Why is atmospheric deposition a concern in MarylandAcidic deposition: Research has demonstrated that surface waters (primarily lakes and streams) are vulnerable to the adverse effects of acidic deposition. A direct effect of
acidic deposition is the lowering of pH levels in surface waters (Click on the map to see national pH's) |
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Results of the National Atmospheric Deposition Program/National Trends Network indicate that Maryland is in or near the region of most acidic precipitation and receives some of the
highest concentrations of sulfate and nitrate deposition in the United States. Sulfate and nitrate are the primary contributors to acidic deposition. In 1987, Maryland's Synoptic Stream
Chemistry Survey concluded that approximately one-third of all headwater streams in Maryland are sensitive to acidification with ANC <200 µeq/l) or are already acidic (ANC <
0 µeq/l) as a result of atmospheric deposition. The MSSCS estimated that most of the acidic or acid-sensitive streams in Maryland are located in the southern Coastal Plain (74% of
streams in the region) and the Appalachian Plateau (52%). Nutrients: In addition to contributing to acidic deposition, nitrogen emissions and subsequent deposition can affect aquatic resources by contributing to their overenrichment with nutrients. Years of intensive research have concluded that nutrient loading to the Chesapeake Bay is the primary cause of the decline of living resources in this unique waterbody. Recent estimates indicate than about 27% of the nitrogen delivered to the Bay is from the atmosphere, including both direct deposition to the Bay’s surface and deposition to the watershed that is later transported to the Bay in runoff. Toxic contaminants: Atmospheric deposition is known to be an important source of particulate-bound trace metals (e.g., chromium, lead, tin, and zinc) to oceanic and inland waters including those in the mid-Atlantic region. The Chesapeake Bay receives an unusually large amount of air pollutants via atmospheric deposition because of its close proximity to heavily polluted urban areas, such as Baltimore, MD, Washington, DC, and Norfolk, VA. Emissions from cars, incinerators, and power plants serve as the primary sources of trace elements and other toxic materials into the atmosphere. The Chesapeake Bay area also receives polluted air containing particulates from the factories and power plants of the heavily industrialized Ohio Valley. Recent studies have also measured atmospheric contributions of organic contaminants to the Chesapeake Bay. |
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