Aircraft Measurements of Long-Range Trans-Boundary Air Pollutants over Yellow Sea

Airborne gaseous and particulate matter was measured above downwind ocean areas from China to the western region of the Korean peninsula for 10 days in the spring and autumn of 2005.

The main objectives of this study were to investigate the spatial distribution of pollution in the ocean atmosphere between Korea and China, and to improve our understanding of acidic deposition in the Korean region in relation to processes affecting the transport of long-range trans-boundary air pollutants from China. The scientific payload on-board an ultra-light aircraft included measurements of the concentrations of SO

2

, NO

x

, O

3

and particulates. Meteorological profiles (air temperature, winds and humidity) were recorded simultaneously at a ground site.

A six-manned aircraft (PA-31-350 type) served the flight scenarios of eight altitude and two azimuth levels for measuring gas fluxes and particulate depositions in the first intensive observation period (IOP) during April 15–25 and a second period during October 15–25, 2005.

The overall mean concentrations of air pollutants in the atmospheric boundary layer were in the range 2.58–6.63 ppbv for SO

2

, 3.74–4.24 ppbv for NO

x

and 48.8–54.28 ppbv for O

3

in both observation periods. Measurements at different altitudes revealed that the pollutants were normally observed in high concentrations in the atmospheric boundary layer. However, the longitudinal measurements of SO

2

concentration showed higher values in areas over the Yellow Sea, though values decreased when approaching the Korean peninsula. Enhanced mass concentrations of SO

2

were observed for altitudinal measurements when a strong westerly air stream occurred in the low level boundary layer from China to Korea.

Aerosol number concentrations varied significantly in the range 32–4,640 ea/cm

3

for aircraft measurements during both periods. The differences in NO

x

level between aircraft and surface measurements play an important role in the chemical form and size of particulate matter.

Keywords

: Airborne gaseous, aircraft measurements, long-range trans- boundary, aerosol sulfate, air pollutants of SO2, NO

x

, O3