Short-term effects of anthropogenic/natural activities on the Tehran criteria air pollutants: Source apportionment and spatiotemporal variation

In this paper, we apply a somewhat new approach to address the data missing issue of the detailed air monitoring dataset of Tehran 2018 (hourly data of over 15 monitoring sites) and to study the short-term effects of anthropogenic/natural activities on the criteria air pollutants (CAP) in the urban and rural areas. A homogenous dataset was produced by the Singular Value Thresholding (SVT) algorithm and source apportionment was then conducted using the absolute principle component scores-multiple linear regression (APCS-MLR) method. The contributions of major sources to the local ozone level and the existing correlations between the CAP concentrations are also discussed. Results show that the vehicular emissions were the predominant contributors to the CAP concentrations, accounting for an average of 45%, and desert dust and industries around the city were ranked as the subsequent principal CAP sources for the summer season. Residential and transportation sectors accounted for an average of 59% and 18.4% of the CAP concentrations in the wintertime, respectively. Aerosols formation was accelerated during the “lunch-time” peak. This phenomenon was attributed to the heavy traffic emission of Tehran in urban environments. The concentrations of CAP, except ozone, gently increase by moving toward the cold days of the year, whereas O₃ concentration usually exceeds 70 μg/m3 in summer days. On-road vehicle emissions were the leading source of ozone formation in Tehran for the studied time. The correlation coefficients of ozone and other CAP vary to some extent by moving from urban areas toward the rural areas of the city.