Lacustrine responses to decreasing wet mercury deposition rates: results from a case study in northern Minnesota

Environmental Science & Technology
By: , and 

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Abstract

We present a case study comparing metrics of methylmercury (MeHg) contamination for four undeveloped lakes in Voyageurs National Park to wet atmospheric deposition of mercury (Hg), sulfate (SO4–2), and hydrogen ion (H+) in northern Minnesota. Annual wet Hg, SO4–2, and H+ deposition rates at two nearby precipitation monitoring sites indicate considerable decreases from 1998 to 2012 (mean decreases of 32, 48, and 66%, respectively). Consistent with decreases in the atmospheric pollutants, epilimnetic aqueous methylmercury (MeHgaq) and mercury in small yellow perch (Hgfish) decreased in two of four lakes (mean decreases of 46.5% and 34.5%, respectively, between 2001 and 2012). Counter to decreases in the atmospheric pollutants, MeHgaq increased by 85% in a third lake, whereas Hgfish increased by 80%. The fourth lake had two disturbances in its watershed during the study period (forest fire; changes in shoreline inundation due to beaver activity); this lake lacked overall trends in MeHgaq and Hgfish. The diverging responses among the study lakes exemplify the complexity of ecosystem responses to decreased loads of atmospheric pollutants.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Lacustrine responses to decreasing wet mercury deposition rates: results from a case study in northern Minnesota
Series title Environmental Science & Technology
DOI 10.1021/es500301a
Volume 48
Issue 11
Year Published 2014
Language English
Publisher American Chemical Society
Contributing office(s) Minnesota Water Science Center, Toxic Substances Hydrology Program
Description 9 p.
First page 6115
Last page 6123
Country United States
State Minnesota
Other Geospatial Voyageurs National Park