Accumulation of of total Hg (THg) and methylmercury (MeHg) was investigated among 50 indica rice varieties cultivated in 3 sites in Guizhou. China, classified as highly-contaminated, moderately-contaminated, and background sites. Concentrations of soil and pore water (depth: 0-2 cm) THg and MeHg were poor predictors of THg and MeHg concentrations in polished white rice and bran, with significantly higher accumulation in the moderately-contaminated site compared to the other 2 sites (ANOVA, p<0.0001). Results indicated other environmental factors played a critical role in the translocation of Hg species from paddy soil to rice grain. We hypothesized alkaline conditions at the highly-contaminated site (surface water pH 11, other 2 sites pH 7.6-8.0), mitigated the uptake of Hg species by decreasing the solubility of micronutrients needed for plant growth, or by reducing the bioavailability of Hg species. White rice MeHg concentrations were associated with genotype but not inorganic Hg(II) concentrations (IHg=THG-MeHg) (MeHg: p<0.001. IHG: p=0.44), while bran MeHg and IHg concentrations were not significantly associated with genotype (p>0.05 for both analyses), indicating there may be genetic markers for the translocation of MeHg from the caryopsis to the endosperm, i.e., from the maternal to the filial tissue. Lastly, calculation of daily MeHg ingestion rates confirmed international guidelines for MeHg exposure were exceeded at the moderately-contaminated site (background: 0.013 +/- 0.0052 mu g kg(-1) d(-1), n=46; highly-contaminated: 0.065 +/- 0.034 mu g kg(-1) d(-1), n=49; moderately-contaminated: 0.42 +/- 0.13 mu g kg(-1) d(-1), n=49). However. MeHg exposure at this site may be decreased up to 69% by cultivating low Hg-accumulating rice varieties. (C) 2012 Elsevier B.V. All rights reserved.

Publication name	SCIENCE OF THE TOTAL ENVIRONMENT　Volume: 426 　Pages: 272-280　 Published: JUN 1 2012
Author(s)	Rothenberg, Sarah E.; Feng, Xinbin; Zhou, Weijia; Tu, Ming; Jin,Bangwen; You, Junmei
Corresponding author	Rothenberg, Sarah E  rothenberg.sarah@sc.edu  1. Chinese Acad Sci, State Key Lab Environm Geochem, Guiyang 550002, Peoples R China　  2. Univ S Carolina, Dept Environm Hlth Sci, Arnold Sch Publ Hlth, Columbia, SC 29208 USA

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