Analysis of polycyclic aromatic hydrocarbons(PAHs) in ambient air
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Date
2001-11-16
Authors
Karunaratne, D. G. G. P.
Jeyalalitha, E.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya, Peradeniya, Sri Lanka
Abstract
Most studies of emissions from combustion for energy generation have been aimed at
abating inorganic emissions COₓ, NOₓ and SOₓ owing to the strict legislations to which these
compounds have been subjected and because they are emitted in large amounts in comparison
to organic emissions. Technical modifications to reduce inorganic emissions have affected
organic emissions so that growing attention is being paid now to volatile organic compounds,
particularly to polycyclic aromatic compounds (PACs) and, especially to polycyclic aromatic
hydrocarbons (PAHs) owing to their carcinogenic character.
Although there is no definitive legislation concerning PAH abatement, the
Environmental Protection Agency (EPA) has fixed 16 PAHs as priority pollutants, the last of
which was included in 1997. These compounds are as follows: naphthalene, acenaphthylene,
acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo (a)
anthracene, benzo( b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno( 1,2,3-c,d)
pyrene, benzo(g,h,i)perylene and dibenzo(a,h)antracene. It is expected that air quality would
improve soon if PAH emission was controlled. The simplest member of the PAH family is
naphthalene, a two-ring compound which can be found in the vapour phase in the atmosphere.
Three-, four-, and five-ring compounds can also be found in both the vapor and particulate
phases in the atmosphere. PAHs consisting of five or more rings tend to be solids adsorbed onto
other particulate matter in the atmosphere. A widely recognized five-ring PAH compound is
benzo (a) pyrene. Naphthalene is by far the predominant airborne PAH. Night time
concentrations of naphthalene are greater than daytime concentrations because of the hydroxyl
radial reaction mechanism which removes naphthalene from the atmosphere in daylight. As
ring size increases, the effect of this removal mechanism diminishes. These gaseous- phase
reactions are important because they also lead to the formation of nitro-P AHs which are direct
acting mutagens.
High volume air samplers equipped with polyurethane foam (PUF) adsorbent have been
a standard device for monitoring semi-volatile organic compounds (SVOCs) in air for a number
of years. In such samplers, air is drawn past a filter to retain particle-phase SVOCs and then
past the PUF adsorbent to retain vopour-phase SVOCs. This sampling geometry has the
potential to cause sampling artifacts, most notably "blow-oft" whereby SVOCs which are
adsorbed on particulate matter in ambient air may be volatilized from the particles after
collection on a filter medium, thus enhancing the apparent vapour-phase concentration. A
second effect which may occur is "blow-on" whereby vapor-phase SVOCs in ambient air are
adsorbed on the filter media or on accumulated particulate and/or organic matter on the surface
of the filter media. This would result in an apparent increase in the particle-phase loading of the
SVOC in question. It is important to note that both of these phenomena can occur
simultaneously.
Description
Keywords
Polycyclic , Aromatic , Hydrocarbons
Citation
Proceedings & abstracts of the Annual Research Sessions 2001,University of Peradeniya, Peradeniya, Sri Lanka,pp.183