The changes in soil use patterns with economic development may lead to the accumulation of heavy metal in soil and then threat food security. Situated at Yangtze Rive Delta (YRD), Zhangjiagang City is an economically developed area. Bnsed on intensive soil sampling from rice-wheat fields and vegetable ones, this paper discussed: (i) the effect of the soil use conversion from rice-wheat rotations to vegetable planting on spatial-temporal distribution of soil heavy metals, such as Cd, Cr, As and Cu, and (ii) the accumulation and pollution trend of soil heavy metals in the current condition with the expansion of vegetable cultivation and the increase of planting years. The results indicated that the concentration of Cd, Cr and Cu in soil were accumulated in the process of vegetable planting except for As. A certain area exceeded the first grade of the national standard for soil environmental quality (background value). If the current trend continued, Cu concentration of 2.4％ of soil area would be over the second grade of national standard in by next 10 years, and that of 0.7％ over the second grade standard of Cd by next 20 years. Therefore the attention should be paid to the accumulation of soil heavy metals in vegetable fields and potential pollution for the future vegetable planting management.%土壤利用方式的改变可能导致重金属的积累,并威胁食品安全.本文以长江三角洲经济发达的典型地区张家港市为例,评价了土壤利用由稻麦轮作转变为蔬菜种植对该市土壤中Cd、As、Cr、Cu时空分布的影响;并预测了目前条件下,蔬菜种植面积的扩大和种植年限的增加对重金属在土壤中的积累趋势及污染潜力.结果表明,在蔬菜种植过程中,土壤中As含量变化不明显:Cd、Cr和Cu的含量有不断累积的趋势,一定面积的土壤超过了土壤环境质量一级限值(背景值):如果按目前的蔬菜种植扩大和重金属积累的趋势发展,未来10年,将有2.4%面积的土壤Cu超过土壤环境二级限值,20年后,Cd亦出现超标现象(约0.7%面积),有可能对蔬菜品质产生影响.因此,对今后蔬菜种植管理过程中引起的土壤重金属积累及潜在污染问题应该得到充分的重视.
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