Study On Passivation And Aftereffect Of Cadmium Pollution In Farmland Soil

With the promulgation of the Law on Prevention and Control of Soil Pollution,the problem of soil environmental pollution has been greatly valued.Cd pollution has been studied by many scholars as soil pollution problem.Study results show that application of repair materials is one of the effective ways to reduce Cd pollution in farmland soil.However,due to frequent use of repair materials,not only does it increases cost of agricultural production,but also reduces soil fertility to some extent.The repairing effect and persistence of materials in Cd contaminated farmland soil are of great significance.Objectives of this study were to study the repairing effect of repairing materials and their after-effects on rice and glutinous wheat in the light Cd-contaminated farmland soil,and to explore the repairing mechanism of the repairing materials and their after-effects in the soil of heavy Cd-contaminated farmland.Field experiments were carried out on light and heavy Cd-contaminated farmland soils,to analyze the adsorption effect of nanomaterials on Cd,and the influence of lime and nanomaterials to the nutrient content,pH value,available Cd content and Cd of the soil in the season and aftereffect,the effects of Cd content and rice-wheat yield in rice and wheat cultivars,and the correlation between Cd content in rice-wheat grains and soil pH,available Cd,and Cd.The main research work and corresponding results are summarized as follows:1)The adsorption process of Cd by nanomaterials is mainly characterized by rapid reaction process and slow reaction process,and the maximum adsorption amount is about 122 mg/g.2)Lime and nanomaterials have a certain effect on the Cd content in rice-wheat grains.The treatment of the repaired material can reduce the Cd content in the mild Cd-contaminated rice brown rice to the Food Safety National Standard(GB2762-2017),and the minimum content can reach 0.11 mg/kg.In the after-effect test,the post-treatment effect of the repair material can reduce the Cd content of the post-wheat wheat by 62.5%.3)Lime and nanomaterials have a certain passivation effect on soil active Cd.The amount of Cd content in the soil can be significantly reduced by 52.9%,and the percentage of acid-soluble Cd in the total amount can be reduced by up to 84.5%.In the aftereffect test,the post-treatment of the repaired material can significantly reduce the effective Cd content of the post-soil soil by 32.7%,and the acid-soluble Cd content can be reduced by 63.0%.4)Lime and nanomaterials can increase the pH value of the soil.The treatment of 0.03%lime+0.4%nanomaterials can increase the pH value of the soil with mild Cd pollution by 1.74.In addition to the single 0.03%lime treatment,the soil pH value of severe Cd contaminated soils was significantly improved in the rest of the application of repair materials to the season,and the maximum increase was 1.64.The post-treatment treatment of 0.03%lime+0.8%nanomaterials significantly increased the pH of the soil after sputum to a maximum of 0.53.5)The repairing materials have a significant effect on the organic matter and alkali nitrogen content of the mild Cd-contaminated soil in the current season.In the mild Cd-contaminated farmland soil,the post-effect of repairing materials had a significant effect on the soil organic matter content in the post-salt soil,and significantly increased the alkaline nitrogen content and the available phosphorus content in the post-salt soil,with the maximum increase of 15.3%and 42.3%,respectively.In the heavily Cd-contaminated farmland soil,the post-treatment of the repaired material significantly increased the organic matter content of the post-soil soil,with the largest increase of 36.1%.6)There was a significant or extremely significant correlation between Cd content in rice and wheat grain and soil available Cd and acid soluble Cd content,which was greatly affected by active Cd in soil.