Stabilization And Earthworm-assisted Phytoremediation Of Pb-Cd Contaminated Soil

Lead?Pb?and cadmium?Cd?are cumulative and long-term in the soil and can affect the health of humans and animals through the food chain.At present,heavy metal contaminated soil remediation technologies mainly focus on physical chemical technology or phytoremediation technology.This thesis comprehensively used chemical remediation technology?stabilization technology?and earthworm-assisted phytoremediation technology to treat lead-cadmium contaminated soil in order to provide technical support for the remediation of soil with severe lead and cadmium pollution.In the experiment,stabilizing material were used to stabilize soils contaminated with lead and cadmium,and then continuous leaching experiments were conducted to study the dynamic changes of the main characteristics of the leachate in the soil.Finally,earthworm-assisted phytoremediation technology was used to treat the soil.The main results of the study are as follows:?1?Trisodium phosphate,Sodium dihydrogen phosphate,Calcium dihydrogen phosphate and Calcium Oxide were used to treat lead-cadmium contaminated soil,and Calcium dihydrogen phosphate and Calcium Oxide were chosen as preferred stabilizing material.Orthogonal experiments found that the leaching concentrations of lead and cadmium in contaminated soils were low when treated with 3%Calcium dihydrogen phosphate,0.2%Calcium Oxide,and 30%moisture content.X-ray diffractometer?XRD?was utilized to observe the mineral of Calcium dihydrogen phosphate and Calcium Oxide induced lead-cadmium contaminated soil.The occurrence of HCa?PO₄??H₂O?₂,Pb₁₀?PO₄?₆?OH?₂)and Pb₃P₄O₁₃ were found.?2?Continuous leaching simulation experiments showed that in the fast and slow leaching groups,the concentrations of lead and cadmium in the leachate of S0?contaminated soil+distilled water?during the continuous leaching process first increased and then decreased.The concentrations of lead and cadmium in the leachate of S1?treated soil+distilled water?and S2?treated soil+acid solution?decreased during the continuous leaching process.The concentrations of phosphorus in the leachate of S1?treated soil+distilled water?and S2?treated soil+acid solution?first decreased and then increased during the continuous leaching process.?3?Earthworm-assisted phytoremediation experiments showed that the earthworm increased the biomass of wheat and rape.Earthworm also increased lead and cadmium concentrations in root part of wheat and rape.In stablilized soil,the leaching concentration of lead after earthworm-assisted wheat phytoremediation was lower than that after single wheat phytoremediation;The leaching concentration of cadmium after earthworm-assisted rape phytoremediation was lower than that after single rape phytoremediation.