Measurements of Peroxyacetyl Nitrate (PAN) During the 1997 and 1998 IGAC Aircraft Observations
Jun MAEDA, Hiroshi BANDOW (College of Engineering, Osaka Prefecture University), Ikuo WATANABE (National Institute for Public Health), Kentaro MURANO, and Shiro HATAKEYAMA(National Institute for Environmental Studies) |
Peroxyacetyl nitrate (PAN) had been known as a harmful
substances in terms of photochemical smog in urban areas.Recently this
substance has been attracting further attention since studies have indicated
that PAN is likely to lead to widespread occurrence of acid deposition
and the vicissitude of compounds within the troposphere, because this
is an important reservoir of reactive nitrogen compounds1,2).Nevertheless,
there have been few observational data of PAN concentrations both in Japan
and Western nations.This may be reflection of the difficulty for its quantitative
measurement since the PAN concentration is less than 1 ppb except in urban
areas.There has been a quite limited data for East Asia, and, therefore,
the actual extent of air pollution. |
Sampling device is composed of a collecting trap, a thermal-mass-flow
controller, a double-stage tank for taking gases in (volume: 1 L), a small
vacuum pump for evacuating the tank, a pump for purging sampling line,
sensors for monitoring the temperature and pressure inside of the tank,
and a small recorder with 6 chopper bars for recording the pressure and
temperature in the tank. |
On the basis of the conventional method6,7),
peroxyocetyl nitrate (PAN) was synthesized by photooxidation of ethyl
nitrite. The concentration of PAN was determined by using the extinction
coefficient (PAN: 13.9* 10-4,
8))based on the absorbance in the infrared regions (PAN: 8.60
um). |
The data obtained in the fiscal years 1997 and 1998 are
listed in Table 1 and Table 2, respectively, along with the sampling time
(start and/or finishing), the average flight altitude at which the sample
air collection was done, and the average concentration of NOx during each
air-sampling period for PAN.Please note that the nitrogen oxides concentration
for 1998 is abbreviated as NOy in the Table 2, because the air-sampling
system for nitrogen oxide analyzer has been modified from the earlier
one, in which the NOx-reducing converter was placed after ca. 2m-long
sampling tube (one quarter inch o.d. stainless-steel tube).The converter
was moved to the position just after the inlet of the sample-tube to minimize
the wall-effect of the tube. This modification made us to call the indicated
value of the NOx instrument as "NOy" from "NOx" or
"NOx*". References
|