During the summer of 1999, tropospheric air chemistry measurements were taken in Centerton, New Jersey, as part of the Northeast Oxidant and Particulate Study (NEOPS). The principal air sampling site for NEOPS was located in Philadelphia, Pennsylvania. At the Centerton site, sodar and RASS (radio acoustic sounding system) determinations of wind direction and boundary layer height were co-located with the chemistry measurements described in this paper. Radiosonde measurements of relative humidity, temperature, and pressure were also taken at the site in the morning, at noon, and in the afternoon. Nitrogen dioxide (NO2) and peroxyacetyl nitrate (PAN) data were obtained by using a new, second-generation fast gas chromatography system with luminol detection. PAN, an important intermediate in the photochemical production of ozone, acts as a reservoir for NO2, a key species in the formation of ozone. The instrumentation will be described briefly. Ozone, nitrogen oxides (NOx), ultraviolet?B (UV?B), and nephelometry data were obtained at Centerton at one-minute intervals for approximately two weeks. Aerosol samples taken with cascade impactors were analyzed for 210Pb, 210Po, and 210Bi as a means of estimating the aerosol residence times. Early morning production rates of PAN and ozone were found to correlate well with UV?B and with boundary layer height. Late afternoon production rates were lower, consistent with higher mixing heights and the lower reaction rates anticipated for reactive hydrocarbon removal. Observations of late afternoon ozone levels exceeding 80 ppb on a number of days will be discussed in terms of local and regional production and transport of ozone. Chemical sources of early morning NO observed at the site will also be discussed.

This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Atmospheric Chemistry Program, under contract W-31-109-Eng-38.