Methods for Determination of Benzo(a)pyrene and High Molecular Weight (>300 Da) Polycyclic Aromatic Hydrocarbons in Particulate Matter from Ambient Air and Vehicle Exhausts
Sammanfattning: Air pollution with particulate matter (PM) raises considerable concern because of its adverse effects on human health. For this reason, and because the mechanisms of PM toxicity are not fully known, there is an urgent need to determine the chemical constituents of atmospheric PM, especially PM emanating from traffic - a major source of urban PM. This thesis describes analytical methods that have been developed for determining polycyclic aromatic hydrocarbons (PAHs) in ambient air and vehicle exhaust PM, focusing particularly on benzo(a)pyrene (B(a)P) and the dibenzopyrenes: dibenzo(a,l)pyrene, dibenzo(a,e)pyrene, dibenzo(a,i)pyrene and dibenzo(a,h)pyrene. Trace amounts in complex matrices have been met by coupling parts or the entire clean-up step using liquid chromatography on-line with the analysis step using gas chromatography-mass spectrometry into one automated system. Application of the methodology, using either ultrasonic assisted extraction (USE) or accelerated solvent extraction (ASE), to a National Institute of Standards and Technology (NIST) urban air standard reference material (SRM) yielded comparable or higher concentrations than the assigned NIST values, validating the approach. However, ASE provided higher extraction yields from diesel particulate SRMs than USE, and ASE of diesel SRMs generally yielded higher concentrations than the corresponding NIST values. Concentrations of dibenzopyrenes in Stockholm air PM, and gasoline- and diesel-fuelled vehicle emissions (ng/km), are reported for the first time. When adjusted in terms of their relative carcinogenic potencies, the dibenzopyrenes were found to pose greater carcinogenic hazards than B(a)P, indicating that the current use of B(a)P as a marker probably leads to underestimates of the carcinogenicity of PAHs in ambient air. The developed methods also worked well for analyzing larger molecular weight PAHs: more than 60 and 170 potential PAHs were detected in ambient air PM and diesel PM, respectively.
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