Studies On Toxicity Indexes Of Cadmium Contamination Soil

This study was performed by using the cabbage(Brassica chinensis) as material under the pot experiment to investigate the effects of external addition of different cadmium levels on the soil biomass,soil microbial, soil enzymes,soil chemical and soil bioluminescence bacteria indicators, and to comprehensively analyze the greatness of the toxicity of cadmium in the contaminated soil.The main results were as follows:1,Under the different concentrations of cadmium,the plant height,the biomass,the root quality,the aerial part quality,the root/shoot ratio has a negative correlation with the increasing of cadmium concentration.As the objective of the study,with reduces the production by 10%as the indicators, The critical concentrations for the heavy metal cadmium to contaminate the soil are 20.19mg·kg^-1,18.52mg·kg^-1,15.63mg·kg.(-1),19.29mg·kg^-1 respectively.2,In the pot experiment,the soil effective cadmium and the totalcadmium content have a significant correlation with the increasing of cadmium concentration,the coefficients of the correlation were: r=0.9994^**;r=0.9846^**respectively.According to the National Unified health Standard vegetables cadmium content 0.20mg·kg^-1is limited for the standard,basing on the soil effective cadmium,the regression equation with the content of the cabbage stem and root in cadmium,considering the soil contamination in cadmium the critical concentration were 3.34 mg·kg^-1, 3.68mg·kg^-1respectively.3,The activity of the soil bacteria,soil fungi soil actinomyces and the soil respiration intensity decreased with the increasing of cadmium concentration.The standard suppress rate of the soil bacteria,soil fungi,soil actinomyces activity and the soil respiration intensity was 50%.Their critical concentrations were:5.08 mg·kg^-1,2.59 mg·kg^-1,5.89 mg·kg^-1and 3.20 mg·kg^-1respectively.4,The high concentration of cadmium had the strong inhibitory action on the sucrase and the urease,but low concentration of cadmium had the slight stimulatory action.According to the inhibition rate 25%as indicator,the critical concentration for the inhibition of soil urease and soil sucrase were: 2.81 mg·kg^-1and 3.68mg·kg^-1respectively.5,Addition of the heavy metal cadmium in a soil can inhibit the illumination intensity of T3 bioluminescence bacteria,and the inhibition rate had a positive correlation with the cadmium added concentration,thus the EC₅₀value of cadmium is 2.43 mg·kg^-1.After addition of the inorganic ions the toxicity of cadmium on T3 bioluminescence bacteria weakens and K⁺＞Mg²⁺＞Ca²⁺.After addition of organic acids,the relative illumination intensity of the T3 bioluminescence bacteria compared to the control significantly improves.That explains that addition of organic acids weaken the biological toxicity of cadmiumon the bacteria and the disintoxication ability was tartaric acid＞oxalic acid.6,The sensitivity of each indicator system on the soil cadmium was: bioluminescence bacteria＞soil enzymes＞soil plant biomass＞soil microbial＞soil agricultural status.As bioluminescence bacteria,fungi and urease were comparatively sensitive the toxicity of cadmium and the relation between these three indicators was better,so bioluminescence bacteria indicator,fungi number indicator,urease vital activity indicator can be comprehensively applied as the indicator to assess the toxicity of the soil heavy metal cadmium contamination,to indicate the situation of the contamination of the soil by cadmium...