Atmospheric aerosols local–regional discrimination for a semi-urban area in India

• Aerosol characterisation of one year measurements
• Higher SOC may contribute to new particle formation, increased growth of aerosols, and potential of cloud condensation nuclei.
• Influence of both local as well as long-range pollutants
• Overlapping and clustering of spatial sectors in terms of source origin is evolved.
• The volume size distributions were in close agreement with source factors.
• PM2.5 is still a respiratory health threat in the region.

In the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI), measurements were carried out with a sequential filter-based aerosol sampler and on-line instruments for aerosol composition and behaviour at Gual Pahari, close to New Delhi. In fine mode (PM2.5), the secondary organic carbon (SOC) to total organic carbon ratio was 46%. This indicated that condensation of SOC on fine size particles could occur rapidly which may be related to the growth of aerosols and the potential to the size of cloud condensation nuclei in the region.Source region discrimination was improved significantly through coupling conditional probability functions with receptor modelling, and validation through volume size distribution. The air masses from industrial and dense populated regions show a mix of local as well as regional emissions to fine mode aerosols. The back-trajectory analysis captured the long-range transport of sea-salt aerosols enriched with mineral dust. The surface wind directions identified the influence of local emission activities.