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Mercury Contents in Rice and Mercury Exposure Risk for Residents

Author: YuanXiaoBo
Tutor: LiHang；FengXinBin
School: Southwestern University
Course: Environmental Science
Keywords: Rice Total mercury Methylmercury The risk of exposure to mercury
CLC: R155.5
Type: Master's thesis
Year: 2011
Downloads: 133
Quote: 1
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Abstract

\Sources of mercury in the environment, including natural and anthropogenic sources, and occupy an important position and the effects of man-made source of mercury in the environment. Hg0 form of mercury into the big climate is very stable, with atmospheric long-range transport and to participate in the global mercury cycle. Inorganic mercury deposition to the surface under certain conditions can be microbial methylation generate methylmercury. Unlike inorganic mercury, methylmercury in the food chain can be biomagnification and progressively enriched. In Japan and Europe and the United States, residents of edible fish, a higher proportion of the most important source of methylmercury exposure of the fish intake. In China, especially in inland areas, the proportion of residents eating fish lower compared with other crops, rice strong bioconcentration of methylmercury MeHg content up to the same conditions under other crops grown by 10 to 40 times, is very important to our contribution of dietary exposure to mercury in rice, the staple food is rice. In this study, 12 rice-producing areas in China in 2009 (the rice production accounts for 81% of national output) of total mercury and methylmercury content analysis contrast, the region's urban and rural residents and the corresponding total mercury and methyl daily mercury intake estimates, evaluation of the regions residents of mercury exposure risk exposure to mercury assess the contribution of various mercury intake pathway. Rice total mercury mixed acid digestion and cold vapor atomic fluorescence spectrometry determination of methylmercury by extraction - back-extraction - aqueous phase ethylation combination of meteorological chromatography - cold vapor atomic fluorescence spectrometry. System analysis obtained the following results: (1) the total mercury content of rice 0.78 ~ 47μg · kg-1, the average levels of 9.3 ± 8.7μg · kg-1, in the value of the content of 5.6μg · kg-1, samples of which 64% of the total mercury content of less than 7μg · kg-1. Sample of Guangdong, Jiangxi, Hubei, Hunan, Guizhou and Jiangsu total mercury content of 11% of the samples exceed the limit prescribed by the State 20μg · kg-1 may be related to the above areas of industrial production activities, fossil fuel combustion, mining activities and non-ferrous metal smelting releasing large amounts of mercury into the environment. (2) rice MeHg an average of 2.3 ± 2.3μg · kg-1, the value of 1.8μg · kg-1, the regional average of 0.29 ~ 3.2μg · kg-1, of which 80% of the samples methylmercury content distribution between 0 ~ 3.0μg · kg-1. Hunan four samples methylmercury content of more than 10μg · kg-1, respectively, 11 μg · kg-1, 17μg · kg-1, 18 μg · kg-1, 18 μg · kg-1. The high rice Methylmercury is the the high methylmercury result of local rice cultivation soil. (3) The total mercury between urban residents and rural residents average daily intake for of 0.075 ~ 0.20μg/kg · bw 0.054 0.22μg/kg · bw and and maximum of 0.36μg/kg · bw. Residents total mercury exposure has an important contribution to a variety of media together, rice, vegetables, aquatic products are in total mercury exposure risk, and the specific contribution rate is due to the total mercury content of different residents of diet and food differ according. The regional urban residents the methylmercury average daily intake of 0.0098 ~ 0.021μg/kg · bw, a maximum of only 76% of the RfD, while rural residents the methylmercury average daily intake for the 0.0070 to 0.025μg / kg · bw. Addition to outside the Hunan outside of methylmercury also are much lower than the provisions of USEPA0.1μg/kg · bw, Hunan the highest methylmercury day intake for 0.12μg/kg · bw, risk of exposure to 120% visible rural Hunan Some residents have been the threat of exposure to methylmercury. The study found that residents' exposure to methylmercury rice and aquatic products, both of methylmercury exposure contribution rate reached more than 94%. Based on these results, we draw the following important conclusions: (1) Overall, the rice has not been a serious mercury pollution content of total mercury and methylmercury levels are at a lower level; (2) In addition to the the Hunan parts crowd the higher methylmercury intake, other regions of total mercury and methylmercury intake are far below the WHO and FAO jointly developed the total mercury temporary body can tolerate intake and USEPA methylmercury intake The main way of criteria; (3) the main way residents total mercury exposure is rice, vegetables and aquatic products, and exposure to methylmercury as rice and aquaculture.

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