水体沉积物中有效砷的测试新方法研究

An innovative method to determine available arsenic in aquatic sediment

一种氧化铁/醋酸纤维素复合膜（FeO/CAM）被用于太湖沉积物中砷的生物有效性评估.结果发现,在水介质中,FeO/CAM对沉积物中砷的富集量随土水比增加而呈乘幂函数减少,在土水质量比为0.025（即1∶40）之后趋于某一平台值;在土水比为0.025并得到充分振荡的条件下,沉积物中释放的有效砷被FeO/CAM富集至膜中,并随时间增加而增加,至24h后逐渐趋于平衡,这一过程恰当地模拟了生物对砷的吸收,因此,FeO/CAM可以用于有效砷的体外测试.利用FeO/CAM对12个总砷含量为6.4-34.6mg·kg^-1的太湖沉积物样品中的有效砷进行了测定.结果发现,FeO/CAM提取的有效砷含量与磷酸盐缓冲液提取的有效砷含量之间显著相关.太湖沉积物中的有效砷含量与总砷、总磷、有机质和吸附磷含量以及磷吸附饱和度显著相关,说明沉积物理化属性对有效砷含量有重要影响.FeO/CAM克服了化学试剂提取过程中引起的非有效态砷释放的根本缺陷,因此,FeO/CAM方法在沉积物有效砷含量的测定时比化学试剂提取法可能更准确.

A new method was developed to assess the bioavailability of arsenic in the sediments of Taihu Lake by using an iron oxide/cellulose acetate membrane （FeO/CAM）. The amount of bioavailable arsenic desorbed from the sediment into the water decreased exponentially with the ratio of sediment to water and then stabilized. When the mass ratio of sediment to water was 0. 025, the amount of bioavailable arsenic extracted by the FeO/CAM increased with shaking time until it reached equilibrium after 24h. This process mimicked biological absorption, so FeO/CAM could be used to measure bioavailable arsenic. The amount of bioavailable arsenic in twelve sediment samples from Taihu lake, in which total concentrations of arsenic ranged from 6.4 - 34.6 mg·kg^-1, were estimated by the FeO/CAM method. The results showed that the concentrations of bioavailable arsenic estimated by FeO/CAM were significantly correlated with those estimated by the phosphate buffer method. The concentrations of bioavailable arsenic in sediments from Taihu Lake were mainly influenced by sediment properties and showed a significant correlation with the concentrations of total arsenic, total phosphorus, organic matter and absorbed phosphorus and the degree of phosphorus sorption. Unlike the chemical extraction method, the FeO/CAM method does not extract nonbioavailable arsenic, therefore, the FeO/CAM method is a closer estimate of bioavailable arsenic.