Effect of Crossing Diesel Fleet in Tehran on Black Carbon Air Pollution

Diesel-fueled engines, despite all their benefits for heavy-duty vehicles, emit a large amount of particulate matter and Nitrogen oxides. Direct measurements of these vehicles’ exhaust have shown that the major part of emitted particulate matter consists of carbon or soot. The pollutant Black Carbon (BC) has a destructive effect on human’s health and environment and it is necessary to control its emission. For this purpose, BC concentration and its sources should be clearly estimated. In this study, direct measurement of BC concentration was conducted at two air quality monitoring stations in Tehran. This measurement, with a special instrument, illustrates the intensity of presence of BC in Tehran’s air. Other prevailing pollutants, including particulate matters with a diameter of 2.5 micrometers or less (PM2.5) and Nitrogen oxides, were monitored in the same period of time and the results were compared with BC in order to source apportionment and find correlations between pollutants concentrations. The results showed that heavy-duty fleet are the main source of BC and Nitrogen oxide pollution in Tehran’s air. BC concentration increased as soon as heavy trucks were admitted into the streets and remained high during their night activity. After sunrise, when heavy trucks were prohibited, BC concentration decreased to a low level and remained steady until night.