| Abstrakt: |
Because the U. S. Environmental Protection Agency (EPA) has changed the National Ambient Air Quality Standards (NAAQS) for ambient particulate matter (PM), there is a great deal of interest in determining recent PM trends. This paper examines trends in PM 10 (i.e., particulate matter less than 10 micrometers in diameter) for areas of the United States based on their attainment status-for PM 10 and ozone nonattainment and attainment areas. The analysis also focuses on urban, suburban, and rural areas, and eastern and western areas. The time period of evaluation is from 1988 through 1995. To shed further light on the ambient PM 10 trends, trends in ambient SO 2 , NO 2 , and volatile organic compounds (VOCs) are also analyzed. Finally, trends in emission inventories of SO 2 , NO x , VOCs, and PM 10 are evaluated. Results of the analysis show that widespread and similar reductions in PM 10 levels have occurred over the last seven years. Annual reductions range from 3.0% to 3.8%, with the greatest reductions coming in PM 10 nonattainment areas, but with very significant reductions also in PM 10 attainment areas, ozone attainment areas, and rural areas. The widespread reductions appear to be due to a set of controls or common factors that are having a fairly uniform effect in all of the areas. The consistency of the reductions in different areas suggests that the reductions may also be primarily in the fine particles (i.e., those less than 2.5 micrometers in diameter, or PM 2.5 ), which are more readily transported than coarse particles. |
