tailieunhanh - Setting Limits: Using Air Pollution Thresholds To Protect And Restore U.S. Ecosystems

As in many large cities, and especially in ones located in valleys with limited ventilation, Mexico City experiences air pollution problems, especially ozone and suspended particles. Stringent controls since 1990 have resulted in major reductions of sulfur dioxide emissions. Sulfur in diesel fuel has been reduced from to . Only one industrial complex still uses residual oil, and it is slated to soon change to gas. Gasoline-powered vehicles were required to have catalytic converters after 1990, and unleaded fuel was introduced at that time to provide cleaner emissions. Within the Distrito Federal, the central core of Mexico City that has its own government, many old diesel. | Issues IN Ecology Published by the Ecological Society of America Setting Limits Using Air Pollution Thresholds to Protect and Restore . Ecosystems Mark E. Fenn Kathleen F. Lambert Tamara F. Blett Douglas A. Burns Linda H. Pardo Gary M. Lovett Richard A. Haeuber David C. Evers Charles T. Driscoll and Dean S. Jeffries Fall 2011 Report Number 14 esa Issues in Ecology Number Fourteen Fall 2011 Setting Limits Using Air Pollution Thresholds to Protect and Restore . Ecosystems Summary More than four decades of research provide unequivocal evidence that sulfur nitrogen and mercury pollution have altered and will continue to alter our nation s lands and waters. The emission and deposition of air pollutants harm native plants and animals degrade water quality affect forest productivity and are damaging to human health. Many air quality policies limit emissions at the source but these control measures do not always consider ecosystem impacts. Air pollution thresholds at which ecological effects are observed such as critical loads are effective tools for assessing the impacts of air pollution on essential ecosystem services and for informing public policy. . ecosystems can be more effectively protected and restored by using a combination of emissions-based approaches and science-based thresholds of ecosystem damage. Based on the results of a comprehensive review of air pollution thresholds we conclude Ecosystem services such as air and water purification decomposition and detoxification of waste materials climate regulation regeneration of soil fertility production and biodiversity maintenance as well as crop timber and fish supplies are impacted by deposition of nitrogen sulfur mercury and other pollutants. The consequences of these changes may be difficult or impossible to reverse as impacts cascade throughout affected ecosystems. The effects of too much nitrogen are common across the . and include altered plant and lichen communities enhanced growth of invasive