水源水库沉积物中重金属形态分布特征及其影响因素

INFLUENCE OF THE ENVIRONMENTAL CONDITIONS ON THE SPECIATION OF HEAVY METALS IN THE RESERVOIR SEDIMENT

利用BCR化学连续提取法和EDTA铵盐单一提取法,考察了微生物作用和不同环境条件(灭菌,未灭菌,好氧,厌氧,添加还原药剂Na2SO3)对饮用水源水库沉积物中重金属的含量和形态分布特征的影响.结果表明,微生物作用和不同环境条件对沉积物中重金属,特别是对Cd和Pb的含量及各形态(F1、F2和F3)分布有着显著的影响;微生物对有机质的矿化作用以及厌氧条件下的微生物还原作用分别是影响沉积物中Cd和Pb形态分布变化以及上覆水体中铁浓度变化的重要原因.沉积物中Cd和Zn具有潜在环境效应的各形态(F1、F2和F3)含量占总量的比例[(F1+F2+F3)/T]均高于灭菌条件下;以EDTA单一提取法表征重金属的生物可给态含量结果表明,不同重金属的生物可给性差异十分显著,Cd和Pb的生物可给态含量占总量的比例(B/T)最高值分别可达24.96%和39.56%,而Zn和Cr的B/T值均小于5%.沉积物中重金属的[(F1+F2+F3)/T]比值(y)和B/T比值(x)两者之间的线性关系为y=0.96x+0.1388(R2=0.8704);重金属的潜在环境效应程度对沉积物中重金属总量变化趋势有着直接的影响,在沉积物-水界面,随着重金属各形态的潜在环境效应的增强,重金属通过沉积物-水界面由沉积物向上覆水体扩散的程度也随之加剧,对水源水库的水质可造成一定程度的潜在危害.

Under microbial and different environmental condition,the BCR sequential extraction and EDTA single extraction method were applied to study the speciation,concentration and bioavailability of the heavy metals in the reservoir sediment. The results showed the microbial and environmental conditions influenced the concentration and speciation of heavy metals in sediment,especially for Cd and Pb. The biomineralization of organic matter and bioreduction were the key factors controlling the change of distribution of different fractions of Cd and Pb,as well as the iron content in the overlying water. The ratios of （F1＋F2＋F3）/T of Cd and Zn under biostimulation were higher than those of Cd and Zn under abiotic control; and it was similar to Pb and Cr in the condition of the untreated sample and after the addition of reducing reagent （Na2SO3）. The EDTA single extraction experiment results showed that the percentage of the bioavailable fraction （B/T） of Cd and Pb in sediment was as high as 24.96% and 39.56% respectively,while those of Zn and Cr were both less than 5%,showing low bioavailability.The positive linear regression equations between the value of （F1＋F2＋F3）/T（y） and B/T（x） of the heavy metals in sediment was as follows：y=0.96x＋0.1388（R^2=0.8704）,which showed the potential environmental effect can be illustrated by the total metal concentration in sediment. At the water-sediment interface,as the potential environmental effect of heavy metals increases,metal diffusion from the sediment to the overlying water also increases,which would pose a thread to water quality.