Review of Researches on Factors Affecting Emission of Ammonia From Agriculture

Ammonia (NH₃) as an alkaline gas in the atmosphere plays a key role in the formation of haze. Control of NH₃ emission at source is hence particularly important to reduction of the concentrations of secondary inorganic salts and PM_2.5 in the atmosphere, control of haze pollution, and improvement of air environment quality. Agriculture is a major source of anthropogenic NH₃ emitted into the atmosphere, and farmland fertilization and livestock and poultry breeding are the two major sources in agriculture. Therefore, the review summarized the researches at home and abroad on NH₃ emissions from agriculture and analyzed factors affecting NH₃ emissions, which is of fundamental significance to the understanding of the process and characteristics of NH₃ emission and designing corresponding control measures. It has been found that fertilizer type, soil physic-chemical properties, field meteorological elements and fertilization practice are the main factors affecting NH₃ emission from farmland fertilization. Nature of feed, barn environment and dung disposal mode are the main factors affecting NH₃ emission from livestock and poultry breeding. However, currently the researches on NH₃ emission from farmland fertilization proceed from the aspects of geochemical recycling of N in farmlands and N demand for higher grain yield, while the researches on NH₃ emission from livestock and poultry breeding do from the aspects of occupation alhygiene and health, both lacking the concerns about the target of controlling the risk of environmental exposure of NH₃ emission. Hence, it is proposed to unfold studies on emission coefficient of NH₃ from agricultural sources with the ambient air as emission interface, determination of priority control zones of NH₃ emissions from agricultural sources, and in the end provision of theoretical basis for formulation of a technical system, strategies, route maps and standards for sub-zonal control of agricultural NH₃ emission, and formation of relevant policies and regulations for environmental management authorities.