Airborne observations of formic acid using a chemical ionization mass spectrometer

Abstract

Abstract. The first airborne measurements of formic acid mixing ratios over the United Kingdom were measured on the FAAM BAe-146 research aircraft on 16 March 2010 with a chemical ionization mass spectrometer using I − reagent ions. The I − ionization scheme was able to measure formic acid mixing ratios at 1 Hz in the boundary layer.In-flight standard addition calibrations from a formic acid source were used to determine the instrument sensitivity of 35 ± 6 ion counts pptv −1 s −1 and a limit of detection of 25 pptv. Routine measurements were made through a scrubbed inlet to determine the instrumental background. Three plumes of formic acid were observed over the UK, originating from London, Humberside and Tyneside. The London plume had the highest formic acid mixing ratio throughout the flight, peaking at 358 pptv. No significant correlations of formic acid with NO x and ozone were found, but a positive correlation was observed between CO and HCOOH within the two plumes where coincident data were recorded.A trajectory model was employed to determine the sources of the plumes and compare modelled mixing ratios with measured values. The model underestimated formic acid concentrations by up to a factor of 2. This is explained by missing sources in the model, which were considered to be both primary emissions of formic acid of mainly anthropogenic origin and a lack of precursor emissions, such as isoprene, from biogenic sources, whose oxidation in situ would lead to formic acid formation.

Online measurements of water-soluble organic acids in the gas and aerosol phase from the photooxidation of 1,3,5-trimethylbenzene

“…Offline methods are labour-intensive and offer usually low time resolution, while available online methods with low detection limits can provide high time resolution, such as chemical ionisation mass spectrometry (Veres et al, 2011;Le Breton et al, 2012;Paulot et al, 2009;de Gouw and Warneke, 2007). However, both offline and online methods are prone to artefacts.…”

Airborne hydrogen cyanide measurements using a chemical ionisation mass spectrometer for the plume identification of biomass burning forest fires

“…The CIMS instrument employed here was built by the Georgia Institute of Technology as previously described by Nowak et al (2007) and has been previously described for formic acid measurements (Le Breton et al, 2012). Subsequently various adjustments have been made to the inlet, and these are described in the following section.…”

Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires

“…CO mixing ratios were measured with an Aerolaser AL5002 UV fluorescence analyser and O 3 by a Thermo Scientific TEi49C UV photometric analyser as part of the standard complement of instrumentation for BAe-146 science flights. Additional instrumentation included a chemical ionisation mass spectrometer (CIMS; Nowak et al, 2007;Le Breton et al, 2012) providing real-time measurements of HCN, which is widely used as a tracer for BB emissions given that vegetation fires constitute its primary global source (Li et al, 2000;Sinha et al, 2003;Yokelson et al, 2007). NO x (NO + NO 2 ) and NO y (NO x oxidation products, including HNO 3 and N 2 O 5 ) act as important tracers for oxidation in aging plumes, and were measured respectively by an Air Quality Design Inc. chemiluminescence NO x analyser and by thermal dissociation-laser induced fluorescence (TD-LIF; Di .…”