Application Of Si-Ca-based Soil Conditioner In The Remediation Of Cd Contaminated Rice Field

Cadmium(Cd)is a highly toxic heavy metal element that is highly mobile and easily harm to human health through the enrichment of the food chain and it is considered as the first type of carcinogen.There are many ways for the body to absorb cadmium,but it is most common to eat through dietary intake.Rice is the most important food crop in the south of China,and it is also the most potent grain for cadmium(Cd).A safe soil environment is the basis for the development of the country's agriculture and guarantee for the healthy life of the people.Therefore,through the comprehensive prevention and control of cadmium-contaminated paddy fields,the reduction of cadmium bioavailability in soil and the reduction of cadmium uptake and accumulation by rice can be made to meet the national food hygiene standards,and it is particularly important to prevent cadmium pollution from directly damaging the human body.In this study,the soil of rice fields in a city was sampled and analyzed to assess the degree of soil cadmium contamination in the area.Through pot experiments and field experiments,A(diatomaceous earth),B(light calcium carbonate),and C(red mud)were studied.Effects of three different types of conditioners on the transfer of heavy metals in soils and heavy metals in plants.The optimal compounding agents and their ratios were selected.The main findings are as follows:(1)In the soil of the study area,the pollution degree of heavy metals polluted by cadmium reached a severe degree of pollution,and the highest cadmium content reached 0.8 mg/kg,far exceeding the national standard.The local food hygiene and safety environment has caused great harm.(2)The results of orthogonal experiments with three different chemical conditioners for A(diatomaceous earth),B(light calcium carbonate),and C(red mud)show that the ratio of A,B,and C is 2:2: At 3 o'clock,the effect of the controlling agent on reducing the effective cadmium in the soil is extremely significant,and three chemical regulators,diatomaceous earth A,light calcium carbonate B,and red mud C,can effectively treat the local cadmium-contaminated soil and rice.Repair effect.(3)Adding calcium-silicon-based soil conditioners to the soil in potting laboratories can effectively reduce the cadmium content in rice crops.The maturation of rice after comparison with the cadmium content of rice in the blank group is reduced,and the chlorophyll content and the activity of peroxidase in the mid-developmental period were higher than those in the blank group,indicating that the absorption of cadmium in rice was related to its physicochemical properties.The pH of the soil also increased,and the average pH increased by 0.3 units compared to the blank group.(4)Through field experiments,the application of calcium-silicon-based soil conditioners can improve the pH value of rice soil,the average pH after treatment is 7.18,and the average pH before transplanting was 6.89,and the pH was increased by 4%.The effective state of soil Cd decreased significantly,from the average of 0.368 mg/kg at the three control sites to 0.172 mg/kg.And the percentage of available cadmium in the soil also decreased significantly after our treatment;it decreased from the original average of 72.7% to 44.7%,a decrease of 28%.The cadmium content of the CK group was significantly higher than that of the other five rice fields that had been treated.The treatment group of the fifth group had the best effect,and the cadmium content of the rice was the lowest.The order of decline was 5 >4>3>2>1,except that the content of cadmium in rice at monitoring site 1 is higher than 0.2 mg/kg,and the cadmium content in rice at the other four monitoring sites is below 0.2,with an average value of 0.14 mg/kg,reaching National food hygiene limit standard.