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The distributions of mercury and its impact factors were studied and discussed at large scale in the Wanshan Hg-mining areas in Guizhou,China.248 rice and soil samples were collected from the rice fields along five rivers in Wanshan.Total mercury(THg)content in rice ranges from 7.92 ng.g-1 to 316.92ng.g-1 with an average of 54.73 ng.g-1.Methylmercury(MeHg)in rice samples range from 2.3ng.g-1 to 43.18ng.g-1 with an average of 13.33ng.g-1,and contributed 7.12%to 71%of total mercury in rice samples.The content of THg and MeHg in rice shows a decreasing trend with increasing distance from the mercury minning area.Simultaneously,SiO2,S,P,N,pH,Se and organic matter in soils were analyzed to understand impact factors of MeHg in rice.MeHg in rice shows a significant positive correlation with P,N,organic matter,pH,THg,MeHg in soil,but a significant negative correlation with SiO2.There is no significant correlation between MeHg in rice and Se in soil,but a significant negative correlation between ratio of THg(or MeHg)in rice to Hg in soil and Se,total S and N in soil is observed.It indicates Se,total S and N reduced bioavailability of mercury in soil.MeHg content in rice is influenced by a wide variety of environmental factors.Understanding the factors reducing bioavailability of mercury in soil is helpful for mercury pollution control in rice.For example,some soil amendments can be used to improve soil and reduced bioavailability of mercury.