Heavy Metals Enrichment in Particulate Organic Matter from Reclaimed Water Irrigated Purple Paddy Soil

In recent studies which occur in various soil-plant systems.The aim of the present study was to investigate the effect of reclaimed water irrigation of different length of time(2,3,5,8,10,12 years) on the heavy metal enrichment in particulate organic matter from purple paddy soil.The results showed that,more than 78% POM were 1~0.05 mm,while the proportion of 1 mm POM was comparatively low.Concentrations of Cu,Pb and Cd in all tested soils were below their criteria values of the second grade in national standards of soil heavy metal environment quality,while heavy metals in the soils were significantly enriched in POM.The coefficients of enrichment of Cu,Pb and Cd were 6.58,5.78 and 4.03,equivalent 8.22%,7.27% and 7.65% of total Cu,Pb and Cd in soil,respectively.Furthermore,the coefficients of metal enrichment in POM were generally decreased with the increasing time of reclaimed water irrigation.The transformation process of the coefficients of metal enrichment in soil as the function of irrigation time can be well simulated by Elovich equation.