Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables Chris S. Eckley a, ⁎, Mike T. Tate b , Che-Jen Lin c , Mae Gustin d , Stephen Dent e , Collin Eagles-Smith f , Michelle A. Lutz b , Kimberly P. Wickland g , Bronwen Wang h , John E. Gray i , Grant C. Edwards j , Dave P. Krabbenhoft b , David B. Smith i a US Environmental Protection Agency, Region-10, Seattle, WA 98101, USA b US Geological Survey, Middleton, WI 53562, USA c Center for Advances on Water and Air quality, Lamar University, Beaumont, TX 77710, USA d Department of Natural Resources & Environmental Science, University of Nevada, Reno, NV 89557, USA e CDM Smith, Portland, OR 97205, USA f US Geological Survey, Corvallis, OR 97331, USA g US Geological Survey Boulder, CO 80303, USA h US Geological Survey, Anchorage, AK 99508, USA i US Geological Survey, Denver, CO 80225, USA j Department of Environment and Geography, Macquarie University, North Ryde, NSW 2109, Australia HIGHLIGHTS • Soil-air Hg fluxes are an important component of the global atmospheric Hg budget. • A database of soil-air Hg flux measure- ments for Western North America was created. • Ecosystem Hg fluxes were influenced by vegetation, light, and soil Hg and moisture. • Vegetation had a large effect on net- ecosystem fluxes due to shading and uptake. • Hg emission from sparsely vegetated landscapes was similar to Hg wet depo- sition. GRAPHICAL ABSTRACT abstract article info Article history: Received 30 October 2015 Received in revised form 4 February 2016 Accepted 17 February 2016 Available online xxxx Mercury (Hg) emission and deposition can occur to and from soils, and are an important component of the global atmospheric Hg budget. This paper focuses on synthesizing existing surface-air Hg flux data collected throughout the Western North American region and is part of a series of geographically focused Hg synthesis projects. A da- tabase of existing Hg flux data collected using the dynamic flux chamber (DFC) approach from almost a thousand locations was created for the Western North America region. Statistical analysis was performed on the data to identify the important variables controlling Hg fluxes and to allow spatiotemporal scaling. The results indicated that most of the variability in soil-air Hg fluxes could be explained by variations in soil-Hg concentrations, solar radiation, and soil moisture. This analysis also identified that variations in DFC methodological approaches were Keywords: Mercury Dynamic flux chamber Science of the Total Environment xxx (2016) xxx–xxx ⁎ Corresponding author. E-mail address: eckley.chris@epa.gov (C.S. Eckley). STOTEN-19347; No of Pages 15 http://dx.doi.org/10.1016/j.scitotenv.2016.02.121 0048-9697/Published by Elsevier B.V. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv Please cite this article as: Eckley, C.S., et al., Surface-air mercury fluxes across Western North America: A synthesis of spatial trends and controlling variables, Sci Total Environ (2016), http://dx.doi.org/10.1016/j.scitotenv.2016.02.121