Study On Arsenic Pollution Characteristics And Its Solidification In Soils Of A Mining Area In Hunan Province

With the influence of a series of human activities such as metallurgy,mining,chemical industry and waste incineration,and the frequent occurrence of natural disasters,the heavy metal pollution of soil becomes more and more serious,and the restoration of heavy metals in soil has become a worldwide problem.Arsenic is a highly toxic element and easily carcinogenic substances,many countries have arsenic is defined as "public disease" and "highly toxic elements" one.Soil arsenic contaminated in China is more serious than in other parts of the world.Nearly 20 million people live in high risk areas of arsenic contaminated in soil.The mining area in Shimen of Hunan province,is Asia's largest realgar mine,is considered one of the five major sources of pollution,seriously endangering the lives and health of local residents.It is an urgent problem to understand the arsenic pollution characteristics of soil and repair it.In this study,arsenic contaminated soil was used as the object of study.Comparison of three(Tessier,Shiowatana,Rauret)SEPs(Sequential Extraction Procedures)for arsenic fractionation in highly polluted sites,the arsenic polluted characteristics of soil in the mining area were systematically analyzed by the correlation analysis of soil arsenic contaminated level and the spatial distribution of concentration,the content of arsenic in different valences,the distribution of arsenic fractionation and the bioavailability of arsenic in the mining area.Conducting risk assessment and proposing evaluation criteria for solidification of arsenic in soils.Through the laboratory study of curing experiments,the curing parameters of the ceramic materials were determined,and the curing effect was tested.The results show that Shiowatana SEP is superior to Tessier SEP and Rauret SEP in terms of recovery rate,reproducibility,bioavailability evaluation and specific fraction extraction.Arsenic concentration exceeded the standard rate of 91%,the distribution of arsenic fraction in the soil is as follows:Residual>Fe/Al associated>HCL extracted>Surface-absorbed>Water soluble.The general distribution of arsenic different valences is as follows:As(V)>As(III)>DMA>MMA,there is a certain correlation between different fractionations and valences.The bioavailability of arsenic and the health risk in the soil is extremely high.The arsenic content in the plant is positively correlated with the water-soluble and surface-absorbed.The curing agent can significantly reduce the soluble arsenic concentration in soils,the best addition of curing agent is 6.4%,and the curing efficiency is 62%at the shortest curing cycle of 6 weeks.Curing agent on the different pH value and temperature have a better tolerance,curing effect will not be affected by environmental conditions,the addition of curing agent can significantly reduce the arsenic enrichment of plants.