Characterisation of selected speciated organic compounds associated with particulate matter in London

Total suspended particulate matter (TSP) was collected and analysed at two sites in central and north London during 1995/6 for particulate-associated total organic carbon (TOC), particulate elemental carbon (PEC), 16 polycycl ic aromatic hydrocarbons (PAHs) and 23 n-alkanes. The analysis revealed sli ghtly higher concentrations of all of these substances at the central Londo n location and generally low correlations between variables. Overall, PEC w as measured as 1-13% of TSP, whilst TOC was measured as 7-45 % of TSP. Seas onal differences in concentrations were identified at both sites, with high er concentrations of combustion related compounds occurring in winter and a utumn. The dominant PAH compounds were found to be the higher molecular wei ght compounds, namely BghiP, BaA and Chrys. n-alkane compound distributions between C-10 and C-34 showed that the highest concentrations of compounds were between C-21 and C-29 Three methods were used to identify specific sou rces of particulate-associated organic compounds. Ratios of PAHs indicated a dominant petroleum source at both sites, with a higher diesel component a t the central London site. Carbon preference index (CPI) values of 1.03 and 1.28 for the central and north London sites, respectively, indicated a str onger anthropogenic (vehicular) influence at the central London location. U sing principal component analysis (PCA), key principal components (PCs) wer e extracted from each data set. These PCs collectively accounted for 76.4 a nd 78.1% of the total variations within the north and central London data s ets, respectively, although differentiation of sources proved difficult bec ause the organic compounds monitored may not be statistically independent. (C) 2001 Elsevier Science Ltd. All rights reserved.