The polycyclic aromatic hydrocarbon content and mutagenicity of the residue from cane burning and vehicle emissions.
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Date
1992
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Abstract
Polycyclic (or polynuclear) aromatic hydrocarbons (PAHs)
are environmental pollutants produced during the incomplete
combustion of organic matter. Since many of these compounds
have been shown to be mutagenic and/or carcinogenic, an
investigation was initiated into determining the PAH
content and mutagenicity of the ash that remains after
sugar cane crop burning, and the soot deposited on toll
booths by vehicle exhaust emissions.
Due to the large amount of sugar cane farming in the Natal
coastal region and that the favoured method of disposing
unwanted leafy trash is crop burning, concern was expressed
as to the nature of the residue that is formed. PAHs have
been identified in the residues from combusted wood and
straw and, due to their intrinsic similarity to sugar cane,
it was considered that the burning of sugar cane could
generate PAHs.
It is well documented that vehicle exhaust emissions
exhibit mutagenic properties and PAHs have been identified
as the major contributors of this observed mutagenicity.
Since a toll plaza is an area of high traffic density, it
was considered to be an ideal location for an investigation
into the build-up of particles emitted by the passing
vehicles, and to study to what extent the operators are
exposed to harmful compounds. In addition, this sample
acted as a control, since the detection of PAHs and
mutagenic activity in the soot would be an indication that
the correct experimental techniques were being employed.
Samples were collected on site. The sugar cane ash was
collected off a field immediately after burning had taken
place, and the soot was collected either by scraping the
toll booth walls and surrounding areas or by wiping the
surfaces with cotton wool swabs. The organic portion of the
samples was separated from the inorganic and carbonaceous
substances by extraction into a suitable solvent; the use
of both acetone and dichloromethane was investigated. The
extracts were divided into two portions - one was used for
the analysis of PAHs and the other for determining
mutagenic activity. Analysis for PAHs involved subjecting
the extracts to a sample clean-up routine and the use of a
number of analytical techniques to characterise the
components. The mutagenic properties of the samples were
investigated by means of two bacterial mutagenicity tests:
the Salmonella typhimurium assay (the Ames test) and a new
commercially available test kit, the SOS Chromotest.
A number of PARs were identified in the extracts by means
of reverse phase high performance liquid chromatography
(HPLC) with both ultraviolet and fluorescence detection,
the latter being the more sensitive method. Mutagenic
activity was detected for both samples in the Ames test and
for the toll booth soot in the SOS Chromotest, and this
observed mutagenicity was attributed to the presence of the
PAHs.
Description
Thesis (M.Sc.)-University of Natal, Durban, 1992.
Keywords
Polycyclic aromatic hydrocarbons., Automobiles--Motors--Exhaust gas., Mutagenicity testing., Theses--Chemistry., Prescribed burning--Environmental aspects., Polutants--toxicology., Polycyclic aromatic hydrocarbons--Carcinogenicity.