Accumulation and translocation of methylmercury and inorganic mercury in Oryza sativa: An enriched isotope tracer study

Strickman, Rachel; Mitchell, Carl P. J.

doi:10.1016/j.scitotenv.2016.08.068

Cited by 76 publications

(43 citation statements)

References 61 publications

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“…The model slightly underestimates the rice THg concentration, likely due to the lack of gaseous Hg 0 uptake via foliage. Assuming that an additional ~20% of IHg in rice comes from gaseous Hg 0 uptake via foliage (Feng et al, ; Strickman & Mitchell, ; R. Yin et al, ), our estimates show rice THg concentration of 16 ng/g and % MeHg (of THg) of 30%, which correspond more closely with the observed median value in China.…”

Section: Resultssupporting

confidence: 83%

“…Atmospheric deposition is calculated using GEOS‐Chem and assumes input of only IHg. The relative contribution of Hg 0 uptake via foliage to rice is constrained from previous mercury stable isotope measurements (Feng et al, ; Strickman & Mitchell, ; R. Yin et al, ) and not modeled explicitly. We consider this fraction only when evaluating the model‐simulated rice THg and MeHg concentrations against measurements from China.…”

Section: Methodsmentioning

confidence: 99%

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Present and Future Mercury Concentrations in Chinese Rice: Insights From Modeling

Kwon

Selin

Giang

et al. 2018

Global Biogeochemical Cycles

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We construct a rice paddy biogeochemical cycle model to investigate processes governing rice mercury sources and to understand factors influencing spatiotemporal variability in Chinese rice mercury concentrations. The rice paddy model takes atmospheric mercury deposition, simulated from a global atmospheric chemistry transport model (GEOS‐Chem), and soil and irrigable surface water mercury concentrations obtained from literature and calculates rice inorganic (IHg) and methylmercury (MeHg) concentrations. We use ranges of GEOS‐Chem‐simulated future atmospheric mercury deposition—no policy and strict policy to regulate mercury emissions from Chinese coal‐fired power plants under the Minamata Convention on Mercury—to simulate future rice IHg and MeHg concentrations. Sensitivity analyses suggest that rice IHg and MeHg concentrations are more sensitive to the process of soil desorption than infiltration of recently introduced mercury (atmospheric and irrigation source). The rate of internal methylation via microbial activity has the largest modeled influence on rice MeHg concentration. We find that soil mercury, rather than atmospheric deposition, explains observed spatial variability in rice IHg and MeHg concentrations and captures locations of rice mercury hot spots (>20 ng/g; China National Standard Limit). Under our future scenarios, the Chinese median rice IHg and MeHg concentration increases by 13% and decrease by 18% under no policy and strict policy, respectively. Regions with the largest percentage decline in rice IHg and MeHg concentrations under strict policy are in central China, which have high rice mercury concentrations, rice production, and consumption. Our study suggests that addressing Chinese rice mercury contamination requires attention to contaminated soil and regulation of anthropogenic mercury emissions.

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Section: Resultssupporting

confidence: 83%

Section: Methodsmentioning

confidence: 99%

Present and Future Mercury Concentrations in Chinese Rice: Insights From Modeling

Kwon

Selin

Giang

et al. 2018

Global Biogeochemical Cycles

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“…The use of stable isotope tracers recently confirmed that MeHg produced in saturated soils is subsequently observed in the plant's rice grains (Strickman and Mitchell 2017), suggesting that the prevalence of methylation in rice paddies is a significant concern due to its potential to cause mercury poisoning directly through a common staple food source. However, Strickman and Mitchell (2017) also found significant MeHg losses between flowering and maturity; evidence of in planta demethylation that has also been observed in the roots rice exposed to more elevated Hg concentrations typical of contaminated rice paddies (Xu et al 2016). Understanding the relationships of the plant life cycle and changes in mercury speciation could have implications for the management of rice production, for example, timing the flooding of fields to reduce the uptake of MeHg from soil before flowering to reduce the translocation of MeHg into grains (Peng et al 2012).…”

Section: Inundated Environmentsmentioning

confidence: 98%

“…However, methylation has been found to occur in non-contaminated rice cultivation sites around the world including Brazil (da Silva et al 2010;Batista et al 2012;Silva et al 2012), China (Rothenberg et al 2011), and Spain (da Silva et al 2013). The use of stable isotope tracers recently confirmed that MeHg produced in saturated soils is subsequently observed in the plant's rice grains (Strickman and Mitchell 2017), suggesting that the prevalence of methylation in rice paddies is a significant concern due to its potential to cause mercury poisoning directly through a common staple food source. However, Strickman and Mitchell (2017) also found significant MeHg losses between flowering and maturity; evidence of in planta demethylation that has also been observed in the roots rice exposed to more elevated Hg concentrations typical of contaminated rice paddies (Xu et al 2016).…”

Section: Inundated Environmentsmentioning

confidence: 99%

Recent advances in the study of mercury methylation in aquatic systems

Paranjape

Hall

2017

FACETS

117

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With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.

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“…It is reported that food consumption accounts for more than 90% of the probable daily intake (PDI) of Total Hg. Specifically, rice accounted for 18.6–25.5%, while inhalation accounted for 3.8–6.8% [17], not to mention that rice can accumulate Hg from both atmosphere and soil [18]. In the same Hg mining region, MeHg levels in hair were shown to well correlate with dietary exposure to MeHg in rice, which could be explained by the overwhelming contribution of the rice consumption [19].…”

Section: Introductionmentioning

confidence: 99%

Assessing the Risk of Hg Exposure Associated with Rice Consumption in a Typical City (Suzhou) in Eastern China

Gang

Gong

Zhu³

et al. 2017

IJERPH

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Recent studies have revealed that not only fish but also rice consumption may significantly contribute to human exposure to mercury (Hg) in Asian countries. It is therefore essential to assess dietary exposure to Hg in rice and its associated health risk. However, risk assessments of Hg in rice in non-contaminated areas are generally lacking in Asian countries. In the present study, Hg concentrations were measured in rice samples collected from markets and supermarkets in Suzhou, a typical city in Eastern China. In addition, the rice ingestion rates (IR) were assessed via a questionnaire-based survey of Suzhou residents. The data were then used to assess the risk of Hg exposure associated with rice consumption, by calculating the hazard quotient (HQ). Hg contents in rice samples were well below the national standard (20 μg/kg), ranging from 1.46 to 8.48 ng/g. They were also significantly (p > 0.05) independent of the area of production and place of purchase (markets vs. supermarkets in the different districts). Our results indicate a low risk of Hg exposure from rice in Suzhou (HQ: 0.005–0.05), despite the generally high personal IR (0.05–0.4 kg/day). The risk of Hg associated with rice consumption for Suzhou residents was not significantly affected by the age or sex of the consumer (p > 0.05). Overall, our results provide a study of human exposure to Hg in rice in Chinese cities not known to be contaminated with Hg. Future studies should examine Hg exposure in different areas in China and in potentially vulnerable major food types.

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Accumulation and translocation of methylmercury and inorganic mercury in Oryza sativa: An enriched isotope tracer study

Cited by 76 publications

References 61 publications

Present and Future Mercury Concentrations in Chinese Rice: Insights From Modeling

Present and Future Mercury Concentrations in Chinese Rice: Insights From Modeling

Recent advances in the study of mercury methylation in aquatic systems

Assessing the Risk of Hg Exposure Associated with Rice Consumption in a Typical City (Suzhou) in Eastern China

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