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

Abstract

This work presents a methodology that combines CALPUFF dispersion model with novel estimates of local concentrations of black carbon and PM2.5 coming from fossil fuel (BCff, PM2.5ff) and wood burning (BCwb, PM2.5wb), 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 Jose de Maipo (SJM) – during the cold season of 2021. For PM2.5wb, 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 BCff, 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 BCwb and BCff, the peaks in local emissions corresponded to times of the day with higher levels of residential combustion and traffic activity. Dispersion modeling of BCff 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 PM2.5wb, PM2.5ff, BCwb and BCff 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.