The APERG program is funded by the Reuben and Alice Wasser A.P.C. Education and Research Charitable Remainder Unitrust.
2003 APERG Scholar: Ann Marie Carlton
Rutgers University
Project Title: Secondary Aerosol Potential from Heterogeneous Isoprene Reactions
Abstract
Development of effective State Implementation Plans for atmospheric fine particulate matter (PM2.5) is complicated by the fact that PM2.5 is both emitted directly (primary) and formed in the atmosphere (secondary). In addition, the sources could be local, they could be within the state, or they could be thousands of kilometers away (U.S. EPA, 1996). Reducing ambient PM2.5 concentrations in a location dominated by local primary PM2.5 would require reductions in permitted particle emissions locally. In contrast, in areas dominated by secondary PM2.5, reductions in ambient concentrations require reductions in precursor gases (i.e., NOx, VOCs, SO2).
Regional transport of secondary particulate matter (PM) is responsible for a large portion of PM2.5 in the southern and eastern U.S., (i.e., the Mid-Atlantic States) even in urban areas (Chuersuwan, 2001; U.S.EPA, 1996). It is likely that cloud processing is a substantial contributor to secondary organic aerosol formation (Blando and Turpin, 2000). Water-soluble vapors, many of which have been measured in cloud droplets, could oxidize further in the aqueous phase to form low volatility species, including organosulfur compounds. Upon cloud droplet evaporation, these species would then add to the burden of atmospheric PM. This process is expected to be particularly important in the Mid-Atlantic States, where regional transport and atmospheric transformation dominates. An analogous example is sulfate. Roughly 50% of sulfate is formed through cloud processing, rather than through homogeneous oxidation (Seinfeld and Pandis, 1998).
