Insights into the Composition and Sources of Rural, Urban and Roadside Carbonaceous PM10

Insights into the nature and sources of the urban and roadside increments in carbonaceous PM10 are gained from bulk chemical analyses on daily filter samples collected at a roadside, urban background and rural site in Edinburgh, UK (not all sampling contemporaneous). The concentrations of PM10 water-soluble organic matter (WSOM) at the three sites were similar, and (where measured concurrently) strongly correlated, indicating a uniform background source, in contrast to the black carbon component (quantified by filter optical reflectance) whose average concentrations at urban background and roadside were, respectively, about 3 and 7 times greater than at the rural site, indicating local urban sources. BC was not a major component of PM10 but was a major component of the urban and roadside PM10 increments (∼50% and ∼60% respectively). The roadside WSOM had greater hydrophobicity than the urban background WSOM. UV-vis spectra indicated increased prevalence of unsaturated bonds and conjugation in urban background WSOM in winter compared with summer. This is consistent with both summertime photochemical production of particle OM and maritime primary aliphatic WSOM. Raman microscopy of a small subset of samples indicated carbon functionality ranged between diesel-like material and more complex humic-like material. Results overall indicate the presence of a background functionalized carbonaceous material, with local BC sources superimposed.