GOM Mercury Project: Update


Wilfred Pilgrim
EMAN Canada, wilfp@gov.nb.ca
March 12, 1997

The mercury issue continues to gain momentum and many agencies are now scrambling to keep- up. The Science Advisory Board for the US EPA Mercury Report to Congress met in March of 1997 and approved the mercury science within the report. The report will go back to Congress, where in the past it has not been approved for public release, mainly due to the uncertainties associated with the data presented on health effects of chronic, low-level human exposures to methylmercury, and lobbying by stakeholders. The report suggested that there were subtle effects on the fetus and children, and that the daily reference dose for methylmercury should be lowered.

One of the most significant accomplishments in the study of mercury has been the recent development of a Canada-US mercury deposition network using the US/NADP and the Canadian EMAN. No longer will data stop at the invisible border between Canada and the US, but will soon include the entire continent. This will promote confidence in models by providing compatible and reliable data results. The Gulf of Maine Council was instrumental in getting this network going and is presently sponsoring two sites as a part of the more comprehensive North American network. Preliminary data for the transition period of the US network was recently released by the NADP, THg deposition values ranged between 3.97-12.89 ug/m2 /yr, with highest values for concentrations and deposition occurring in the summer. The preliminary data confirm that the US EPA model results are fairly accurate with higher deposition in the northeast US. As a part of the Northeast Mercury Study, NESCAUM which is headquartered in Boston is re-running the mercury model to include additional sources in the northeast US and easternCanada. Deposition results for the GOM sites are only now starting to come in as part of the NADP/MDN. For the first few weeks, volume weighted mean concentrations were 13.80 ng/L for the GOM New Brunswick site and 13.50 ng/L for GOM Nova Scotia site, with higher values associated with small amounts of precipitation. This compares to a VWM of 10.25 ng/L for the yearly average for all the US MDN sites in 1996.

A further evaluation of historic mercury deposition in the Gulf of Maine Airshed was carried out in 1996 and 1997. A lake sediment survey was conducted by EMAN through the University of Quebec (Lucotte Team) in late fall of 1996 which showed that mercury levels have increased 2-3 fold since the beginning of the industrial period. Scuba divers with special coring devices were brought in as a part of the team to conduct the survey. Additional information on mercury in loons, fish and air are continuing to be collected in the region.