Monday, 15 January 2001: 2:00 PM
During the summer of 1999, tropospheric chemistry measurements were taken as part of the Northeast Oxidant and Particulate Study (NEOPS) in Centerton, New Jersey. The primary air sampling station was located in Philadelphia, Pennsylvania. At the Centerton site, sodar and RASS (radio acoustic sounding system) soundings were obtained to determine the wind direction and the boundary layer height. Balloon soundings with relative humidity, temperature, and pressure sensors were 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, which is 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 also 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. NO emissions from nearby cornfields were observed during the period. Early morning production rates of PAN and ozone were found to correlate well with UV-B and with boundary layer height. Late afternoon 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.
This work was supported by the U.S. Department of Energy, Office of Biological and Environmental Research, Atmospheric Chemistry Program, under contract W-31-109-Eng-38.
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