Ethylene oxide monitor with part-per-trillion precision for in situ measurements
Tara I. Yacovitch, Christoph Dyroff, Joseph R. Roscioli, Conner Daube, J. Barry McManus, and Scott C. Herndon
Atmospheric Measurement Techniques
Atmos. Meas. Tech., 16, 1915-1921
Publication Date: April 13, 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
Abstract.
An Aerodyne tunable infrared laser direct absorption spectrometer with a multipass cell with a 413 m path-length for the detection of ethylene oxide (EtO) is presented (TILDAS-FD-EtO). This monitor achieves precisions of <75 ppt or < 0.075 ppb s−1 and < 20 ppt in 100 s (1σ ). We demonstrate precisions averaging down to 4 ppt h−1 (1σ precision) when operated with frequent humidity-matched zeroes. A months-long record of 2022 ambient concentrations at a site in the eastern United States is presented. Average ambient EtO concentration is on the order of 18 ppt (22 ppt standard deviation, SD). Enhancement events of EtO lasting a few hours are observed, with peaks as high as 600 ppt. Back-trajectory simulations suggest an EtO source nearly 35 km away. This source along with another are confirmed as emitters through mobile near-source measurements, with downwind concentrations in the 0.5 to 700 ppb range depending on source identity and distance downwind.