Replacing the AMOR by the miniDOAS in the ammonia monitoring network in the Netherlands
A. J. C. Stijn Berkhout1, Daan P. J. Swart1, Hester Volten1, Lou F. L. Gast1, Marty Haaima1, Hans Verboom1,a, Guus Stefess1, Theo Hafkenscheid1, and Ronald Hoogerbrugge11National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, the Netherlands anow at: Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, 3730 AE De Bilt, the Netherlands
Received: 16 Oct 2016 – Accepted for review: 23 Feb 2017 – Discussion started: 03 Mar 2017
Abstract. In this paper we present the continued development of the miniDOAS, an active differential optical absorption spectroscopy (DOAS) instrument to measure ammonia concentrations in ambient air. The miniDOAS has been adapted for use in the Dutch National Air Quality Monitoring Network. The miniDOAS replaces the life-expired continuous-flow denuder ammonia monitor (AMOR). From September 2014 to December 2015, both instruments measured in parallel before the change from AMOR to miniDOAS was made. The instruments were deployed on six monitoring stations throughout the Netherlands. We report on the results of this intercomparison.
Both instruments show a good uptime of ca. 90 %, adequate for an automatic monitoring network. Although both instruments produce minute values of ammonia concentrations, a direct comparison on short timescales such as minutes or hours does not give meaningful results, because the AMOR response to changing ammonia concentrations is slow. Comparisons between daily and monthly values show a good agreement. For monthly averages, we find a small average offset of 0.65 ± 0.28 µg m−3 and a slope of 1.034 ± 0.028, with the miniDOAS measuring slightly higher than the AMOR. The fast time resolution of the miniDOAS makes the instrument not only suitable for monitoring but also for process studies.
Berkhout, A. J. C. S., Swart, D. P. J., Volten, H., Gast, L. F. L., Haaima, M., Verboom, H., Stefess, G., Hafkenscheid, T., and Hoogerbrugge, R.: Replacing the AMOR by the miniDOAS in the ammonia monitoring network in the Netherlands, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-348, in review, 2017.