Abstract: In order to study the characteristics of heavy metal Cd absorption and transportation due to intercropping maize and Amaranthus mangostanus L., Lolium perenne L. and Solanum nigrum L. under Cd contamination conditions, we selected accumulators suitable for maize intercropping and achieved remediation of heavy metal contaminated soil. In this paper, we used the Cd contaminated brown clay from Henan Province as test soil. In pot experiments, we studied the mechanism of Cd accumulation, absorption and transportation due to intercropping hyperaccumulator S.nigrum and accumulators Lolium perenne L. and Amaranthus mangostanus L., based on the changes of Cd contents in various organs of maize and changes of enrichment coefficient, translocation coefficient, total Cd in soil and available Cd content. The results showed that (1) intercropping significantly decreased Cd contents in above ground parts of maize (P<0.05), with maximum decrease in maize grain, where the Cd contents decreased by 67.6%, 75.7% and 79.9% under intercropping Amaranthus mangostanus L., Lolium perenne L. and S.nigrum, respectively; (2) compared with moncropping, intercropping the three plants decreased the Cd enrichment factor in maize by 49.3%, 39.7% and 68.5%, respectively; and (3) intercropping S.nigrum decreased the Cd transfer factors in maize by 27.5% and 24.2% compared with Amaranthus mangostanus L. and Lolium perenne L., respectively, and the difference reached a significant level. Safety value calculation for daily Cd uptake indicated that after intercropping treatments, the total Cd content should be less than 2.26 mg·kg-1 and effective Cd content lower than 0.88 mg·kg-1. Therefore, intercropping ameliorates Cd exposure risk for maize consumption in the contaminated farmland. In conclusion, intercropping Amaranthus mangostanus L., Lolium perenne L., S.nigrum and maize could inhibit both Cd uptake by maize and Cd transfer from maize roots to shoots or specially roots to grain. This scheme of intercropping not only reduces Cd accumulation in maize and ensures the safety and high quality of maize planting, it also achieves the purpose of soil remediation.

Key words: Cd, maize, intercropping, absorption and translocation mechanism