Semi-Urban particulate matter sources: Implications for particulate matter concentrations and cloud condensation nuclei

In addition to the harmful biological impacts of aerosols when inhaled, atmospheric particulate matter can also have climactic effects, both by directly blocking the sunlight, serving as cloud and ice condensation nuclei. However, the influences of different sources on aerosol amounts are difficult to partition, especially in areas influenced by both urban and rural airmasses. To understand the sources of aerosols within the context of cloud condensation nuclei availibility, we examine six years of summertime trace-gas, aerosol, and meteorology data at a site located just outside Washington, D.C. Correlations of PM 2.5 concentration and isoprene mixing ratio are slightly stronger than those between PM 2.5 and sulfur dioxide, although this varies from year-to year. In general, both PM 2.5 and sulfur dioxide are shown to have decreased slightly over the past few years. We also examine the PM 2.5 speciation information, as well as the airmass transport path, to understand what sources in this area are contributing both to particulate pollution and cloud condensation nuclei availibility.