English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The investigation of hydroxyl radical (OH) chemistry during intensive fieldcampaigns has led to the development of several techniques dedicated toambient measurements of total OH reactivity, which is the inverse of the OHlifetime. Three techniques are currently used during field campaigns,including the total OH loss rate method, the pump–probe method, and thecomparative reactivity method. However, no formal intercomparison of thesetechniques has been published so far, and there is a need to ensure thatmeasurements of total OH reactivity are consistent among the differenttechniques. An intercomparison of two OH reactivity instruments, one based on thecomparative reactivity method (CRM) and the other based on the pump–probemethod, was performed in October 2012 in a NOx-rich environment, whichis known to be challenging for the CRM technique. This study presents anextensive description of the two instruments, the CRM instrument from MinesDouai (MD-CRM) and the pump–probe instrument from the University of Lille(UL-FAGE), and highlights instrumental issues associated with the twotechniques. It was found that the CRM instrument used in this study underestimatesambient OH reactivity by approximately 20 % due to the photolysis ofvolatile organic compounds (VOCs) inside the sampling reactor; this value isdependent on the position of the lamp within the reactor. However, this issuecan easily be fixed, and the photolysis of VOCs was successfully reduced to anegligible level after this intercomparison campaign. The UL-FAGE instrumentmay also underestimate ambient OH reactivity due to the difficulty toaccurately measure the instrumental zero. It was found that the measurementsare likely biased by approximately 2 s-1, due to impurities inhumid zero air. Two weeks of ambient sampling indicate that the measurements performed by thetwo OH reactivity instruments are in agreement, within the measurementuncertainties for each instrument, for NOx mixing ratios up to100 ppbv. The CRM technique has hitherto mainly been used inlow-NOx environments, i.e. environments with ambient NOx mixing ratioslower than a few ppbv, due to a measurement artifact generated by ambient NOinside the sampling reactor. However, this study shows that this techniquecan also be used under NOx-rich conditions if a NOx-dependentcorrection is carefully applied on the OH reactivity measurements. A full suite of 52 VOCs, NOx, and other inorganic species weremonitored during this intercomparison. An investigation of the OH reactivitybudget for this urban site suggests that this suite of trace gases canaccount for the measured total OH reactivity

Intercomparison of the comparative reactivity method (CRM) and pump–probe technique for measuring total OH reactivity in an urban environment