| With the rapid development of industry and agriculture,the problem of heavy metal pollution in cultivated land in China is increasingly serious.As“town of nonferrous metals”,Hunan Province is suffering from great impact by mining and smelting of mineral resources to ecological environment.How to manage the farmland suffering Cd-Ni-As complex pollution and control the uptake of Cd,Ni and As by rice is an urgent environmental problem.Surrounding the remediation of paddy soil suffering Cd-Ni-As complex pollution,a combined amendment SF?sepiolite+iron-manganese composite oxide?was developed in this paper through investigating the paddy soil with Cd-Ni-As pollution based on amendment screening experiment and rice pot experiment.Furthermore,the mechanism of applying SF to reduce the bioavailability of Cd,Ni and As was systematically expounded.The results were as follows:?1?By soil culture test,developed a combined amendment SF with a certain mass ratio of sepiolite,iron-manganese composite oxide and biochar as the material,which had better immobilization effect on soil Cd,Ni and As,and the available concentrations of their's was decreased by 30.94%,25.15%,and 60.11%,respectively.?2?Soil pH and cation exchange capacity?CEC?were increased,and soil available concentrations of Cd,Ni and As reduced in a paddy soil with Cd,Ni and As combined pollution after application of combined amendment SF.The soil pH value increased 0.180.93?early rice?and 0.130.79?late rice?units,and the soil CEC content increased 25.6%59.7%?early rice?and 20.4%63.3%?late rice?with the combined amendment SF treatment.The soil available concentrations of Cd and Ni decreased by 11.5%80.8%,10.5%73.7%?early rice?and 20.0%-88.0%,17.1%58.5%?late rice?with the combined amendment SF treatment,respectively.When the application of SF at 0.52 g·kg-1,the soil available concentration of As could be reduced by 17.44%23.98%?early rice?and 24.4%34.8%?late rice?,but when SF application rate was>2.0 g·kg-1,the available concentration of As was no significant difference with the control?CK??p>0.05?.The soil pH values and CEC contents were significantly positively correlated with the available concentrations of Cd and Ni of the soil?p<0.05?,the soil pH value was positively correlated with the available concentrations of As of the soil?p>0.05?.The mechanism of Cd,Ni and As availability reduction was an outcome of rising soil pH and CEC,and soil pH increased was the major factor.?3?The application of SF significantly reduced the concentrations Cd,Ni,and As in rice organs.The Cd content of brown rice were decreased by 28.1%56.5%?early rice?and24.3%48.5%?late rice?;the Ni content decreased by 12.3%50.1%?early rice?and21.6%45.5%?late rice?;the As content decreased by 26.2%82.9%?early rice?and22.7%64.7%?late rice?.When the application rate of SF was 0.5 g kg-1,the concentrations of Cd,Ni and As in brown rice were lower and the cost was lower also.The concentrations of Cd,Ni and As in brown rice were significantly positively correlated with available concentrations of Cd,Ni and As in soil?p<0.05?.The concentrations of Cd and Ni in brown rice of late rice were significantly negatively correlated with available concentrations of Cd and Ni in soil?p<0.01?,the concentrationt of As in brown rice was positively correlated with soil available concentration of As?p>0.05?.By decreasing the available concentrations of Cd,Ni and As in soil,the uptake and accumulation of rice could be reduced with the combined amendment SF treatment.?4?After the application of combined amendment SF,the Fe concentration of iron plaque on root surface decreased by 8.7%25.8%and 12.2%27.1%respectively,the Mn concentration of iron plaque on root surface increased by 0.8%32.1%and 3.8%40.9%respectively,the Cd concentration of iron plaque on root surface increased by 6.4%37.0%and 1.5%43.7%respectively,the Ni concentration of iron plaque on root surface increased by 7.3%37.5%and 11.7%46.3%respectively,the As concentration of iron plaque on root surface increased by 2.6%27.6%and 3.8%40.9%respectively.The Fe concentration was significant negatively correlated with Cd concentration of iron plaque on root surface,and was significant positively correlated with As concentration of iron plaque on root surface,and was significant positively correlated with Cd,Ni,and As concentrations of the root.The Mn concentration was significant negatively correlated with Ni concentration of iron plaque on root surface,and was significant negatively correlated with the concnetrations of Cd and Ni of the root.By affecting the iron plaque of rice root surface and its Fe,Mn contents,it affects the adsorption and immobilization of Cd,Ni,and As on the iron plaque at the root surface of rice,and then affects the rice absorption.?5?Application of SF gradually decreased bio-accumulation foctor?BAF?of Cd,Ni and As in rice,increased translocation factor?TF?of root-to shoot of Cd,Ni and As in rice,and has an effect of decreasing and then increasing the translocation factor of other parts. |
PDF Full Text Request