Mercury Isotope Signatures of Methylmercury in Rice Samples from the Wanshan Mercury Mining Area, China: Environmental Implications

Abstract

Rice consumption is the primary pathway of methylmercury (MeHg) exposure for residents in mercury-mining areas of Guizhou Province, China. In this study, compound-specific stable isotope analysis (CSIA) of MeHg was performed on rice samples collected in the Wanshan mercury mining area. An enrichment of 2.25‰ in total Hg (THg) δHg was observed between rice and human hair, and THg ΔHg in hair was 0.12‰ higher than the value in rice. Rice and human hair samples in this study show distinct Hg isotope signatures compared to those of fish and human hair of fish consumers collected in China and other areas. Distinct Hg isotope signatures were observed between IHg and MeHg in rice samples (in mean ± standard deviation: δHg at -2.30‰ ± 0.49‰, ΔHg at -0.08‰ ± 0.04‰, n = 7; δHg at -0.80‰ ± 0.25‰, ΔHg at 0.08‰ ± 0.04‰, n = 7). Using a binary mixing model, it is estimated that the atmospheric Hg contributed 31% ± 16% of IHg and 17% ± 11% of THg in the rice samples and the IHg in soil caused by past mining activities contributed to the remaining Hg. This study demonstrated that Hg stable isotopes are good tracers of human MeHg exposure to fish and rice consumption, and the isotope data can be used for identifying the sources of IHg and MeHg in rice.

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

“…The boundary and initial conditions are regridded from the output of a global 3-D chemical transport model (GEOS-Chem) into the specification of study domain (Song et al, 2015). Other emission data, such as SO 2 , NO x , CO, and so forth, are obtained from Multiresolution Emission Inventory for China (M. Li et al, 2015) and regridded using ArcGIS 10.1 and National Center for Atmospheric Research Command Language.…”

“…Hence, accurate inventories for these pollutants not only provide a good foundation for air quality modeling but also improve model performance for atmospheric Hg modeling. High-resolution (0.25°× 0.25°) regional emission inventory data (M. Li et al, 2015) developed from recent Chinese government-led projects (e.g., Multiresolution Emission Inventory for China) enable new modeling assessments to better understand the chemical transport of atmospheric Hg in a region undergoing rapid emission changes caused by diverging drivers of economic growth and air pollution control implementation.…”

“…Once deposited, Hg methylation and bioaccumulation of methylated Hg in the food chain pose a threat to ecosystems and human health. Methylated Hg pollution in fish and rice has been a public health concern worldwide (Driscoll et al, ; P. Li et al, ).…”

Advances in the Determination of Xenobiotics in Foods

“…In such regions, the most important MeHg exposure source is not fish, but rice consumption [8]. MeHg intake through rice ingestion has been reflected on the levels of MeHg in hair of inhabitants of such areas [7,9]. Rice seeds consist of a hull and a nutritious bran coat layer surrounding the endosperm and inner embryo.…”

“…Rice is one of the scarce food matrices where the analysis of Hg is not restricted to the quantification of its most common species, Hg(II) and MeHg. In view of the public health concern associated to the consumption of this staple product, several studies focus on the understanding of Hg accumulation pathways by different approaches as molecular speciation [10,14], imaging [10], and isotopic analysis [9,14].…”