Abstract
Abstract. Observations of aerosol chemical composition in Cabauw, the Netherlands, are presented for two intensive measurement periods in May 2008 and March 2009. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) and is compared to observations from aerosol size distribution measurements as well as composition measurements with a Monitor for AeRosol and GAses (MARGA) based instrument and a Thermal-Desorption Proton-Transfer-Reaction Mass-Spectrometer (TD-PTR-MS). An overview of the data is presented and the data quality is discussed. In May 2008 enhanced pollution was observed with organics contributing 40% to the PM1 mass. In contrast the observed average mass loading was lower in March 2009 and a dominance of ammonium nitrate (42%) was observed. The semi-volatile nature of ammonium nitrate is evident in the diurnal cycles with maximum concentrations observed in the morning hours in May 2008 and little diurnal variation observed in March 2009. Size dependent composition data from AMS measurements are presented and show a dominance of organics in the size range below 200 nm. A higher O:C ratio of the organics is observed for May 2008 than for March 2009. Together with the time series of individual tracer ions this shows the dominance of OOA over HOA in May 2008.
Highlights
Aerosol particles directly and indirectly affect the global climate
A measurement cycle of the TD-PTRMS system is as follows: While the PTR-mass spectrometer (MS) is connected to the gas phase inlet, ambient air is pulled through the CTD cell and the aerosol particles are collected on a sharp point in the CTD cell
Ambient temperature (T ) and the relative humidity (RH) at 40 m height are given in the second upper panel
Summary
Aerosol particles directly and indirectly affect the global climate. Depending on their optical properties, particles can scatter or absorb long and short wave radiation. The measurements were linked to the intensive observation periods of the European Integrated Project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) (Kulmala et al, 2009) and activities of the European Monitoring and Evaluation Programme (EMEP, http://www.emep.int/) Previous work on this data set has focused on the aerosol direct effect (Roelofs et al, 2010; Morgan et al, 2010a) and showed that the high fraction of ammonium nitrate observed in May 2008 largely impacts the aerosol optical thickness (Roelofs et al, 2010). In particular the O/C ratio and individual tracer ions are used to track OOA and HOA in both observation periods To our knowledge, this is the first time that online analysis of the organic particulate aerosol phase is reported for that measurement location
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