Size fractionated PM chemical composition characteristics at microenvironments with contrasting local emission scenarios

KRYSTAL J. Godri (1,2), Roy M. Harrison (2), Ian S. Mudway (1), Frank J. Kelly (1), Maciek M. Strak (3), Maaike Steenhof (4), Paul H.B. Fokkens (3), A. John F. Boere (3), Daan L.A.C. Leseman (3), Kaas Meliefste (4), G. Hoek (4), Bert Brunekreef (4), Erik Lebret (3), Ilse Gosens (3), Flemming R. Cassee (3), Nicole A.H. Janssen (3)

(1) MRC-HPA Center for Environment and Health, King’s College London, London, United Kingdom, (2) Division of Environmental Health & Risk Management, University of Birmingham, Edgbaston, United Kingdom, (3) RIVM (National Institute for Public Health and the Environment), Bilthoven, the Netherlands, (4) IRAS (Institute for Risk Assessment Sciences), Utrecht University, Utrecht, the Netherlands

     Abstract Number: 311
     Last modified: November 9, 2009

Abstract
Background: Exposure to elevated ambient particulate matter (PM) concentrations has been associated with negative cardio-respiratory health effects. It has been hypothesised that the magnitude and type of response observed is a function of PM physical and chemical characteristics; with certain PM components identified as contributing to the observed toxicity: transition metals, surface adsorbed organics and endotoxin. The Risks of Airborne Particles: a hybrid Toxicological- Epidemiological Study (RAPTES) seeks to investigate how heterogeneities in PM composition affect the magnitude of acute airway and systemic responses in humans exposed to ambient PM in microenvironments with source specific emissions.

Objective: To characterise the chemical characteristics of size fractionated PM at selected microenvironments with contrasting air pollution sources including traffic (urban intersection, carriageway, diesel), background (farm, urban background) and industrial (steel mill, harbour) locations.

Methods: Fine and coarse PM samples were collected at seven locations with a high volume cascade impactor. Sites were visited 4 to 10 times for six hour sampling campaigns running approximately between 9:00 and 15:00. Chemical composition characterisation included water soluble inorganic ions (Cl$^-, NO$_3$^-, SO$_4$^2-, PO$_4$^3-, NH$_4$^+, Na$^+, K$^+, Ca$^2+), total and water soluble trace metals (Al, Ba, Cr, Cu, Fe, Hf, Ni, Sb, Ti, V, Zn), organic (OC) and elemental (EC) carbon, plus endotoxin. A total of 18 polycyclic aromatic hydrocarbons (PAHs) and 16 quinones (including 1,4-benzoquinone, 1,2-naphthoquinone, 1,4-naphthoquinone, 9,10-phenanthrene quinone, 9,10-anthraquinone) were also quantified.

Results: Total trace metal concentrations of Fe, Cu, Sb, Cu and Cr were the greatest at the traffic microenvironments in both the fine and coarse fractions indicative of non-tail pipe vehicular emission contributions. Equivalent trends in PM$_2.5 OC/EC ratios were found across the traffic sites (0.59+/-0.02) suggestive of diesel emissions. Significantly decreased EC concentrations were observed at the background sites yielding OC/EC ratios of 1.53+/-0.42. This carbonaceous material ratio was further increased at the industrial microenvironments (2.22+/-0.02) given elevated OC concentrations. Total PAH concentrations across site types were not significantly different (mean 3.44+/-0.88 ng m$^-3); urban background site excluded (8.18 ng m$^-3) due to a local combustion source rich in low molecular weight (LMW) PAHs. Concentrations of high molecular weight (HMW) PAHs at the carriageway and diesel traffic sites were 2.5 times greater than LMW PAH concentrations. Elevated LMW PAH concentrations (specifically fluoranthrene and pyrene) occurred in parallel with enrichment of Ni and V concentrations at the intersection site. This compositional signature allied to the proximity of shipping waterways implicated fuel oil combustion as a potential emission source. The steel mill site was also confounded by shipping related emissions noted by elevated concentrations of these representative trace metal and PAH species.

Conclusions: Non-tail pipe emissions yielded elevated total trace metal concentrations at all traffic sites compared to other sampling locations. Microenvironments were not isolated to a single emission source. Proximity of sites to shipping waterways resulted in a PM enrichment with Ni, V and LMW PAHs.