An experimental technique for studying heterogeneous reactions of polyaromatic hydrocarbons on particle surfaces

Abstract

An experimental technique for studying atmospheric heterogeneous reactions of polyaromatic hydrocarbons (PAH) on particle surfaces is reported. Particle bound organics were reacted in a 200 liter Teflon continuous stirred tank reactor (CSTR), with vapor phase oxidants. To provide a source of chemically stable particles for the CSTR, soot particles from a residential wood stove were first introduced during under darkness into a 25 m' outdoor Teflon chamber. Air containing the particles was then added at a constant flow to the CSTR. The rates of heterogeneous reactions were obtained by comparing reacted particle samples with unreacted ones. The derivation of rate expressions for heterogeneous reactions in the CSTR is described. The use of the technique for a study of the nitration of selected soot particle bound PAH species by NOz and HNO, is demonstrated.

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

“…The occurrence of heterogeneous reactions of PAHs with NO 2 was initially demonstrated through experimental studies exposing PAHs on various substrates to NO 2 in the presence of nitric acid, at ambient or elevated levels, resulting in the formation of nitro-PAH products. This has been observed on a number of different surfaces including filters, 267,268 wood smoke particles, 269 soot particles, 270 propane flame-generated soot, 271 coal fly ash, 272 silica plates, 273 274 Details of these studies are summarized by Finlayson-Pitts and Pitts. 1 More recently, full kinetic investigations of this process have been carried out with rate coefficient values for the reaction of NO 2 adsorbed on various particle surfaces calculated.…”

Quantifying the reactive uptake of OH by organic aerosols in a continuous flow stirred tank reactor

“…(2). 26 To reliably determine k f in this way requires the concentrations in the CFSTR to reach steady state which can take many hours.…”

“…24,25 Fewer studies have applied CFSTR's to heterogeneous reactions on aerosol particles. 26,27 In these previous studies, the rate of a heterogeneous or homogeneous reaction inside a CFSTR was obtained by measuring the difference between the reactant concentrations entering and exiting the reaction volume divided by the residence time, once the CFSTR has reached steady state. 26,27 In this paper, the photochemical evolution of aerosol particles within a CFSTR is studied in real time by monitoring the removal of particle phase reactant molecules.…”

Characteristics of PM2.5-Bound Polycyclic Aromatic Hydrocarbons and Nitro-Polycyclic Aromatic Hydrocarbons at A Roadside Air Pollution Monitoring Station in Kanazawa, Japan

“…PAHs originate from fossil fuel and biomass combustion [7]. Some NPAHs are directly emitted from combustion sources [5], and several NPAHs are formed from the reactions of their parent PAHs with hydroxyl (OH) and nitrate (NO 3 ) radicals in the presence of nitrogen oxides (NO x ) [8,9]. Because individual congeners are produced in similar ways, PAHs and NPAHs are often considered mixtures.…”