Air Quality Modeling Study on the Controlling Factors of Fine Particulate Matter (PM2.5) in Hanoi: A Case Study in December 2010

Meteorology and emission sources are the two main factors determining concentrations of air pollutants, including fine particulate matter. A regional air quality modeling system was used to analyze the sources of fine-particulate air pollution in Hanoi, Vietnam, in December 2010. The impacts of precipitation and winds on PM(2.5)concentrations was investigated. Precipitation was negatively correlated with PM(2.5)concentrations. However, winds showed both positive and negative correlations with PM(2.5)concentrations, depending on wind direction (WD) and the level of upwind concentrations. Sensitivity simulations were conducted to investigate the contribution of local and non-local emissions sources on total PM(2.5)by perturbing the emission inputs of the model. Overall, local and non-local sources contributed equally to the total PM(2.5)in Hanoi. Local emission sources comprised 57% of the total PM(2.5)concentrations for the high PM(2.5)pollution levels, while only comprising 42% of the total PM(2.5)for low levels of PM(2.5)concentrations. In Hanoi's urban areas, local sources contributed more to the total PM(2.5)than non-local sources. In contrast, non-local sources were the main contributors to the PM(2.5)in Hanoi's rural areas. Additional sensitivity simulations were conducted to identify the main local emission sources of PM(2.5)concentrations in December 2010. The industrial and residential sectors collectively comprised 79% of the total PM(2.5)concentrations while the transport and power sectors comprised only 2% and 3%, respectively. This is the first case study which used a regional air quality modeling system to provide new and informative insights into PM(2.5)air pollution in Hanoi by estimating the contributions of local and non-local emissions sources, as well as the contribution of local emission sectors to PM(2.5)concentrations in Hanoi.