Study on Evaluation of Soil Heavy Metal Pollution of Greenhouse Vegetable in North China

With 1~10cultivation years soil from Liaoning typical facilities planting base and the surrounding crop field as samples,the content of the nutrient and the heavy metal in them were determined,and it were evaluated by Pollution-free Vegetable Production Requirements and Environmental Quality of Green Food.The results showed that there was positive correlation among the content of heavy metals,especially among Hg,Cd,Cu(P0.05).Except for As and Cr, the content of other heavy metal elements had positive correlation with cultivation years of greenhouse.Compared with soil outside the greenhouse,the content of heavy metal elements in the greenhouse soil were all significantly higher than that of the natural background value.Hg,Cd,Cu in the greenhouse soil with several years significantly exceeded the standard and had significantly positive correlation with the content of the organic matter,nitrogen and phosphorus, reaching significant difference at 0.01level.It was proved that heavy fertilizing may be the main cause of the increasing heavy metal content in the greenhouse soil.