Study On The Sensitivity Of Mercury In Soil Under Acid Rain Condition In ChengDu Area

Mercury pollution is a common phenomenon in global world. Mercury pollution is becoming a big problem to threat the health and living environment of human being. Soil mercury can be actived by acid rain and pollute the underground water, stream, pool, then absorbed by plants and aquatic animal and further through the food chain to enter into human body and cause harm. Thus, the research concerning about mercury pollution in soil can not be neglected.The study focused on mercury in two typical agricultural surface layer soils (paddy soil and yellow soil) in east and west suburban area of Chengdu city. The quantity of total mercury and methyl mercury, the charactristic of soil and the relationship between mercury and charactristic of soil were researched. The desorption action under acid rain condition is key researched. The leaching experiment is performed to determine desorption behavior of mercury influnced by the different factors of acid rain. The results analyzes the pollution status of mercury in soil and the mobility, transformation characteristic of mercury under acid rain impact, and can offer suggestions to prevent the mercury pollution in the soils of Chengdu area.The results indicate that the pollution of mercury in soil is not serious, it is between the clear and warn line but not up to slight pollution. The concentration of methyl mercury and total mercury in soil is low, and the rate of [MeHg]/[HgT] also low. The methyl mercury and total mercury in soil are positive correlation. The comparision made between the soils of the two areas shows that the concentration of total mercury in QingYang area is higher than ChengHua area, but the situation of methyl mercury is converse.The results show that there exists some linear correlation between mercury concentration and properties of soil, the sequence is CEC>organic matter>total sulfur>pH.Among these factors, the quantity of methyl mercury is strongly influnced by organic matter and CEC than others. In addition, acid rain has accelerated the rate of mercury release from soil. The velocity and desorption extent of mercury are enhanced with the increase of leaching time and quantity. Different soils have different release action under the same acid rain. As same as the former, different acid rain is expressed different effect for the same soil. pH value, positive and negative ion are all influnce desorption of mercury in soil. Lower pH value, increase the cencentration rate of SO42- and NO3-, enlarge the concentration of Ca2+和NH4+ are also enhance the mercury release of paddy and yellow soil. The influnce order is: pH>[SO42-]:[NO3-]>[Ca2+]>[NH4+].The Eh-pH diagram of Hg-H2O at 25℃was used to explain the transformation mechanism of soil mercury. The results shows good agreement with the Eh-pH diagram of Hg-H2O system. It is conformed that this diagram explaination is coincidence with the conclusion, so it have a good meaning to perform it to explain mercury transformation mechanism, this also enlarge the application of Eh-pH diagram in environment field.