[Geochemical cycling of mercury in the sediment of Hongfeng Reservior].

Spatial and temporal distributions of total and methyl mercury and controlling factors were investigated based on cold vapor atomic fluorescence detection. Total mercury levels in the whole sediments are (0.392 +/- 0.070) microg/g, without significant variations between different seasons, but generally increase toward the sediment-water interface. Total mercury levels are higher compared to data reported in other uncontaminated reservoirs and Wujiangdu Reservoir. This indicates there are mercury contaminations in Hongfeng Reservoir. Methyl mercury concentrations are highest in spring, without significant variations in other seasons. The peak values of methyl mercury typically appear in the upper 8 cm of the sediment profiles which are also the zones of sulfate-reducing bacteria activities. The seasonal variation and maximum peak value distributions of methyl mercury in sediment are mainly controlled by seasonally migration of oxic/anoxic boundary layer. Total mercury concentrations in the pore water and partition coefficients for THg in solid phase and water phase are mainly controlled by temperature or redox potential. Total mercury concentrations in the pore water have no relationship with total mercury concentrations in solid phase. However, the methyl mercury concentrations in the pore water have a strong relationship with those in solid phase (r = 0.70, p < 0.001). The methyl mercury concentrations in solid phase and pore water are controlled by solid/water partition coefficient, as well as methyl mercury production.

[Mercury exchange fluxes between air and soil interface over different type of land in Wanshan Hg mine area].

Air/soil Hg exchange fluxes were measured using field chamber-automated air mercury analyzer method over different land in Wanshan Hg mine area in two seasons. The results showed that the air/soil Hg exchange fluxes were very strong. The highest Hg emission flux from soil was 27 827 ng/(m2 x h), the highest Hg deposition flux from the atmosphere was 9 434 ng/(m2 x h). Because of Hg emission from anthropogenic activities and natural lands, the Hg concentrations in air in Wanshan Hg mine area are 1 - 3 orders of magnitude greater than background area. The highest average Hg concentration in air reached 1 101.8 ng/m3, and the lowest average Hg concentration in air still reached 17.8 ng/m3. These indicated that the atmosphere was polluted seriously in Wanshan Hg mine area. The Hg exchange fluxes are influenced by solar irradiation and the Hg concentrations in air. The solar irradiation accelerates the Hg emission from soil. Conversely, the Hg concentration in air restrained the Hg emission from soil, and even leads the Hg concentration depositing to soil surface. The Hg emission fluxes from uncovered soil are higher than that from covered soil by vegetations significantly. And the slag becomes net atmospheric Hg source.

[Mercury emission from the indigenous method of mercury smelting in Wuchuan mercury mining areas, Guizhou Province].

By determining mercury concentrations in mercury ore and smelting slag samples, we used a mass balance method to calculate mercury emission factors and annual mercury emission from the indigenous method of mercury smelting in Wuchuan mercury mining areas, Guizhou Province. The mercury emission factors of the indigenous method ranged from 6.9% to 32.1% with the recovery from 78.4% to 93.6% and the annual mercury emission was up to 3.7-9.6 tons. The results highlighted that the indigenous mercury smelting was one of the most important anthropogenic atmospheric mercury emission sources in this region.

[Comparison of air/soil mercury exchange between warm and cold season in Hongfeng Reservoir region].

In July 2002 and March 2003, the mercury exchange flux between soil and air was measured using dynamic flux chamber method in Hongfeng Reservoir region. Mercury exchange flux is (27.4 +/- 40.1) ng x (m2 x h)(-1) (n = 255) and (5.6 +/- 19.4) ng x (m2 x h)(-1) (n = 192) in summer and winter respectively. The correlation coefficient between mercury flux and solar radiation, air temperature, soil temperature is 0.74, 0.83 and 0.80 in summer, and 0.88, 0.56 and 0.59 in winter. From the data, it was found that the mercury emission is stronger in summer than that in winter, and compared to winter, mercury exchange between soil and air depends more on meteorological conditions in summer.