Contrasting aerosol regimes and radiative forcing across the Andean–Amazonian transition: A seven-year analysis of biomass burning impacts

Victoria-Barros C.; Estevan R.; Raymundo O.F.; Navarro-Barboza H. · Environment International (2026) · DOI: 10.1016/j.envint.2026.110340

Resumen

Biomass burning in the Amazon Basin is a major source of atmospheric aerosols affecting regional climate and air quality across tropical South America, yet the contrasting impacts on high-altitude Andean and lowland Amazonian environments remain poorly quantified. Here we present a seven-year (2015–2021) integrated analysis of aerosol transport pathways, composition, and radiative forcing at two contrasting receptor sites: Huancayo Observatory (3313 m a.s.l.) in the Peruvian Andes and Rio Branco (212 m a.s.l.) in the southwestern Brazilian Amazon. By combining AERONET Level 2.0 observations, HYSPLIT backward trajectories, VIIRS-SNPP active fire detections, and MERRA-2 speciated aerosol products, we identify two fundamentally distinct aerosol regimes within the same regional system. Rio Branco experiences direct, near-field exposure (<200 km) to intense biomass burning during June–October, with extreme aerosol loading (AOD440 up to 1.25; PM2.5 exceeding 50μg m−3), pronounced organic carbon dominance (>90% of PM2.5), and atmospheric radiative forcing of +75 W m−2 during the SON peak—among the highest reported for Amazonian biomass-burning conditions. In contrast, Huancayo receives diluted, aged smoke via long-range transport (300–600 km), with mixed composition including persistent mineral dust (18%–30%) and sulfate (12%–23%), and a substantially lower atmospheric forcing of +33 W m−2. The resulting 2.3-fold inter-site difference in atmospheric radiative forcing, robust within an SSA-perturbation uncertainty envelope, illustrates how source proximity and topographic barriers jointly modulate aerosol–climate interactions across the Andean–Amazonian transition zone, with implications for regional circulation, precipitation feedbacks, and Andean cryosphere stability.

Instituciones: Universidad Nacional Mayor de San Marcos