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2006-2007 Measurements of Atmospheric Mercury Species at a Coastal Site in Atlantic Canada

John Dalziel
Air Quality Science Division,
Meteorological Service of Canada,
Environment Canada
Dartmouth, Nova Scotia CAN

Environment Canada has been continuously measuring the levels of three gaseous Hg species gaseous elemental mercury (GEM), reactive gaseous mercury (RGM), particulate (P-Hg) fine fraction (<2.5 m) - at an urban coastal site since January 2006. This poster illustrates and discusses data collected at our site in Halifax, Nova Scotia (Canada) from January 2006 to June 2007. This 18 month data set show GEM (5 minute sampling) having a median of 1.7 ng m-3 and a range of 0.72 to 46.5 ng m-3 ; RGM (3 hour sample) a median of 2.5 pg m-3 with a range from the detection limit (dl) to 140 pg m-3 and P-Hg (3 hour sample) a median of 1.73 pg m-3 and a range from dl to 31 pg m-3. The median levels of RGM and P-Hg are only a small percentage of the Total Gaseous Mercury (TGM), 0.14% for RGM and 0.10% for P-Hg.

Temporal trends of elevated GEM were noted in the spring and early summer and more uniform levels observed during winter months. P-Hg events were more predominant in winter and early spring periods. For RGM, elevated levels occurred during the spring and early summer. A diurnal trend in RGM shows elevated levels beginning near mid day and continuing through the evening and night time period. The lowest levels of RGM are generally measured in the early morning to about noon. A diurnal trend for P-Hg was not evident.

RGM did show significant associations with air temperature, solar radiation and relative humidity. An observed trend of decreased levels of RGM during precipitation events coincided with the negative relationship observed with relative humidity. The significance of wind direction contributing to RGM levels was also observed and attributed to an effect from local sources. An analysis of air quality parameters versus Hg species shows ozone having its most significant association with RGM and an inverse association with GEM. Also noted, were PM2.5 and NO2 have varying degrees of association with all three Hg species