Effects And Mechanism Of Blast Furnace Slag Application On Reducing Soil Cadmium Bioavailability

Soil cadmium pollution in farmland has caused food safety risk and restricted the sustainable development of agriculture in China to a certain extent.Therefore,it is of farreaching significance for ensuring food security and realizing sustainable development of farmland to carry out relevant research on the remediation effect and mechanism of cadmiumpolluted soil and explore effective ways of safe utilization of cadmium-polluted soil.It has been recognized that furnace slag can alleviate the stress of heavy metals on crops,but its chemical mechanism is not completely clear.Therefore,it is of practical significance for scientific application of furnace slag to remediation of polluted farmland.In this study,taking acidic soil as an example,through a combination of potted rice and indoor analysis,the application of blast furnace slag to alleviate the cadmium toxicity of rice and its effect on the chemical behavior of cadmium at the liquid,solid and solid-liquid interfaces of the soil was studied.Provide a reference for the scientific application of blast furnace slag to passivate Cadmium-contaminated soil and ensure safe rice production.The main conclusions obtained are as follows:1.Blast furnace slag alleviated the toxic effect of Cadmium on rice,increased the yield,and reduced the Cadmium content in the rice.Compared with the Cadmium treatment,the application of blast furnace slag(0.3% and 0.6%)increased rice yield by 73.30% and 82.77%,respectively(p<0.01),and increased the root retention rate of Cadmium by 4.25% and 6.23%,respectively.When the blast furnace slag dosage is 0.6%,the Cadmium content in rice is 0.1832 mg/kg,which meets the requirements in the National Food Safety Standard in China(GB 2762-2017).2.Furnace slag changed the factors dominating Cadmium activity in soil solution and reduced the concentration of Cadmium in soil solution.During the growing period of rice,the p H,Eh and EC value of soil were increased after application of blast furnace slag,and the content of water-soluble Cadmium was decreased.3.Blast furnace slag promoted the transformation of Cadmium to invalid state in the solid phase of the soil and reduced the bioavailability of Cadmium.Blast furnace slag reduced the soil acid extractable,reducible,and DGT extractable Cadmium content,and increased the oxidizable and residual Cadmium content.4.Blast furnace slag increased the adsorption of Cadmium in the soil and reduced the desorption of Cadmium in the soil.The equation of Freundlich could better fit the adsorption and desorption of Cadmium in the soil.After applying the blast furnace slag,the adsorption capacity of Cadmium increased,and the adsorption strength decreased in the soil.In summary,furnace slag promoted the conversion of cadmium to an ineffective state in soil liquid and solid phase,and changed some chemical behaviors in relation to the inhibited cadmium desorption in solid phase,which was caused by the combination of various factors.