城市路面径流重金属固液分配系数及其影响因素

Dissolved-particulate partitioning of heavy metals in urban road runoff of Shanghai

以上海市中心城区为例，探讨路面径流重金属在颗粒物一水相间的分配特征及其影响因素。研究表明，路面径流cr的25％分位数浓度值，以及Zn、Pb、cd的90％分位数浓度值超出地表V类水标准，cu和Ni污染程度较轻。径流重金属Pb、zn、cu及cd总量浓度与悬浮颗粒物（1胬）含量呈现较明显的正相关关系，M与TSS浓度相关性不显著。径流冲刷过程中cu和Ni溶解态含量比例平均值为35％；Zn和cr平均值为19％～22％；Cd和Pb溶解态比例最低，平均值为4％～8％。应用扣除残渣态后的颗粒物重金属含量计算固液分配系数依次为Pb〉Cd〉Zn〉Ni〉Cu〉Cr。径流中悬浮颗粒物浓度与固液分配系数存在显著负相关关系，呈现明显的“颗粒物浓度效应”，径流pH值在6．4～7．2区间时对固液分配系数影响相对较小。

The partitioning characteristics between the dissolved and particulate-bound fractions of heavy metals in nmoff wa- ters in roads are preliminarily investigated in this paper. 56 runoff samples were collected in two rainfall-nmoff events in five different areas located in the central area of Shanghai. The results indicate that during the wash-off processes, the 25th per- centile concentrations of Cr and the 90th percentile concentrations of Zn, Pb and Cd are over the fifth classified values of the National Surface Water Standards, while the pollution levels of Cu and Ni are relatively lower. The results also show the high positive correlations between the total heavy metal concentrations and the total suspended sediment （TSS） concentrations are in the order of Pb 〉 Cu 〉 Zn 〉 Cd, and the correlation of Ni and TSS is not obvious. The fractions of dissolved-to-total metals are ranked by Cu and Ni of 35%, Zn and Cr of 19% - 22%, and Cd and Pb of 4% - 8%. With the modified dissolved-particu- late partitioning（Kd）calculated method, the order of Ko is Pb 〉 Cd 〉 Zn 〉 Ni 〉 Cu 〉 Cr. The Kd values of metals show the similar spatial distribution pattern among the different areas. The results also show that TSS concentration has the great negative ＂ influence and shows the so-called particle concentration effect＂ on Ko values. When pH values of runoff belong to the interval of 6.4 - 7.2, it has a relatively weaker effect on KO values.