title: Environment and genotype controls on mercury accumulation in rice (Oryza sativa L.) cultivated along a contamination gradient in Guizhou, China.
abstract: Accumulation 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 μg kg(-1) d(-1), n=46; highly-contaminated: 0.066±0.034 μg kg(-1) d(-1), n=49; moderately-contaminated: 0.42±0.13 μg 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.
authors.affiliation: State Key Laboratory of Environmental Geochemistry, Chinese Academy of Sciences, 46 Guanshui Road, Guiyang 550002, PR China. rothenberg.sarah@sc.edu
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Rothenberg
authors.forename: Xinbin
authors.initials: X
authors.lastname: Feng
authors.forename: Weijia
authors.initials: W
authors.lastname: Zhou
authors.forename: Ming
authors.initials: M
authors.lastname: Tu
authors.forename: Bangwen
authors.initials: B
authors.lastname: Jin
authors.forename: Junmei
authors.initials: J
authors.lastname: You
mesh_terms: D000222:Adaptation, Physiological; D002681:China; D004777:Environment; D004784:Environmental Monitoring; D005838:Genotype; D008628:Mercury / Q000032:analysis* / Q000378:metabolism; D012275:Oryza / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000378:metabolism
chemical_list: D014874:Water Pollutants, Chemical; D008628:Mercury