Abstract:

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/(hm2·a), accounting for 8520％ of the total input

flux Water Downward infiltrating (234 g/(hm2·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 23 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％

Key words:

Key words: ecogeochemical assessment; agroecosystem; Cd; Chengdu economic region