Articles | Volume 16, issue 14
Research article
19 Jul 2016
Research article |  | 19 Jul 2016

Aerosol source apportionment from 1-year measurements at the CESAR tower in Cabauw, the Netherlands

Patrick Schlag, Astrid Kiendler-Scharr, Marcus Johannes Blom, Francesco Canonaco, Jeroen Sebastiaan Henzing, Marcel Moerman, André Stephan Henry Prévôt, and Rupert Holzinger

Abstract. Intensive measurements of submicron aerosol particles and their chemical composition were performed with an Aerosol Chemical Speciation Monitor (ACSM) at the Cabauw Experimental Site for Atmospheric Research (CESAR) in Cabauw, the Netherlands, sampling at 5 m height above ground. The campaign lasted nearly 1 year from July 2012 to June 2013 as part of the EU-FP7-ACTRIS project (Q-ACSM Network). Including equivalent black carbon an average particulate mass concentration of 9.50 µg m−3 was obtained during the whole campaign with dominant contributions from ammonium nitrate (45 %), organic aerosol (OA, 29 %), and ammonium sulfate (19 %). There were 12 exceedances of the World Health Organization (WHO) PM2.5 daily mean limit (25 µg m−3) observed at this rural site using PM1 instrumentation only. Ammonium nitrate and OA represented the largest contributors to total particulate matter during periods of exceedance.

Source apportionment of OA was performed season-wise by positive matrix factorization (PMF) using the multilinear engine 2 (ME-2) controlled via the source finder (SoFi). Primary organic aerosols were attributed mainly to traffic (8–16 % contribution to total OA, averaged season-wise) and biomass burning (0–23 %). Secondary organic aerosols (SOAs, 61–84 %) dominated the organic fraction during the whole campaign, particularly on days with high mass loadings. A SOA factor which is attributed to humic-like substances (HULIS) was identified as a highly oxidized background aerosol in Cabauw. This shows the importance of atmospheric aging processes for aerosol concentration at this rural site. Due to the large secondary fraction, the reduction of particulate mass at this rural site is challenging on a local scale.

Short summary
This work provides chemical composition data of atmospheric aerosols acquired during 1 year in the rural site of Cabauw, the Netherlands. In some periods, we found unexpected high particle mass concentrations exceeding the WHO limits. Using these composition data, we found that reducing ammonia emissions in this region would largely reduce the main aerosol component ammonium nitrate, whereas the local mitigation of the organics turned out to be difficult due to the lack of a designated source.
Final-revised paper