT device was built for the measurement of heavy metals in seawaters.The molecular diffusion coefficient（D）of various metals through a polyacrylamide gel had been determined.Using Chelex-100 as the ion-exchange resin,pH in the range of 5.6-8.6and the ionic strength between 10mmol/L to 700mmol/L would not influence the enrichment.The DGT devices had been applied for the pre-concentration of Mn,Co,Ni,Cu,Zn,Cd and Pb in coastal seawaters of Xiamen for seven days.The result showed that the DGT-labile part in the fraction of0.45μm filterable portion varied from 6.672%-45.33%for these metals.And the relative standard deviation was all below 10%（n=3）.DGT had been confirmed to be a very promising tools for preconcentrating trace metals in waters and better understanding their bioavailability.