典型农耕区黑土和沼泽土团聚体颗粒中重金属的分布特征解析

了解重金属在土壤中的富集特征是其风险评价和土壤修复的基础。分别以黑龙江省典型的农耕黑土和沼泽土为研究对象，采用干筛法获得〉4000、4000～2000、2000～1000、1000～250、250～53和〈53衄16个粒级的土壤团聚体颗粒组。利用等离子质谱（ICP-MS）测定了本土和各级团聚体颗粒中Cr、Cd、As和Pb的含量，并对其颗粒组分布特征及对有机碳的响应进行了解析。研究表明，2种土壤中的重金属Cr、Cd和Pb的富集因子均大于1，而As则存在明显的流失。除了黑土中的As和Pb外，其他重金属随着团聚体粒径的增加而呈现富集减弱的趋势。其中，cr和cd主要趋向分布在粉．黏团聚体（〈53wn）颗粒中；Pb在黑土中易赋存于1000～2000μm大团聚体中，在沼泽土中则富集于53～250μm的微团聚体中；As不但趋向被吸附在53～250μm的微团聚体中，而且在黑土中也容易被吸附在〉l000μm的大团聚体中。金属质量负载计算表明，大粒径颗粒组对土壤中重金属含量的总体贡献较大。土壤中有机碳含量均随着团聚体粒径减小而升高，cr和Cd分布与颗粒有机碳含量正相关，黑土中As的分布与颗粒中有机碳含量负相关而在沼泽土中呈弱正相关，Pb的分布则与有机碳含量均无明显的相关性。

Characterization of the particle size fractionation associated heavy metals in typical black and bog arable soils

Understanding the distribution characters of heavy metals in soil is the premise of risk assessment and soil remediation. In this study, the typical black and bog arable soils from Heilongjiang Province were collected and six particle size fractions （〉4 000, 4 000-2 000, 2 000-1 000, 1 000-250, 250-53 and 〈53 orn） were separated by using standard dry-sieving procedure. The contents of heavy metals in both bulk soils and particle size fractions were determined by ICP-MS. The distribution characters and response to the organic carbons were discussed as well. Except for As, the enrichment factors of Cr, Cd and Pb were higher than 1 in both soils. Generally, the distribution of heavy metals increased with decrease of particle size except for As and Pb in black soil. The accumulation of Cr and Cd was predominantly in particles finer than 〈53 μm, and Pb was mainly in particles of 1 000-2 000 pm in black soil and of 〈250 jxtn in bog soil, while As not only enriched in particle of 53-250 μm but also in 〉1 000 μm size soils in black soil. The mass loading showed that large size particles contributed more to the total contents of heavy metals due to their high fraction in bulk soil. Results of correlation analysis between heavy metals with organic carbon in soil particle size fractions showed that the residues of Cr and Cd were positively correlated with the contents of organic carbon in both soils, and As were weak positively correlated in bog soil and negatively correlated in black soil. In addition, no correlation between Pb and organic carbon was found in both soils.