Remediation And Long-Term Effects Of Combined Amendment And Silicon Fertilizer On Paddy Soil Contaminated With Cd And As

The situation of heavy metal pollution in farmland soil in Hunan Province is severe,especially the problem of cadmium and arsenic compound pollution is the most prominent and thorny,it is of great significance to seek a method for the simultaneous treatment of moderate to severe cadmium and arsenic compound pollution of soil.In this study,through three consecutive seasons of field trials,it is explored that the combined amendment limestone+sepiolite(referred to as LS)combined base application of Si fertilizer and foliar application of Si fertilizer,single and combined treatments,can treat moderately and severely cadmium and arsenic compound polluted rice fields.The role and mechanism of different application methods of silicon(Si)in the process of soil heavy metal remediation and plant safety production have been studied,and feasible technical measures for simultaneous remediation of moderate to severe cadmium and arsenic pollution have been proposed,it aims to provide technical support and practical reference for the remediation of cadmium-arsenic compound contaminated soil and the application of Si in the field of soil remediation.The main research results are as follow:(1)The combined amendment LS and base application of Si fertilizer increase soil pH by 0.32～1.07 units and 0.17～0.37 units,respectively,and increase soil CEC value by 13.2%～41.9%and 12.1%～32.7%.Combined amendment LS and Si the combined effect of fertilizer is more significant,while the foliar spraying of Si fertilizer has no obvious effect on soil pH and CEC value.(2)The combination of amendment LS and base application of Si fertilizer can significantly reduce the bioavailability of cadmium and arsenic in the soil.The combined reduction effect of the two technologies is more significant.Foliar spraying of Si fertilizer has no significant effect on the bioavailability of cadmium and arsenic in the soil.(3)The three single technologies can effectively reduce the absorption of cadmium and arsenic by rice.The effect of reducing the Cd content of brown rice is from the highest to the smallest as the combined amendment LS>basic Si fertilizer>foliar application of Si fertilizer,which reduces the As content of brown rice.The effect of reducing the As content of brown rice is:spraying Si fertilizer on the foliar surface>applying Si fertilizer as a base>combined amendment LS.The combined reduction effect of multiple technologies is more significant,JL2F2 and JL1F2 treatments can achieve the cadmium and arsenic content in brown rice under the conditions of cadmium and arsenic compound pollution of rice fields(total Cd:2.83 mg·kg-1,total As:90.45 mg·kg-1).(4)There is a significant correlation between the Si content in each part of the rice and the cadmium and arsenic content in that part.For brown rice,the correlation coefficients between the silicon-cadmium ratio and the brown rice Cd content,and the silicon-arsenic ratio and the brown rice As content are 0.954 and 0.910,respectively.(5)For the remediation of moderate to severe cadmium-arsenic compound contaminated soil,it is recommended to use JL1F2 treatment(2250 kg·hm-2 application rate LS+base application 90 kg·hm-2 silicon fertilizer+foliar spraying 0.4 g·L-1 silicon fertilizer)Increasing the amount of Si in the soil can realize that the cadmium and arsenic content of at least three seasons of rice meets the safety standards.