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OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM
Citation:
Conner, C., B. Gay, Jr., W. Karches, AND R. Stevens. OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/A-92/125 (NTIS PB92192160).
Description:
A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging from 202 to 816 meters in length. he longest path crosses a highway wile all the shorter paths are located near parking lots. emi-continuous measurements of S02, 03, N0, and N02 were made. he measurement cycle involves measurements on each path in sequence. he total of all measurements on all paths requires approximately 20 minutes to complete, thus there are three values for each unique gas-path combination per hour. hese values are averaged into hourly averages. ontinuously operating Federal Reference Method (FRM) instruments were also located in the DOAS shelter. hese instruments were measuring the same gases. heir results are also reported as hourly averages. omparison on the long-path DOAS measurements with the FRM point measurements indicates a high level of correlation. onsidering the potential problem of comparing a long-path measurement to a point measurement, the high correlation is encouraging. he shorter DOAS paths yielded the highest correlations with the point measurements, as expected.