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

Abstract

We measured monomethyl mercury (MMHg) and total mercury (THg) concentrations and Hg stable isotope ratios (δ 202 Hg and Δ 199

Tracing Mercury Pollution along the Norwegian Coast via Elemental, Speciation, and Isotopic Analysis of Liver and Muscle Tissue of Deep-Water Marine Fish (Brosme brosme)

“…These sediments were found to be strongly affected by Hg contamination (THg concentration of 1.40 ± 0.25 mg kg –1 ), and isotopic analysis of Hg showed δ 202 Hg and Δ 199 Hg values of −0.34 ± 0.04 and 0.00 ± 0.03 ‰, respectively. These values were found to be similar (both for MDF and MIF) to those reported on in literature for sediments impacted by a Zn smelter via atmospheric deposition, and contaminated with byproducts of ore roasting (e.g., Hg waste calcine) and/or mining. ,,, In this work, slightly more negative δ 202 Hg values were obtained for muscle tissue of tusk from the Sørfjord location relative to the sediments collected near the Zn smelter (Figure C), which can be explained by the net MDF accompanying the methylation and demethylation processes. , The small differences in Δ 199 Hg values can be explained by the input of iHg from atmospheric deposition and/or the contribution of the diet in an open marine Hg isotope composition, i.e., MeHg with high Δ 199 Hg anomalies. Thus, on the basis of the Hg isotope ratio results obtained in this work, the Hg pollution affecting the tusks collected at the Sørfjord location can most likely be attributed to the impact of the Zn smelter.…”

“…58,61,64,65 In this work, slightly more negative δ 202 Hg values were obtained for muscle tissue of tusk from the Sørfjord location relative to the sediments collected near the Zn smelter (Figure 2C), which can be explained by the net MDF accompanying the methylation and demethylation processes. 66,67 The small differences in Δ 199 Hg values can be explained by the input of iHg from atmospheric deposition and/or the contribution of the diet in an open marine Hg isotope composition, i.e., MeHg with high Δ 199 Hg anomalies. Thus, on the basis of the Hg isotope ratio results obtained in this work, the Hg pollution affecting the tusks collected at the Sørfjord location can most likely be attributed to the impact of the Zn smelter.…”

The Contribution of Rice Agriculture to Methylmercury in Surface Waters: A Review of Data from the Sacramento Valley, California

“…Rice is grown on more than 240,000 ha and is the main crop in the low‐lying central drainage area of the valley (USDA–NASS, 2016). Naturally enriched Hg conditions, plus a legacy of Hg and gold mining (which used elemental mercury to amalgamate the gold) in the mountains surrounding the valley, have resulted in elevated Hg concentrations in river sediments, water, and fish (Domagalski, 1998, 2001; Davis et al, 2008; Springborn et al, 2011; Singer et al, 2013; Domagalski et al, 2016; Donovan et al, 2016a, 2016b). Elevated MeHg concentrations in fish have led to fish consumption advisories and enactment of a Total Maximum Daily Load to reduce MeHg loads into the Sacramento–San Joaquin Delta (Delta Mercury Control Program, 2010).…”

Remains of the 19th Century: Deep storage of contaminated hydraulic mining sediment along the Lower Yuba River, California

“…In this form, mercury can be easily taken up by the biota and then pass through the blood-brain barrier in animals, creating developmental problems, deformities, and other acute health problems (Mergler et al, 2007;Cristol et al, 2008). There is a large body of evidence that mercury delivered to rivers and streams in the Sierra Nevada foothills during the 19 th century has been converted to MMHg and is subsequently being taken up by aquatic migratory biota including algae, aquatic insects, bivalves, forage fish, salmonids, sportfish, and waterfowl throughout the geographical region downstream of hydraulic mining sites (Heim et al, 2007;Davis et al, 2008;Wiener and Suchanek, 2008;Henery et al, 2010;Windham-Myers et al, 2014;Donovan et al, 2016a). Mercury isotope analyses performed by Donovan et al (2016b) suggest that MMHg contamination of food webs within the Yuba River watershed is associated with the HMS, which corroborates a previous isotopic study in the Bay-Delta (Gehrke et al, In this context, 19 th Century HMS stored along the Yuba River can be conceived of as a reservoir of toxicity to local migratory food webs, with potentially adverse consequences for the broader Bay-Delta region.…”