Abstract
A portable open long-path Fourier-transform infrared system (POPFT-IR) operable at pathlengths of up to 961m has been constructed for the detection and measurement of trace gases in ambient air and for photochemical smog formation studies. The long optical path is achieved by using a three-mirror multiple reflection cell with a 15.5m base path. The combination of a retro-reflection mirror with one of three mirrors eliminates any air-turbulence interference. The design, construction, advantage, and use of this novel folded open-path optical system and calibration spectrum for quantitative analysis are described in detail. Preliminary ambient air measurements were made at a variety of locations in Taiwan from urban, suburban and rural to remote areas. The existing trace gases in the background atmosphere were measured as nitrous oxide (N2O), methane (CH4), carbon monoxide (CO) and carbon dioxide (CO2). Major pollutants such as ethylene (C2H4), propylene (C3H6), ammonia (NH3), ozone (O3) and peroxyacetyl nitrate (PAN) were measured in the polluted urban atomosphere.
