{
  "abstract": "Even though emissions regulations have successfully reduced concentrations of some road traffic-originated air pollutants, road traffic is still an important source of many unregulated emerging pollutants such as semi-volatile ultrafine particles, non-exhaust emissions and volatile organic compounds (VOCs) in urban areas. In addition, road traffic can have season- and location-dependent inverse and indirect effects on the urban aerosol which are not well understood. In our study, we investigate wintertime vehicle fleet emission factors (EF) of road traffic in a street canyon environment in central Helsinki, Finland, by using CO ₂ as a tracer for fuel consumption. We report EFs for particle number and size distribution, black carbon, PM ₁₀ , PM 2.5 , NO x , NO ₂ , NO, CO as well as for organic and inorganic chemical components of particulate matter, and VOCs, including aromatic hydrocarbons, alkanes, and polycyclic aromatic hydrocarbons. The obtained fleet EFs of PM and NO x were considerably higher than required for new vehicles in Europe since 2014, showing the major role of older vehicles and heavy-duty traffic on the urban aerosol. In addition to direct EFs, we show that CO ₂ -based EF determination enables detection of inverse and indirect effects of road traffic. For example, road traffic had an inverse effect, i.e., negative EF, on O ₃ and small ion (<2 nm) concentrations. Also, we found that road traffic contributes to compounds that are not necessarily considered to be traffic-derived such as terpenoid VOCs. We introduce a term impact factor (IF) to describe the found inverse and indirect effects of road traffic.",
  "abstract_shown": true,
  "affiliations": [
    "Tampere University (Tampere, Finland)"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 17,
  "authors": [
    {
      "name": "Lauri K. Savolainen",
      "orcid": "0009-0001-6461-2204"
    },
    {
      "affs": [
        0
      ],
      "name": "Teemu Lepistö",
      "orcid": "0000-0001-8085-3852"
    },
    {
      "name": "Heidi Hellén",
      "orcid": "0000-0001-7022-3857"
    },
    {
      "name": "Henna Lintusaari",
      "orcid": "0000-0003-4624-5508"
    },
    {
      "name": "Milja Jäppi"
    },
    {
      "name": "Jarkko V. Niemi"
    },
    {
      "name": "Kimmo Teinilä"
    },
    {
      "name": "Minna Aurela",
      "orcid": "0000-0001-7561-2974"
    },
    {
      "name": "Markus Lampimäki"
    },
    {
      "name": "Anu Kousa"
    },
    {
      "name": "Janne Lampilahti"
    },
    {
      "name": "Katrianne Lehtipalo",
      "orcid": "0000-0002-1660-2706"
    },
    {
      "name": "Tuukka Petäjä",
      "orcid": "0000-0002-1881-9044"
    },
    {
      "name": "Miikka Dal Maso",
      "orcid": "0000-0003-3040-3612"
    },
    {
      "name": "Hanna E. Manninen"
    },
    {
      "name": "Hilkka Timonen",
      "orcid": "0000-0002-7987-7985"
    },
    {
      "name": "Topi Rönkkö",
      "orcid": "0000-0002-1555-3367"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2f8s3ea3f4x9m.bib",
  "cited_by": 0,
  "doi": "10.5194/acp-26-14823-2026",
  "fulltext_url": null,
  "id": "2f8s3ea3f4x9m",
  "issns": [
    "1680-7324"
  ],
  "landing_url": "https://acp.copernicus.org/articles/26/14823/2026/",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "1902|Atmospheric chemistry and aerosols"
    ]
  ],
  "openalex": "W7161623644",
  "pdf_url": "https://acp.copernicus.org/articles/26/14823/2026/acp-26-14823-2026.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-22",
  "publisher": "Copernicus GmbH",
  "ris": "https://research.draconitic.com/paper/2f8s3ea3f4x9m.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:20:34Z",
      "native_id": "10.5194/acp-26-14823-2026",
      "source": "crossref",
      "url": "https://acp.copernicus.org/articles/26/14823/2026/"
    }
  ],
  "subjects": [
    {
      "field": "earth",
      "origin": "openalex:1902|Atmospheric chemistry and aerosols",
      "subfield": "atmospheric"
    }
  ],
  "title": "From direct emission factors to inverse and indirect impact factors of road traffic: influence of emerging and unregulated pollutants",
  "title_text": "From direct emission factors to inverse and indirect impact factors of road traffic: influence of emerging and unregulated pollutants",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:20:34Z",
  "url": "https://research.draconitic.com/paper/2f8s3ea3f4x9m",
  "venue": "Atmospheric Chemistry and Physics",
  "versions": [
    {
      "doi": "10.5194/egusphere-2026-1692",
      "pid": null,
      "relation": "preprint",
      "title": null,
      "venue": null
    }
  ]
}