6. Measurements of Atmospheric Trace Gases During the 1996, 1997, and 1998 IGAC/APARE/PEACAMPOT Aircraft Observations
Yuichi KOMAZAKI and Shigeru TANAKA
(Faculty of Science and Technology, Keio University)
|The present state and effects of the long-range transport of atmospheric pollutants from the East Asian Continent was studied by conducting aircraft observation over the East China Sea. Two automated measurement systems, which consisted of a diffusion scrubber and either an ion chromatograph or a high-performance liquid chromatograph, were installed on the aircraft for measuring trace acidic gases and aldehydes. The gases of interest in the aircraft observation were hydrogen chloride (HCl), nitric acid (HNO3), sulfur dioxide (SO2), formaldehyde (HCHO), and acetaldehyde (CH3CHO). Aerosol number concentrations in four different size-ranges were also measured by laser particle counter.|
1) Trace acidic gases (HCl, HNO3, and SO2)
Trace acidic gases in the atmosphere were measured every 15 min by using an automated continuous measurement system consisting of two parallel diffusion scrubbers and an ion chromatograph1).
The diffusion scrubber used for collecting acidic gases had the following specifications. A porous polytetrafluoroethylene (PTFE) tube (5 mm in outer diameter, 4 mm in inner diameter, and 50 cm in effective length) and a Pyrex glass tube (9 mm in outer diameter and 6.6 mm in inner diameter) were used as the inner tube and the outer tube, respectively, for each diffusion scrubber. Deionized water was used as a scrubbing solution for the collection of acidic gases (HCl, HNO3, and SO2), which were dissociated to ion species (Cl-, NO3-, SO32-, and SO42-). After the collection of gases using the diffusion scrubber, the total amount of anions in the scrubbing solution was preconcentrated in an anion concentrator column. All analyte ions were separated and determined by an ion chromatograph (PIA1000, Shimadzu).The sampling air flow rate was 2.0 L/min.
2) Aldehydes (HCHO and CH3CHO)
HCHO and CH3CHO in the atmosphere were measured using another automated continuous measurement system made up of a diffusion scrubber and a high-performance liquid chromatograph.2)
The diffusion scrubber used for collecting aldehydes had the following specifications. A porous polytetrafluoroethylene (PTFE) tube (5 mm in outer diameter, 4 mm in inner diameter, and 50 cm in effective length) and a Pyrex glass tube (9 mm in outer diameter and 5.8 mm in inner diameter) were used as the inner tube and the outer tube, respectively. 2,4-Dinitrophenylhydrazine (DNPH) was used as the scrubbing solution for collecting HCHO and CH3CHO, which were derivatized to DNPH-HCHO and DNPH-CH3CHO, respectively. The aliquot of the sample solution was automatically injected into a HPLC (HC-2001, Asahi Techneion) equipped with a semi-micro ODS column and an UV detector (360 nm) for separating and determining DNPH-HCHO and DNPH-CH3CHO. The sampling airflow rate was 0.5 L/min.
3) Aerosol number concentration
Concentrations of aerosol number in four different size ranges (0.3, 0.5, 1.0, 3.0, 5.0 um) were simultaneously measured by laser particle counter (Model 237, Met One) every 60 sec. The sampling air flow rate was 0.1 cf/min (2.83 L/min).
Tables 1-3 shows the results of aircraft observations for atmospheric trace gases (HCl, HNO3 SO2, HCHO, and CH3CHO) over the East China Sea for FY1996, 1997, and 1998 observations, respectively. The concentration variations of those trace gases are plotted out in Figures 1-3, respectively. The differential counts of aerosols (per 1 cft) in each size range (0.3-0.5, 0.5-1.0, 1.0-3.0, 3.0-5.0 um) were plotted in Figures 4-6.
1) Yuichi Komazaki, Yuichi Hamada, Shigeru Hashimoto, Tomomi Fujita and Shigeru Tanaka, Development of an automated, simultaneous and continuous measurement system by using a diffusion scrubber coupled to ion chromatography for monitoring trace acidic and basic gases (HCl, HNO3, SO2 and NH3) in the atmosphere, The Analyst, 124, 1151-1157(1999).
2) Yuichi Komazaki, Masashi Hiratsuka, Yasushi Narita and Shigeru Tanaka, The development of an automated continuous measurement system for the monitoring of HCHO and CH3CHO in the atmosphere by using an annular diffusion scrubber coupled to HPLC, Fresenius' Journal of Analytical Chemistry, 363, 686-695 (1999).