Abundance and distribution of gaseous ammonia and particulate ammonium at Delhi, India

[摘要] This study reports abundance and distribution of gaseous NH₃ andparticulate NH₄⁺ at Delhi. Gaseous NH₃ and particulateNH₄⁺ concentrations were measured during pre-monsoon, monsoon andpost-monsoon seasons of the years 2010 and 2011. Average concentrations ofgaseous NH₃ during pre-monsoon, monsoon and post-monsoon seasons wererecorded as 26.4, 33.2 and 32.5 μg m⁻³, respectively. GaseousNH₃ concentrations were the highest during monsoon, thought to be due todecay and decomposition of plants and other biogenic material under wetconditions, leading to increased NH₃ emission. The results showed thatparticulate NH₄⁺ was always lower than the gaseous NH₃ duringall the seasons. The concentrations of particulate NH₄⁺ were recordedas 11.6, 22.9 and 8.5 μg m⁻³ during pre-monsoon, monsoon andpost-monsoon seasons, respectively. The percent fraction of particulateNH₄⁺ was noticed to be highest during the monsoon season, which isattributed to increased humidity levels favouring partitioning into theaerosol phase. On an average, 33.3% of total N-NH_x was presentas particulate NH₄⁺. Higher concentrations of NH₃ noticed duringnight time may be due to stable atmospheric conditions. The study highlightedthat, as compared with rural sites, urban sites showed higher concentrationsof gaseous NH₃ in India, which may be due to higher population density,human activities and poor sanitation arrangements.

[学科分类] 地球化学与岩石