Abstract: We studied the concentration of different mercury (Hg) species in Hongjiadu Reservoir within Guizhou Province, China, and discussed the distribution and speciation of different Hg species and the mechanism of methylmercury (MeHg) production in the water column in Hongjiadu Reservoir. The results showed that total Hg (THg) concentration ranged from 0.32 to 6.75 ng·L^-1, dissolved Hg (DHg) concentration was between 0.23 and 2.27 ng·L^-1, particulate Hg (PHg) concentration ranged from 0.03 to 4.51 ng·L^-1, total MeHg (TMeHg) concentration ranged from 0.04 to 0.18 ng·L^-1, dissolved MeHg (DMeHg) concentration ranged from 0.02 to 0.08 ng·L^-1, particulate MeHg (PMeHg) concentration ranged from 0.01 to 0.13 ng·L^-1. The concentrations of different Hg species changed with season. In summer and autumn, THg, DHg and PHg concentrations were significantly higher than in spring and winter. In spring and summer, TMeHg, DMeHg and PMeHg concentrations were significantly higher than in autumn and winter. Spatially, total MeHg levels did not increase with depth in water column, nor did MeHg levels increase spatially, from upstream to the dam. Total MeHg concentration in water column of Hongjiadu Reservoir was much lower than those reported (range: 0.01-6.6 ng·L^-1) in North America and Europe. Hongjiadu Reservoir did not show the obvious characteristics of Hg methylation in water column, which was correlated with the low levels of nutrient and organic matter in flooded soil.

Key words: Bt transgenic cotton, Flavonoid chemicals, HPLC, Spatio temporal dynamics