Northeast oxidant and particle study (NEOPS) : preliminary results from the Centerton, New Jersey, field site. Page: 1 of 6
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NORTHEAST OXIDANT AND PARTICLE STUDY (NEOPS):
PRELIMINARY RESULTS FROM THE CENTERTON, NEW JERSEY, FIELD SITE
Nancy A. Marley* and Jeffrey S. Gaffney
Environmental Research Division
Argonne National Laboratory, Argonne, Illinois
During the summer of 1999, the Northeast Oxidant
and Particle Study (NEOPS), as part of the North
American Research Strategy for Tropospheric Ozone
(NARSTO), investigated the factors leading to the
occurrence of increased levels of ozone and fine
particles during the summer months in the northeastern
United States. The primary NEOPS air sampling station
was located in the city of Philadelphia, Pennsylvania, at
the Baxter Water Treatment Plant on the west bank of
the Delaware River, northeast of the city center.
Supplemental chemistry and meteorology
measurements were taken at Centerton, New Jersey, a
rural site 30 miles south of Philadelphia and 25 miles
north of Delaware Bay. This paper reports the
preliminary atmospheric chemistry and aerosol results
obtained at the rural sampling site near Centerton. In
particular, the nitrogen dioxide (NO2) and peroxyacetyl
nitrate (PAN) data obtained with our second-generation
luminol instrument are discussed and compared to
results obtained with conventional nitrogen oxides
Ozone (03), NOy, ultraviolet-B (UV-B), and
nephelometry data were obtained at Centerton at 1-min
intervals for a period of 20 days (July 24-August 12).
Aerosol samples collected with cascade impactors were
analyzed for 210Pb, 210Po, and 210Bi as a means of
estimating the aerosol residence times.
Data on NO2 and PAN were obtained at 1-min
intervals by using a new, second-generation fast gas
chromatography (GC) system with luminol detection.
Measurements of these species at time intervals shorter
than 1 min have been difficult in the past. The rapid
analysis time allowed for the determination of nighttime
nitrate radical (NO3) production rates, as well as
PAN/03 and PAN/NO2 concentration ratios. An
important intermediate in the photochemical production
of 03, PAN acts as a reservoir for NO2
*Corresponding author address: Nancy A. Marley,
Environmental Research Division, Argonne National
Laboratory, Argonne, IL 60439; email: email@example.com
(Singh, 1987; Finlayson-Pitts and Pitts, 2000). Its
stability at low temperatures, low reactivity with OH
radical, photochemical stability, and low aqueous
solubility give PAN a longer atmospheric lifetime than
other reactive nitrogen species; therefore, it is a key
species in determining the apparent age of a
background air parcel when measured simultaneously
with NO2 (Gaffney et al., 1989, 1993, 1998). Results will
be discussed in terms of local and regional production
and transport of ozone.
2. SECOND-GENERATION LUMINOL SYSTEM
The peroxyacyl nitrates are typically monitored by
using GC with electron capture detection (see reviews
by Gaffney et al., 1989; Roberts, 1990). However, this
approach is affected by significant responses due to
oxygen and water vapor, and time resolution faster than
about 4 min is difficult to achieve. Typically
measurements are obtained at 15- to 30-min resolution
(for example, see Gaffney et al., 1999).
We have demonstrated that fast capillary GC
coupled with luminol detection can accomplish direct
measurement of NO2 and PAN simultaneously in less
than 1 min. The first-generation fast GC-luminol
detection system for NO2 and PAN was described in
detail previously (Gaffney et al., 1998). We modified the
first instrument by replacing the Unisearch (Scintrex)
LMA-3 luminol detection system with a reaction cell and
a Hamamatsu photon counting detection module
(HC-135), which is computer controlled with Q-Basic
software. A smaller peristaltic pump and mass flow
controllers were added to maintain flow rates in the
system. The second-generation instrument is now
capable of 30-sec time resolution. Calibration standards
for PAN were made by using diffusion tubes containing
PAN synthesized by the wet chemical method (Gaffney
et al., 1984). Field calibrations were accomplished with
commercially available NO2 gas standards.
3. OTHER INSTRUMENTATION
Ozone measurements were taken by using UV
absorption (Dasibi Model AH-8000). The UV-B radiation
measurements, used to assess the effective
photochemical light intensity, were taken with a
Robertson-Berger radiometer (Solar Light Co.). This
radiometer allows direct continuous measurement of
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Marley, N. A. & Gaffney, J. S. Northeast oxidant and particle study (NEOPS) : preliminary results from the Centerton, New Jersey, field site., article, October 12, 2001; Illinois. (digital.library.unt.edu/ark:/67531/metadc724278/m1/1/: accessed July 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.