Ammonia emission and ammonium formation by photochemical mechanisms of urban aerosol

Abstract

Ammonia is a pungent gas in atmosphere that was emitted by many sources. So, in this study, ammonia concentrations were measured using 2 different methods which were honeycomb denuder and real-time measurement for compare collection efficiency of 2 methods in daytime and nighttime, indoor and outdoor ammonia concentrations were collected at Chai Nan University (CNU) Tainan, Taiwan. These was characterized using ion chromatography (IC). At flow rate 10 l/min was chosen in this study. The collection efficiency of honeycomb tube was 76.75 ± 14.18%, 13.37 ± 8.15% and 9.88 ± 6.32% for stage 1, 2 and 3 respectively. In the nighttime, the collection efficiency of honeycomb tube in 1st, 2nd and 3th stage was 89.22 ± 3.28%, 6.03 ± 1.99% and 4.74 ± 1.40% respectively, and in the daytime was 64.27 ± 8.22%, 20.71 ± 4.10% and 15.02 ± 4.88% respectively and ambient temperature was 27.3 ± 1.5 °C for daytime and 24.1 ± 1.3 °C for nighttime. In the daytime the collection efficiency of honeycomb tube was lower than nighttime because temperature which effect to absorption. The outdoor ammonia concentrations by denuder were low in daytime and high in nighttime but indoor ammonia concentrations were contrasted. The indoor ammonia concentrations by honeycomb denuder and real time measurement had same pattern, high in daytime and low in nighttime. The ammonia concentrations of 2 methods at ammonia concentrations which were set at 50 and 100 ppb were similar to each other so, collection efficiency of 2 methods were also similar to each other (NH3 concentration by honeycomb denuder at 50 ppb, 34.31 ± 0.19 µg/m3: n = 4 and at NH3 concentration 100 ppb 68.89 ± 3.07 µg/m3: n = 10) and NH3 concentration by real-time measurement at 50 ppb, 34.05 ± 0.50 µg/m3: n = 20 and at NH3 concentration 100 ppb 68.17 ± 0.65 µg/m3: n = 20). Average indoor ammonia concentrations were collected by real time measurement was fluctuated which depend on number of people in that time which ammonia can excrete from body. Ammonia concentrations at CNU were influenced from ammonia sources such as wastewater treatment plant, drain and natural sources and exhaust gas from vehicles. Using honeycomb denuder with 3 honeycomb tubes suited for ammonia in Southern Taiwan.