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Title: Bio-monitoring of PM₂.₅ vehicular roadside exposure via INAA and PIXE analysis
Author: Butler, Carol
ISNI:       0000 0001 3512 3463
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2008
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Particle Induced X-ray Analysis (PIXE) and Instrumental Neutron Activation Analysis were undertaken by the author to enable multi-elemental determination in the PM10 range of urban roadside particulate fractions. A thermal neutron flux of 2.3 x 10e12 cm-2s-1 (ICIS, short irradiation) and short time irradiation scheme of 5 - 2 - 5 minutes, (ti - tw - tc) allowed the processing of (delayed) y-ray spectra. Air particulate samples were irradiated by accelerated charged particles from a 2.5 MeV proton beam (tc = 5 minutes); and x-rays emitted by the deexcitation of atoms were detected using a high resolution Si(Li) detector. The accuracy of quantitative results of the relative and absolute standardization methods (against the certified values) in INAA and PIXE analysis have been discussed in this thesis. In INAA, all calculations performed by the absolute standardization method have shown higher accuracy against the certified values; whereas, relative methods showed higher accuracy in the calculated concentration (of certified values) over the absolute method in PIXE. In this study, PM10 roadside measurements have significantly exceeded the national regulatory standards, 24-hour mean of 40 mug/m3 in the size distribution of PM10; predominantly due to intermixing effects from background sites and high amounts of re-suspended coarse fraction associated with minerals and sea spray salts. Trace level concentrations, < 0.02 mug/m3 detected in PM10 collected mass were similar to the urban roadsides concentrations in Glasgow (National Multi-Element Survey); with the exception of Co and Sb, which was three magnitudes higher, at background levels. PM10 (mean values) of 1568 mug/m3 had shown values, seven times higher at major roadside locations in contrast to minor (suburban) roadsides locations; with high particle number concentration (>90%) strongly correlated with traffic density. A selected spectrum of essential trace elements (Br, Ca, Cu, I, Mg, Mn, S) and contaminants (Cd and Pb) was analyzed in sampled hair using nuclear analytical methods. Inter-group (mean) values between 'exposed' and 'control' groups had shown a positive correlation between the fuel derivative metal, V, and most trace metals; with statistical significance (Pearson Correlation, P<0.01) between Ti and Br in the inner city (Major, A, B) roads; and between the indictor metal, V and A1 (r = 0.62), Cu (r =0.70) and Co(r =0.76) at minor roadsides and predominately upwind from the major roadsides. Negative correlation seen between metal concentrations, between exposed and 'control' (i.e. low exposure/background) areas, suggest that ambient concentrations at minor roads, may be influencing (NE and NW) down-wind, pollutant concentrations in the inner city areas. There is also the possibility that lower speed zones in these areas are contributing to higher particulate emissions due to inefficient diesel combustion at lower engine temperatures. Human hair, in general, is able to accumulate the heavy metals with time; and accumulation can be triggered by chronic disease which trigger imbalance in metabolism. Hair samples from residents of high exposure areas (N=72, 20m from major roadsides) and control exposure areas (N=40, 0.75km from major roadsides) were submitted for INAA multi-elemental analysis. All analytical calculations were performed by the absolute standardization method enabling the determination of 17 elements (with Sn, and La, below the analytical detections limits). A general positive correlation between metal concentrations in ambient particulates and levels in hair was seen in populations from both exposure areas. On the whole, the obtained data on elemental content in hair are in agreement with the world average data.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available