Mercury Isotope Signatures as Tracers for Hg Cycling at the New Idria Hg Mine

Abstract

Mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes provides a new tool for tracing Hg in contaminated environments such as mining sites, which represent major point sources of Hg pollution into surrounding ecosystems. Here, we present Hg isotope ratios of unroasted ore waste, calcine (roasted ore), and poplar leaves collected at a closed Hg mine (New Idria, CA, U.S.A.). Unroasted ore waste was isotopically uniform with δ(202)Hg values from -0.09 to 0.16‰ (± 0.10‰, 2 SD), close to the estimated initial composition of the HgS ore (-0.26‰). In contrast, calcine samples exhibited variable δ(202)Hg values ranging from -1.91‰ to +2.10‰. Small MIF signatures in the calcine were consistent with nuclear volume fractionation of Hg isotopes during or after the roasting process. The poplar leaves exhibited negative MDF (-3.18 to -1.22‰) and small positive MIF values (Δ(199)Hg of 0.02 to 0.21‰). Sequential extractions combined with Hg isotope analysis revealed higher δ(202)Hg values for the more soluble Hg pools in calcines compared with residual HgS phases. Our data provide novel insights into possible in situ transformations of Hg phases and suggest that isotopically heavy secondary Hg phases were formed in the calcine, which will influence the isotope composition of Hg leached from the site.

Mercury Inputs to Chinese Marginal Seas: Impact of Industrialization and Development of China

“…By plotting Δ 202 Hg versus Δ 199 Hg signals, the three Hg sources are characterized by distinct “ δ 202 Hg‐Δ 199 Hg” signatures (Figure ). The isotopic signature of industrial Hg can be estimated using Hg polluted sediments with their locations in the vicinity of known industrial sources (Balogh et al, ; Bartov et al, ; Bonsignore et al, ; Cooke et al, ; Donovan et al, ; Guédron et al, ; Ma et al, ; Mil‐Homens et al, ; Gray et al, ; Perrot et al, ; Sonke et al, ; Wiederhold et al, ; Yin et al, ), and hydrothermal ores which are the major source of Hg used in industry (Blum & Bergquist, ; Cooke et al, ; Feng et al, ; Foucher & Hintelmann, ; Gray et al, ; Smith et al, ; Stetson et al, ; Wiederhold et al, ; Yin et al, ). Based on the summarization of previous data, we estimated that industrial Hg has mean δ 202 Hg of −0.53 ± 0.51‰ and mean Δ 199 Hg of −0.02 ± 0.11‰ (σ, n = 481).…”

“…Journal of Geophysical Research: Oceans Cooke et al, 2013;Donovan et al, 2013;Guédron et al, 2016;Ma et al, 2013;Mil-Homens et al, 2013;Gray et al, 2015;Perrot et al, 2010;Sonke et al, 2010;Wiederhold et al, 2015;Yin et al, 2016a), and hydrothermal ores which are the major source of Hg used in industry Cooke et al, 2013;Feng et al, 2010;Foucher & Hintelmann, 2009;Gray et al, 2013;Smith et al, 2008;Stetson et al, 2009;Wiederhold et al, 2013;Yin et al, 2013Yin et al, , 2016c. Based on the summarization of previous data, we estimated that industrial Hg has mean δ 202 Hg of À0.53 ± 0.51‰ and mean Δ 199 Hg of À0.02 ± 0.11‰ (σ, n = 481).…”

Methylmercury degradation and exposure pathways in streams and wetlands impacted by historical mining

“…Therefore, a small mass of high THg sediment from upstream could significantly alter the isotopic composition of Cache Creek sediment. Bear Creek sediment had δ 202 Hg (−0.31±0.17‰) and Δ 199 Hg (0.08±0.01‰; mean±1SD, n=3) that was comparable to unroasted Hg mine waste from New Idria (δ 202 Hg of −0.43 to +0.16‰) [39][40][41] and Hg ores from the CA Coast Range (δ 202 Hg of −0.64±0.84‰, mean± 1SD, n=91). 38 Sediment collected in Cache Creek was located 13 …”

“…[31][32][33][34][35] Hg isotopes have also been measured in a variety of Hg mine waste materials, including calcines and CA Coast Range Hg-ores. [36][37][38][39][40] Hg mine wastes can vary widely in isotopic composition over very small spatial scales (e.g., δ 202 Hg range of >5‰ within a single calcine sample), 31,32 but sediment downstream of individual mines is thought to largely integrate these different mining sources. 35,39,41 We hypothesized that the isotopic composition of high THg sediment in Cache Creek downstream of individual mining districts would enable us to distinguish the contribution of Hg mining (Coast Range) vs. Aumining (Sierra Nevada) Hg sources to Yolo Bypass.…”

“…[36][37][38][39][40] Hg mine wastes can vary widely in isotopic composition over very small spatial scales (e.g., δ 202 Hg range of >5‰ within a single calcine sample), 31,32 but sediment downstream of individual mines is thought to largely integrate these different mining sources. 35,39,41 We hypothesized that the isotopic composition of high THg sediment in Cache Creek downstream of individual mining districts would enable us to distinguish the contribution of Hg mining (Coast Range) vs. Aumining (Sierra Nevada) Hg sources to Yolo Bypass. Furthermore, we hypothesized that this Hg mining signature would provide a fingerprint of the IHg that is methylated locally and bioaccumulated as MMHg in the Cache Creek food web.…”