| Environmental mercury has been a concern for a number of years due to the ability of mercury to both bioaccumulate in selected tissues of organisms and biomagnify progressively higher up the trophic food chain. Recent developments in technologies directed at improving the precision and accuracy of mercury measurements in the environment as well as renewed concerns regarding mercury levels in biota have led to a resurgence in research into the environmental fate and effects of mercury. |
 |
|
The sources and pathways of chemicals released into the environment can be varied and complex. Mercury is such a chemical because of its wide use in industry, its abundance in the natural environment and its ability to deposit and revolatilize, thus continually recycling in the environment. Nevertheless, it is important to understand the dynamics of mercury emissions, transport, chemical transformation, deposition and movement in the environment as well as the effects of mercury on biota in order to gain an understanding of the relationship between naturally occurring and anthropogenic mercury and thus, the feasibility and efficacy of controls on releases of anthropogenic mercury into the environment.
|
Air-Surface Exchange Research:
Air-Surface Exchange of Mercury Over Natural and Impacted Surfaces in Atlantic Canada
Total Gaseous Mercury (TGM) Research:
Mercury in Air, Water and Biota in Kejimkujik National Park, Nova Scotia, Canada
|
Atmospheric Mercury
Mercury is found in the atmosphere as a gas which consists primarily of elemental mercury but also other small amounts of other mercury containing compounds (eg mercuric chloride). The sum of all gas phase mercury is referred to as total gaseous mercury (TGM). TGM is measured at 2 sites in the Atlantic region (Kejimkujik National Park in Nova Scotia and at St. Andrews in New Brunswick. Total gaseous mercury research in the Atlantic region is part of the Canadian Atmospheric Mercury Network (CAMNet), a national atmospheric mercury program in Canada which ensures data comparability through the use of standard operating procedures, audit protocols and data management (quality assurance, quality control metadata).
Canadian total gaseous mercury data will soon be available through the National Atmospheric Chemistry Database.
Mercury also exists in the atmosphere in the liquid phase as water droplets (eg cloud water) and in precipitation (rain and snow). Mercury concentration in precipitation is measured at the same 2 sites as TGM. Measurements are made in collaboration with the US National Atmospheric Deposition Program (NADP) Mercury Wet Deposition Network (MDN).
In addition to these forms of mercury in the atmosphere, mercury is also exchanged between the atmosphere and the earth surface. Research into the direction and rates of mercury exchange are important in understanding the overall dynamics of mercury as well as cycling in the environment. Mercury air-surface exchange research is currently being conducted through the Canadian Toxic Chemicals Research Initiative (TSRI).
Overall, the national atmospheric mercury science program is based on a number of science and policy related questions:
- what portion of the mercury in the atmosphere is of natural vs. anthropogenic origin?
- what portion of the mercury in the atmosphere is new emissions vs. re-emitted?
- what is the spatial (3-D) and temporal distribution of atmospheric mercury (3 phases)?
- what are representative background mercury concentrations?
- what causes deviations from these levels?
- what proportion of mercury in the atmosphere is derived from local sources vs. long range transport?
- how do Canadian ambient mercury concentrations and deposition levels compare on a continental and global scale?
- how and how fast is mercury transformed in the atmosphere?
- what relationships exist between mercury and other pollutants?
- what are the major processes regulating air-surface mercury exchange (deposition and/or evasion)?
- are regional ecosystems a net source or sink for atmospheric mercury?
- are mercury concentrations in the atmosphere and deposition responding to changes in anthropogenic emissions (on a local, regional, continental or global scale)?
|
