凤凰铅锌矿区土壤铅的化学形态及污染特征

以湘西凤凰铅锌矿区土壤为对象,基于BCR三步法和ICP-MS技术,研究了该矿区土壤中Pb的化学形态及污染特征。结果表明,矿区土壤中Pb以残渣态为主,其次为有机-硫化物结合态,酸交换态和Fe-Mn氧化物结合态所占比例较少,各形态Pb的分配系数依次为:残渣态(44.0%)>有机-硫化物结合态(29.3%)≈Fe-Mn氧化物结合态(24.3)>酸交换态(2.4%);矿区土壤中各形态Pb含量存在明显的空间分异,并因土地利用类型不同而差异明显;土壤理化性质影响土壤Pb的形态分配,各形态Pb含量与砂粒含量正相关,并随土壤pH升高而增加,这与人为排放输入的含Pb物质以类似于土壤砂粒形式存在有关。人类活动引起的外源输入性Pb污染对矿区土壤中Pb的污染特征产生了重要影响。

Chemical Speciation and Pollution Characteristics of Soil Pb in Fenghuang Pb-Zn Mining Area

Soil pollution by total Pb was characterized in the mine tailings and surrounding soils of an old Fenghuang Pb-Zn mine.It is important to characterize the partitioning of Pb behavior than studies of total concentrations,which provide limited information on the mobility and bioavailability of the element.In the present study,soil samples(natural and arable lands)from the mining area were analyzed,determining the chemical fractionation of Pb by the BCR protocol and the ICP-MS technique.It was found that most of the Pb in soils was associated with residual faction,followed by organic-sulfide faction and Fe-Mn oxides faction,and acid-exchangeable faction is rather low.The average percentage of each Pb fraction extracted from the soils with respect to the corresponding total Pb content,in parentheses,followed the trend:residual faction(44.0%)> organic-sulfide faction(29.3%)≈ Fe-Mn oxides faction(24.3%)> acid-exchangeable faction(2.4%).Soil physico-chemical parameters were key factors affecting the presence of Pb fractions.Generally,Pb fraction concentrations were positively correlated with the sand contents and soil pH values,which was presumably due to the basic anthropogenic input of Pb-containing materials and their similarity to sand in physical characteristics.Meanwhile,a spatial variation in Pb fraction concentration in soils from the mining area has been observed;the concentrations varied with soil samples from different land use type.The results indicated that the exogenous Pb input caused by human activities had an important impact on the pollution characteristics of Pb in soils from the mining area.