Temporal variations of atmospheric black carbon and its relation to other pollutants and meteorological factors at an urban traffic site in Istanbul

Özet

This study aimed to investigate the variability of Black Carbon (BC) at one traffic site in Istanbul as a function ofother pollutants, traffic density and meteorological parameters in order to identify the source and determinantsof concentration. This was carried out through the statistical analyses of data measured in the period of May2016–December 2018. The mean concentration of BC was observed as 6.5 ± 3.5 μg m−3. Daytime BC wasobserved to be higher than nighttime during the weekdays but slightly lower at the weekend, similar to oxides ofnitrogen (NOx). However, nighttime traffic during the weekend was found to be higher than the weekdays. Thediurnal pattern showed two peaks of BC corresponding to the traffic rush hours in the morning and evening.Since the traffic density did not change during the day, the sharp decrease after the morning rush hour isattributed to enhanced atmospheric mixing, due to an increased wind speed and boundary layer depth. In addition, polar plots indicated that the only major source of BC is in the vicinity of the monitoring site, consistentwith road traffic. Moreover, episodic north-easterly atmospheric transport events from the ship activity in theBosphorus in summer can contribute to elevated BC concentrations. These results suggest that vehicular emissions heavily impact the environmental concentrations of BC and affect NOx concentrations more than otherpollutants. BC concentrations are highly correlated with NOx, reflecting a common source in diesel vehicleemissions. Since the proportion of diesels in total vehicles in Istanbul is increasing every year, there may befuture increases in BC and NOx unless exhaust after-treatment works effectively on newer vehicles entering thefleet.