Effect Of Straw Returning On Cd Transformation And Bioavailability Of Soil

Cadmium pollution in agricultural land is very harmful to crop growth and food security.In China,the Cd pollution of cultivated land has the characteristics of wide area and scattered distribution,which poses huge challenges to agricultural production.At the same time,with the improvement of agricultural technology,China's straw resources are becoming more and more abundant.In the general direction of satisfying the sustainable development of agriculture,on the one hand,arable land needs to reduce the harm of Cd pollution,and on the other hand,it also needs a large amount of organic waste to be returned.Therefore,finding out the feasibility of using straw's returning to the field to reduce the harm of Cd in polluted soil is of great significance.In this study,a heavily Cdcontaminated soil in a mining area in Tongling was selected to carry out thermodynamics,kinetic solution adsorption test,soil adsorption test,soil culture test and pot experiment.The systematic study of Cd conversion and its biological effectiveness in the soil-plant system with the help of subcellular grading,DGT and other testing methods has provided a basis for returning straw to the field to control Cd pollution in cultivated land.The details are as follows:1.Thermodynamic results showed that at the same temperature,the adsorption capacity of the four groups of adsorbents per unit mass is?from large to small?: decayed DOM+ nanoceramic material group>nanoceramic material group> wheat straw+nanoceramic material group>the wheat straw group.Among them,the decayed DOM+nanoceramic material group has significantly higher activation energy and adsorption capacity than the other three groups;the kinetic solution adsorption test results showed that the addition of wheat straw decomposed DOM can increase the Cd²⁺ adsorption rate of the nanoceramic material and quasi-second-order kinetic equation can better describe the adsorption kinetic process;the soil adsorption test results showed that the greater the amount of ceramic nanomaterials added,the longer the straw decay time,the greater the adsorption of Cd²⁺ in the soil,The lower the desorption rate.2.The results of soil culture experiments showed that decomposing DOM of rice,wheat and irradiated rice straw can promote the conversion of effective Cd to ineffective Cd in Cd-contaminated soil and reduce the effectiveness of Cd in soil.With the increase of cultivation time,the proportion of soil exchanged Cd continued to decrease,and the proportion of organically bound Cd and residual Cd increased.3.The results showed that wheat straw returning treatments decreased the content of Cd in the cell wall?F1?,organelle?F2?,and soluble matter?F3?of rice roots?by 11.0%⁵1.1% compared with CK?at seedling and tillering stages of rice,while increased the content of Cd in F1,F2 and F3 of rice stems?by 10.1%³5.5%?at filling and mature stages of rice.Meanwhile,the results showed that wheat straw returning significantly reduced the content of Cd in F1 and F2 of rice stems?by 31.3%⁴7.4%?at filling and mature stages of rice,and the content of Cd in F3 of rice stems?49.4%⁵1.1%?at tillering and filling stages of rice;When compared HDWS and FDWS with CK,both straw returning treatments decreased the total accumulation of Cd in shoot remarkably?P<0.05?.