The Investigation of Organic Nitrogen Species and Inorganic Constituents in Particulate Matter in Polluted Asian Megacities

Delhi and Beijing are known to experience exceedingly high and often dangerous levels of outdoor ambient air pollution, ubiquitously spread as to expose tens of millions of inhabitants. Particulate Matter of diameter < 2.5 μm (PM2.5) is one of the most harmful and abundant pollutants, adversely affecting both human health and the environment. The inorganic constituents comprise a substantial (and often dominant) fraction of PM2.5 which directly affects the particle’s physical and chemical properties. In addition, Organic Nitrogen (ON) species are a highly carcinogenic and mutagenic class of species known to be present in megacity PM2.5 and contribute greatly to the toxic nature of Asian megacity PM2.5.
Ion Chromatography (IC) was used on filter samples collected during the Air Pollution and Human Health (APHH) campaigns during Delhi pre- (DPEM) and post-monsoon (DPOM) seasons and Beijing winter (BWIN) and summer (BSUM) seasons. A substantially higher fraction of ionic species were present during the warmer months of DPEM (78.5 %) and BSUM (62.5 %), compared to the cooler months of DPOM (33.7 %) and BWIN (35.7 %) which was attributed to higher photooxidation under higher solar flux, temperatures and differing emission sources.
This thesis also explores the reaction of highly abundant BVOCs and the NO3 radical in the formation of Org-NO3 species during chamber experiments of the NO3ISOP campaign using a Particle-Into-Liquid-Sampler coupled to IC (PILS-IC). The identification of acid catalysed hydrolysis of these species has indicated that the formation of Org-NO3 within Asian megacities may be a contributing factor to NO3-. A comprehensive Two-Dimensional Gas Chromatography Coupled to Nitrogen Chemiluminescence Detection (GC × GC - NCD) technique was also exploited to assess the concentration of nitrosamines during BWIN. It was found that inhabitants in Beijing are at significantly higher risk of developing cancer from PM2.5 compared to London.