中文摘要：

选择成都经济区作为典型研究区，以Cd为代表，在生态地球化学填图的基础上开展农田生态系统生态地球化学评价的示范性研究。布置采集了58个大气干湿沉降、86个化肥、121个灌溉水、276个农作物样品，分析和计算了Cd等重要元素的含量和通量。结果显示，研究区局部地段地表土壤Cd环境质量较深部有恶化之势，部分水稻籽实Cd含量已超过无公害食品标准；大气干湿沉降物输入到农田生态系统中的Cd平均通量为17．76g／（hm^2·a），占总输入通量的85．20％，是研究区外源Cd的主要输入途径；下渗水（2．34g／（hm^2·a））和作物收割（1．87g／（hm^2·a））是Cd的主要输出途径；全区外源输入Cd可使土壤中的Cd含量以0．006mg／kg的年速率递增；在Cd输入一输出通量不变的情况，预测未来20a研究区三级土壤面积将增加2～3倍，适耕土地面积将全面缩小；研究区因酸雨沉降和施肥等因素使土壤pH值下降的平均速率为0．106a^-1，其中化肥施用的贡献率为89．62％。预警研究显示，目前研究区95％的水稻生产是安全的，但预测20a后研究区土壤质量退化明显，近70％安全土壤等级降为一般土壤，须报警土壤面积也将由目前的不足4％快速上升至27％。

英文摘要：

Chengdu economic region is selected as an example for eco-geochemical assessment of agroecosystem for Cd. 58 samples of dry and wet atmospheric deposition, 86 of chemical fertilizers, 121 of irrigation water and 276 of plants were collected. Concentrations of Cd and other elements in those samples were analyzed and fluxes of input and output for the agroecosystem were calculated. The results indicated that Cd was more concentrated in the surface soil than in the deep one and Cd concentrations in some rice samples exceeded the standards for the pollution free agricultural products. The flux of Cd inputting to the agroecosystem is averaged to 17.76 g/（hm^2·a）, accounting for 85.20% of the total input flux. Water Downward infiltrating （2.34 g/（hm^2·a）） and crop harvesting （1.87 g/（hm2·a）） are the two maximal Cd outputs. The average increasing rate of Cd content in soil resulted from sources outside of the agroecosystem is 0. 006 mg/（kg·a）. It was forecasted that the area of the third class soil would increase by 2-3 times under the condition of constant input and output fluxes of Cd. The rate of acidification is 0. 106 a^-1 and the contribution of chemical fertilization for soil acidification is 89.62%, preponderating over that of acid rain. The study of eco-geochemical alarming indicated that though 95% of rice production was safe at present, however, 70% of safe soil would degenerate to ecumenical one, and the area of soil in alarm would increase from 4% to 27%.