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Dietary mercury exposure: Mercury isotopes can tell the source


Mercury is a global pollutant. Following emission mainly from combustion sources, inorganic mercury is readily transformed to methylmercury, a toxin causing neurological damages. Methylation of Hg occurs microbially in aquatic ecosystems, and bioaccumulation of MeHg along the food chain can result in high levels of MeHg in fish and other organisms at the top of the food chain. Therefore, fish consumption is considered the major exposure route of Hg to humans. Dietary mercury exposure due to terrestrial sources is generally lower, due to shorter food chain length. Unfortunately, heavy mercury pollution can also lead to contaminated crops. Rice paddies have been shown to enhance Hg methylation, explaining high MeHg levels in rice. For health risk assessment of populations living in such contaminated areas, the identification Hg exposure pathways is a prerequisite. Unfortunately, such evaluation is not straightforward, since numerous dietary and other sources must be investigated for their Hg levels and speciation.

Mercury stable isotope geochemistry has been demonstrated to provide useful information to trace Hg sources and bio-geochemical processes of Hg in the environment. The seven stable isotopes of mercury can undergo fractionation depending either on mass or magnetic isotope effects or nuclear volume.  Combining the mass-depending fractionation (MDF) and the mass-independing fractionation (MIF) of Hg isotopes can provide information about sources and pathways of Hg in the environment. While no significant MDF and MIF of Hg isotopes has been observed during bioaccumulation of dietary MeHg in fish, an offset ~2‰ in δ202 Hg was observed between fish and tissues of fish-consumers, indicating that MDF of Hg isotopes occurs during metabolic processes in mammals.

The new study:
The international research group hypothesized that populations from Guizhou Province, China may have distinct hair isotopic signatures compared to previous results, since rice consumption is the most important pathway for human Hg exposure in Guizhou. To test this hypothesis, the group investigated the isotopic composition of Hg in hair samples of residents from three different areas in Guizhou Province (South China) representing a mining, an urban and rural area. Also potential dietary sources, such as fish, rice and vegetables were studied as well.

Rice and vegetables showed low δ202 Hg and small negative to zero  Δ199 Hg, while fish showed relatively higher δ202Hg and positive Δ199 Hg.  Also human hair samples from the different areas showed distinct isotopic signatures. Hair samples from residents of a mining area and a rural area displayed near zero Δ199 Hg, pointing to rice as the major exposure source. The hair from residents of the urban area showed positive Δ199 Hg likely caused by consumption of fish. A binary mixing model based on Δ199 Hg showed that rice and fish consumption accounted for 59% and 41% of dietary Hg source for residents of the urban area, respectively, whereas rice is the major source for residents of the mining an rural area. These results were cross-checked by calculations of probable daily intakes suggesting that the Hg isotope approach can be used to quantify exposure sources.  

The original study:

Buyun Du, Xinbin Feng, Ping Li, Runsheng Yin, Ben Yu, Jeroen E. Sonke, Benjamin Guinot, Christopher William Noel Anderson, Laurence Maurice, Use of mercury isotopes to quantify mercury exposure sources in inland populations, China; Environ. Sci. Technol., 2018. DOI: 10.1021/acs.est.7b05638

Related studies:

S. Rothenberg, R. Yin, J.P. Hurley, D.P. Krabbenhoft, Y. Ismawati, C. Hong, A. Donohue, Stable mercury isotopes in polished rice (Oryza Sativa L.) and hair from rice consumers. Environ. Sci. Technol., 51/11 (2017) 6480–6488. DOI: 10.1021/acs.est.7b01039

P. Li, B. Du, L. Maurice, L. Laffont, C. Lagane, D. Point, Mercury isotope signatures of methylmercury in rice samples from the Wanshan mercury mining area, China: environmental implications. Environ. Sci. Technol., 51/21 (2017) 12321-328. DOI: 10.1021/acs.est.7b03510

G. Sun, J. Sommar, X. Feng, C.J. Lin, M. Ge, W. Wang, R. Yin, X. Fu, L. Shang, Mass -dependent and -independent fractionation of mercury isotope during gas-phase oxidation of elemental mercury vapor by atomic Cl and Br. Environ. Sci. Technol. 50/17 (2016) 9232-9241. DOI: 10.1021/acs.est.6b01668

W. Zheng, D. Obrist, D. Weis, B.A. Bergquist, Mercury isotope compositions across North American forests. Global. Biogeochem. Cy., 30/10 (2016) 1475-1492. DOI: 10.1002/2015GB005323

M. Li, A.T. Schartup, A.P. Valberg, J.D. Ewald, D.P. Krabbenhoft, R. Yin, P.H. Balcom, E.M. Sunderland, Environmental origins of methylmercury accumulated in subarctic estuarine fish indicated by mercury stable isotopes. Environ. Sci. Technol., 50/21 (2016) 11559-11568. DOI: 10.1021/acs.est.6b03206

M. Enrico, G.L. Roux, N. Marusczak, L.E. Heimbürger, A. Claustres, X. Fu, R. Sun, J.E. Sonke, Atmospheric Mercury Transfer to Peat Bogs Dominated by Gaseous Elemental Mercury Dry Deposition. Environ. Sci. Technol., 50/5 (2016) 2405−2412. DOI: 10.1021/acs.est.5b06058

B. Yu, X. Fu, R. Yin, Isotopic composition of atmospheric mercury in china: new evidence for source and transformation processes in air and in vegetation. Environ. Sci. Technol., 50/17 (2016) 9262-9269. DOI: 10.1021/acs.est.6b01782

C. Feng, Z. Pedrero, P. Li, B. Du, X. Feng, M. Monperrus, E. Tessier1, S. Berail1, D. Amouroux, Investigation of Hg uptake and transport between paddy soil and rice seeds combining Hg isotopic composition and speciation. Elementa: Sci. of the Anthro., 4 (2016) 87. DOI: 10.12952/journal.elem enta.000087

M. Bonsignore, S. Tamburrino, E. Oliveri, A. Marchetti, C. Durante, A.  Berni, Tracing mercury pathways in Augusta bay (southern Italy) by total concentration and isotope determination. Environ. Pol., 205 (2015) 178-185. DOI: 10.1016/j.envpol.2015.05.033

L.S. Sherman, J.D. Blum, N. Basu, M. Rajaee, D.C. Evers, D.G. Buck, J. Petrlik, J.P. Gangi, Assessment of mercury exposure among small-scale gold miners using mercury stable isotopes. Environ. Res., 137 (2015) 226-234. DOI: 10.1016/j.envres.2014.12.021

P. Li, X. Feng, H.M. Chan, X. Zhang, B. Du, Human body burden and dietary methylmercury intake: the relationship in a rice-consuming population. Environ. Sci. Technol., 49/16 (2015) 9682-9689. DOI: 10.1021/acs.est.5b00195

M. Jiskra, J.G. Wiederhold, U. Skyllberg, R.M. Kronberg, I. Hajdas, R. Kretzschmar, Mercury Deposition and Re-emission Pathways in Boreal Forest Soils Investigated with Hg Isotope Signatures. Environ. Sci. Technol., 49/12 (2015) 7188-7196. DOI: 10.1021/acs.est.5b00742

Z. Wang, J. Chen, X. Feng, H. Holger, L. Sheng, Y. Liu, H. Cai, S. Wang, Mass-dependent and mass-independent fractionation of mercury isotopes in precipitation from Guiyang, SW China. C. R. Geosci., 347/7-8 (2015) 358-367. DOI: 10.1016/j.crte.2015.02.006

J.D. Blum, L.S. Sherman, M.W. Johnson, Mercury isotopes in earth and environmental sciences. Ann. Rev. of Earth Planet Sc., 42/1 (2014) 249-269. DOI: 10.1146/annurev-earth-050212-124107

M. Li, L.S. Sherman, J.D. Blum, P. Grandjean, B. Mikkelsen, P. Weihe, E.M. Sunderland, J.P. Shine, Assessing sources of human methylmercury exposure using stable mercury isotopes. Environ. Sci. Technol., 48/15 (2014) 8800-8806. DOI: 10.1021/es500340r

R. Yin, X. Feng, X. Li, B. Yu, B. Du, Trends and advances in mercury stable isotopes as a geochemical tracer. Trend. Anal. Chem., 2 (2014) 1-10. DOI: 10.1016/j.teac.2014.03.001

M.T. Tsui, J.D. Blum, J.C. Finlay, S.J. Balogh, Y.H. Nollet, W.J. Plen, M.E. Power. Variation in terrestrial and aquatic sources of methylmercury in stream predators as revealed by stable mercury isotopes. Environ. Sci. Technol., 48/17 (2014) 10128-10135. DOI: 10.1021/es500517s

S.Y. Kwon, J.D. Blum, M.A. Chirby, E.J. Chesney, Application of mercury isotopes for tracing trophic transfer and internal distribution of mercury in marine fish feeding experiments. Environ. Toxicol. Chem., 23 (2013) 2322-2330. DOI: 10.1002/etc.2313

L.S. Sherman, J.D. Blum, A. Franzblau, N. Basu, New insight into biomarkers of human mercury exposure using naturally occurring mercury stable isotopes. Environ. Sci. Technol., 47/7 (2013) 3403-3409. DOI: 10.1021/es305250z

R. Yin, X. Feng, B. Meng, Stable mercury isotope variation in rice plants (Oryza Sativa L.) from the Wanshan mercury mining district, SW China. Environ. Sci. Technol., 47/5 (2013) 2238-2245. DOI: 10.1021/es304302a

R. Yin, X. Feng, J. Wang, P. Li, J. Liu, Y. Zhang, J. Chen, L. Zheng, T. Hu, Mercury speciation and mercury isotope fractionation during ore roasting process and their implication to source identification of downstream sediment in the Wanshan mercury mining area, SW China. Chem. Geol., 336/SI (2013) 72-79. DOI: 10.1016/j.chemgeo.2012.04.030

J.D. Demers, J. D. Blum, D.R. Zak, Mercury isotopes in a forested ecosystem: Implications for air-surface exchange dynamics and the global mercury cycle. Global Biogeochem. Cy., 27/1 (2013) 222−238. DOI: 10.1002/gbc.20021

S.Y. Kwon, J.D. Blum, M.J. Carvan, N. Basu, J.A. Head, C.P. Madenjian, S.R. David, Absence of fractionation of mercury isotopes during trophic transfer of methylmercury to freshwater fish in captivity. Environ. Sci. Technol., 46/14 (2012) 7527-7534. DOI: 10.1021/es300794q

M.T. Tsui, J.D. Blum, S.Y. Kwon, J.C. Finlay, S.J. Balogh, Y.H. Nollet, Sources and transfers of methylmercury in adjacent river and forest food webs. Environ. Sci. Technol., 46/20 (2012) 10957-64. DOI: 10.1021/es3019836

V. Perrot, M.V. Pastukhov, V.N. Epov, S. Husted, O.F.X. Donard, D. Amouroux, Higher Mass-Independent Isotope Fractionation of Methylmercury in the Pelagic Food Web of Lake Baikal (Russia). Environ. Sci. Technol., 46/11 (2012) 5902-5911. DOI: 10.1021/es204572g

L. Laffont, J.E. Sonke, L. Maurice, S.L. Monrroy, J. Chincheros, D. Amouroux, P. Behra, Hg speciation and stable isotope signatures in human hair as a tracer for dietary and occupational exposure to mercury. Environ. Sci. Technol., 45/23 (2011) 9910-9916. DOI: 10.1021/es202353m

G.E. Gehrke, J.D. Blum, D.G. Slotton, B.K. Greenfield, Mercury Isotopes Link Mercury in San Francisco Bay Forage Fish to Surface Sediments. Environ. Sci. Technol., 45/4 (2011) 1264-1270. DOI: 10.1021/es103053y

R.S. Yin, X.B. Feng, D. Foucher, W.F. Shi, Z.Q. Zhao, J. Wang, High precision determination of mercury isotope ratios using online mercury vapor generation system coupled with multicollector inductively coupled plasma-mass spectrometer. Chinese. J. Anal. Chem., 38/7 (2010) 929−934. DOI: 10.1016/S1872-2040(09)60055-4

J.G. Wiederhold, C.J. Cramer, K. Daniel, I. Infante, B. Bourdon, R. Kretzschmar, Equilibrium mercury isotope fractionation between dissolved Hg(Ⅱ) species and thiol-bound Hg. Environ. Sci. Technol., 44/11 (2010) 4191-7. DOI: 10.1021/es100205t

N. Estrade, J. Carignan, J.E. Sonke, O.F.X. Donard, Measuring Hg Isotopes in Bio-Geo-Environmental Reference Materials. Geostand. Geoanal. Res., 34/1 (2010) 79−93. DOI: 10.1111/j.1751-908X.2009.00040.x

D.B. Senn, E.J. Chesney, J.D. Blum, M.S. Bank, A. Maage, J.P. Shine, Stable isotope (N, C, Hg) study of methylmercury sources and trophic transfer in the Northern Gulf of Mexico. Environ. Sci. Technol., 44/5 (2010) 1630-1637. DOI: 10.1021/es902361j

J.E. Sonke, J. Schäfer, J. Chmeleff, S. Audry, G. Blanc, B. Dupré, Sedimentary mercury stable isotope records of atmospheric and riverine  pollution from two major European heavy metal refineries. Chem. Geol., 279/3 (2010) 90-100. DOI: 10.1016/j.chemgeo.2010.017

L. Laffont, J.E. Sonke, L. Maurice, H. Hintelmann, M. Pouilly, B.Y. Sánchez, T. Perez, P. Behra, Anomalous mercury isotopic compositions of fish and human hair in the bolivian amazon. Environ. Sci. Technol., 43/23 (2009) 8985-8990. DOI: 10.1021/es9019518

N. Estrade, J. Carignan, J.E. Sonke, O.F.X. Donard, Mercury isotope fractionation during liquid-vapor evaporation experiments. Geochim. Cosmochim. Acta., 73 (2009) 2693−2711. DOI: 10.1016/j.gca.2009.01.024

K. Kritee, T. Barkay, J.D. Blum, Mass dependent stable isotope fractionation of mercury during Mer mediated microbial degradation of monomethylmercury. Geochim. Cosmochim. Acta., 73 (2009) 1285-1296. DOI: 10.1016/j.gca.2008.11.038

X.B. Feng, P. Li, G.L. Qiu, S.F. Wang, G.H. Li, L.H. Shang, B. Meng, H.M. Jiang, W.Y. Bai, Z.G. Li, X.W. Fu, Human exposure to methylmercury through rice intake in mercury mining areas, Guizhou Province, China. Environ. Sci. Technol., 42 (2008) 326-332. DOI: 10.1021/es071948x

B.A. Bergquist, J.D. Blum, Mass-dependent and mass-independent fractionation of Hg isotopes by photo-reduction in aquatic systems. Science, 318 (2007) 417−420. DOI: 10.1126/science.1148050

K. Kritee, J.D. Blum, M.W. Johnson, B.A. Bergquist, T. Barkay, Mercury stable isotope fractionation during reduction of Hg (II) to Hg (0) by mercury resistant microorganisms. Environ. Sci. Technol., 41 (2007) 1889−1895. DOI: 10.1021/es062019t

J.D. Blum, B.A. Bergquist, Reporting of variations in the natural isotopic composition of mercury. Anal. Bioanal. Chem., 388/2 (2007) 353−359. DOI: 10.1007/s00216-007-1236-9

 Related EVISA Resources

Link Database: Mercury exposure through the diet
Link Database: Environmental cycling of methylmercury
Link Database: Environmental cycling of inorganic mercury
Link Database: Environmental pollution of methylmercury
Link Database: Environmental pollution of inorganic mercury
Link Database: Toxicity of mercury

December 21, 2011: Tracing the source of mercury pollution
January 21, 2011: Arctic Mercury Cycling May Be Linked to Ice Cover
October 9, 2006: Linking atmospheric mercury to methylmercury in fish

last time modified: April 16, 2018

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