重庆渝北地区土壤重金属形态特征及其有效性评价

Speciation Characteristics and Effectiveness Assessment of Heavy Metals in Soils in Yubei District,Chongqing

结合渝北地区土壤重金属全量及形态分析,对区内主要土壤类型(紫色土、石灰土、黄壤、水稻土)中的As、Cd、Cr、Pb形态构成特征、影响因素及有效性进行研究.结果表明:不同土壤类型重金属形态构成差异明显,Cr、Pb在各土壤类型中均以残渣态为主;Cd在黄壤、紫色土中以离子态、残渣态为主,其中离子态平均构成在2类土中分别高达37.44%、29.97%.w(可利用态As)和w(可利用态Cr)在紫色土中的平均值分别为0.04和0.96 mg/kg,w(可利用态Cd)在水稻土和紫色土中的平均值分别为0.13和0.09 mg/kg,w(可利用态Pb)在黄壤中的平均值为1.94 mg/kg,表现出较高生物有效性;石灰土中各重金属可利用态总体较低.w(可利用态As)、w(可利用态Cd)分别与As全量(以w计,下同)、Cd全量呈显著正相关;w(可利用态Cd)和w(可利用态Pb)与pH,w(可利用态Cr)与w(有机质)均呈显著负相关.紫色土中w(可利用态Cd)、w(可利用态Cr)和w(可利用态Pb)与各重金属全量、pH和w(有机质)三者显著服从多元非线性对数回归,通过该回归可对研究区紫色土这3个元素的可利用态含量进行预测.

Speciation characteristics, influencing factors and effectiveness of As, Cd, Cr and Pb in four main types of soils （ purplish soil, limestone soil, yellow soil and paddy soil） were investigated through analyzing total contents and fractions of heavy metals in soils in Yubei District, Chongqing. The results showed that fractions of heavy metals significantly varied among different types of soils. Cr and Pb were the main components of the residual in all kinds of soils. Cd was mainly ion-exchangeable and residual speciated in yellow soils and purplish soils, which counted for 37.44% and 29.97% of the total Cd contents, respectively. The contents of available speciation of heavy metals in soils was as follows： w （available As） and w （available Cr） were 0.04 and 0.96 mg/kg in purplish soil respectively, w （available Cd） 0. 13 and 0. 09 mg/kg in paddy and purplish soil respectively, w （available Pb） was 1.94 mg/kg in yellow soil, which perhaps indicated a strong bio-effectiveness, when the bio-effectiveness of heavy metals in limestone-soil was lower. Available As and Cd significantly positively were correlated with total contents in main factors influencing on the chemical speciation and transformation process of heavy metals. However, there were significant negative correlations between available contents of Cd and Pb with pH, and between available Cr with soil organic matters. Available Cd, Cr, and Pb have a multivariate nonlinear logarithmic regressive relationship with total contents, pH and SOM in purplish soil. In conclusion, the equation can be used to effectively predict available contents of the heavy metals in the study area.