Open-path tunable diode laser absorption spectroscopy for acquisition of fugitive emission flux data.
Air pollutant emission from unconfined sources is an increasingly important environmental issue. The U.S. Environmental Protection Agency (EPA) has developed a ground-based optical remote-sensing method that enables direct measurement of fugitive emission flux from large area sources. Open-path Fourier transform infrared spectroscopy (OP-FTIR) has been the primary technique for acquisition of pollutant concentration data used in this emission measurement method. For a number of environmentally important compounds, such as ammonia and methane, open-path tunable diode laser absorption spectroscopy (OP-TDLAS) is shown to be a viable alternative to Fourier transform spectroscopy for pollutant concentration measurements. Near-IR diode laser spectroscopy systems offer significant operational and cost advantages over Fourier transform instruments enabling more efficient implementation of the measurement strategy. This article reviews the EPA's fugitive emission measurement method and describes its multipath tunable diode laser instrument. Validation testing of the system is discussed. OP-TDLAS versus OP-FTIR correlation testing results for ammonia (R2 = 0.980) and methane (R2 = 0.991) are reported. Two example applications of tunable diode laser-based fugitive emission measurements are presented.
Thoma
Eben D
ED
Office of Research and Development, National Risk Management Research Laboratory, Air Pollution Prevention and Control Division, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA. thoma.eben@epa.gov
Shores
Richard C
RC
Thompson
Edgar L
EL
Harris
D Bruce
DB
Thorneloe
Susan A
SA
Varma
Ravi M
RM
Hashmonay
Ram A
RA
Modrak
Mark T
MT
Natschke
David F
DF
Gamble
Heather A
HA
D000393:Air Pollutants / Q000032:analysis*; D000641:Ammonia / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D007834:Lasers; D008697:Methane / Q000032:analysis; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis
D000393:Air Pollutants; D000641:Ammonia; D008697:Methane