Long-range aerosol transport from Europe to Istanbul, Turkey

Northern and western parts of Turkey frequently experience air pollution episodes. Transport of air pollutants from Europe to these regions has not been studied sufficiently. This study aims to identify and analyze the contribution of long-range aerosol transport to air pollution in the city of Istanbul. Istanbul is the largest urban settlement in Northwestern Turkey, with more than 12 million inhabitants in the metropolitan area. The methodology developed for the study as well as the results obtained are presented here. Meteorological modeling provided the wind fields that were first used in a trajectory analysis and then, along with other meteorological data, input to an advanced air quality model. Backward trajectories suggested that when the prevailing wind direction is westerly or northwesterly, such as in the case of the episode studied here, a significant fraction of the pollutants emitted from Europe may be transported to and deposited in Turkey. An emission processing module was developed to prepare the emission inputs required by the air quality modeling system. The long-range aerosol transport simulations demonstrated and quantified the source/receptor relationships between Europe and Turkey. For the selected episode, it has been found through model simulations that the responses of Istanbul background PM10 levels to the emissions of individual European countries can range from 0.5 to 13%. The response of Istanbul background PM10 concentrations can be as much as 26% according to the sensitivity analysis results, when anthropogenic emissions throughout Europe are changed by 50%. This result suggests that trans-boundary sources may be responsible for as much as half of the background PM10 in Istanbul.