Environmental context. Amines are of interest to atmospheric chemistry as they may be important gas-phase precursors for secondary aerosol formation. We describe a mass spectrometer for real-time in-situ measurements of gaseous alkyl amines in the atmosphere. This measurement technique will help to evaluate the contribution of amines to the formation of secondary aerosols, including secondary organic aerosol and new particle formation.

Environmental context. The effects of atmospheric fine particulate matter (aerosols) on climate and human health can be strongly influenced by the chemical transformations that the particles undergo in the atmosphere, but these ‘aging’ reactions are poorly understood. Here diesel exhaust particles are aged in the laboratory to better understand how they could evolve in the atmosphere, and subtle but unmistakable changes in their chemical composition are found. These results provide a more complete picture of the atmospheric evolution of aerosols for inclusion in atmospheric models.

Environmental context. Aqueous-phase processes in fogs and clouds can significantly alter atmospheric fine particles with consequences for climate and human health. We studied the influence of fog and rain on atmospheric aerosol properties, and show that aqueous-phase reactions contribute to the production of secondary aerosol species and change significantly the composition and microphysical properties of aerosols. In contrast, rains effectively remove aerosols and reduce their concentrations.

Environmental context. Secondary organic aerosols formed from the oxidation of volatile organic compounds make a significant contribution to atmospheric particulate matter, which in turn affects both global climate change and human health. We investigate the mechanisms of formation and the chemical properties of secondary organic aerosols derived from isoprene, the most abundant non-methane-based, volatile organic compound emitted into the Earth’s atmosphere. However, the exact manner in which these aerosols are formed, and how they are affected by environmental conditions, remains unclear.

Environmental context. Secondary organic aerosols derived from biogenic gases are ubiquitous in the atmosphere. We found that biogenic secondary organic aerosol in Nepal accounted for 6 to 23 % of organic carbon. Primary and secondary biogenic sources combined accounted for approximately half of the observed organic aerosol, suggesting that additional aerosol sources or precursors are significant in this region of the Himalayas.

Environmental context. Aerosol water-soluble organic carbon is a complex mixture of thousands of organic compounds which may have a significant influence on the climate-relevant properties of atmospheric aerosols. Using ultrahigh resolution mass spectrometry, more than 4000 individual molecular formulas were identified in non-urban aerosol water-soluble organic carbon. A significant fraction of the assigned molecular formulas were matched to assigned molecular formulas of laboratory generated secondary organic aerosols.

Environmental context. Understanding the molecular composition and chemical transformations of organic aerosols during atmospheric aging is a major challenge in atmospheric chemistry. Ultra-high resolution mass spectrometry can provide detailed information on the molecular composition of organic aerosols. Aerosol samples collected in summer and winter at an urban site are characterised and compared in detail with respect to the elemental composition of their components, especially nitrogen- and sulfur-containing compounds, and are discussed with respect to atmospheric formation processes.