Yanna Guo

Human co-exposure to mercury vapor and methylmercury in artisanal mercury mining areas, Guizhou, China.

Mercury (Hg) concentrations were determined in human urine and hair samples from Gouxi (GX, n=25) and Laowuchang (LWC, n=18), Tongren, Guizhou, China, to evaluate human exposure from artisanal Hg mining. Geometric means of urinary Hg (U-Hg) were 216 and 560 μg g(-1) Creatinine (μg g(-1) Cr) for artisanal mining workers from GX and LWC, respectively, and clinical symptoms (finger tremor) were observed in three workers. The means of hair Me-Hg concentrations were 4.26 μg g(-1) (1.87-10.6 μg g(-1)) and 4.55 μg g(-1) (2.29-9.55 μg g(-1)) for the population in GX and LWC, respectively. Significant relationship was found between estimated rice Me-Hg intake and hair Me-Hg levels (r=0.73, p<0.001). Co-exposure to Hg vapor and Me-Hg may pose health risks for the study population.

Mercury and methylmercury concentrations in two newly constructed reservoirs in the Wujiang River, Guizhou, China

We studied the distribution of different mercury species in two newly created reservoirs (Hongjiadu [HJD] and Suofengying [SFY] Reservoir) within the Wujiang River, Guizhou Province, China. These reservoirs were sampled four times between January, 2007, and November, 2007. Water, soil, and fish tissue samples were collected and analyzed for organic (methylmercury) and total Hg. Dissolved organic carbon (DOC) content in water was measured as well. In both reservoirs, the DOC concentration was low (range 0.5-4.9 mg/L). Organic matter content in soil collected near the bank of both reservoirs was also low (range 0.4-6.9%). The total MeHg level did not increase significantly with depth in water column, nor did it exhibit a pronounced spatial pattern moving from upstream to the dam. The total MeHg level did not increase significantly with depth in water column, nor did it exhibit a pronounced spatial pattern moving from upstream to the dam. The total Hg content in fish tissue was on average 0.044 mg/kg wet weight, which is a very low content in an international comparison. It is suggested that the studied reservoirs were not active sites of net Hg methylating. Low levels of organic matter (OM) may constrict the evolution of the bulk Hg methylation process occurring in flooded soil. Therefore, we hypothesize that newly constructed reservoirs in the karstic region of Southwest China appear to be much less beset by the problems of MeHg pollution that have been reported for corresponding reservoirs in North America and Europe. However, further research is required to verify this finding.

Seasonal distributions of mercury species and their relationship to some physicochemical factors in Puding Reservoir, Guizhou, China

A comprehensive study was conducted in July 2006, January 2007 and March 2007 to determine the impacts of some major physicochemical parameters on the level of mercury (Hg) in Puding Reservoir, Guizhou, China. The concentrations of Hg species in the summer campaign were significantly higher (p<0.01, generally 2 to 3 times higher) than those in the winter and spring campaigns, and no statistical differences were found between the same parameters for the latter two campaigns (p>0.05). Ancillary parameters including suspended particulate matter (SPM), dissolved organic carbon (DOC), temperature (T), dissolved oxygen (DO), pH, nitrate (NO3-) and chloride (Cl-) were also measured. During the sampling campaign in July 2006, average values for SPM, DOC, T, and NO3- were all higher compared to the other two campaigns, which suggested a similar seasonal trend between these parameters and Hg species. Seasonal variability may be related to increased runoff. High runoff volume due to abundant precipitation in the summer carried Hg-laden particulates into the reservoir, whereas there was less precipitation in the winter and spring when Hg levels were lower. Increased agricultural activity in the summer season also increased Hg levels in Puding Reservoir.

Probing Hg evasion from surface waters of two Chinese hyper/meso-eutrophic reservoirs.

Measurements of water/air exchange flux of gaseous elemental mercury (GEM) were conducted in a hyper-eutrophic reservoir and a meso-eutrophic reservoir in southwest China in both warm and cold seasons by using a dynamic flux chamber (DFC) method coupled with an automatic gaseous Hg analyzer. Both strong diurnal and seasonal variations of GEM fluxes were observed. The diurnal cycle of the GEM flux was more pronounced during sunny days compared to cloudy and rainy days, which highlights the effect of solar intensity on the GEM flux. GEM fluxes in warm seasons were considerably higher (2.5 to 4.1 times higher) than in cold seasons, which was attributed to the combined factors including meteorological factors, water quality parameters and water Hg concentrations. Clear variation in GEM fluxes was observed between the two reservoirs. Mean GEM fluxes in the hyper-eutrophic reservoir (WJD) (3.2-20.1 ng m(-2)h(-1)) were significantly higher than those in the meso-eutrophic reservoir (SFY) (0.6-4.4 ng m(-2)h(-1)). Evasion of Hg played a distinct role in the mass balance of Hg in the two reservoirs. In WJD, evasion was the second most important mechanism for Hg losses from the reservoir (17.5% of the total losses); whereas in SFY, loss of Hg via volatilization constituted an extremely little portion to the total losses of Hg (0.8%).