Abstract
BackgroundAn Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to investigate the size and chemical composition of fine concentrated ambient particles (CAPs) in the size range 0.2–2.6 μm produced by a Versatile Aerosol Concentration Enrichment System (VACES) contained within the Mobile Ambient Particle Concentrator Exposure Laboratory (MAPCEL). The data were collected during a study of human exposure to CAPs, in Edinburgh (UK), in February-March 2004. The air flow prior to, and post, concentration in the VACES was sampled in turn into the ATOFMS, which provides simultaneous size and positive and negative mass spectral data on individual fine particles.ResultsThe particle size distribution was unaltered by the concentrator over the size range 0.2–2.6 μm, with an average enrichment factor during this study of ~5 (after dilution of the final air stream). The mass spectra from single particles were objectively grouped into 20 clusters using the multivariate K-means algorithm and then further grouped manually, according to similarity in composition and time sequence, into 8 main clusters. The particle ensemble was dominated by pure and reacted sea salt and other coarse inorganic dusts (as a consequence of the prevailing maritime-source climatology during the study), with relatively minor contributions from carbonaceous and secondary material. Very minor variations in particle composition were noted pre- and post-particle concentration, but overall there was no evidence of any significant change in particle composition.ConclusionThese results confirm, via single particle analysis, the preservation of the size distribution and chemical composition of fine ambient PM in the size range 0.2–2.6 μm after passage through the VACES concentration instrumentation.
Highlights
An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to investigate the size and chemical composition of fine concentrated ambient particles (CAPs) in the size range 0.2–2.6 μm produced by a Versatile Aerosol Concentration Enrichment System (VACES) contained within the Mobile Ambient Particle Concentrator Exposure Laboratory (MAPCEL)
The ATOFMS detects particles with diameter in the range 0.2– 3.2 μm, only a proportion of particles are detected, and this proportion varies with particle diameter [16,20]
It should be recognised that EFs derived from ATOFMS data will be subject to uncertainty introduced by the inevitable instant-by-instant variability in the proportion of particles detected by the ATOFMS
Summary
An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to investigate the size and chemical composition of fine concentrated ambient particles (CAPs) in the size range 0.2–2.6 μm produced by a Versatile Aerosol Concentration Enrichment System (VACES) contained within the Mobile Ambient Particle Concentrator Exposure Laboratory (MAPCEL). Two of the most important challenges for researchers in this field are to establish (i) the physicochemical properties of the inhaled particles responsible for observed illhealth associations, and (ii) the consequent biological mechanisms of causation. Progress on the former requires enhanced size and chemical characterisation of the ambient particles to which populations or panel members are exposed, whilst progress on the latter requires experiments testing potential causal mechanisms either in vitro or, ideally, in vivo using model or genuine particulate matter. In example studies using human volunteers, exposure to fine or coarse CAPs has been shown to induce mild pulmonary inflammation in healthy adults [7], and to change heart rate variability in the elderly [8] and in asthmatic and healthy younger adults [9]
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