Lacustrine Responses to Decreasing Wet Mercury Deposition Rates鈥擱esults from a Case Study in Northern Minnesota

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• 作者：Mark E. Brigham ; Mark B. Sandheinrich ; David A. Gay ; Ryan P. Maki ; David P. Krabbenhoft ; James G. Wiener
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：June 3, 2014
• 年：2014
• 卷：48
• 期：11
• 页码：6115-6123
• 全文大小：458K
• 年卷期：v.48,no.11(June 3, 2014)
• ISSN：1520-5851

文摘

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^鈥?), and hydrogen ion (H⁺) in northern Minnesota. Annual wet Hg, SO₄^鈥?, 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 (MeHg_aq) and mercury in small yellow perch (Hg_fish) 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, MeHg_aq increased by 85% in a third lake, whereas Hg_fish 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 MeHg_aq and Hg_fish. The diverging responses among the study lakes exemplify the complexity of ecosystem responses to decreased loads of atmospheric pollutants.