Study On The Impact Factors Of Mercury Emission Flux From Forest Soil

Mercury is defined as one of the most harmful heavy metals in the environment by governments and the World Health Organization. It has long-range transboundary nature of the global transport of pollutants. Mercury pollution has become increasingly widespread concerned by the governments. The release of mercury from soil is one important natural sources. In recent years, a lot of international studies found that the release of soil Hg0 was declined in Europe and North America, while it increases in Chinese. Compared with other countries, the relative research is lacking in China. It can provide a reference for estimation of regional mercury emission flux to investigate soil Mercury emission flux.This dissertation was supported by under the auspices of the National Natural Science Foundation of China (20937002). To study the effect of environmental impact factors on soil mercury emissions, intact surface soil samples (0 to 5 cm) was collected from a Masson pine forest in Tieshanping, Chongqing to conduct controlled experiments. soil mercury emission flux and other influencing factors under different conditions were measured by dynamic flux chambers, Lumex(?) Zeeman effect mercury analyzer, pyrolysis unit, HOBO weather station and so on. Mercury fluxes calculated using the formulaF= (co-ci) A-1 Q, and analyze the relationships among factors affecting mercury fluxes using SPSS/Origin/MS Office software.Results showed that the mercury emission increased significantly with the enhancement of solar radiation, air temperature, and soil water content. The mercury emissions in sunlight were 3 to 9 times higher than those in shade, but the latter condition should be more similar to the actual condition in the field. Air humidity had no clear effect on soil mercury emission. Effect of soil temperature on soil mercury emission depends on air temperature and radiation intensity. The mercury emission flux was significantly higher in summer than in spring and autumn, and lowest in winter. The soil mercury emission flux was higher in summer daytime than night. Higher in air temperature, soil water content had a stronger effect on soil mercury emission. Removal of litterfall significantly decreased soil mercury emission, mainly because the mercury content of litterfall was higher than that in mineral soil layer. In addition, soil mercury emission had an obvious trend of decay during a day, indicating that relatively low mercury content in forest soil might be a limiting factor of mercury emission. The mercury emission flux in the daytimemeasured in this study was (14.3±19.6) ng·(m2·h)-1 in summer, (3.50±5.36) ng-(m2·h)-1 in spring and autumn, and (1.48±3.27) ng-(m2·h)-1 in winter. The steady-state results above might therefore be overestimation of the actual emission in the field.