Index System Design And Application Of Safety Assessment Of Vegetable Growth On Cd-,As-contaminated-soil After Remediation With Inhibitors

Due to“three waste”discharged into environment from the process of mine exploition,which caused the concentrations of heavy metals like arsenic and cadmium in soil environment were higher than those of world average.As"the hometown of nonferrous metals",and the"land of fish and rice",Hunan province faced the problem that the concentrations of heavy metals in farm land exceeding the national standard values.Heavy metals would be accumulated by crop and enter into human body through food chain,even be harmful for human health and ecology environment.Therefore,the heavy metals pollution in rice and vegetable were paid by society,and there many measures for reducing the concentrations of heavy metals in rice and vegetable.However,after remediation the lands contaminated by heavy metals,the effectiveness evalution of those measures were only according to the concentrations of heavy metals in crop,not assess the quality of soil whether effect or not.In the present study,based on literatures,the safety evaluation system was designed and assessed on the vegetable growth on the Cd-,As-contaminated-soil after remediation with inhibitors such as three inhibitors and nano-MnO₂.The main results are as follows:?1?The questionnaire which are from the 25 experts use the method of expert to soil science,environmental science and plant nutrition three disciplines,finally it is concluded that includes physical indicators?soil texture,soil porosity?and chemical indicators?pH value and CEC of organic matter,soil nutrient?,crop index?crop growth,crop yields?,heavy metals index?heavy metal content of soil heavy metal total,crops,soil heavy metal biological effectiveness?11 indicators.Using analytic hierarchy process it is concluded that the weight of all indacators,finally it is conclude that the repaired vegetable safety evaluation system.?2?By three kinds of common soil conditioner?lime,red mud and activated carbon?according to the different proportion,and accounted for 0.2%and 0.5%of the soil heavy mixed,to repair contaminated soil samples,pick out the effect is better than 10 groups for restoration of potted plant experiment.Study found that,soil improver added quantity weight 0.5%when 0.2%of the soil heavy repair effect is better.After the use of heavy metal contaminated soil repair vegetable safety evaluation system for the evaluation,found that more than 10 groups P values in experimental group were higher than 40.Adding amount of 0.20%of the soil heavy L:RM=2:1:1,and adding amount of 0.50%of the soil heavy L:RM=1:2,L:AC=2:1,L:RM:AC=1:1:2 four group mixed soil conditioner,repair ability to the best of heavy metals,and have less effect on the soil quality.To illustrate the four groups of repair effect is better,and less impact on soil quality,to continue as agricultural land.?3?With nanoscale manganese dioxide after repairing contaminated soil,the indicators show that with the increase of concentration of added to repair the better the results,four added concentration of total scores?P values?were greater than 38%of the total P value.Although did not reach 50%of the total P values,and fixed number of year of the repair has been for three years,but still the repair effect of Mn-2.0%for adding the best concentration.From the point of three indicators,Mn-1.0%than of Mn-0.5%effect is good,but comprehensive all index,Mn-0.5%of the P value is higher.Repair instructions for heavy metal concentration with better effect,not necessarily is the smallest of soil damage,cannot prove single value as the index,to evaluate the repair effect of heavy metal polluted soil,the integrated soil heavy metals and soil fertility index of the evaluation more scientific.?4?In this study,three kinds of mixed soil conditioner is P values higher than the P value of nanoscale manganese dioxide,does not necessarily means that the former repair is better than the latter.Existence of the reasons are as follows:first,restoration of nanometer manganese dioxide experiment in the open field,no good conditions of greenhouse soil conditioner;Second,adding nanometer manganese dioxide on the management of soil heavy metals arsenic,the cadmium time have up to three years,and the soil conditioner repairing time is only three months,repair years too long,morphological changes of heavy metals in the soil,after evaluation of various indicators have no ideal of three kinds of mixed soil conditioner.Therefore,it is the repair ability of heavy metals by three kinds of soil conditioner is higher,or repair of nanoscale manganese dioxide fixed number of year is not the best,or for other reasons,also need to be further explored.