title: Mass balances of mercury and nitrogen in burned and unburned forested watersheds at Acadia National Park, Maine, USA.
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 microg/m(2)/year) than Cadillac (9.4 microg/m(2)/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 microg/m(2)/year) than from Hadlock Brook watershed (1.3 microg/m(2)/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 approximately 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.
authors.affiliation: Senator George J. Mitchell Center for Environmental and Watershed Research, University of Maine, 5710 Norman Smith Hall, Orono, ME 04469-5710, USA. sarah.nelson@umit.maine.edu
authors.forename: S J
authors.initials: SJ
authors.lastname: Nelson
authors.forename: K B
authors.initials: KB
authors.lastname: Johnson
authors.forename: J S
authors.initials: JS
authors.lastname: Kahl
authors.forename: T A
authors.initials: TA
authors.lastname: Haines
authors.forename: I J
authors.initials: IJ
authors.lastname: Fernandez
mesh_terms: D017753:Ecosystem; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis*; D005390:Fires; D005843:Geography; D049673:History, 20th Century; D049674:History, 21st Century; D008281:Maine; D008628:Mercury / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D011157:Population Dynamics; D045483:Rivers; D013997:Time Factors; D014197:Trees / Q000737:chemistry; D014835:Volatilization; D014872:Water Movements
chemical_list: D004785:Environmental Pollutants; D008628:Mercury; D009584:Nitrogen