Long-Term Trends of Ambient PM: Concurrent Effects of Emissions and Dispersion

YUNLE CHEN, David Q. Rich, Philip K. Hopke, University of Rochester

     Abstract Number: 148
     Working Group: Urban Aerosols

Abstract
In the past several decades, a variety of efforts have been made in the United States to improve air quality, and ambient particulate matter (PM) concentrations have been used as a metric to evaluate the efficacy of environmental policies. However, ambient PM concentrations result from a combination of source emission/formation rates and meteorological conditions, which also change over time. Dispersion normalization was recently developed to account for the influence of meteorological dispersion on measured ambient PM concentrations.

In this presentation, we will present how dispersion normalization brings new insights into our understanding of long-term particulate size distribution, concentration, and composition variations in the northeastern US. We showed that for the past two decades, meteorological dispersion and emission/formation rate changes could work in the same or opposite directions to change the ambient PM, which veiled the efficacy of implemented air pollution mitigation measures in reducing air pollutants. In addition, source apportionment approaches like positive matric factorization (PMF) highly rely on temporal variations to separate factors. The variation caused by meteorological conditions could influence the accurate resolution of PM factors. Meteorological dispersion is an essential factor in determining ambient pollutant concentrations, and it is necessary to incorporate it in future studies.