Use of Mercury Isotopes to Quantify Mercury Exposure Sources in Inland Populations, China

Mercury (Hg) isotopic compositions in hair and dietary sources from Wanshan (WS) Hg mining area, Guiyang (GY) urban area, and Changshun (CS) rural area were determined to identify the major Hg exposure sources of local residents. Rice and vegetables displayed low δ<sup>202</sup>Hg and small negative to zero Δ<sup>199</sup>Hg, and are isotopically distinguishable from fish which showed relatively higher δ<sup>202</sup>Hg and positive Δ<sup>199</sup>Hg. Distinct isotopic signatures were also observed for human hair from the three areas. Shifts of 2 to 3‰ in δ<sup>202</sup>Hg between hair and dietary sources confirmed mass dependent fractionation of Hg isotopes occurs during metabolic processes. Near zero Δ<sup>199</sup>Hg of hair from WS and CS suggested rice is the major exposure source. Positive Δ<sup>199</sup>Hg of hair from GY was likely caused by consumption of fish. A binary mixing model based on Δ<sup>199</sup>Hg showed that rice and fish consumption accounted for 59% and 41% of dietary Hg source for GY residents, respectively, whereas rice is the major source for WS and CS residents. The model output was validated by calculation of probable daily intake of Hg. Our study suggests that Hg isotopes can be a useful tracer for quantifying exposure sources and understanding metabolic processes of Hg in humans.