Assessment of 222Radon progeny loss in long tubing based on static
filter measurements in the laboratory and in the field
Ingeborg Levin1, Dominik Schmithüsen1, and Alex Vermeulen2,a1Institut für Umweltphysik (IUP), Heidelberg University, 69120 Heidelberg, Germany 2Energy research Centre of the Netherlands (ECN), 1755LE Petten, The Netherlands anow at: ICOS ERIC - Carbon Portal, Lund, Sweden
Received: 01 Apr 2016 – Accepted for review: 27 Jun 2016 – Discussion started: 30 Jun 2016
Abstract. Aerosol loss in air intake systems potentially hampers the application of one-filter systems for progeny-based atmospheric 222Radon (222Rn) measurements. The artefacts are significant when air has to be collected via long sampling lines, e.g. from elevated heights at tall tower observatories. Here we present results from a study, determining 222Rn progeny loss from ambient air sampled via 8.2 mm inner diameter (ID) Decabon tubing (laboratory test) and from pre-installed 10 mm ID tubing at the Cabauw meteorological tower in the Netherlands. Progeny loss increased exponentially with length of the tubing, decreasing sampling efficiency to 66 % for 8.2 mm ID rolled-up tubing of 200 m length. Theoretical estimation of the loss yielded a sampling efficiency of 64 % for the same tubing, when taking into account turbulent inertial deposition of aerosol to the walls as well as loss due to gravitational settling. At Cabauw tower, theoretical estimates of the loss in vertical tubing with 10 mm ID and 200 m lengths yielded a total efficiency of 75 %, while we observed a slightly smaller sampling efficiency of 73 %. 222Rn progeny loss increased strongly at activity concentrations below 1 Bq m−3. Based on our experiments, an empirical correction function for 222Rn progeny measurements when sampling through long Decabon tubing was developed, allowing correction of respective measurements with an estimated uncertainty of 10–20 % for activity concentrations above 1 Bq m−3 and less than 10 % for activity concentrations above 2 Bq m−3.
Levin, I., Schmithüsen, D., and Vermeulen, A.: Assessment of 222Radon progeny loss in long tubing based on static
filter measurements in the laboratory and in the field, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-112, in review, 2016.