Modeling the dispersion of traffic-derived black carbon emissions into hilly terrain

Abstract

This study examines hilly terrain's effect on black carbon (BC) dispersion. The apportionment of distinct sources obtained by a two-component mixing model (Aethalometer: AE-33) using improved radiative transfer equations showed the dominance of tra c-derived black carbon (BCFF) emissions in the study region. The AERMOD was used to model BC emissions from moving tra c as line source and parking lot as area source using observational and WRF-processed meteorology for the winter (Jan to Mar 2020). The model results showed that the BC levels substantially vary with local meteorological conditions, tra c volume, and composition. The hilly terrain obstructs the winds and develops a negative pressure loading to a vacuum on the other side of the hills, which promotes the accumulation of emissions, causing high BC concentrations. The pockets of higher concentration were seen at the locations where steep slopes were associated with low winds (<1 m-s−1) and hill fogs. The AERMOD model, after statistical evaluation against the observational datasets, has been applied to study the reduction in BCFF concentrations due to the implementation of Indian emission norms as mitigation measures, i.e., BS-IV (equivalent to Euro 4) and BS-VI (equivalent to Euro 6). It was found that the BCFF concentrations for BS-IV and BS-VI reduced by 35% and 75%, respectively. The model was also used to study the contribution of the different vehicular categories to BC concentration. HighlightsFirst time, the AERMOD model was employed to study the dispersion of fossil-fuel-originated black carbon into hilly terrain.Low wind with hill fog facilitated the rise of BC concentration in the complex terrain.On-site meteorological data produce more reliable dispersion calculations than WRF modeled data.Application of the model to study the impacts showed that tra c-derived BC for BS-IV decreased by 35% and 75% for BS-VI emission norms.