Assessing the influence of long-range transport of aerosols on the PM_2.5 chemical composition and concentration in the Aburrá Valley

Abstract. Assessing long-range transport (LRT) of pollutants recognizes that multiple sources of varying scale and location can impact air quality. In the Aburrá Valley, Colombia, and other cities in Northern South America, biomass burning (BB), dust, and volcanic degassing have been identified as sources of LRT of aerosols. However, the impact of these sources on air quality and their characterization have yet to be thoroughly studied. This work investigates the influence of these sources on the chemical composition of PM2.5 during annual and intra-annual high-load aerosol events. We identified, tracked, and meteorologically characterized LRT events and evaluated their influence on PM2.5 concentration and chemical composition. We ran a Positive Matrix Factorization (PMF) for each kind of event, identifying high contribution in organic carbon (OC1, OC2), F- and secondary aerosols trace SO42- and NO3- for the BB events, crustal mineral along with Ti and Ca contribution for dust events and SO42-, Na, Al and Ca for volcanic events. The increasing concentration of some ions and toxic heavy metals (Cr, Mn, Cd, and Ni) were also related to BB and volcanic degassing influence. During these LRT events, the BB fraction of PM2.5 dominates by frequency and amount, averaging 11.14 μg / m3 (38 %). On average, dust and volcanic degassing contribute 6.77 μg / m3 (34 %) and 6.46 μg / m3 (30 %) of the concentrations. Of the three, dust events showed fewer affected days. The study highlighted hotspot zones such as the Orinoco and Middle Magdalena Valley for BB aerosols, the Caribbean for dust, and the Nevado del Ruíz volcano for volcanic aerosols. This study gives insights for future chemical transport modeling studies in the region and supports strategies to manage internal and external pollution sources and effects for the Aburrá Valley and the region.