000171779 001__ 171779 000171779 005__ 20260603114407.0 000171779 0247_ $$2doi$$a10.1016/j.envpol.2026.128232 000171779 0248_ $$2sideral$$a149521 000171779 037__ $$aART-2026-149521 000171779 041__ $$aeng 000171779 100__ $$0(orcid)0000-0001-8227-5689$$aEscudero, Miguel$$uUniversidad de Zaragoza 000171779 245__ $$aPM2.5 composition at an atmospheric ammonia hotspot in Europe 000171779 260__ $$c2026 000171779 5060_ $$aAccess copy available to the general public$$fUnrestricted 000171779 5203_ $$aFine particulate matter (PM2.5) pollution poses a significant environmental risk to human health, ecosystems, and climate, both across Europe and globally. Ammonia (NH), primarily emitted by agro-livestock activities, is a major precursor gas for secondary particulate formation; critically, however, it remains largely unregulated in European directives and is seldom monitored within conventional air quality networks. This study investigates the chemical composition, formation mechanisms, and potential sources of PM2.5 within a critical European agricultural region (Central Ebro Valley, CEV), recognized as a major atmospheric NH hotspot. NH concentration and PM2.5 chemical composition data were collected during two intensive campaigns spanning distinct winter and summer seasonal regimes. Results demonstrate that the study area is characterized by an NH-saturated environment, which fundamentally controls PM2.5 formation dynamics and leads to severe regional pollution episodes. The high ammoniacal availability is identified as a key factor promoting the generation of high concentrations of Secondary Inorganic Aerosols (SIA), particularly during winter. Furthermore, the characteristic summer atmospheric dynamics, featuring high vertical dispersion driven by the intense development of the Planetary Boundary Layer (PBL), enhances the region’s role as an atmospheric NH reservoir for the wider Mediterranean Basin, establishing it as a major source area in Southern Europe. A preliminary source contribution analysis based on Positive Matrix Factorization (PMF) identified five factors with marked seasonality, confirming the unquestionable impact of agro-livestock NH emissions, biomass burning, mineral resuspension from arid land surfaces, and African dust intrusion during summer. This study underscores the critical importance of policy decisions targeting emission controls within the agricultural and livestock sectors to effectively mitigate PM2.5 levels locally and regionally. 000171779 536__ $$9info:eu-repo/grantAgreement/ES/DGA/E02-23R$$9info:eu-repo/grantAgreement/EUR/INTERREG POCTEFA-EFA 2021-2027$$9info:eu-repo/grantAgreement/ES/MICINN/PID2022-142160OB-I00 000171779 540__ $$9info:eu-repo/semantics/openAccess$$aby-nc-nd$$uhttps://creativecommons.org/licenses/by-nc-nd/4.0/deed.es 000171779 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion 000171779 700__ $$0(orcid)0000-0002-1807-5049$$aMiguel, Natividad$$uUniversidad de Zaragoza 000171779 700__ $$aHernández de la Torre, José 000171779 700__ $$aArner, Miguel 000171779 700__ $$0(orcid)0000-0001-6899-1005$$aMarín-Sáez, Julia$$uUniversidad de Zaragoza 000171779 700__ $$aHierro, Juan 000171779 700__ $$aAlastuey, Andrés 000171779 700__ $$aQuerol, Xavier 000171779 700__ $$aReche, Cristina 000171779 700__ $$aMuñoz, Amalia 000171779 700__ $$aBorrás, Esther 000171779 700__ $$aPey, Jorge 000171779 7102_ $$12002$$2385$$aUniversidad de Zaragoza$$bDpto. Física Aplicada$$cÁrea Física Aplicada 000171779 7102_ $$15005$$2790$$aUniversidad de Zaragoza$$bDpto. Ing.Quím.Tecnol.Med.Amb.$$cÁrea Tecnologi. Medio Ambiente 000171779 773__ $$g401 (2026), 128232$$pEnviron. pollut.$$tEnvironmental Pollution$$x0269-7491 000171779 8564_ $$s3021568$$uhttps://zaguan.unizar.es/record/171779/files/texto_completo.pdf$$yVersión publicada 000171779 8564_ $$s2556549$$uhttps://zaguan.unizar.es/record/171779/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada 000171779 909CO $$ooai:zaguan.unizar.es:171779$$particulos$$pdriver 000171779 951__ $$a2026-06-03-11:05:12 000171779 980__ $$aARTICLE