Seasonal variation of PM10 main constituents in two valleys of the French Alps. I: EC/OC fractions

[摘要] Daily PM₁₀ samples were collected at two urban sites within two valleysin the French Alps (Chamonix and St Jean de Maurienne) during a period oftwo and a half years. The carbonaceous species EC (elemental carbon) and OC(organic carbon) were analysed to investigate the possible sources of EC andOC, and their seasonal variations. Mean OC concentrations are in the veryhigh range of concentrations measured for other European sites, andrepresent at least one third of the PM₁₀ mass on each site. On thebasis of the comparison between EC and OC concentrations with severaltracers, we were able to show that their main sources are local primarycombustion sources. Biomass burning emissions (residential heating) have asignificant impact on OC concentrations while heavy duty traffic emissionshave an impact only on EC concentrations. Finally, we estimated thecontribution of SOA (secondary organic carbon) to OC, using the EC-to-OCprimary ratio method (Castro et al., 1999) and demonstrated that thecalculation of SOA mass with this method is highly uncertain, if thehypothesis of a constant primary EC-to-OC ratio is not very closelyexamined.

[学科分类] 大气科学