Effect Of Remediation Mechanism Of Lime-type Passivator On Soil Cadmium And Cadmium Uptake By Leccuces

In the matter of increasing number of polluted soil contaminated by heavy metals which made the quality of soil decreased a lot,it's of great practical significance to restorate and retreat the soil contaminated by Cadmium to ensure the safety of agricultural products.selected as materials.The pot experiment aims to find out the the change of form of Cd in soil after using the calcite,red mud,calcium carbonate,and how to decrease the accumulation of Cd in Lettuces.The findings are as follows:1.The pH values of all the treatments were significantly increasing compared to the control treatment,the pH values of the treatment which added red mud to pot experiment changed the most,it rose 0.82?1.50 units;while the treatment which added calcite behave familiar to calcium carbonate treatment,the pH values were increased respectively 0.84?1.23 units and 0.89?1.01 units.2.Three passivating agents can effectively reduce the available cadmium content.The treatment which added red mud reduced the effective state of Cd about 2.7%?33.3%,the treatment which added calcium carbonate reduce the effective cadmium about 6.7%?27.9%,the treatment which added calcite reduce the effective cadmium about 14.3%?33.2%.The correlation analysis between pH value and available state of all the treatments showed that the red mud treatment was negatively correlated,the calcium carbonate treatment was significantly negatively correlated,while there was no correlation in the the calcite treatment.3.The analysis of the cadmium form in the soil showed that the cadmium in the soil was changed after adding the three passivating agents.The exchangeable cadmium content and the iron-manganese oxide-bound cadmium all showed a tendency that the doses of increase more,they decrease more..the conversion efficiency of exchangeable cadmium influenced by calcite>red mud>caleite carbonate.The content of cadmium in Carbonate bound state and Residual state increased a lot with the increasing of the dose of passivating agents.The change of organic binding was not so obvious.4.The results showed that the cadmium content in the above ground and underground was significantly decreased after adding the passivating agent.In addition,the content of cadmium in the aboveground and underground of Lettuces were decreased respectively about 12.57%?48.01%and 12.63%?58.72%.Three kinds of passivating agent in experiment effect on lettuce about reducing Cd accumulation in stem and leaf in the order of:carbonate calcite>red mud>calcium,while the rule of underground content in the order of:calcium carbonate>calcite>Red mud;The higher the dose,the better the passivation effects.The treatment in the dose of 5%dose effect significantly different from others;in the lower dose treatment,red mud and calcite effect significantly better than calcium carbonate,in the higher dose treatment,The three had no significant differences.5.The soil contaminated by Cd influenced the growth of Lettuces.The fresh weight and height of the Lettuces in contaminated soil compared with clean soil treatment(CKO)decreased respectively about 44.18%and 34.46%,The application of the passivating agent ease the decreasing the effects.The treatment which add the red mud was firstly increased then decreased with the application dosage,1%dose got the maximum biomass,3%and 5%doses decreased the fresh weight in lettuce;The treatment which add the calcium carbonate made the biomass increased with the increasing of dosage of passivating agents.The biomass of calcite treatment firstly increase then decrease slightly then reach a point that the biomass didn't change any more.The 3%dos'e of calcite treatment made the biomass reached the maximum of all the treatments.