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

Patrick M. Donovan; Joel D. Blum; Michael B. Singer; Mark C. Marvin-DiPasquale; Martin T.K. Tsui

doi:10.1016/j.scitotenv.2016.04.139

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

Science of the Total Environment

By: Patrick M. Donovan, Joel D. Blum, Michael B. Singer, Mark C. Marvin-DiPasquale, and Martin T.K. Tsui

https://doi.org/10.1016/j.scitotenv.2016.04.139

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Abstract

Monomethyl mercury (MMHg) and total mercury (THg) concentrations and Hg stable isotope ratios (δ²⁰²Hg and Δ¹⁹⁹Hg) were measured in sediment and aquatic organisms from Cache Creek (California Coast Range) and Yolo Bypass (Sacramento Valley). Cache Creek sediment had a large range in THg (87 to 3870 ng/g) and δ²⁰²Hg (−1.69 to −0.20‰) reflecting the heterogeneity of Hg mining sources in sediment. The δ²⁰²Hg of Yolo Bypass wetland sediment suggests a mixture of high and low THg sediment sources. Relationships between %MMHg (the percent ratio of MMHg to THg) and Hg isotope values (δ²⁰²Hg and Δ¹⁹⁹Hg) in fish and macroinvertebrates were used to identify and estimate the isotopic composition of MMHg. Deviation from linear relationships was found between %MMHg and Hg isotope values, which is indicative of the bioaccumulation of isotopically distinct pools of MMHg. The isotopic composition of pre-photodegraded MMHg (i.e., subtracting fractionation from photochemical reactions) was estimated and contrasting relationships were observed between the estimated δ²⁰²Hg of pre-photodegraded MMHg and sediment IHg. Cache Creek had mass dependent fractionation (MDF; δ²⁰²Hg) of at least −0.4‰ whereas Yolo Bypass had MDF of +0.2 to +0.5‰. This result supports the hypothesis that Hg isotope fractionation between IHg and MMHg observed in rivers (−MDF) is unique compared to +MDF observed in non-flowing water environments such as wetlands, lakes, and the coastal ocean.

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Additional publication details
Publication type	Article
Publication Subtype	Journal Article
Title	Methylmercury degradation and exposure pathways in streams and wetlands impacted by historical mining
Series title	Science of the Total Environment
DOI	10.1016/j.scitotenv.2016.04.139
Volume	568
Year Published	2016
Language	English
Publisher	Elsevier
Contributing office(s)	National Research Program - Western Branch, Toxic Substances Hydrology Program
Description	12 p.
First page	1192
Last page	1203
Country	United States
State	California
Other Geospatial	Cache Creek, Yolo Bypass
Online Only (Y/N)	N
Additional Online Files (Y/N)	N
Google Analytic Metrics	Metrics page