|
 
The Series 8400N
Ambient Particulate Nitrate Monitor from Rupprecht & Patashnick
provides a continuous record of the ambient particulate nitrate
concentration at a number of sites in California's San Joaquin Valley.
This part of the state tends to experience elevated particulate
nitrate concentrations on a seasonal basis, especially during the
wintertime.
Particulate nitrate is typically formed as a secondary pollutant,
through the mixing of different gases in ambient air under the proper
meteorological conditions. It can represent a significant fraction
of the fine particulate matter (PM-2.5) concentration in areas such
as the San Joaquin Valley, and can cause reductions in visibility.
In a recent article [1] authored by individuals affiliated with
the California Air Resources Board, Aerosol Dynamics Inc., and Sonoma
Technology Inc., time series data for particulate nitrate contained
in fine particulate matter (PM-2.5) are presented for different
locations. Monitoring sites included Fresno and Bakersfield, two
of the valley's most populous urban areas, as well as two rural
sites.
Fresno and Bakersfield are located approximately 175 km (110 miles)
apart. Yet the particulate nitrate concentrations at these two sites
expressed in micrograms per cubic meter show similar temporal patterns
(see graph below). The researchers collected this data set during
the wintertime, when particulate nitrate concentrations are typically
at their highest.
Angola is an unincorporated rural background site in a cotton farming
area. At this location, particulate nitrate data were collected
from two Series 8400N monitors--one at ground level and one on a
tower 95 m above the ground. The tower particulate nitrate concentrations
tend to be lower than those recorded at ground level (see graph
below).
Walnut Grove is located at the northwest boundary of the San Joaquin
Valley in the river delta region. The area is influenced by air
transported from the San Francisco Bay, a large urban center. Two
Series 8400N monitors installed at ground level and on a 245 m tower
provide a record of the particulate nitrate concentration. When
the concentrations differ, they are generally higher at ground level
(see graph below).
Reference:
1. J. Aerosol Sci. Vol 32, No. S1, p. 631-632.
Sources:
California Air Resources Board, Aerosol Dynamics Inc., and Sonoma
Technology Inc.
|
San Joaquin Particulate Nitrate Trends 
