Original Article

Environmental Monitoring and Assessment

, Volume 126, Issue 1, pp 69-80

First online:

Mass Balances of Mercury and Nitrogen in Burned and Unburned Forested Watersheds at Acadia National Park, Maine, USA

  • S. J. NelsonAffiliated withSenator George J. Mitchell Center for Environmental and Watershed Research, University of Maine Email author 
  • , K. B. JohnsonAffiliated withSenator George J. Mitchell Center for Environmental and Watershed Research, University of Maine
  • , J. S. KahlAffiliated withSenator George J. Mitchell Center for Environmental and Watershed Research, University of Maine
  • , T. A. HainesAffiliated withU.S. Geological Survey, Orono Field Station, Leetown Science Center
  • , I. J. FernandezAffiliated withDepartment of Plant, Soil, and Environmental Sciences, University of Maine

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Abstract

Precipitation and streamwater samples were collected from 16 November 1999 to 17 November 2000 in two watersheds at Acadia National Park, Maine, and analyzed for mercury (Hg) and dissolved inorganic nitrogen (DIN, nitrate plus ammonium). Cadillac Brook watershed burned in a 1947 fire that destroyed vegetation and soil organic matter. We hypothesized that Hg deposition would be higher at Hadlock Brook (the reference watershed, 10.2 μg/m2/year) than Cadillac (9.4 μg/m2/year) because of the greater scavenging efficiency of the softwood vegetation in Hadlock. We also hypothesized the Hg and DIN export from Cadillac Brook would be lower than Hadlock Brook because of elemental volatilization during the fire, along with subsequently lower rates of atmospheric deposition in a watershed with abundant bare soil and bedrock, and regenerating vegetation. Consistent with these hypotheses, Hg export was lower from Cadillac Brook watershed (0.4 μg/m2/year) than from Hadlock Brook watershed (1.3 μg/m2/year). DIN export from Cadillac Brook (11.5 eq/ha/year) was lower than Hadlock Brook (92.5 eq/ha/year). These data show that ∼50 years following a wildfire there was lower atmospheric deposition due to changes in forest species composition, lower soil pools, and greater ecosystem retention for both Hg and DIN.

Keywords

mercury nitrogen DIN methylmercury forest fire effects watershed mass balances Acadia National Park Maine, USA