Abstract
An airborne survey was conducted for several years as part of the IGAC (International Global Atmospheric Chemistry) project to investigate the influence of air pollutants emitted from East Asia on the chemical characteristics of the atmosphere. In this study, airborne peroxyacetyl nitrate (PAN) and total nitrogen oxide (NOy) measurements from the IGAC project in December 1997 and in February 1999 were determined over the East China Sea from Nagasaki Airport.
Mean value and standard deviation of PAN concentrations from this survey were 0.088±0.053 ppbv (Dec. 9, 12 and 13 in 1997) and 0.56±0.50 ppbv (Feb. 2, 4 and 6 in 1999). Concentration of PAN in 1997 was the lowest level measured in the survey, and the PAN/NOy ratio was very small. On February 4 and 6, 1999, concentrations of PAN were in the range of 0.08-0.48 ppbv and the PAN/NOy ratio was between 14-85%, which were similar to the results of past airborne measurements over the same area.
Concentrations of NOy were in the range of 0.20-3.0 ppbv except for February 2, 1999. The concentration of NOy dramatically increased as theaircraft became more distant from Japan at an altitude of 2500m during the 1997 survey. On the other hand, this increase was not observed below the altitude of 900m, a marine boundary layer. This was due to the transfer of a polluted air mass from the Asian Continent over a bundary layer through the free troposphere.
