Investigation On Methods To Evaluate Impacts Of "Phytoremediation Coupled With Agro-production" Patterns For Remediating Cd-contaminated Farmland Soils

Phytoremediation coupled with agro-production(PCA)is an emerging technology for soil pollution remediation while ensuring agricultural production.The knowledge of the benefits evaluation of different PCA patterns is still scarce.Based on the three-year field positioning demonstration,the study compares the comprehensive benefits of four PCA patterns from three aspects: environmental benefits,ecological benefits and economic benefits.Four PCA patterns: sedum alfredii H/rice rotation PCA(SA/R-PCA),rapeseed/rice rotation PCA(OS/R-PCA),wheat/rice rotation PCA(W/R-PCA),and early-late rice continuous cropping PCA(E-LR-PCA).The main results are as follows:(1)Environmental benefits: the safety utilization of agricultural products has been improved after applying these PCA patterns.The soil total Cd and DTPA-Cd concentration could be effectively reduced.Phytoremediation ratio of Cd concentration of SA/R-PCA was 5 times more than the others,the concentration of soil total Cd was decreased by 50.7%.The evaluation of the environmental benefits of each PCA pattern is as follows: SA/R-PCA > OS/R-PCA > W/R-PCA > E-LR-PCA.(2)Ecological benefits: all PCA patterns can improve soil p H and soil fertility(organic matter,bulk density).The results of the 16 S amplicon sequencing showed that bacterial diversity was significantly improved after applying SA/R-PCA and E-LR-PCA.The evaluation of the ecological benefits of each PCA pattern is as follows: SA/R-PCA > OS/R-PCA > E-LR-PCA > W/R-PCA.(3)Economic benefits: All PCA patterns could improve the yield of agricultural products.The annual total input of SA/R-PCA was 3 times more than the others,however the input of removing unit Cd and the long-term investment were about 10 times less.According to the calculation method of the production/investment ratio in this study,the evaluation of the economic benefits of each PCA pattern is as follows: W/R-PCA > E-LR-PCA > OS/R-PCA > SA/R-PCA.In this study,evaluation criteria and methods of environmental,ecological and economic benefits of soil remediation technologies were preliminarily put forward.The comprehensive benefits of remediation of four PCA patterns were evaluated for the first time,which has practical significance for the selection and application of remediation technology in heavy metal polluted farmland.