. The last decade has seen tremendous advances in atmospheric aerosol particle research that is often performed in the context of climate and global change science. Biomass burning, one of the largest sources of accumulation mode particles globally, has been closely studied for its radiative, geochemical, and dynamic impacts. These studies have taken many forms including laboratory burns, in situ experiments, remote sensing, and modeling. While the differing perspectives of these studies have ultimately improved our qualitative understanding of biomass-burning issues, the varied nature of the work make inter-comparisons and resolutions of some specific issues difficult. In short, the literature base has become a milieu of small pieces of the biomass-burning puzzle. This manuscript, the second part of four, examines the properties of biomass-burning particle emissions. Here we review and discuss the literature concerning the measurement of smoke particle size, chemistry, thermodynamic properties, and emission factors. Where appropriate, critiques of measurement techniques are presented. We show that very large differences in measured particle properties have appeared in the literature, in particular with regards to particle carbon budgets. We investigate emissions uncertainties using scale analyses, which shows that while emission factors for grass and brush are relatively well known, very large uncertainties still exist in emission factors of boreal, temperate and some tropical forests. Based on an uncertainty analysis of the community data set of biomass burning measurements, we present simplified models for particle size and emission factors. We close this review paper with a discussion of the community experimental data, point to lapses in the data set, and prioritize future research topics.

/pdf/a-review-of-biomass-burning-emissions-part-iii-intensive-4onlsstr3d.pdf

A review of biomass burning emissions part III: intensive optical properties of biomass burning particles

A review has been written to assess the sources, fate and behavior of polycyclic aromatic hydrocarbons (PAH) in the atmosphere. PAH are formed mainly by anthropogenic processes, especially the combustion of organic fuels. PAH concentration in air will reflect the location of source emitters, with high concentrations corresponding with urban and industrial areas. PAH are however ubiquitous contaminants of the environment having been detected in remote areas of the world. This is thought to be due to long term transport in the atmosphere. PAH can also be subjected to chemical and/ or photochemical change whilst resident in the atmosphere prior to their removal by either wet or dry deposition.

A review of atmospheric polycyclic aromatic hydrocarbons : sources, fate and behavior

Quantification of urban organic aerosols at a molecular level: Identification, abundance and seasonal variation

Polycyclic aromatic hydrocarbons (PAHs) are of considerable concern due to their well-recognised toxicity and especially due to the carcinogenic hazard which they present. PAHs are semi-volatile and therefore partition between vapour and condensed phases in the atmosphere and both the vapour and particulate forms undergo chemical reactions. This article briefly reviews the current understanding of vapour-particle partitioning of PAHs and the PAH deposition processes, and in greater detail, their chemical reactions. PAHs are reactive towards a number of atmospheric oxidants, most notably the hydroxyl radical, ozone, the nitrate radical (NO3) and nitrogen dioxide. Rate coefficient data are reviewed for reactions of lower molecular weight PAH vapour with these species as well as for heterogeneous reactions of higher molecular weight compounds. Whereas the data for reactions of the 2-3-ring PAH vapour are quite extensive and generally consistent, such data are mostly lacking for the 4-ring PAHs and the heterogeneous rate data (5 and more rings), which are dependent on the substrate type and reaction conditions, are less comprehensive. The atmospheric reactions of PAH lead to the formation of oxy and nitro derivatives, reviewed here, too. Finally, the capacity of PAHs for long range transport and the results of numerical model studies are described. Research needs are identified.

/pdf/chemical-reactivity-and-long-range-transport-potential-of-50ilbeaous.pdf

Chemical reactivity and long-range transport potential of polycyclic aromatic hydrocarbons - a review

The diesel engine is the most efficient prime mover commonly available today. Diesel engines move a large portion of the world's goods, power much of the world's equipment, and generate electricity more economically than any other device in their size range. But the diesel is one of the largest contributors to environmental pollution problems worldwide, and will remain so, with large increases expected in vehicle population and vehicle miles traveled (VMT) causing ever-increasing global emissions. Diesel emissions contribute to the development of cancer; cardiovascular and respiratory health effects; pollution of air, water, and soil; soiling; reductions in visibility; and global climate change. Where instituted, control programs have been effective in reducing diesel fleet emissions. Fuel changes, such as reduced sulfur and aromatics content, have resulted in immediate improvements across the entire diesel on- and off-road fleet, and promise more improvements with future control. In the United States, for example, 49-state (non-California) off-road diesel fuel sulfur content is 10 times higher than that of national on-road diesel fuel. Significantly reducing this sulfur content would reduce secondary particulate matter (PM) formation and allow the use of control technologies that have proven effective in the on-road arena. The use of essentially zero-sulfur fuels, such as natural gas, in heavy-duty applications is also expected to continue. Technology changes, such as engine modifications, exhaust gas recirculation, and catalytic aftertreatment, take longer to fully implement, due to slow fleet turnover. However, they eventually result in significant emission reductions and will be continued on an ever-widening basis in the United States and worldwide. New technologies, such as hybrids and fuel cells, show significant promise in reducing emissions from sources currently dominated by diesel use. Lastly, the turnover of trucks and especially off-road equipment is slow; pollution control agencies need to address existing emissions with in-use programs, such as exhaust trap retrofits and smoke inspections. Such a program is underway in California. These and other steps that can be continued and improved will allow the use of the diesel engine, with its superior fuel consumption, to continue to benefit society while greatly reducing its negative environmental and health impacts. The next ten years can and must become the "Decade of Clean Diesel."

https://energy.gov/sites/prod/files/2014/03/f9/2002_deer_lloyd.pdf

Diesel engines: environmental impact and control.

Little is known about the stability of nitro-polycyclic aromatic hydrocarbons (NPAH) on atmospheric aerosols. In this study, the photostability of particle-associated NPAH was investigated under natural sunlight. Deuterated and native NPAH along with diesel exhaust or wood smoke particles were added to a 190-m3 outdoor smog chamber and permitted to age under sunlight in cold and warm temperatures. Ozone (O3), nitrogen oxides (NOx), and volatile hydrocarbons in the gas phase were monitored. A sampling train consisting of an annular denuder filter plus another denuder was used for the collection of gas- and particle-phase PAH and NPAH. Rapid degradation of deuterated and native NPAH was observed in sunlight, over a temperature range of −19 to +38 °C. Deuterated 1-nitropyrene (d9-1NP) displayed the same behavior as native 1-nitropyrene (1NP), which indicated that it was reasonable to use deuterated NPAH as substitutes for native NPAH. The photolysis rate of NPAH was referenced to the NO2 photolysis rate in o...

Photostability of Nitro-Polycyclic Aromatic Hydrocarbons on Combustion Soot Particles in Sunlight

Little is known about atmospheric reaction mechanisms or products of polycyclic aromatic hydrocarbons associated with aerosol particles. Products of benz[a]anthracene photodegradation were determined after irradiation of benz[a]anthracene in the presence of three common constituents of atmospheric aerosols previously found to accelerate benz[a]anthracene photodegradation; 9,10-anthraquinone, 9-xanthone, and vanillin. Irradiation was carried out in toluene, benzene, and benzene-d6, and products were analyzed by GCMS, FTIR, and NMR. Among the major tentatively identified products were benz[a]anthracene-7,12-dione, phthalic acid, phthalic anhydride, and 1,2-benzenedicarboxaldehyde. Evidence for production of polycylic dicarboxylic acids and dialdehydes was also obtained. Product distribution was strongly influenced by solvent effects and dissolved aerosol constituents. The results suggest that products of PAH photodegradation in atmospheric aerosols are likely to be quite complex and strongly influenced by t...

Products of benz[a]anthracene photodegradation in the presence of known organic constituents of atmospheric aerosols

Polynuclear aromatic hydrocarbon degradation by heterogeneous reactions with N2O5 on atmospheric particles

published in Advance ACS Abstracts, September 15, 1994. Envlron. Scl. Technol., Vol. 28, No. 12, 1994 2153

Effect of composition and state of organic components on polycyclic aromatic hydrocarbon decay in atmospheric aerosols.

Benz[a]anthracene photodegradation rates in toluene solutions containing co-solutes were compared using a photochemical turntable reactor. Each co-solute investigated was found at relatively high concentrations in atmospheric particulate matter. Benz-[a]anthracene photodegradation was accelerated by the presence of 9,10-anthraquinone, xanthone, 2-furaldehyde, 2,4-dimethylbenzaldehyde, 9,10-phenanthrenequinone, 2-acetylfuran, and furfuryl alcohol. Decay was inhibited by 7-benzanthrone. Other compounds had little or no effect on benz[a]-anthracene decay. Possible photochemical reaction mechanisms are discussed, and it is concluded that several competing mechanisms may be responsible, including electronic energytransferfollowed by reaction from the triplet state, singlet oxygen attack, and radical chain reactions initiated by hydrogen abstraction of aerosol constituents. The results suggest that particle organic composition can strongly influence polycyclic aromatic hydrocarbon photodegradation rates in atmospheric aerosols.

Stephen R. McDow

Papers

Photostability of Nitro-Polycyclic Aromatic Hydrocarbons on Combustion Soot Particles in Sunlight

Products of benz[a]anthracene photodegradation in the presence of known organic constituents of atmospheric aerosols

Polynuclear aromatic hydrocarbon degradation by heterogeneous reactions with N2O5 on atmospheric particles

Effect of composition and state of organic components on polycyclic aromatic hydrocarbon decay in atmospheric aerosols.

Benz[a]anthracene photodegradation in the presence of known organic constituents of atmospheric aerosols