title: A synthesis of progress and uncertainties in attributing the sources of mercury in deposition.
abstract: A panel of international experts was convened in Madison, Wisconsin, in 2005, as part of the 8th International Conference on Mercury as a Global Pollutant. Our charge was to address the state of science pertinent to source attribution, specifically our key question was: "For a given location, can we ascertain with confidence the relative contributions of local, regional, and global sources, and of natural versus anthropogenic emissions to mercury deposition?" The panel synthesized new research pertinent to this question published over the past decade, with emphasis on four major research topics: long-term anthropogenic change, current emission and deposition trends, chemical transformations and cycling, and modeling and uncertainty. Within each topic, the panel drew a series of conclusions, which are presented in this paper. These conclusions led us to concur that the answer to our question is a "qualified yes," with the qualification being dependent upon the level of uncertainty one is willing to accept. We agreed that the uncertainty is strongly dependent upon scale and that our question as stated is answerable with greater confidence both very near and very far from major point sources, assuming that the "global pool" is a recognizable "source." Many regions of interest from an ecosystem-exposure standpoint lie in between, where source attribution carries the greatest degree of uncertainty.
authors.affiliation: Oak Ridge National Laboratory, USA. Lindberg@Now2000.com
authors.forename: Steve
authors.initials: S
authors.lastname: Lindberg
authors.forename: Russell
authors.initials: R
authors.lastname: Bullock
authors.forename: Ralf
authors.initials: R
authors.lastname: Ebinghaus
authors.forename: Daniel
authors.initials: D
authors.lastname: Engstrom
authors.forename: Xinbin
authors.initials: X
authors.lastname: Feng
authors.forename: William
authors.initials: W
authors.lastname: Fitzgerald
authors.forename: Nicola
authors.initials: N
authors.lastname: Pirrone
authors.forename: Eric
authors.initials: E
authors.lastname: Prestbo
authors.forename: Christian
authors.initials: C
authors.lastname: Seigneur
mesh_terms: D001272:Atmosphere; D004784:Environmental Monitoring / Q000706:statistics & numerical data*; D004787:Environmental Pollution / Q000032:analysis*; D005843:Geography; D006802:Human Activities / Q000706:statistics & numerical data; D008628:Mercury / Q000737:chemistry / Q000633:toxicity*; D008962:Models, Theoretical
chemical_list: D008628:Mercury