Multiphase measurement of atmospheric ammonia

Measurement of ammonia in vapour phase, particulate and rain was made at a suburban site of India. Vapour phase concentrations varied between 0.97 and 25.5 μg m⁻³ (57.1–1500.0 nmol m⁻³) and diurnal variation study showed high concentration of NH₃ during night time and minimum at 0600 h (early morning). Particulate phase NH₄ values ranged between 1.2 and 5.3 μg m⁻³ (66.7–294.4 nmol m⁻³). Dry deposition flux was determined from model calculations. Day time NH₃ flux was found to be 8.4±4.0 mg m⁻² d⁻¹ and that of night 2.2±1.2 mg m⁻² d⁻¹. With respect to particulate deposition flux was found 0.2±0.1 mg m⁻² d⁻¹ while in precipitation values of NH₄ ranged between 0.7 and 74.4 μeq l⁻¹. Regression analysis of ammonium concentration with rain volume and deposition indicates that NH₃ concentration is being controlled by both gas and particulate ammonium. Annual inputs for wet and dry deposition were found to be 0.34±0.3 and 3.9±1.9 g m⁻² y⁻¹.