Investigations of Ozone and Fine Particles in the Northeast

Anthropogenic emissions from urban sprawl, traffic, and industrialization along the northeast corridor of the United States should have an increasingly profound effect on urban and regional air quality. Surface air quality over populated areas is an important issue given persuasive data linking high levels of atmospheric oxidants and particulate matter to deleterious human health effects. An improved understanding of the sources, sinks, transport, mixing, and photochemical transformations controlling the observed abundances of photochemical oxidants and fine particle haze over the U.S. mid-Atlantic region is key to developing any capability in the future to forecast such pollution events reliably. Model and forecast skill are often compromised due to complex interrelationships between near-surface air, the atmospheric boundary layer, and lower free troposphere.

This paper reports on results and findings from the EPA-sponsored North American Research Strategy for Tropospheric Ozone - Northeast Oxidant and Particle Study (NARSTO-NEOPS). This intensive characterization of urban corridor air quality was conducted 20 km northeast of Philadelphia during a nine-week field intensive in July-August 1999, and involved a consortium of investigators from several institutions and government laboratories.

The advanced research techniques brought into the field for data collection included Raman lidar, tethered balloons, ground based particle/chemical samplers (TEOMS, HEADS, HV-TOX, and trace gas analyzers), and the latest airborne sampling techniques onboard the DOE-G1 and University of Maryland aircraft. The Penn State Raman lidar provided high frequency sequences of ozone, temperature, water vapor, and optical extinction to six kilometers. Millersville University used two tethered balloons to deploy instruments and samplers to 300 m AGL to measure meteorological variables, ozone, integrated fine particle dry mass, fine particle concentration, and VOCs. The regional distributions of particulate matter, chemical species and meteorology were obtained using the University of Maryland aircraft and the DOE-G1 aircraft. Harvard SPH, Drexel University, and Brigham Young University used advanced techniques to measure atmospheric gas and particle properties such as size distribution, EC/OC, sulfate, nitrate, toxics, high-volume speciation, and the volatile mass component. In addition, PNNL, ANL, and the City of Philadelphia provided surface, upper air, and criteria pollutant measurements using conventional techniques. The measurements obtained from these platforms are being integrated into a database that will be used to investigate the factors responsible for high ozone and fine particle concentrations along the northeast corridor. This collaboration between the chemistry, atmospheric science, and public health research communities, in concert with local, state, federal government agencies, to understand the temporal and spatial distribution of the particulate matter/co-pollutant complex, serves as an example of the current interdisciplinary nature of atmospheric chemistry research.

During the NARSTO-NEOPS Summer 1999 field intensive eight significant pollution/particle episodes were documented covering a broad range of atmospheric conditions. Results from the NEOPS field intensive will be presented that will focus on two of the eight cases: 1) the ramp-up recirculation event of 15-19 July 1999, and 2) the passage of a sea breeze front on 31 July 1999. These cases are interesting for their scientific merit as well as their approach to multi-disciplinary collaborative research.