Enrichment of Heavy Metals in Particulate Organic Matter from Non-polluted Soils

In order to understand whether heavy metals are enriched by particulate organic matter(POM)in non-polluted soils,23 soil samples were collected from northern Zhejiang plain.Contents of organic matter and POM,and concentrations of heavy metals in the soils and POM fractions were characterized using physical and chemical methods. The concentrations of Cu,Pb,Zn and Cd in all the soils were below their criteria values of the second grade in national standards of the soil heavy metals environmental quality,but heavy metals in the soils were significantly enriched in particulate organic mater.The enrichment factors of Cu,Pb,Zn,and Cd were 5.4～13.5、4.7～10.3、3.8～10.4 and 3.8～12.3,respectively,and increased with decreasing size of the POM fraction.The enrichment factors were generally higher in sandy soils than loamy and clayey soils.Soil organic matter also had effect on the enrichment factor.The enrichment of metals in the POM fractions was not completely due to decomposition of plant debris.Our results emphasized that POM metal enrichment is liked to SOM-heavy interactions in the non-polluted soil.