Evaluation and comparison of continuous BC and NOX measurement in three Swedish cities Stockholm, Göteborg and Malmö) in relation to sources and temporal variability

Black Carbon (BC) and Nitrogen Oxides (NOX) possess environmental and human health risks. Concentrations of these air pollutants are highly influenced by road traffic emissions. The study aims to evaluate and compare temporal trends and sources of these pollutants at the kerbside in three Swedish cities-Stockholm, Göteborg and Malmö based on measurements in 2015 and 2016. The highest NOX (about 150 µgm¯ 3 ) and BC (about 2000 ngm¯ 3 ) concentrations, in the diurnal variation, were observed less in 2015 at the Stockholm kerbsides compared to observations in 2013 (NOX 270 µgm¯ 3 ; BC 4000 ngm¯ 3 ). The winter to summer NOX emission ratios were 2.1 and 1.36 in Göteborg and Malmö, respectively. The ratios were 1.18 and 1.23 in 2005 and 1.15 and 1.16 in 2000 in the western Europe and central Europe, respectively. However, the BC370 and BC880 emissions ratios were reported to be 0.97 and 0.89 in Stockholm, 1.56 and 1.44 in Göteborg, and 1.35 and 1.26 in Malmö in 2015. The ratios were mostly lower than the BC ratios recorded at 1.34 and 1.76 in 2005 and 1.59 and 1.92 in 2000 in the western Europe and central Europe, respectively. The relative pollutants emission ratio observed were further lower in 2016 than in 2015.