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Title:
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Ambient and laboratory observations of organic ammonium salts in PM1
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Author(s):
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Schlag, P.; Rubach, F.; Mentel, T.F.; Reimer, D.; Canonaco, F.; Henzing, J.S.; Moerman, M.; Otjes, R.P.; Prevot, A.S.H. ; Rohrer, F.; Rosati, B.; Tillmann, R.; Weingartner, E.; Kiendler-Scharr, A.
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Published by:
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Publication date:
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ECN
Environment & Energy Engineering
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4-9-2017
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ECN report number:
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Document type:
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ECN-W--17-024
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Article (scientific)
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Number of pages:
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21
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Published in: Faraday Discussions (The Royal Society of Chemistry), , 2017, Vol.200, p.331-351.
Abstract:
Ambient measurements of PM1 aerosol chemical composition at Cabauw, the Netherlands, implicate higher ammonium concentrations than explained by the formation of inorganic ammonium salts. This additional particulate ammonium is called excess ammonium (eNH4). Height pro?les over the Cabauw Experimental Site for Atmospheric Research (CESAR) tower, of combined ground based and airborne
aerosol mass spectrometric (AMS) measurements on a Zeppelin airship show higher concentrations of eNH4 at higher altitudes compared to the ground. Through ?ights across the Netherlands, the Zeppelin based measurements furthermore substantiate eNH4 as a regional phenomenon in the planetary boundary layer. The excess ammonium correlates with mass spectral signatures of (di-)carboxylic acids, making a heterogeneous acid–base reaction the likely process of NH3 uptake. We show that this excess ammonium was neutralized by the organic fraction forming particulate
organic ammonium salts. We discuss the signi?cance of such organic ammonium salts for atmospheric aerosols and suggest that NH3 emission control will have bene?ts for particulate matter control beyond the reduction of inorganic ammonium salts.
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