Backward and forward simulation of polycyclic aromatic hydrocarbons by the grid-scale model _validation and applications for environmental management

Polycyclic aromatic hydrocarbons (PAHs) associated with fine particulate matter (PM2.5) can cause serious health problems, but data are scarce. We have previously developed a grid-scale model (GSM) to simulate PM2.5-PAH levels on an hourly basis. This study aims to verify the applicability of the model to different years and to reasonably assess the long-term spatiotemporal effects on PAH variation in Kaohsiung. From the resulting database, the annual mean of PM2.5-PAH was found to have decreased from 3.18 in 2005 to 1.78 ng m−3 in 2018, representing an overall decrease of 44%. Thus, this study found that the progressive decrease in PAH levels was closely related to green transport and the gradual tightening of industrial operation regulations. Namely, in the urban area near the central public transport hubs, the estimated PAHs had significantly decreased by 16% (0.37 ng m−3) in 2009 with the operation of the high-speed railway in 2007 and the mass rapid transit in 2008. Near industrial areas, PAHs were reduced by environmental regulations, including air pollution control fees and cap-and-trade policies. By using GSM simulation, this study demonstrated a useful and feasible urban planning tool, and can serve as a reference for future studies related to epidemiology and environmental management.