This study aims to determine the concentration of 16 Polycyclic Aromatic
Hydrocarbons (PAHs) in urban soils from West Yorkshire in order to determine what
the factors are controlling their distribution and abundances. Although PAHs have
been reported before from soils and sediments, the majority of these studies have
come from China, sometimes with contrasting results, which emphasises the need to
obtain equivalent data from other areas. Therefore this work provides the first
measurements of their type from the area studied.
Soil samples were collected from one hundred sites across an area from Bradford to
Leeds on two occasions, one in autumn and one in the following summer. The soil
samples were analyzed by X-ray diffraction and all found to have similar mineralogical
composition, which was mainly silica and calcite. Trials using iodine as a marker for
PAHs showed there were notable interactions between the minerals and PAHs, with
calcium carbonate absorbing PAHs much more than silica. There is a negative
correlation between the soil organic content (determined by loss on ignition) and
PAHs, which confirms the PAH-mineral interaction. Gas chromatography with mass
spectrometry (GC-MS) using targeted selected ion monitoring was used to determine
and quantify PAHs in the one hundred soil samples with the aid of PAH external
standards.
The results showed highest concentrations of total PAHs in the same sample from
Leeds from the autumn (1,525 ng/g) and in the summer (1,768 ng/g). In Bradford there
was only moderate pollution of PAHs, the maximum being 122 ng/g. However the
majority of data from Bradford showed lower levels of pollution in both summer and
autumn. On the basis of prior published information, the ratio of these compounds has been used to help in identifying sources. In the samples collected from Bradford in
both seasons and Leeds in autumn the PAH pollution originated from pyrogenic,
biomass and petroleum combustion, however in the summer the source appeared
more to be from a petrogenic source. These ratios in the samples which were collected
from the area between Bradford and Leeds implied pyrogenic, biomass source of
pollution in the autumn, but in the summer another source of organic compounds was
indicated namely petroleum combustion. When the locations were resampled nine
months later, after taking into account within-site variability, there was a strong
indication that the PAH concentrations were higher. This might have been due to a
seasonal effect, but when a further (third) subsample was taken at a later date it
showed a further increase in PAH level which suggests the effect is accumulative
rather than seasonal.
The results were analysed using Principal Component Analysis (PCA) to determine
whether the type of road had an effect on the concentration of the 16 PAHs
compounds, but it was concluded that there was no such effect. However, the distance
from the soil sample to the nearest road did have an effect on the concentration of the
16 PAH compounds, especially in soil samples having the shortest distance to the
road. Traffic volume was also tested and found to influence the PAH concentrations.
It is notable that, comparing the groupings from autumn with those from summer by
cluster analyses, they largely had the same compounds grouping together in both cases; only two compounds differed at all in where they occurred in the clusters, with
consistent patterns of grouping found for the other compounds. These analyses
indicate that PAH compounds behave in a consistent way amongst groups of PAH
compounds. The grouping of PAHs appears linked to their sources rather than number
of rings or molecular weight. / Libyan Government and Embassy
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/19074 |
| Date | January 2018 |
| Creators | Hamed, Heiam A.M. |
| Contributors | Hale, William H.G., Stern, Ben |
| Publisher | University of Bradford, Faculty of Life Sciences |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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