Advanced Online Monitoring for Atmospheric Composition Characterization, Source Apportionment, and Impact Assessment

Advancements in instrumentation for monitoring the rapidly changing atmospheric chemical composition and physical properties have enabled the quantitative characterization of a broader range of aerosol and gaseous pollutant sources at high temporal resolution. Beyond improving our understanding of the dynamic nature of emissions and atmospheric transformations, this knowledge is essential for designing targeted mitigation strategies and implementing short-term interventions during pollution events.

Based on online ground-based measurements and supported by the robust receptor modeling framework, the short-term contributions of specific sources and processes to aerosol components, particle number size distributions, and volatile organic compounds have been assessed across diverse environments. While developments in online mass spectrometry and elemental analysis continue to reveal the complexity of atmospheric composition, the increasing maturity of the field calls for a holistic consideration of sources and an expansion toward evaluating their trends and impacts. Online instruments can provide data to health studies for identifying the missing source-effect links, but also offer opportunities to explore fine-scale impacts from short-term exposure. Moreover, the high-frequency source apportionment of climate-relevant aerosol components and radiative properties can enhance the representation of aerosol–cloud–radiation interactions in climate models, while enabling the evaluation of co-benefits and trade-offs between air quality management and climate mitigation.

We invite Original Research, Reviews and Perspectives exploring, but not limited to, the following topics:

• Field campaigns using cutting-edge instrumentation for atmospheric composition characterization at the molecular level.
• Long-term source apportionment studies in high temporal resolution for aerosol chemical composition, particle number size distributions, and organic gases.
• Cross-platform, real-time receptor modeling applications for composite pollutants, including PM_2.5, carbonaceous aerosol, and VOCs.
• Valorization of multi-area, online source apportionment data by chemical transport models for validation and refinement of emission inventories.
• Source apportionment for oxidative potential and toxic micro-pollutants at sub-daily scales, as well as studies integrating online source apportionment data into epidemiological research.
• Novel methods and applications for source apportionment of aerosol optical and physical properties, and their implications for climate impact assessment.