Content Changes and Pollution Evaluation of Heavy-metals in Different Cultivation Ages of Greenhouse Soils

The status quo of heavy-metals accumulation in the different cultivation ages of greenhouse soils from Jinhua suburb was studied.The results showed that when applying manures from big scale farm to the greenhouse soil,the contents of heavy-metals(Cr,Pb and Cu) in greenhouse soil increased with increasing cultivation age(0-8 years),and there were significant positive correlation between them;particularly,when Cu content in the soil increased at an average annual rate of 7.565mg/kg,the Cu content in 24.14% of the greenhouse soil exceeded standard,but the change of Cd content had no apparent regularity;75% of the greenhouse soil with five years cultivation age reached the second level of warning limit,and 100% of the greenhouse soil with eight years cultivation age exceeded the warning limit level.Therefore,under the present cultivation management conditions,the greenhouse cultivation will lead the accumulation of heavy metals,and critical period of the greenhouse soil for clean use was about five years.It suggested that during cultivation process in the greenhouse,using organic fertilizers,such as composting manures,as much as possible;meanwhile,adopting some measures timely,such as irrigation treatment,applying lime nitrogen and phytoremediation,to ensure the ecological safety of the greenhouse soil.