Effects Of Cadmium And Chlorpyrifos Combined Pollution On Soil Enzymatic Activities And Physiological And Biochemical Characteristics Of Pakchoi(Brassica Chinensis. L)

Combined contamination of pesticide and heavy metals is ubiquitous in the world. However, the information on biological effects of combined pollution of pesticide and heavy metals is little. In this study, a batch pot experiment was conducted in yellow-brown soil spiked with cadmium and chlorpyrifos to investigate the effects of cadmium and chlorpyrifos combined pollution on soil enzymatic activities and vegetable physiological and biochemical characteristics. The results showed as following:1. Cadmium and chlorpyrifos pollution had significant impact on soil enzyme activities. Dealing with low concentrations of cadmium promoted the activity of acid phosphatase, whereas with high concentrations inhibited its activity. Chlorpyrifos alone promoted the activity of acid phosphatase; however, the combined treatment of chlorpyrifos and cadmium had lower activity of acid phosphatase than separate handling of the two chemicals. Urease activities of low cadmium alone, the combined treatment with low cadmium and low chlorpyrifos, and chlorpyrifos alone were slightly higher than that of the control. Urease activities of both high cadmium alone and the combined treatment of high cadmium and chlorpyrifos were lower than that of the control, and the later treatment had the lowest urease activity. Cadmium alone, chlorpyrifos alone, and combined treatment of cadmium and chlorpyrifos increased the activity of catalase.2. The impact of cadmium and chlorpyrifos soil pollution on physiological and biochemical characteristics of the investigated pakchoi was related to plant growth stage. In the seedling stage, SOD activities increased in all treatment, while CAT activities increased at low cadmium treatment, and decreased in high cadmium and chlorpyrifos alone or combined. In the maturity stage, soluble sugar content in plants increased in the treatment of low cadmium alone, but decreased in other treatment. Biomass (fresh weight) of the vegetable was higher in high cadmium treatment than in the control, but was lower in each of the other treatments than in the control.3. Of soil cadmium and chlorpyrifos combined pollution on soil and vegetables have absorbed the impact of chlorpyrifos.4. The uptake of cadmium by the vegetable was dependent on available cadmium content in soil and plant growth stage. The higher the available cadmium content in soil and the longer the plant growth stage, the more the cadmium uptake by the plant.