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

Abstract

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.

Global long-range transport and lung cancer risk from polycyclic aromatic hydrocarbons shielded by coatings of organic aerosol

“…Gas-phase reaction of BaP with the hydroxyl radical (OH) is included. The second-order rate coefficient for reactions of BaP with OH is set as 5 × 10 −11 cm 3 per molecule per second (11,12).…”

“…We also include heterogeneous reactions of particle-phase BaP with ozone and OH radicals (12,18,19). We assume a constant second-order heterogeneous reaction rate constant with OH radicals (2.9 × 10 −13 cm 3 per molecule per second) (48).…”

“…Despite decades of research, the mechanisms responsible for the observed atmospheric persistence and long-range transport of PAHs are not well understood, mainly due to incomplete knowledge of gas−particle partitioning and chemical loss rates of PAHs (9). Although gasphase BaP is rapidly degraded by oxidants such as OH radicals (10)(11)(12), most of the gaseous BaP rapidly partitions to atmospheric particulate matter due to its low volatility (12). Therefore, heterogeneous chemical degradation of particle-bound BaP is an important loss mechanism (13)(14)(15)(16)(17)(18)(19).…”

Characterization of Polycyclic Aromatic Hydrocarbons (PAHs), Iron and Black Carbon within Street Dust from a Steel Industrial City, Central China

“…PAHs are ubiquitous pollutants in different environment mediums, such as atmosphere, soil, sediment and surface dust (Xing et al, 2011;Jiang et al, 2014;Pozo et al, 2015). Atmosphere is a major approach for the transport and deposition of PAHs Keyte et al, 2013), and the aromatic hydrocarbon in atmospheric adhere mainly on theatmospheric particulate matter.…”

Long-range atmospheric transport of polycyclic aromatic hydrocarbons is worldwide problem - results from measurements at remote sites and modelling

“…1,5 The relevance of PAHs is given by their potential to form carcinogenic and mutagenic metabolites and, partly, by being carcinogenic themselves.…”