Effect Of Humus On Paddy Soil Chemical Behavior Of Cadmium And Their Toxicity To Plants

The objectives of this study were to examine the effect of the two fractions of humus (FA and HA) on the adsorption behavior of paddy soil for Cd, the desorption behavior of Cd in paddy soil, the dissolving ability of them for Cd in paddy soil and their toxicity to plants. The results were showed as follows:1 .The adsorption behavior of paddy soil for Cd was significantly correlated with humus fractions. HA could promote the adsorbing rate of paddy soil for Cd and FA suppressed it.2.The two fractions of humus all could decreased the desorption behavior of Cd in soil.3.The dissolving ability of HA and FA for Cd in paddy soil were different. FA could increase the extraction rate of Cd in paddy soil, whereas HA decreased it.4.Humus could affect greatly the uptake of Cd of Brassica chinensis in Cd contaminated soil. FA promoted the uptake of Cd of Brassica chinensis shoots and HA depressed it.5.The two fractions of humus all could promote the fresh weight of Brassica chinensis in Cd contaminated soil. With the increase of their fractions concentration the fresh weight of Brassica chinensis increased.6.In Cd contaminated soil, the content of Acid-soluble Cd were correlated with humus fractions and their concentration. FA could accelerate the content of Acid-soluble Cd. The Reducible Cd was not significantly correlated with humus fractions. The two fractions of humus all could promote the content of Oxidisable Cd with a magnitude sequence of FA>HA. Humus treatments all could inhibit the content of Residual Cd.