Remediation Of Mercury-contaminated Soils By Using Low Temperature Thermal Desorption In Guizhou Qingzhen

As one of the prior controlled pollutants, mercury and its components concern researchers both domestic and overseas with their serious neuronal toxicity, teratogenic effect, cumulative effect and genotoxicity. It is reported that about 32 thousand hectares of arable land in China have been polluted by mercury being generated rice by 1.9×10⁸ kilograms per year. From the 50 to the middle of 80 years, Guizhou province, being considered as one of the most important mercury mine in China, even in the world, contributes 70% of the total mercury output of China. The long-time mercury exploitation,smelt and production brought enormous impact on the surrounding entironment, especially to the farm soils. As a result, mercury content in soil nearby a chemical plant in Guizhou Qingzhen irrigated by waste water reaches as high as 24 to 347 mg.kg^-1, even over 700 mg.kg^-1, Remediation of mercury pollution is becoming a more and more urgent problem that calls for public attention.Low-temperature thermal desorpiton application, this article mainly refers to ex-situ low temperature thermal desorption application, is a soil heating method to separated the contaminants from the soil, particularly applicable to the soil that has high mercury content, soft, the volatile mercury is the main species in the soil, such as elemental mercury or methyl mercury. In the basis of saving energy, this method has less damage to the soil, that is making backfill soil after the treatment and recovery agricultural possible. So it especially applicable to the karst soils region.In this paper, low-temperature thermal desorption application was selected to repair the mercury-contaminated soils in Guizhou qingzhen. It also explored the changes of physical and chemical nature, the mercury species before and after the application,and the possibility of reclaiming the soils. The conclusions are:1.Temperature,time and soil moisture are all carry weight of the removal of mercury from the soil. The temperature is the most pivotal factor and time is the second key. The soil moisture also has a certain extent effect.2.Before the thermal desorption application, Organic-bound and Residual form is the major form in the soil samples. After the application, the mercury residue in the soil is most of the residue form.3.The reclamation experiment on the thermal desorbed soil shows that through appropriate meliorative measures, soil fertility is completely possible gradually improves to the state that fit the cropper growth.