Insitu Remediation Of Cadmium-contaminated Cropland Soil In Date City By Biochar And Limestone

Contamination of heavy metals has caused a wide attention of the society,heavy metal contamination in cropland is closely related to food security and human health.The field experiment was conducted in Wangci village,Daye city,Hubei province.We added the biochar and limestone into the soil to immobilize the cadmium.Because the region is located in a mining area,the soil cadmium concentration was 2.84 mg kg-1 that have reached high levels of pollution standards.Four treatments were set to add different ratio of the biochar and limestone in soil,lettuce was grown as an indicator plant.The experiment was last for two years.After the lettuce were harvested,we analyzed soil pH,soil organic matter,cadmium concentration of lettuce,the species of cadmium in the soil to evaluate the remediation effect and stability of the materials.Research results are as follows:The soil pH increased by 0.42~1.40 units.Soil exchangeable Cd decreased by 4.64%~36.81%.The content of residual Cd increased by 27.88%~58.02%,the increase order was control < biochar < limestone < biochar and limestone.Soil organic matter increased by 3.75%~10.66% in the biochar and limestone treatment.The concentration of Cd in leaf and root decreased by 3.75%~10.66% and 20.86%~61.00%,respectively.The mixed treatment decreased cadmium concentration in leaf to 0.35 mg kg-1.The single treatment(biochar,limestone)could increase pH value and last for 1 year,while the effect of mixed treatment could last for 2 years.The single treatment(biochar,limestone)could decrease soil available Cd and last for 1 year.The mixed treatment could decrease soil available Cd and last for 2 years.In conclusion,the limestone,biochar and mixed treatment can all improve soil properties,decreased the soil available Cd and the content of Cd in lettuce significantly.The mixed treatment was best for cadmium remediation and could last for 1~2 years.