Airborne particulate organic matter was characterized in the Northeast Oxidant and Particulate Study to assess the relationship between particulate organic composition and ozone formation and transport. Particulate organic matter (POM) is a mixture of primary emissions from several important sources and secondary formation from atmospheric photochemical reactions. Elevated concentrations of secondary POM often coincide with high ozone levels. POM represents a significant fraction of fine particulate matter (PM-2.5) in the Northeast, but little is known about its overall composition or the relative importance of potential sources. As information on health effects of specific PM-2.5 particle types and components becomes available from on-going studies, a better understanding the relationship between ozone and secondary POM in the Northeast would help to assess potential consequences of PM-2.5 during summer air pollution episodes in the Northeast corridor.

Air samples were collected using a high volume low cut-off inertial impactor (HVLI) during the in the summer 1999 field intensive. The HVLI uses a thin polyurethane foam (PUF) strip as the impactor substrate, which allows the collection of large amounts of particulate matter on a relatively small substrate collection surface that can be easily extracted with a very small amount of organic solvent.

Samples were analyzed by gas chromatography/mass spectrometry for n-alkanes, polycyclic aromatic hydrocarbons, n-alkanoic acids, aliphatic dicarboxylic acids, and other organic compounds associated with ambient particulate organic matter. Malonic and succinic acids are known atmospheric photochemical reaction products, and were usually the most abundant species present, suggesting an important contribution of secondary POM, especially during periods of high ozone concentrations. The relative abundance of n-alkanes and n-carboxylic acids suggest that there is also an important, but variable contribution of biogenic emissions to POM. Polycyclic aromatic hydocarbon concentrations were similar to previously reported observations for urban Northeast samples. We conclude that the properties of urban particulate organic matter in the Northeast are likely to change considerably during episodes of high ozone concentration.