A Research Paper titled “New measurements reveal a large contribution of nitrogenous molecules to ambient organic aerosol” authored by Prof. Jian Zhen YU (Chair Professor, Division of Environment and Sustainability) and her postgraduate research students was recently published on npj Climate and Atmospheric Science, a journal focusing the physical, chemical and biological components of the climate and atmospheric sciences. 

Nitrogen is a significant element that constitutes ambient organic aerosol. Individual N-containing organic molecules are known to have both natural and anthropogenic sources and implicated in a wide-ranging health and environmental effects. Yet, unlike carbon (C), the total quantity of aerosol organic nitrogen (ON) remains largely unquantified, hindering a quantitative understanding of their major sources and impacts. 

HKUST Research Team led by Prof. Jian Zhen YU has developed a novel measurement that permits simple, and yet sensitive, simultaneous detection of inorganic and organic nitrogen, to effectively address this challenge. The team applied the new method and quantified ON in more than 600 aerosol filter samples collected from multiple sites of varying urban influence in China and spanning a whole year at most sites. The relative quantities of aerosol ON and IN and their typical varying ranges in urban and suburban atmospheres are established in this study. 

The data showed that annual average ON concentration was in the range of 0.4–1.4 μg N m−3, representing 17–31% of aerosol total nitrogen. Monte Carlo simulations constrained by paired ON and OC measurements suggest N-containing organic molecules contributed typically 37–50%, with a 95% confidence interval of [12%, 94%], to ambient organic aerosols. 

Source apportionment analysis reveals that biomass burning and secondary formation are dominant ON sources, accounting for 21–24% and ~ 30% of ON, respectively. Primary biological aerosol is also a significant source of ON (7–18%), with its contribution more prominent in non-urban atmospheres. 

The results provide the quantitative data on the extent of presence of organic nitrogenous aerosol and the origin of their major sources. It’s anticipated that this data will bring forth a breakthrough in our ability to describe and model organic aerosols and to assess their environmental impacts, such as atmospheric nitrogen nutrient inputs to ecosystems.