Assessment of acid deposition over Dhaka division using CAMx–MM5 modeling system

Asif Iqbal, Nguyen Thi Kim Oanh
2011 Atmospheric pollution research  
This study provided an insight into the complex phenomenon of acid deposition over Dhaka division of Bangladesh. The 10-day HYSPLIT back trajectories showed that majority of air masses arriving to Bangladesh were originated from the west. The gridded emissions (0.055° or ~5.5 km) for Dhaka division was prepared for 2006 by updating a preliminary emission inventory (EI) available for 2000 and by conducting a new EI for two major source categories, brick kilns and traffic. In Dhaka division as of
more » ... 2006, the brick kilns contributed the largest SO 2 emission (about 70%), while residential emissions had the highest share of CO and PM 10 (over 60%) and substantial NMVOC (about 40%). Emission rates of SO 2 and NO x in the dry season of 355 t/d and 183 t/d, respectively, were higher than the corresponding rates in the wet season of 60 t/d and 146 t/d, which was mainly due to the operation of brick kilns in the dry season. The acid deposition was simulated, using CAMx-MM5 model, for December and June to represent the dry and wet seasons, respectively. Model performance was reasonable considering the simulated spatial distribution of acid deposition with simulated wind and precipitation fields. The model results for SO 2 and NO x concentrations were in the same ranges of the limited monitoring data available. However, the acid deposition simulation was still largely experimental due to the lack of acid deposition monitoring data for the model evaluation. The preliminary acid deposition simulation results suggested that the nitrogen wet deposition was the major contributor over the Dhaka division that could be the reason of exceeding the critical load for the local ecosystem. Further research is still required to refine the emission inventory and to gather the monitoring data to confirm the modeling results.
doi:10.5094/apr.2011.052 fatcat:vmfxd6gbgvarzcxkqarrhoache