The Effects Of Low Molecular Organic Acids On Vertical Transport Of Cd In Contaminated Soils

Soil and sand pot experiment was carried out to study the effect of exogenous Cd pollution on accumulation of Cd in Brassica juncea under the conditions of the two types of growth medium-soil and sand. Aiming at the problem of different low molecular organic acids leaching, according the soil colum leaching experiment on the basis of the influencing factor with addition and irrigation amount, was studied the on the vertical transport of soil Cd induced by EDTA, citric acid, oxalic acid and acetic acid, and the vertical distribution rule of available Cd in the soil,. Main results of the experiments were summarized as follows:1. Brassica juncea could grow normally in soil culture, but because of the high effective concentration of heavy metals in the sand, its toxic to its and inhibit its growth. At the same treatments, accumulation of heavy metals in the sand were more than its in soil culture.2. In the EDTA treatments, Cd content of surface soil decresed , available Cd in surface soil increased, and the migration depth of Cd increased with the increasing of addition .maximum migration depth could reach 40 cm. The content of total Cd decreased with the increasing of soil depth, and the content of available Cd in the soil showed the similar changing trend.3. In the citric acid treatments, Cd content of surface soil was less change in low addition, the content range of Cd was 3.01～3.07mg/kg. But at the higher addition, all treatments Cd content of surface soil were gradually decreased, the content range of Cd was 2.16～2.81mg/kg, reduced by 8.5～29% compared with control. With the increasing of addition the migration depth of Cd increased. And the content of available Cd in the soil showed the similar changing trend.4. In the oxalic treatments, migration depth of Cd could reach in the range of 0～30 cm with the increasing of addition increased, compared with EDTA and citric acid treatments Cd content of each soil layer were decreased, maximum migration depth could reach 30 cm. With the increasing of addition, available cadmium increased in the proportion of total Cd, but available cadmium less than EDTA and citric acid. 5. In the acetic acid treatments, the changing trend of vertical transport of soil Cd was roughly identical with the oxalic treatments. available cadmium content in surface soil were in direct proportion with acetic acid addition. Available cadmium increased with the increase of acetic acid addition, and the changing trend was similar with total Cd.6. With increasing in irrigation, Cd content of surface soil gradually decreased, but became slower. It shows that Cd could transfer with warter continuously at the direction of vertical with the increase in irrigation; and the transport depth of Cd in the soil layers increasd with the increasing of irrigation amount. Cd migration depth increased with increasing, maximum migration depth could reach 40 cm. In the EDTA and citric acid treatments, available cadmium increased with the increasing of irrigation amount. Available cadmium was no remarkable difference in all treatments, and available cadmium show decreasing trend in soil layers with the increasing of depth.