Intercomparison of in situ CRDS and CEAS for measurements of atmospheric N2O5 in Beijing, China

Zhiyan Li; Renzhi Hu; Pinhua Xie; Haichao Wang; Keding Lu; Dan Wang

doi:10.1016/j.scitotenv.2017.08.302

Intercomparison of in situ CRDS and CEAS for measurements of atmospheric N₂O₅ in Beijing, China

Sci Total Environ. 2018 Feb 1:613-614:131-139. doi: 10.1016/j.scitotenv.2017.08.302. Epub 2017 Sep 12.

Authors

Zhiyan Li¹, Renzhi Hu², Pinhua Xie³, Haichao Wang⁴, Keding Lu⁴, Dan Wang⁵

Affiliations

¹ Key Lab. of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China.
² Key Lab. of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China. Electronic address: rzhu@aiofm.ac.cn.
³ Key Lab. of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; CAS Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361000, China. Electronic address: phxie@aiofm.ac.cn.
⁴ State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
⁵ School of Mathematics and Physics, Anhui University of Technology, Maanshan 243032, China.

PMID: 28910715
DOI: 10.1016/j.scitotenv.2017.08.302

Abstract

Dinitrogen pentoxide (N₂O₅) is one of the basic trace gases which plays a key role in nighttime atmosphere. An intercomparison and validation of different N₂O₅ measurement methods is important for determining the true accuracy of these methods. Cavity ring down spectroscopy (CRDS) and cavity enhanced absorption spectrometer (CEAS) were used to measure N₂O₅ at the campus of the University of Chinese Academy of Sciences (UCAS) from February 21, 2016 to March 4, 2016. The detection limits were 1.6ppt (1σ) at 30s intervals for the CEAS instrument and 3.9ppt (1σ) at 10s time resolution for the CRDS instrument respectively. In this study, a comparison of the 1min observations from the two instruments was presented. The two data sets showed a good agreement within their uncertainties, with an absolute shift of 15.6ppt, slope of 0.94 and a correlation coefficient R²=0.97. In general, the difference between the CRDS and CEAS instruments for N₂O₅ measurement can be explained by their combined measurement uncertainties. However, high relative humidity (>60%) and high PM2.5 concentration (>200μg/m³) may contribute to the discrepancies. The excellent agreement between the measurement by the CRDS and CEAS instruments demonstrates the capability of the two instruments for accurately measuring N₂O₅ with high sensitivity.

Keywords: CEAS; CRDS; N(2)O(5); PM2.5; RH.