砂质土壤不同粒径颗粒中有机碳、养分和重金属状况

DISTRIBUTION OF ORGANIC CARBON,NUTRIENTS AND HEAVY METALS IN DIFFERENT SIZE FRACTIONS IN SANDY SOILS

用分散、筛分和悬浮相结合的物理方法，研究了砂质土壤中养分和重金属在不同粒径有机、无机颗粒中的分布。研究表明，砂质土壤中Cd、Co、Cr、Cu、Ni、Pb、Zn和Mn在颗粒状有机质（POM）有明显的富集，富集程度以Cu和Zn最为明显。粒径较小（0．05～1mm）的POM组分中重金属的平均富集高于粒径较大（〉1mm）的POM组分。POM中重金属的富集因土壤重金属污染水平和重金属类型而异，并与土壤重金属的积累呈正相关。分析数据表明，土壤POM中重金属的积累不完全是植物分解残留的结果，土壤POM对重金属有强吸持能力可能是POM中重金属富集的主要原因之一。

Bioavailability of heavy metals in soil depends on composition of the soil. Characterization of heavy metal distribution among different size fractions of the soil is needed for better understanding of the fate of heavy metals. This study investigated distribution of organic carbon, nutrients, and heavy metals among different size fractions in sandy soil. Results show that heavy metals, including Cd, Co, Cr, Cu, Ni, Pb, Zn and Mn, in the sandy soil were significantly enriched in particulate organic matter （POM）, with Cu and Zn in particular, which were much higher in concentration than the others. It was more significant in 0.05 - 1 mm POM fraction than in 〉 1 mm POM fractions. The enrichment in the POM fractions varied with soils, and was positively related to accumulation of the metals in the soils. The enrichment of heavy metals in the POM fractions was not completely due to decomposition of plant debris. The strong heavy metal adsorption capacity of POM in the soil might be an important machenism of heavy metal enrichment in POM fractions.