Oceanic influence on atmospheric mercury at coastal and inland sites: a springtime noreaster in New England

Abstract

Continuous measurements of elemental (Hg⁰) and reactive mercury were conducted at two sites in New Hampshire during a powerful April 2007 noreaster. During the most intense period of the storm, enhancements of ~30–50 ppqv in Hg⁰ were observed at a coastal and a high elevation inland site. This enhancement occurred simultaneously with elevated mixing ratios of three marine tracers, CH₃I, CH₂Br₂ and CHBr₃. These observations suggest a marine source of Hg⁰, possibly outgassing from the ocean surface during strong turbulence. The Hg⁰ enhancement observed 100 km inland suggests that the impact of coastal storms on terrestrial Hg cycling may not be limited to near-shore environments. Combining Hg⁰ and marine tracer measurements during the storm with estimates of oceanic tracer fluxes during previous strong storms yields an order-of-magnitude estimate of the oceanic source of Hg⁰ during the storm (~7 ppqv h^−1) which can account for the observed enhancement at the field sites.