Air quality related values (AQRVs) in national parks: Effects from ozone; visibility reducing particles; and atmospheric deposition of acids, nutrients and toxics

Sullivan, Timothy

A variety of air pollutants are emitted into the atmosphere from human-caused and natural emissions sources throughout the United States and elsewhere. These contaminants are transported with prevailing winds and impact sensitive natural resources in the national parks. This report provides a compilation and synthesis of current scientific understanding regarding the causes and effects of these pollutants within more than 270 Inventory and Monitoring national park lands throughout the United States. The pollutant categories of greatest concern and those that are evaluated here include ground-level ozone, which is not emitted directly from pollution sources, but rather is formed in the atmosphere in response to photochemical reactions that involve nitrogen oxides and volatile organic compounds. Other pollutants considered here include atmospheric particles that cause haze and degrade visibility and deposition from the atmosphere of acids (mainly sulfur, but also nitrogen), nutrients, and toxics. Emitted nutrients include oxidized and reduced forms of nitrogen. Toxics include mercury (a potent neurotoxin), a variety of historic and current-use pesticides, and other toxic materials. These contaminants are released into the air from such source types as power plants, motor vehicles, agriculture, industry, and others. The level of adverse impact that occurs on national park resources in response to air pollution and pollutant deposition is governed primarily by the amount and types of pollutant exposure and by the inherent sensitivity of the park resources. Atmospheric deposition of acids, nutrients, and toxic materials varies considerably from park to park. Some parks receive quite substantial pollutant deposition loads; others are more remote from pollutant emissions sources and receive relatively low pollutant deposition loads. Vegetation in the parks is exposed to varying levels of atmospheric ozone that damages foliage. Varying levels of haze impair the ability of visitors to experience the scenic vistas offered by many of the parks. Nevertheless, harm to park resources is not governed solely, or in many cases even mostly, by pollutant exposure. Parks also differ greatly in their inherent sensitivity to air pollution damage. Some park resources are highly sensitive to damage caused by inputs of acid precursors or nutrients. Some parks contain ecosystems that are highly sensitive to methylation that converts inorganic mercury to a form that can bioaccumulate to dangerously high levels in the food web. Some plant species are especially sensitive to foliar damage from exposure to atmospheric ozone. Some parks have outstanding visual resources such that even relatively low levels of haze dramatically affect visitor enjoyment of the park experience. This report describes these pollutant emissions and deposition and the reasons for differences in resource sensitivity. Recent trends in pollutant exposure and adverse effects are highlighted. Mechanisms of impact are elucidated. Where possible, this report identifies the critical (tipping point) loads of pollutant deposition at which adverse impacts are manifested. Monitoring data are discussed along with mathematical model projections of future changes in resource conditions. File size: 12.6 MB

Air quality related values (AQRVs) in national parks: Effects from ozone; visibility reducing particles; and atmospheric deposition of acids, nutrients and toxics

Series

See also

Collections