Mercury in fog on the Bay of Fundy (Canada)

Mercury concentrations in fog water, collected during the summer of 2003, were found to vary along a geospatial gradient from Grand Manan (an island at the mouth of the Bay of Fundy, with Hg levels 42–435 ng l−1), the main coastline of New Brunswick at Point Lepreau (2–33 ng l−1), to an inland location in Fredericton, Canada (3.5 ng l−1). Hg concentrations were higher during days when air masses were stationary and fog conditions were extended over several days. High concentrations on Grand Manan were most likely due to continued atmospheric deposition of Hg into fog banks of long duration, high air turbulence along the steep 100 m cliffs, and decreasing droplet size with increasing air temperature during the course of the day. We found that fog Hg deposition was about 0.4–7.5% of wet Hg deposition along the coastal area, whereas on Grand Manan Island, fog Hg deposition from was 31–74% of wet Hg deposition.