Release Characteristics Of Mercury From Purple Soil In Dry-Wet Rotation Systems

As a global pollutant, since Minamata Disease event, which was occurred in Japan during the early 1950s, mercury brought a series of pollution issues which have always been one of the research focuses of environmental science field. People have realized many important aspects of mercury pollution such as its sources, transportation, transformation and harm. However, researches on quantitative relation between sources and sinks of mercury in environment have not been satisfactorily obtained, especially emission of mercury from nature sources is to be estimated rigionally and globally, and extensive measurement of mercury exchange flux over air-surface is of great importance. Mercury exchange flux over different environmental interfaces (air-soil, air-water, wate-deposition and organism etc) and its influence factors was researched detailedly, but not thoroughly in time and regional scale. Thereafter a Dynamic Flux Chamber (DFC) technique was applied to measure air-surface exchange flux of mercury over 13 farm field plots of National Purple Soil Base of SWU in dry-wet rotation systems for a year, and searching influence factors and characteristics of mercury release over soil and water surfaces varing with different fertilization, seasons, terms of rotation and crops. The data of measurement in these plots were used to evaluate emission of mercury from natural source such as farm fields in dry-wet rotation systems of Chongqing.Results showed, the mercury fluxes over different plots and over different interfaces of same plot have significant difference. In general, air-water interface exchange fluxes of mercury in paddy fields are lower than that of air-soil interface in dry fields; the overall average value of mercury flux was 65.09±77.3 ng m^-2h^-1 and 129.2±139.9 ng m^-2h^-1, respectively. In 13 farm field plots during rotation terms, flux was about 1-3 fold greater than minimum. Among dry fields (inclunding rape/wheat fields in cold and warm seasons, fallow fields in warm season) plot 0 (236.1±227.3ng m^-2 h^-1) was of maximum mercury flux from soil, plot 1 (184±166.5ng m^-2h^-1) took the second place, and plot 12 (87.1±127.8ng m^-2h^-1) was of minimum. Of all paddy fields, plot 1 (135.3±135.8ng m^-2h^-1 ) was of maximum mercury flux over water, plot 0 (121.4±227.3ng m^-2h^-1), comparatively lower,...