Research On The Sensitivities Of Vegetable And Soil Enzyme To Heavy Metal

The pollution of heavy metal has become serious in soil, heavy metal was accumulated in the vegetable, then transformed into people's bodies by the food chain. Thus pollution of heavy metal in vegetable and monitoring of soil heavy metal pollution have always been the hotspots of environment science.The heavy metal pollution of different species and concentrations have been simulated by adding heavy metals in the vegetable soil according to pot experiment outside. Copper, zinc and lead, which are three heavy metals, were selected in the experiment. Leaf-used lettuce, brassica chinensis and lettuce, which are three vegetables, were also selected in the experiment.On the basis of testing the content of heavy metal in vegetables, the relationship between the content of heavy metal in vegetable and in soil were analysed, while the sensitivities of heavy metal to vegetables were also analysed, the residual capacity of copper, zinc and lead in the garden soil were predicted. The richment capability and sensitivity to heavy metals of brassica chinensis is the strongest and highest, the highest richment coefficient is 0.51. The adsorption capability of leaf-used lettuce to copper, zinc and lead is different, the richment capability to copper, zinc is higher than lead. The content of heavy metal is accord with Soil Environmental Quality Standard(GB15618-1995) II in vegetable soil in southern of Xi'an. The environmental residual capacity to the three kinds heavy metal are: 59.2mg/kg, 205.8mg/kg and 3.2mg/kg, the content of lead is close to threshold value.On the basis of testing soil enzyme activities, the sensitivities of soil enzyme to heavy metal is analysed in the paper. The biochemical indexes'feasibility of soil enzyme evaluating heavy metal pollution has been examined. The quota relationship between enzyme activeness and Soil Environmental Quality Standard has been determined. As the concludes are drawn, the sensitivities of the same enzyme to different kinds and concentrations of heavy metal are different. The sensitivities of the different enzyme to one heavy metal are also different. The sensitivities of enzyme to heavy metal are less influnced by rhizosphere soil, the heavy metal is predominant factor which influnces the activities of soil enzyme. Only the hydrogen peroxide enzyme can be considered as the evaluating indicator of soil polluted by heavy metal. The quota relations is, when the inhibition rate is 0～-2.4, -2.4～-22.1 and -22.1～-62.0, the copper content corresponds the second-level, third-level and over third-level of Soil Environmental Quality Standard. When the inhibition rate is 0～-35.2, -35.2～-46.8 and -46.8～-70.3, the zinc content corresponds the second-level, third-level and over third-level of Soil Environmental Quality Standard. When the inhibition rate is 0～-24.6, -24.6～-42.1 and 42.1～-68.5, the lead content corresponds the second-level, third-level and over third-level Soil Environmental Quality Standard.The richment of brassica chinenisis to heavy metal is superior to leaf-used lettuce and lettuce in this test, which rhizosphere soil enzyme activities is also highest, the reason is that great transfer and adsorptive capacity of brassica chinenisis to heavy metal lead to the decrease of heavy metal rhizosphere concentration, so the inhibition activities of heavy metal to soil enzyme becomes weak.