Air Quality and Atmospheric Deposition in Southern U.S. Forests

Characterizations of chemical exposures (air quality and atmospheric deposition) as well as physical conditions (meteorology and climatology) in rural environments are essential to evaluate the hypothesis that exposure of forests to acidic deposition and airborne pollutants may influence forest health in the southern United States. Air quality and atmospheric deposition in rural areas are a result of local and regional emissions of pollutants originating from anthropogenic and biogenic sources and their dispersion, transport, and transformation. Elements that require quantification are the atmospheric concentrations of gaseous chemical species in the vicinity of the forested landscapes (air quality) to evaluate exposure indexes, and the fluxes of chemicals to the forest canopy and soil are necessary to estimate wet and dry acid deposition inputs. Long-term, widespread measurements of these variables are generally not available to describe adequately a region as large as the southeastern United States. Mesoscale meteorological-chemical models are used to predict the distributions of atmospheric chemical variables over large, nonmonitored subregions. Regional models, such as the Regional Acid Deposition Model (RADM) and Sulfate Transport Eulerian Model-II (STEM-II), are useful in predicting air quality and acid deposition patterns because of the sparse temporal and spatial data available from field observations. Monitoring data, however, are valuable in testing and calibrating these regional models.