Total Peroxy Nitrates (ΣPNs) in the atmosphere: the Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) technique and comparisons to speciated PAN measurements

Abstract

Abstract. Peroxyacetyl nitrate (PAN) and its chemical analogues are increasingly being quantified in the ambient atmosphere by thermal dissociation (TD) followed by detection of either the peroxyacyl radical or the NO 2 product. Here we present details of the technique developed at University of California, Berkeley which detects the sum of all peroxynitrates ( PNs) via laser-induced fluorescence (LIF) of the NO 2 product. We review the various deployments and compare the Berkeley PNs measurements with the sums of PAN and its homologue species detected individually by other instruments. The observed TD-LIF PNs usually agree to within 10% with the summed individual species, thus arguing against the presence of significant concentrations of unmeasured PAN-type compounds in the atmosphere, as suggested by some photochemical mechanisms. Examples of poorer agreement are attributed to a sampling inlet design that is shown to be inappropriate for high NO x conditions. Interferences to the TD-LIF measurements are described along with strategies to minimize their effects.

The production and persistence of ΣRONO<sub>2</sub> in the Mexico City plume

“…Comparison of TD-LIF observations of an isoprene nitrate standard to observations made using a PTR-MS show both instruments to be consistent to within 10% (Perring et al, 2009b). Comparisons of NO 2 and PNs have also been described and indicate similar or better accuracy for these species Fuchs et al, 2010;Wooldridge et al, 2010).…”

Global and regional effects of the photochemistry of CH<sub>3</sub>O<sub>2</sub>NO<sub>2</sub>: evidence from ARCTAS

“…HO 2 NO 2 dissociation is minimal and results in a median calculated NO 2 interference of less than 1 ppt (6 % of the XNO 2 signal) and a maximum absolute interference during a 1 minute period of 10.3 ppt (19 % of the NO 2 signal). This molecule is detected with near unit efficiency in the PNs channel as described previously (Murphy et al, 2004;Wooldridge et al, 2010).…”

“…Briefly, total peroxy nitrates ( PNs), total alkyl and multifunctional nitrates ( ANs), and NO 2 were measured using the Thermal Dissociation-Laser Induced Fluorescence (TD-LIF) instrument described in detail by Wooldridge et al (2010). NO 2 is measured using laser induced fluorescence (Thornton et al, 2000) with supersonic expansion (Cleary et al, 2002 (0.06 cm −1 ) at 585 nm.…”

Development of a photochemical source for the production and calibration of acyl peroxynitrate compounds

“…An increasingly popular method is thermal-dissociation chemical ionization mass spectrometry (TD-CIMS) for the measurement of APNs (Slusher et al, 2004;Phillips et al, 2013;Zheng et al, 2011). Comparisons of the TD-CIMS method with other techniques, such as GC and TD-LIF, show reasonably good agreement (Wooldridge et al, 2010;Tyndall et al, 2005). However, there exists the potential for various interferences, such as peroxy acetic acid and carboxylic acids, requiring additional consideration (Phillips et al, 2013).…”

“…Liquid chromatography has also been used for the measurement of PAN, with limited results (Grosjean et al, 1991). Optical techniques such as Fourier transform infrared spectroscopy (FTIR; Tuazon et al, 1978) and thermal-dissociation laser-induced fluorescence (TD-LIF; Wooldridge et al, 2010) have been employed with more recent developments, such as cavity ring-down spectroscopy (Paul et al, 2009), showing promise as fast-response measurement techniques.…”