Study On The Distribution Characteristics Of Mercury And Methylmercury In The Typical Wetlands, Yellow River Delta

The Yellow River Delta is the youngest estuary wetland ecosystem in warm areaof China, with complex and diverse wetland type and rich biological resources.Wetland is the sink of mercury and the source of methylmercury. So the research onthe distribution of mercury and methylmercury in the wetland environment is of greatsignificant to the wetland creatures and the human health.The soil and water samples were collected in the typical wetlands of the YellowRiver Delta in summer and autumn, and then the content of mercury andmethylmercury were determined. The distribution characteristics of mercury andmethylmercury in soil and water were analyzed according to the physical chemistryand biological parameters, including the content influences of mercury. The results areas follows:1. The concentration of total mercury in wetland water in autumn was higher thanthat in summer. The exogenous input raised the mercury content in water, such asthe X11position. The methylmercury content in wetland water (0.07~3.29ng/L) ishigher than the natural water (0.02~0.1ng/L), its concentration in summer ishigher than that in autumn. The methylation ratio in summer ranges3.61%~12.8%.In autumn, the ratio is0.29%~30.06%, with the average8.28%. So mercurymethylation ratio was higher in summer. In the Yellow River Delta wetland water,the concentration of mercury and methylmercury is higher than the natural waterbody, but lower than the class1surface water quality standards of China. Thecontent of total mercury is not high compared to the other areas at home andabroad.2. Total mercury in the surface and horizon soil in autumn is higher than that insummer. The mercury content were higher in soil inundated water or higher claycontent than the dry wetland soil or the sandy soil. Total mercury concentration isin deep soil is higher than that in surface soil in summer. In autumn, the distribution of mercury in dry wetland soil is similar to summer, and mercurycontent of surface soil was higher than the deep soil in the other typical wetland.Long-term flooded environment is in favor of the accumulation of mercury, anddrought environment could cause the release of mercury.3. The concentration of methylmercury in surface and deep soil is higher in autumnthan that in summer. Methylmercury content in soil would decrease after drought.In the vertical direction, the concentration of methylmercury in deep soil is higherthan that in surface soil. The methylation ratio in autumn is higher than in summer.And in the inundated wetland methylmercury content in soil was higher than thedrought wetland. The peak of methylation ratio in summer appeared under the8cm. The methylation rate ranges from0.071%to1.477%. In autumn, the peakappeared at the deep of10cm, and the methylation ratio range is0.1%~2.5%. Thechange of water environment in wetland influences the content of mercury andmethylmercury, as well as the distribution in vertical direction.4. The amount of TB and SRB in soil was much more in autumn than that in summer.The influence of the SRB quantity to the methylation in surface soil is larger. SRBis not the major biological factor of the concentration of methylmercury.