| In order to effectively control Cd pollution in rice fields,the treatment efficiency of 5 passivation materials on Cd pollution in rice field were analyzed,at the same time,in order to ensure soil quality safety,the influence of 5 kinds of passivation materials on soil quality in paddy field was analyzed by screening soil quality indicators.The main results were as follows:(1)In 5 kinds of passivation materials,on the whole,N materials(organic fertilizer+biochar)and M material(TSP+lime)decreased the Cd content in rice is better.M material had the best effect on reducing Cd content in the rice,in the level of middle concentration(375 g·m~2),the Cd content in rice decreased 66%,under the level of high concentration(450 g·m~2)decreased by 49%compared with the control.Followed by N,Y materials,in which N2(750 g·m~2)and Y3(300 g·m~2)works best,the content of Cd in rice decreased by 13%compared with the control.Group B(microbial fertilizer+biochar)and W(montmorillonite+apatite)material,no matter which level of concentration,Cd content in rice increased.(2)In the 5 kinds of passivation materials,the content of available Cd in soil decreased the largest with adding W material(montmorillonite+apatite),with the increase of concentration,the content of available Cd is lower.The content of available Cd in soil decreased by 14%~27%compared with the control.N,M,Y,the three kinds of materials only in high concentration level(N3:1200 g·m~2,M3:450g·m~2,Y3:300 g·m~2),the content of available Cd decreased by 6%,8%,7%,respectively,compared with the control.In the 5 kinds of passivation materials,only W3 reduced the total Cd content in the soil and decreased by 2%compared with the control.(3)Adding 5 kinds of passivation materials,in N group materials,the yield of brown rice have the lagest increase,its increased by 9~13%;Followed by Y materials,the yield of brown rice decreased only by 1%at low concentration;The yield of brown rice have the lagest decrease at the low and medium concentration of W.(4)By correlation analysis,the content of Cd in rice is not related to the content of Cd in other different parts of rice,Mainly affected by the ability of each part to transfer Cd to rice.The Cd content in milled rice had a very significant positive correlation with the transfer factors of bran-rice and the enrichment ability of milled rice to Cd,and it was significantly positively correlated with leaf-rice transfer factors,this means the closer to the rice,the ability to transfer Cd to rice is stronger.Difference of Cd content in milled rice with different passivation materials,probably because the passivation material changes the soil environment,at the same time,it can indirectly affect the accumulation factors of milled rice to Cd and the Cd transfer factors of each part of rice.(5)Adding 5 kinds of passivation materials,B material and Y material had the best effect on soil quality,soil available nutrients and organic matter contents increased,the content of available phosphorus increased by 20~69%and 30~79%,and the content of available K increased by 14~49%and 7~23%,and the content of available nitrogen increased by 35~42%and 18~28%,and the organic matter increased by 17~21%,7~26%.Followed by M materials,the available K content was decreased by 11%and 7%compared with the control at low(300 g·m~2)and high concentration(450 g·m~2).With the addition of 5 kinds of passivation materials,the soil pH all did not reach significant differences.(6)Adding 5 passivation materials,the remediation effects of Cd pollution in rice fields and their effects on soil quality were analyzed.In general,the effect of Y material and M material is relatively good,especially in the high concentration level,the soil available Cd content decreaded 9%and 7%,the Cd content in rice decreased 49%and 14%,respectively;And the yield increased;The soil quality has improved as a whole.Therefore,the high concentration levels of these two materials are more suitable for the treatment of Cd pollution in this soil. |
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