Effects Of Immobilization Remediation Of Combined Pollution Of Cd And Atrazine In Farmland Soil

Farmland soil is threatened by combined pollution of heavy metals and pesticides,which deteriorate crops quality and soil environment.In addition,the long residue herbicide atrazine also affects the normal growth of vegetables and other crops seriously.In this paper,sepiolite and biochar were selected as remediation materials,and the simultaneous remediation of cadmium?Cd?and atrazine compound pollutants in farmland soil was carried out by immobilization remediation method,and the effect of remediation technology on vegetable physiological and soil environmental quality was further discussed.The main findings are as follows:1.Sepiolite and biochar immobilized and fixed Cd and atrazine in soil by adsorption,group coordination,and increasing pH,so that Cd and atrazine bioavailability decreased.The germination rate and growth of pakchoi tended to be normal.The available Cd in soil decreased significantly.The absorption of Cd and atrazine by pakchoi decreased after fixation and immobilization,and Cd in pakchoi was lower than China's national food safety standards.Of two remediation materials,sepiolite played a major role in Cd immobilization,and biochar played a major role in atrazine immobilization.After 6 months,the remediation technology still had good immobilization function.2.At the first harvest,pakchoi cell membrane structure was repaired,so the chlorophyll content of pakchoi increased,and the photosynthetic rate was increased due to the decrease of soluble sugar.The enzymes activities changed different due to their characteristics.The contents of Ca,Mg and K in pakchoi increased,but the addition of remediation materials under acidic conditions significantly enhanced the adsorption capacity of P by soil,which was not easy to be absorbed by pakchoi,so the P in pakchoi decreased.SOD can dismutate ASAFR into H₂O₂,so the decrease of SOD leaded to ASAFR increase.Since contents of GSH and MDA increased,and GSH could inhibited NO₂^-and H₂O₂,so the contents of NO₂^-and H₂O₂ decreased.The contents of amino acids that make up proteins vary,so there was no significant rule in changes of pakchoi protein.The remediation materials contained a large amount of salt and absorped various substances made pakchoi ash rise.The decrease of Cd in pakchoi decreased activity of APX and increased V_C of pakchoi.The results at two harvest showed that the effects of remediation technology on most physiological indexes of pakchoi were stable.3.At the first pakchoi harvest,alkaline remediation materials increased soil pH,increased negative charge on the soil particles surface,and decreased Zeta potential.Soil enzymes responded differently to soil environment due to different characteristics.The content of available P,available K and available N in soil increased due to the fixation of remediation materials.The introduction,adsorption and fixation of salt ions by remediation materials increased soil EC.The adsorption,polymerization and self-decomposition of biochar increased the soil organic matter,while the increase of pH and organic matter promoted the increase of soil CEC.The improvement of soil environmental quality made the microbial community more abundant and diverse.The results at two harvest showed that the effects of remediation technology on most soil physicochemical indicators were stable.4.The improvement of soil environmental quality made the structure of microbial community more abundant and the species more diverse at most taxonomic classifications,and influenced the abundance of microbial composition.In conclusion,the addition of sepiolite and biochar to the polluted soil effectively immobilized and fixed Cd and atrazine compound pollutants in soil,to made their bioavailability decrease,and guaranteed the safety of the pakchoi harvested with the two-pollutant residual up to standards.After 6months,the two remediation materials still had good immobilization remediation ability to contaminated soil.In addition,sepiolite and biochar also improved some physiological and biochemical properties of pakchoi and improved soil environment and quality.