Seasonal and spatial BVOC emission variability from native Atlantic Forest trees under contrasting anthropogenic influences in Southeast Brazil

Biogenic volatile organic compound (BVOC) emissions from vegetation are major precursors of ozone (O₃) and secondary organic aerosols (SOAs), yet their behavior in tropical megacities remains poorly understood. We quantified BVOC emissions from four native Atlantic Forest tree species: Alchornea sidifolia (AS), Casearia sylvestris (CS), Guarea macrophylla (GM), and Machaerium nyctitans (MN), sampled during dry and rainy seasons in two forest remnants of the Metropolitan Area of São Paulo with contrasting anthropogenic influence: Matão-IAG (higher) and RMG (lower). Using dynamic enclosure sampling and TD-GC-MS analysis, we measured emission rates (ERs) and estimated O₃ formation potential (OFP) and SOA potential (SOAP). Species identity was the main factor shaping emission patterns, with sesquiterpenes (SQTs) dominating under all conditions. Four emission strategies emerged. CS showed a high and seasonally variable profile, with the highest ERs, OFP, and SOAP, peaking at RMG during the dry season (11.85, 23.24, and 213.30 µg gDM⁻¹ h⁻¹). AS exhibited moderate and compositionally stable emissions (ER 0.81 to 0.98 µg gDM⁻¹ h⁻¹). GM had moderate and compositionally variable emissions (ER 0.98 to 1.66 µg gDM⁻¹ h⁻¹). MN presented low and compositionally heterogeneous emissions, with a dry-season spike at RMG (ER 2.91 µg gDM⁻¹ h⁻¹). Compound-level analysis revealed potential biomarkers: ledene was associated with the dry season, while 2-ethylhexyl salicylate and β-linalool were linked to urban stress. These findings improve the spatiotemporal characterization of BVOCs in the Atlantic Forest and offer an evidence-based framework for sustainable urban forestry in tropical megacities.