Characterization of urban particulate matter for a health-related study in southern Finland

Particulate matter was physically and chemically characterized in November 2005–May 2006 concurrently with an epidemiological study among cardiac patients in Kotka, Finland. The daily PM2.5 concentrations (campaign mean 10.6 g m–3) typically displayed a similar pattern to that in Helsinki, suggesting that the air masses were well-mixed over a large area of southern Finland. There were occasionally increased short-term PM2.5 and particle number concentrations, most likely due to emissions from local industrial sources. A strong relationship was detected between high particle number concentrations (> 30 000 cm–3) and north-easterly winds. PM2.5, black carbon (BC) or nitrogen oxides (NOx) did not show corresponding connection. The mean contribution of local traffic to BC and NOx were estimated at 30% and 55%, respectively, during the campaign. The main chemical component of PM2.5 was particulate organic matter (37% ± 14%) followed by non-sea-salt sulphate (26% ± 11%), whereas main component of PM2.5–10 was soil-derived crustal material (49% ± 11%).