宝鸡城市土壤重金属生物活性与环境风险

在野外调查与前期研究的基础上,根据一点多样混合采样法收集宝鸡市工业区土壤分析样品50个,采用Tessier连续形态分析法对城市土壤重金属Pb、Zn、Cd、Cr、Cu、Sb形态进行分级并使用ICP-OES对其各形态含量进行测定.在对6种重金属活性系数(MF)、迁移系数(MJ)、综合潜在生态风险指数(RI)及人群健康风险研究的基础上,对重金属地球化学形态分布、迁移能力、生物活性与环境风险进行了探讨.结果表明,宝鸡工业区城市土壤重金属Zn、Cd、Cr、Cu、Sb形态均以残渣态为主,而Pb主要以铁锰氧化物结合态为主;在各形态含量所占百分比中,重金属Cr可交换态含量最低.化学形态分析结果显示,6种重金属整体迁移的顺序为:Pb(77.60%)Zn(47.36%)Cu(35.86%)Cd(30.91%)Sb(16.46%)Cr(11.31%);土壤Pb(MF=35.77%)的生物活性最强,Cd(MJ=0.091)的迁移能力最大.城市土壤重金属Cd和Cr对儿童和成人的致癌风险处于中低等水平,但Cr对儿童将产生较大的非致癌风险.而重金属Pb对儿童和成人均产生非常明显的非致癌风险和中等程度的致癌风险,可见,重金属Pb是宝鸡市城市土壤最主要的环境污染物与健康风险因子.重金属Pb、Zn、Cd、Cr、Cu、Sb工业排放与化石燃料燃烧的来源和城市儿童高铅血症的检出率说明宝鸡工业区重金属的干湿尘降污染应该引起高度重视.

Bioactivity and environment risk of heavy metals in urban soil from Baoji City, P.R.China

Based on previous studies and field investigation, a total of 50 analytical samples were collected from the 0~20 cm top soil in Baoji industrial areas based on the classical cone and quarter technique. The concentrations, chemical fractionations, bioactivity, mobility and environment risk of heavy metals Pb, Zn, Cd, Cr, Cu and Sb in urban soil were studied. The results showed that Pb was strongly associated with the Fe-Mn oxide phases (ca. 62.87%), whereas other metals were predominantly bound to the residual fractions extracted with Tessier sequential procedure. A negligible proportion of Cr was recovered in the exchangeable phase (ca. 0%). Results of this study suggested that the mobility and bioavailability of the six metals probably declined in the following order: Pb(77.60%)> Zn(47.36%)> Cu(35.86%)> Cd(30.91%)> Sb(16.46%)> Cr(11.31%). The highest value of mobility factor (MF) with 35.77% indicated that Pb was the most mobile and bioavailable element among the selected metals, while the value of transfer coefficient (MJ) with 0.091 suggested that Cd had the highest transfer ability in the environment. On the other hand, hazard indexes (HI) of Pb in urban soils were higher than 1, indicating that Pb posed a high non-cancer risk to children and adults, while Cr only posed a high non-cancer risk to children. However, other heavy metals were below the limits of harmful levels. The carcinogenic risk levels of Cr and Cd for adults and children ranged from low to moderate risk and Pb in moderate risk. Therefore, Pb was the main pollutant and environment risk factor in Baoji, which also confirmed and was consistent with the observation of the highest blood lead (BPb) in urban children below 12 years old. Multivariate statistical analysis suggested that the heavy elements Pb, Cu, Cr, Zn and Sb were predominated by industrial sources, whereas, Cd was highly influenced by coal combustion. Therefore, attention should be paid on monitoring the rate and risk of dry and wet depositions of heavy metals due to the industrial emissions and fossil fuel combustion in Baoji city.