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ROADSIDE AMMONIA MEASUREMENTS USING OPTICAL REMOTE SENSING INSTRUMENTS
Citation:
SHORES, R. C., E. D. THOMA, SUE KIMBROUGH, R. VARMA, R. HASHMONAY, AND R. H. KAGAN. ROADSIDE AMMONIA MEASUREMENTS USING OPTICAL REMOTE SENSING INSTRUMENTS. Presented at A&WMA'S 98th Annual Conference & Exhibition, MInneapolis, MN, June 21 - 24, 2005.
Impact/Purpose:
To inform the public.
Description:
Fine particles less than 2.5 microns in diameter have been identified as a causal agent of excess mortality and other undesirable health impacts. A large part of these airborne particles, generally more than one-half, are formed in the atmosphere by reactions of ammonia with acid gases of sulfur and nitrogen oxides through a series of gas and aqueous phase reactions. Nationally, the largest portion of ammonia emissions are from agricultural management of livestock and the application of fertilizers, but in urban areas the emissions of ammonia are primarily attributed to vehicle exhaust. For example, in the New York City metropolitan area, 49% of ammonia is attributed to onroad mobile sources. Light duty vehicle emissions of most pollutants declined significantly in the 1990s. However, while use of three way catalytic converters has contributed to decreases in Nox, non-methane hydrocarbons, and CO emissions, their use has also resulted in an increase of NH3 emissions from mobile sources. Open-path optical remote sensing technologies were used to measure ammonia emissions over a segment of I-40 in the Research Triangle Park area of North Carolina. The instruments included Open Path Fourier Transform Infrared Spectrometer (OP-FTIR) and two different Open Path Tunable Diode Lasers. A digital video recorder documented the vehicles passing through the optical path and this recording was used to classify vehicles into categories. Results indicated that ammonia emissions from the road were measurable with OP-FTIR and were not measurable with the near infrared TDL instruments. The average passenger vehicle emissions determined to be 0.165 gm/mi and are similar to other emission factors found in the literature. The time resolved emissions showed significant variations (0.011-0.877 gm/mi). The highest emissions occurred during high traffic events and stop and go traffic, resulting in hard accelerations. The calculated emission factors are based on a change in concentration from background concentrations. Background concentrations were estimated using two methods, representing the highest and lowest possible emission estimates. This paper describes the experimental setup, the correlation between ammonia emissions and traffic conditions and the types of vehicles on the road.