A methodology for estimation of local black carbon and PM2.5 emissions in suburban zones. Case study of Santiago, Chile

This work presents a methodology that combines CALPUFF dispersion model with novel estimates of local concentrations of black carbon and PM_2.5 coming from fossil fuel (BC_ff, PM_2.5ff) and wood burning (BC_wb, PM_2.5wb), to improve local emission estimates without the need to specify boundary conditions. We have applied this methodology in three suburbs of Santiago, Chile — Colina, Melipilla and San José de Maipo (SJM) — during the cold season of 2021. For PM_2.5wb, local emission rates were estimated at 74.8 ton year⁻¹ for Colina, 93.3 ton year⁻¹ for Melipilla, and 24.3 ton year⁻¹ for SJM, which correspond to 0.5, 0.4, and 0.3 times the 2012 inventory, respectively. For BC_ff, the estimated emission rates were 2.2 ton month⁻¹ in Colina, 0.2 ton month⁻¹ in Melipilla, and 0.2 ton month⁻¹ in SJM, which represent 5.2, 0.7, and 2.8 times the respective values at each site according to the 2017 inventory. For both BC_wb and BC_ff, the peaks in local emissions corresponded to times of the day with higher levels of residential combustion and traffic activity. Dispersion modeling of BC_ff from Zone B (the studied suburbs) to Zone A (Greater Santiago) showed that the highest contributions occurred in July 2021 in the wee hours. Dispersion modeling of PM_2.5wb, PM_2.5ff, BC_wb and BC_ff from Zone A to Zone B and wind trajectory analysis suggest that non-local contributions reaching the studied suburbs originate not only from Santiago but also from nearby and distant localities. This novel methodology may be applied to any suburban area.