Ultrafine particles in Amsterdam, Antwerp, Leicester and London

Work package 1 of Joaquin aimed at a better understanding of UFP’s in urban environments by evaluating the temporal variation of UFP number concentration and size distribution in four NW- European cities (Amsterdam, Antwerp, Leicester and London). Apart from the temporal variation, relations of UFP with more commonly monitored pollutants such as nitrogen oxides (NOx), particulate matter (PM10, PM2.5) and black carbon (BC) were evaluated. The total particle number concentration was measured with a condensation particle counter (TSI EPC-3783, water based, particles > 7 nm) and BC with a MAAP (Thermo-5012). The particle size distribution between 10-1000 nm was obtained by a scanning mobility particle sizer (Grimm-5420/L-DMA) in Amsterdam and Antwerp. In Leicester and London, spectra between 20 and 200 nm were gathered with a differential mobility analyser with corona discharger and electrometer (TSI UFP-3031). Measurements were conducted between April 2013 and March 2015. Results showed a traffic-related diurnal variation of UFP, NO2 and BC with distinct morning and evening rush hour peaks on weekdays. In the weekends, only an evening peak could be observed. The relative UFP size distribution was quite similar for all cities with highest particle numbers in the 30-50 nm size class. The monitoring site of Antwerp showed highest NO2, BC and UFP concentrations which can be explained by the proximity of a traffic-intensive thoroughfare of Antwerp. Based on the experienced wind fields, site-dependent local and urban UFP sources could be identified which pleads for thoughtful consideration when positioning urban background stations in typical heterogeneous urban environments.