Ammonia in the atmosphere: a review on emission sources, atmospheric chemistry and deposition on terrestrial bodies

Gaseous ammonia (NH 3 ) is the most abundant alkaline gas in the atmosphere. In addition, it is a major component of total reactive nitrogen. The largest source of NH 3 emissions is agriculture, including animal husbandry and NH 3 -based fertilizer applications. Other sources of NH 3 include industrial processes, vehicular emissions and volatilization from soils and oceans. Recent studies have indicated that NH 3 emissions have been increasing over the last few decades on a global scale. This is a concern because NH 3 plays a significant role in the formation of atmospheric particulate matter, visibility degradation and atmospheric deposition of nitrogen to sensitive ecosystems. Thus, the increase in NH 3 emissions negatively influences environmental and public health as well as climate change. For these reasons, it is important to have a clear understanding of the sources, deposition and atmospheric behaviour of NH 3 . Over the last two decades, a number of research papers have addressed pertinent issues related to NH 3 emissions into the atmosphere at global, regional and local scales. This review article integrates the knowledge available on atmospheric NH 3 from the literature in a systematic manner, describes the environmental implications of unabated NH 3 emissions and provides a scientific basis for developing effective control strategies for NH 3 .