Project No: 16307820

Title: Aerosol Organic Nitrogen: Abundance, Sources, and Environmental Impacts in the Pearl River Delta, China

Principal Investigator: Prof. Jianzhen YU

Co-Investigator: Prof. Tzung-May FU

Abstract:

Nitrogenous aerosols are ubiquitous in the atmosphere, serving as a significant source of supplementary nutrition for ecosystems after deposition. They also contribute to a sizable fraction of aerosol mass, impacting visibility and affect global and regional climate. Chemically, they fall into two groups, i.e, inorganic nitrogen (IN) and organic nitrogen (ON). While aerosol IN mainly consists of ammonium (NH4+) and nitrate (NO3-) and their atmospheric abundance and chemistry are largely established, aerosol ON is hugely complex in its molecular composition and the total ON quantity is almost un-characterized. Limited measurements of the water-soluble ON indicate this subfraction of ON is responsible for approximately one third of water-soluble total nitrogen in aerosols on a global scale. The water-insoluble ON has not been previously measured, due to lack of suitable analytical methods, leaving an important data gap in quantifying the various roles that aerosol ON plays in our atmospheric environment and ecosystems.

In this work, we propose to develop an aerosol C, ON & IN analyzer that enables direct and simultaneous measurements of carbon content, ON and IN in filter-based aerosol samples. Aerosol carbonaceous and nitrogenous materials will be thermally evolved from the filter substrate and oxidized to CO2 and nitrogen oxides followed by non-dispersive infrared detection for CO2 and NO-O3 chemiluminescence detection for NO. As IN is associated with zero amount of C and ON is always associated with C, we hypothesize that the novel joint determination of C&N, along with thermal separation, will facilitate the differentiation of ON and IN by this analyzer. This instrument is envisioned to provide fast determination (30 min per analysis) of both ON and IN in filter samples, making feasible to analyze hundreds of filter samples within this project. We aim to quantify the ON presence and to investigate ON sources through analyzing ~300 archived filters of fine particulate matter collected at five sites in the Pearl River Delta, China throughout a year. This large data set will be used in conjunction with regional atmospheric chemistry modeling to assess the environmental impacts of aerosol ON via dry and wet deposition for our study region.