Ambient Ozone Concentration Trends in the South Central U.S. During the Period 1986-2000

摘要

Lower tropospheric ozone pollution continues to be a challenging air quality problem in many South Central U.S. cities. Ambient monitors in many of these cities record 1-hour and 8-hour ozone concentrations that exceed the current ozone National Ambient Air Quality Standards (NAAQS). This paper presents robust ozone concentration trends in many cities in the States of New Mexico, Oklahoma, Arkansas, Louisiana, and Texas. The first five years of the study period (1986-1990) occur before the November 15, 1990 enactment of the Clean Air Act Amendments of 1990, and this period will be compared to the next two five year periods (i.e. 1991-1995, and 1996-2000). Both 1-hour and 8-hour ozone concentration trends will be analyzed using three indicators: (1) design values, (2) number of summer daytime hours with ozone concentrations exceeding the standards, and (3) number of summer daytime hours with ozone concentrations close to the standards. All ozone data analyzed were downloaded from the U.S. EPA Aerometric Information Retrieval System (AIRS) database. Meteorological data were also extracted from AIRS and the National Climatic Data Center for use in interpretation of the ozone concentration trends. Key results of the analyses show a long-term decline in ambient ozone concentrations across a majority of the South Central U.S. area, especially for 1-hour ozone concentrations, but that both 1-hour and 8-hour ozone NAAQS attainment status has not notably changed in the Region.