Diurnal Variation of Ambient NH3 in Relation with Agricultural Activities and Meteorological Factors at a Rural Site in North India

Abstract

Ammonia is a chemically active gas which accelerates particulate matter formation by combining with nitrate (NO3−) and sulphate (SO42-) in acid cloud droplets, thereby reducing air quality. Since pre-industrial times, NH3 emissions have more than doubled globally, owing to increase in agricultural activities and fertilizer usage. In this study, ambient NH3 monitoring was done during selected periods on event basis in summer season (kharif crop) at a rural site of Jhajjar district of Haryana. Collected gaseous NH3 samples in absorbing solution (1.4ml H2SO4 in 1 litre water) at a flow rate of 1 LPM were prepared with the indo phenol-blue method and analyzed using spectrophotometer at 630nm. Here, we present the day-night variation in ambient NH3 concentrations emitted from various agricultural activities such as synthetic fertilizers, animal manure, biological N-fixation, the crop residue in the field after harvest, biomass burning, etcin relation with meteorological parameters. Its emission was recorded as 1 to 45; 63 to 190; 98 to 187 and 56 to 249 µg m-3 during sowing, fertilizer addition, grain filling and biomass burning respectively.Concentration during the sowing period i.e. 1 to 45 µg m-3can be considered as baseline values.Concentration of ambient NH3 reached itsmaxima at night and minima duringmidday.NH3 concentration was observed to be high during night time which might be due to reduced dispersion as the atmospheric conditions are stable at night. Concentration of NH3 is majorly influenced by wind speed and wind direction & its dependence on these meteorological parameters suggested a local source influence indicating that the nearbyagricultural fields might be the major NH3contributors at the observational site.This study suggests that the knowledge of NH3 levels measured at various stages can help in implementing N efficient management system and emissions can be reduced by minimizing the Nitrogen (N) input during different stages. These measurements are also helpful in making fertilizer policy, and guidelines for farmers.