Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

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The formation, properties and impact of secondary organic aerosol: current and emerging issues

http://joenschem.com/yahoo_site_admin/assets/docs/atkinson2000r.93190106.pdf

Atmospheric chemistry of VOCs and NOx

Aqueous ion-containing interfaces are ubiquitous and play a key role in a plethora of physical, chemical, atmospheric, and biological processes, from which we mention just a few illustrative examples: (i) Ions at the air/water interface are important for atmospheric chemistry involving ocean surfaces and seawater aerosols, 1-5 as well as that of the Arctic snowpack covered by sea spray. 6,7 (ii) Many salts (such as NaCl) tend to inhibit bubble coalescence, 8-12 which is one of the reasons why foam is formed when waves break in the ocean but not in freshwater lakes. (iii) Brine rejection occurring at the seawater/ice interface has profound climatic effects in polar regions. 13 (iv) The aqueous electrolyte/metal interface is involved in electrode and corrosion processes. 14,15

Specific ion effects at the air/water interface.

Gas-phase tropospheric chemistry of biogenic volatile organic compounds: a review

http://acmg.seas.harvard.edu/publications/2000/jacob2000.pdf

Heterogeneous chemistry and tropospheric ozone

A combination of experimental, molecular dynamics, and kinetics modeling studies is applied to a system of concentrated aqueous sodium chloride particles suspended in air at room temperature with ozone, irradiated at 254 nanometers to generate hydroxyl radicals. Measurements of the observed gaseous molecular chlorine product are explainable only if reactions at the air-water interface are dominant. Molecular dynamics simulations show the availability of substantial amounts of chloride ions for reaction at the interface, and quantum chemical calculations predict that in the gas phase chloride ions will strongly attract hydroxl radicals. Model extrapolation to the marine boundary layer yields daytime chlorine atom concentrations that are in good agreement with estimates based on field measurements of the decay of selected organics over the Southern Ocean and the North Atlantic. Thus, ion-enhanced interactions with gases at aqueous interfaces may play a more generalized and important role in the chemistry of concentrated inorganic salt solutions than was previously recognized.

https://science.sciencemag.org/content/sci/288/5464/301.full.pdf

Experiments and Simulations of Ion-Enhanced Interfacial Chemistry on Aqueous NaCl Aerosols

Halogen atoms from the reactions of sea-salt particles may play a significant role in the marine boundary layer. Reactions of sodium chloride, the major component of sea-salt particles, with nitrogen oxides generate chlorine atom precursors. However, recent studies suggest there is an additional source of chlorine in the marine troposphere. This study shows that molecular chlorine is generated from the photolysis of ozone in the presence of sea-salt particles above their deliquescence point; this process may also occur in the ocean surface layer. Given the global distribution of ozone, this process may provide a global source of chlorine.

https://science.sciencemag.org/content/sci/279/5347/74.full.pdf

Formation of molecular chlorine from the photolysis of ozone and aqueous sea-salt particles

There is increasing evidence that bromine atoms play a role in tropospheric chemistry in the marine boundary layer. In addition, they are believed to lead to rapid depletion of surface level ozone in the Arctic at polar sunrise. While mechanisms have been proposed for recycling bromine atoms from sea salt particles, the initial reaction(s) leading to the formation of bromine atom precursors is not known. We report here the formation of gaseous Br2 from the reaction of seawater ice with O3 in the dark. These observations suggest that this reaction is a potential source of tropospheric photolyzable bromine in high latitude coastal regions in winter. In addition, it may be the source of the photolyzable bromine gas measured recently in the Arctic by Impey et al. (1997), which is believed to be responsible for the ozone destruction at polar sunrise.

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Bromine activation in the troposphere by the dark reaction of O3 with seawater ice

Infrared absorption cross sections for nitrous acid (HONO) were measured using HONO spectra recorded simultaneously by UV/visible and FTIR spectroscopy. HONO was prepared by the reaction of HCl(g) and NaNO2(s) and was introduced into a 561 L environmental chamber equipped with parallel sets of White optics with total path 52.5 m for UV/visible and FTIR spectroscopy. Alternatively, HONO was prepared in situ by reaction of ClNO(g) with water vapor. Absolute concentrations of HONO were determined independently using the UV spectrum and published UV absorption cross sections. All experiments were carried out at 750 Torr total pressure in N2 at 294−297 K. We report both Q-branch intensities and integrated absorbances for the HONO modes trans-ν3 (1263 cm-1), cis-ν4 (852 cm-1), and trans-ν4 (790 cm-1). For trans-ν3 and cis-ν4 we also include synthetic reference spectra composed of Gaussian functions which give an accurate reproduction of our experimental references, and can easily be generated by computer for ea...

/pdf/infrared-absorption-cross-section-measurements-for-nitrous-z6e80fjvkj.pdf

Infrared Absorption Cross-Section Measurements for Nitrous Acid (HONO) at Room Temperature

Although the formation and reactions of gaseous nitrous acid (HONO) in the atmosphere are of great interest, it is difficult to accurately measure HONO both in the atmosphere and in laboratory systems. We report a new technique for quantifying gaseous HONO in laboratory systems. The method utilizes the reaction of gas phase HONO with an excess of HCl gas to produce nitrosyl chloride (ClNO), which is readily quantified using FTIR. HONO was formed by flowing N2 over the surface of an aqueous HCl solution and through a bed of NaNO2, then directly into a 561 L chamber. An excess of gaseous HCl was added to the chamber to initiate the reaction in N2 at room temperature and 1 atm total pressure. The loss of HONO was followed by DOAS and FTIR and the formation of ClNO was measured by FTIR. While direct measurement of HONO by FTIR is limited by uncertainties in the available infrared absorption cross sections, calibration for ClNO is readily carried out since ClNO can be synthesized with high purity. The stoichio...

M. J. Lakin

Papers

Experiments and Simulations of Ion-Enhanced Interfacial Chemistry on Aqueous NaCl Aerosols

Formation of molecular chlorine from the photolysis of ozone and aqueous sea-salt particles

Bromine activation in the troposphere by the dark reaction of O3 with seawater ice

Infrared Absorption Cross-Section Measurements for Nitrous Acid (HONO) at Room Temperature

A Unique Method for Laboratory Quantification of Gaseous Nitrous Acid (HONO) Using the Reaction HONO + HCl → ClNO + H2O