The Research Of Organic Acid Induced Rape On Cd Contaminated Soil Restoration

Rape is one of the main edible oil sources in our country. In recent years, a large number ofheavy metals have been discharged in the soil environment with the China’s industrializationprocessing forward, especially the soil which is contaminated by Cd has gradually expanded andposed a great threat to our health. In this paper, the author myself resort to the pot experiment inwhich the total content and the distribution characteristics of different forms of heavy metal Cdwill be analyzed through adding organic acid into the pot soil to induce and stress while plantingmustard rape crop in the soil polluted by heavy metal Cd, then inspect the concentration changetrend of Cd by effect of rape in soil under the induction of the organic acid as well as the effect ofexperimental conditions to sucrose, amylase and catalase in soil. The main research contents are asfollows:Firstly, by adding the five different types of organic acid respectively which are acetic acid,oxalic acid, citric acid, malic acid and tartaric acid, designing1,2,3,4,5,6mol·kg-1of differentconcentration gradient according to different growth period of rape when choosing4mg·kg-1potting soil which treated by heavy metal Cd and in which planted the rape, the authormyself analyze the change trend of enrichment coefficient and transfer coefficient of heavy metalsCd in soil by effect of rape. The results show that:(1) comparing to the blank control group samplewithout adding organic acid when adding4mmol·kg-1acetic acid,3mmol·kg-1oxalic acid,2mmol·kg-1citric acid,1mmol·kg-1tartaric acid to soil which contain heavy metal Cd to inducewhich can effectively promote the activation of the Cd so that make the Cd absorption capacity ofthe rape significantly increase in soil, but the higher concentration of organic acid for theimprovement (2)after induced by malate, the values of Cd enrichment coefficient of rape have littlechange along with the change of malic acid concentration and the heavy metal Cd transfercoefficient of rape aboveground part is lower than the control sample which indicates that theaddition exogenous malate has weaker activation or inhibition effect on Cd in soil;Besides, by analysis of the feature of distribution of different Cd forms in the soil ofrape-potting system experiment. The results show that: Under rape-soil system induced and treated by4mmol·kg-1oxalic acid,1mmol·kg-1citric acid and1mmol·kg-1tartaric acid, the highestproportion of effective state in soil (exchangeable, carbonate bound and total Fe Mn bound oxides)respectively is89.25%,89.43%,89.67%while the highest proportion of effective state in soil is77.40%and73.59%respectively under the induction of acetic and malic acid. That is to say theoxalic acid, citric acid, tartaric acid in proper concentration is more beneficial to increase themobility of heavy metal Cd in soils, more conducive to the enrichment of heavy metals in rapeplant while promoting effect of acetic acid and malic acid is poor;Finally, under the analysis of the disposition of five kinds of organic acid1-6mmol·kg-1andthe change trend of enzyme activity of sucrose, amylase and catalase in soil, the results show that:adding respectively the4mmol·kg-1concentration of acetic acid, the1mmol·kg-1concentration ofoxalic acid, the6mmol·kg-1concentration of citric acid, the3mmol·kg-1concentration of malicacid into soil, the sucrose activity showed the highest.In the induced range of1-5mmol·kg-1tartaricacid, the sucrose activity in soil was lower than that of the control group, higher than that of thecontrol group were only appeared when the concentration reached6mmol·kg-1. It indicated thatlow concentration of acetic acid, oxalic acid, citric acid, malic acid has a significant promotingeffect on Sucrose Enzyme activity, and low concentration of tartaric acid has a significant inhibitioneffect on Sucrose Enzyme activity;(2) Under the induction of five kinds of organic acids in soil, theamylase activity is almost all higher than that in the control group, that is to say in the experimentalconcentration range, the activation effect of organic acids on the activity of amylase is obvious, theactivity of amylase shows the strongest degree in the2mmol·kg-1concentration of the acetic acid,the3mmol·kg-1concentration of oxalic acid, the3mmol·kg-1concentration of citric acid, the2mmol·kg-1concentration of malic acid, the4mmol·kg-1concentration of tartaric acid.(3)Theactivity of catalase shows the strongest degree in the5mmol·kg-1concentration of the acetic acid,the2mmol·kg-1concentration of oxalic acid, the4mmol·kg-1concentration of citric acid, the2mmol·kg-1concentration of malic acid, the3mmol·kg-1concentration of tartaric acid in soil. Thiscan be illustrated that the proper amount of low concentration of acetic acid, oxalic acid, citric acid,malic acid, tartaric acid are in favor of the improvement of catalase activity.