Field inter-comparison of eleven atmospheric ammonia measurement techniques

Abstract

Abstract. Eleven instruments for the measurement of ambient concentrations of atmospheric ammonia gas (NH3), based on eight different measurement methods were inter-compared above an intensively managed agricultural field in late summer 2008 in Southern Scotland. To test the instruments over a wide range of concentrations, the field was fertilised with urea midway through the experiment, leading to an increase in the average concentration from 10 to 100 ppbv. The instruments deployed included three wet-chemistry systems, one with offline analysis (annular rotating batch denuder, RBD) and two with online-analysis (Annular Denuder sampling with online Analysis, AMANDA; AiRRmonia), two Quantum Cascade Laser Absorption Spectrometers (a large-cell dual system; DUAL-QCLAS, and a compact system; c-QCLAS), two photo-acoustic spectrometers (WaSul-Flux; Nitrolux-100), a Cavity Ring Down Spectrosmeter (CRDS), a Chemical Ionisation Mass Spectrometer (CIMS), an ion mobility spectrometer (IMS) and an Open-Path Fourier Transform Infra-Red (OP-FTIR) Spectrometer. The instruments were compared with each other and with the average concentration of all instruments. An overall good agreement of hourly average concentrations between the instruments (R2>0.84), was observed for NH3 concentrations at the field of up to 120 ppbv with the slopes against the average ranging from 0.67 (DUAL-QCLAS) to 1.13 (AiRRmonia) with intercepts of −0.74 ppbv (RBD) to +2.69 ppbv (CIMS). More variability was found for performance for lower concentrations (<10 ppbv). Here the main factors affecting measurement precision are (a) the inlet design, (b) the state of inlet filters (where applicable), and (c) the quality of gas-phase standards (where applicable). By reference to the fast (1 Hz) instruments deployed during the study, it was possible to characterize the response times of the slower instruments.

A Chemical Ionization Mass Spectrometer for ambient measurements of Ammonia

“…There have been four different CIMS instruments used for NH 3 detection, reported in the literature (Nowak et al, 2006(Nowak et al, , 2007Norman et al, 2007;von Bobrutzki et al, 2010). Table 1 summarizes these NH 3 -CIMS including the present study, with respect to the sampling inlet and CIMS configuration.…”

“…Recently, chemical ionization mass spectrometers (CIMS) have been used for fast time resolution detection for NH 3 (Nowak et al, 2006(Nowak et al, , 2007Norman et al, 2007;von Bobrutzki et al, 2010). These instruments were used in both ground-based (Nowak et al, 2006;Norman et al, 2007;von Bobrutzki et al, 2010) and aircraft studies (Nowak et al, 2007).…”

“…These instruments were used in both ground-based (Nowak et al, 2006;Norman et al, 2007;von Bobrutzki et al, 2010) and aircraft studies (Nowak et al, 2007). A summary of NH 3 -CIMS from these pre-existing techniques is given in Table 1 and will be discussed in detail in Sect.…”

TRANC – a novel fast-response converter to measure total reactive atmospheric nitrogen

“…This is due to the fact that dry N r exchange constitutes a variety of compounds with different exchange patterns and that in general, concentration and flux measurements of N r species are challenging from a metrological point of view (e.g. von Bobrutzki et al, 2010;Wolff et al, 2010a). Well-established measurement techniques (e.g.…”

“…Aerosol particles were generated using a collision-type atomizer (TSI, St. Paul, USA) with a 0.3 mm nozzle from aqueous solutions of either NaNO 3 , NH 4 NO 3 , or (NH 4 ) 2 SO 4 (0.5 g l −1 , 1 g l −1 , 0.5 g l −1 , respectively), the three most common nitrogen containing aerosol compounds (e.g. Wexler and Seinfeld, 1991;Nemitz et al, 2009). The aerosol particles were dried and flushed into a stainless steel chamber of 1 m 3 , which was kept at ambient pressure.…”