Resolving atmospheric mercury loading and source trends from isotopic records of remote North American lake sediments

Ryan F. Lepak; Sarah E. Janssen; Daniel R. Engstrom; David P. Krabbenhoft; Michael T. Tate; Runsheng Yin; William F. Fitzgerald; Sonia A. Nagorski; James P. Hurley

doi:10.1021/acs.est.0c00579

USGS · 70283019

Resolving atmospheric mercury loading and source trends from isotopic records of remote North American lake sediments

Ryan F. Lepak·Sarah E. Janssen·Daniel R. Engstrom·David P. Krabbenhoft·Michael T. Tate·Runsheng Yin·William F. Fitzgerald·Sonia A. Nagorski·James P. Hurley

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Abstract

The strongest evidence for anthropogenic alterations to the global mercury (Hg) cycle comes from historical records of mercury deposition preserved in lake sediments. Hg isotopes have added a new dimension to these sedimentary archives, promising additional insights into Hg source apportionment and biogeochemical processing. Presently, most interpretations of historical changes are constrained to a small number of locally contaminated ecosystems. Here, we describe changes in natural Hg isotope records from a suite of dated sediment cores collected from various remote lakes of North America. In nearly all cases, the rise in industrial-use Hg is accompanied by an increase in δ 202 Hg and Δ 199 Hg values. These trends can be attributed to large-scale industrial emission of Hg into the atmosphere and are consistent with positive Δ 199 Hg values measured in modern-day precipitation and modeled increases in δ 202 Hg values from global emission inventories. Despite similar temporal trends among cores, the baseline isotopic values vary considerably among the different study regions, likely attributable to differences in the fractionation produced in situ as well as differing amounts of atmospherically delivered Hg. Differences among the study lakes in precipitation and watershed size provide an empirical framework for evaluating Hg isotopic signatures and global Hg cycling.

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Source-reported bounding extent: 14.7170616° to 83.1256532° latitude; -171.3484751° to -49.47863246681641° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Ryan F. Lepak, Sarah E. Janssen, Daniel R. Engstrom, David P. Krabbenhoft, Michael T. Tate, Runsheng Yin, William F. Fitzgerald, Sonia A. Nagorski, James P. Hurley. 2020-06-27. Resolving atmospheric mercury loading and source trends from isotopic records of remote North American lake sediments. https://doi.org/10.1021/acs.est.0c00579

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