| Abstract Title: | Continuous monitoring of ammonia concentrations with Cavity Ring-Down Spectroscopy |
| Presenter Name: | Mr Rob Peters |
| Co-authors/Co-presenters: | Dr Magdalena E.G. Hofmann Mr Steve Foster Dr Ruthger van Zwieten Dr John Hoffnagle Dr Chris Rella |
| Company/Organisation: | The Dutch Scientist B.V. |
| Country: | Netherlands |
Abstract Information :
High-precision trace gas measurements are essential for a range of industrial and air quality monitoring purposes. Picarro’s Cavity Ring-Down analyzers (CRDS) have become the reference technology for continuous, high precision trace gas measurements, and they are used for numerous gas monitoring purposes like measuring continuously the ammonia concentration in ambient air, including in situ studies [1]. Key features of Picarro’s concentration CRDS analyzers are: (i) virtually calibration-free, (ii) field deployable, (iii) negligible interference (‘interference-free’), (iv) long term unattended operation, and (v) the possibility to measure multiple species. rnThe high stability of Picarro analyzers is particularly important for reactive trace gas measurements such as those for NH3, as calibration standards for reactive gases are inherently instable and not readily available. To facilitate the Picarro generally recommended yearly calibration verification, we developed an alternative method which avoids the use of reactive trace gas standards, termed the surrogate gas validation method.rnThe principle of the surrogate gas validation is that two adjacent adsorption lines of individual species behave in similar manners. As such, the accuracy and linearity of the analyzer can be validated using surrogate gases. Picarro selected these surrogate gases based on the spectroscopy for each analyzer. Key criteria for this selection process were: A. non-reactive gas, B. Commercially available certified cylinders, and C. Adsorption line adjacent to the primary gas. rnHere we present the independently characterized ppt-level performance for the Picarro G2103 NH3 analyzer [e.g. 2] as well as the recently released Picarro G2509 multi species analyzer that allows to measure NH3, CH4, CO2, N2O and H2O simultaneously. In addition, we detail the surrogate gas validation method.rnrn1. Twigg, M. M. et al. AMTD - In-situ measurements of NH3: instrument performance and applicability. Atmos. Meas. Tech. Discuss. (2022).rn2. Kamp, J. N., Chowdhury, A., Adamsen, A. P. S. & Feilberg, A. Negligible influence of livestock contaminants and sampling system on ammonia measurements with cavity ring-down spectroscopy. Atmos. Meas. Tech. Discuss. 1–20 (2019). doi:10.5194/amt-2018-377rnrn
