Atmospheric Pollution Enters Water
Non-Point Source Contaminants in Air Damage Rivers, Lakes and Oceans
Persistent pollutants enter waterways via air, affecting wildlife habitats. Ecosystem protection needs air and water agencies to control organics, mercury and nitrogen.
Point source pollution of waterways is easy to understand. Discharges into rivers, lakes and oceans from sewage outfalls and other sources are often visible. But non-point source pollution takes many forms and tends to be harder to control. One way that contaminants get into waterways, causing long-term damage, is through atmospheric pollution. Tracing their source can be nearly impossible, but recognizing their impact is not.
What are Airsheds?
Like a watershed, which is the region draining into a river, river system or other body of water, an airshed comprises the area that contains emissions sources which contribute 75% of the pollutants deposited into a watershed. The airshed of a particular water body may be hundreds of miles.
Atmospheric Pollutants Affecting Waterbodies
Three groups of airborne pollutants are recognized as dangerous to waterways:
- Persistent organic pollutants such as PCBs and the PBDEs (PolyBrominated Diphenyl Ethers), which are found in flame-retardants, water-repellent coatings and synthetic fragrances
- Oxidized mercury
- Atmospheric nitrogen
Persistent Organic Pollutants
The persistent organic pollutants of most concern are the ones that accumulate in water, on land and in the atmosphere. These ‘multimedia’ chemicals include nearly all the compounds identified by the Stockholm Convention on Persistent Organic Pollutants (POPs). Because they are persistent they continue to be revolitalized when contaminated soils are disturbed.
Products such as PBDEs from flame retardants have been found in increasing levels in the tissues of harp seals in western Arctic Canada. Perfluorinated surfactants, used to treat fabrics for stain resistance, are found in birds, fish, and mammals throughout the world. They are the most consistent contaminant in polar bears, already facing threats from climate change and oil exploration. Synthetic fragrances now being found in rivers and lakes have been identified as causing hormone disruption in exposed fish.
Oxidized Mercury
Mercury is regularly in the news as a contaminant in fish. But not everyone is aware of how much of that mercury gets into the water from the air. Municipal trash burning, high sulfur coal burning, gold mining and even the off-gassing of mercury based fungicides in paints contribute to its presence in the air. While the level of mercury contamination is decreasing, it does not go away quickly.
Atmospheric Nitrogen
Atmospheric nitrogen rounds out the list. Deposited by rain, snow or dust it contributes to deoxygenation of waterways and harmful algal blooms which are increasing in frequency and intensity around the world. This nitrogen comes from the burning of fossil fuels and from the ammonia gasses produced during livestock production.
Monitoring and Prevention
At present there is not a great deal of effort being put into monitoring of air quality in sensitive habitats. Exposure risks for these areas should include a review of wind direction and speed patterns from potential atmospheric pollution sources near these important ecosystems. Cooperation between air pollution agencies and their counterpart in water pollution control should be increased to develop a better understanding of non-point source contaminant issues within an area. These efforts will need to be long-term as most of the pollution problems are the result of the more persistent contaminants which are also the ones most likely to remain on land as well as in water and air.
Source:
Impacts of Atmospheric Pollutants on Aquatic Ecosystems,
Deborah L. Swackhamer, Hans W. Paerl, Steven J. Eisenreich, James Hurley, Keri C. Hornbuckle, Michael McLachlan, David Mount, Derek Muir, and David Schindler, Issues in Ecology, Issue 12
