广东韶关主要矿区周边农田土壤铅、镉的形态分布及生物有效性研究

采用改进BCR法和DTPA提取法研究了韶关主要矿区周边农田土壤Pb、Cd的形态分布和生物有效性。结果表明，参照土壤环境质量标准二级标准，韶关主要矿区周边农田土壤Pb、Cd的超标率分别为14.1%和92.3%；参照食品中污染物限量标准，调查的5种蔬菜样品Pb、Cd的超标率分别为57.7%和48.7%。土壤Pb以可还原态为主，占到4种形态和的76.13%，Pb各形态的分布顺序为：可还原态〉残渣态〉可氧化态〉酸提取态；土壤Cd以酸提取态和可还原态为主，占到4种形态和近89%，Cd各形态的分布顺序为：酸提取态〉可还原态〉可氧化态〉残渣态。用DTPA提取得到的土壤Pb、Cd有效态均值分别为24.91、1.29 mg·kg-1。相关性分析表明，除了胡萝卜Cd，5种蔬菜Pb、Cd含量与土壤酸提取态、可还原态、可氧化态及土壤有效态含量显著相关，与土壤pH和有机质相关性不大。逐步回归分析表明，只有土壤残渣态含量对蔬菜Pb、Cd含量影响不显著。

Fractionation and Bioavailability of Pb and Cd in Agricultural Soils Around Mining Area in Shaoguan Guangdong Province, China

The fraction and bioavailability of lead （Pb） and cadium （Cd） in the agficuhural soil around mining areas in Shaoguan were extracted by modified BCR sequential extraction procedure and DTPA extraction method. The results indicated that 14.1% and 92.3% of soil samples had exceeded the class 1I threshold of Soil Environmental Quality Standard（ GB 15618--1995 ） for Pb and Cd, respectively. The over standard rate of Pb and Cd in vegetables were 57.7% and 48.7%, respectively, when compared with the maximum levels of contaminants in foods according to the national standard GB 2762--2005. The greatest proportion of Pb in soils was the reducible fraction, which account- ed for 76.13 % of total Pb, followed by thd residual, oxidizable, acid-soluble. Cd was dominated in the acid-soluble and reducible fractions and they accounted for 89% of the total amounts, and followed by the order of acid-soluble 〉 reducible 〉 oxidizable 〉 residual. According to the DTPA extraction method, the content of available Pb and Cd in soils were 24.91 rag＂ kg-1 and 1.29 mg. kg-~, respectively. Concentrations of Pb and Cd in vegetables were significantly related with contents of acid-soluble, reducible, oxidizable and the bioavailable form, except for Cd in carrot. No significant correlations were observed between the concentrations of Pb and Cd in vegetables with soil pH and organic matter contents. Results of the stepwise muhiple linear regression analysis revealed that only the residual fraction of Pb and Cd in soils had no signif- icant influence on the concentrations of Pb and Cd in vegetables.