Ethane-Based Chemical Amplification Measurement Technique for Atmospheric Peroxy Radicals
2017
Wood, Ezra C. | Deming, Benjamin L. | Kundu, Shuvashish
Peroxy radicals play important roles in the atmospheric oxidation of organic compounds and the formation of ozone and secondary organic aerosol. There are few peroxy radical measurement techniques; the most common, chemical amplification using CO and NO, requires the use of toxic reagents, and its calibration factor is very sensitive to relative humidity. We present a new method for quantifying atmospheric peroxy radicals, ECHAMP (Ethane CHemical AMPlifier). Sampled air is mixed with NO and C₂H₆ (rather than CO), effecting a series of reactions that ultimately produces 25 molecules of NO₂ per sampled peroxy radical under dry conditions. This “amplification” factor decreases to 17 at a relative humidity of 50%, yielding a 1σ precision for 90 s average measurements of 0.8–2.5 ppt depending on the atmospheric variability of ozone. We demonstrated the utility of the new technique with measurements in Bloomington, IN, in July 2015.
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