Abstract
<jats:p>Microplastics (MPs) have emerged as an atmospheric contaminant of growing concern due to their widespread presence, long-range transport potential, and possible impacts on human health and ecosystems. While numerous studies have investigated airborne MPs in urban and remote environments, the contribution of wildfires to atmospheric MP emissions remains largely unexplored. Vegetation, soils, litter, and anthropogenic materials accumulated in forested areas can contain substantial amounts of plastic particles, which may be released into the atmosphere during combustion processes.This work presents a preliminary assessment of the atmospheric transport and distribution of wildfire-derived microplastics over Portugal using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem). A novel emission database for MPs released by biomass burning was developed based on available literature, emission factor estimates, wildfire inventories, and assumptions regarding the plastic content of combustible fuels. MPs were represented as inert particulate matter and incorporated into the modelling framework as a passive tracer to investigate their transport pathways and atmospheric fate.The model was applied to selected wildfire episodes in Portugal, with particular emphasis on large fire events characterised by intense smoke emissions and regional-scale atmospheric transport. Simulations were used to quantify the spatial and temporal evolution of airborne MPs concentrations, identify source-receptor relationships, and evaluate the potential for long-range transport beyond the affected regions.The results indicate that wildfire emissions can generate detectable MP plumes extending hundreds of kilometres from the source areas under favourable meteorological conditions. Elevated concentrations were found not only in the vicinity of the fires but also in downwind urban and rural regions, highlighting the role of atmospheric transport in redistributing MPs across large spatial scales.The study demonstrates the feasibility of incorporating MPs into chemistry transport models, and provides a first step towards understanding the contribution of extreme events to atmospheric MP concentrations. Future work will focus on refining emission estimates, improving the representation of MP physicochemical properties and deposition processes, and evaluating simulations against field measurements collected within the framework of the PlasURE project. These developments will contribute to a more comprehensive assessment of the environmental and health implications of airborne MPs under present and future climate conditions. Acknowledgments: This work was supported by: (i) national funds through FCT/MECI: LEPABE, UID/00511/2025 (https://doi.org/10.54499/UID/00511/2025) and UID/PRR/00511/2025 (https://doi.org/10.54499/UID/PRR/00511/2025) and ALiCE, LA/P/0045/2020 (https://doi.org/10.54499/LA/P/0045/2020); (ii) COMPETE 2030, Portugal 2030, and the European Union, within project PlasURE - Impact of airborne microplastics: urban and rural environments and extreme events, with number 16721 and operation code at the Funds Platform COMPETE2030-FEDER-00790200; (III) the ARUBA project (PID2023-149080OB-I00/MCIN/AEI/10.13039/501100011033, Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación, Spain & FEDER, EU); (IV) and project INSIEME (FSRM/10.13039/100007801).</jats:p>