Total OH Reactivity Measurements in the Boreal Forest

Abstract:

INTRODUCTION Atmospheric total OH reactivity (R_total) can be measured (Kovacs and Brune, 2001; Sinha et al., 2008) or it can be calculated according to R_total = ∑_i k_{OH+X_i} [X_i] where k_{OH+X_i} corresponds to the reaction rate coefficient for the reaction of OH with a given compound X_i and [X_i] its concentration. Studies suggest that in some environments a large fraction of missing reactivity, comparing calculated R_total with ambient total OH reactivity measurements (Di Carlo et al., 2004; Hofzumahaus et al., 2009).

In this study R_total has been measured using the Comparative Reactivity Method (Sinha et al., 2008). Levels of the reference compound (pyrrole, C₄H₅N) are monitored by gas chromatography every 2 minutes and R_total is derived from the difference of reactivity between zero and ambient air.

RESULTS Around 36 hours of preliminary total OH reactivity data (30 May until 2 June 2015) are presented in Fig. 1. Its range matches previous studies for this site (Nölscher et al., 2012; Sinha et al., 2010) and is similar to values in another pine forest (Nakashima et al., 2014). The setup used during the period presented here has been updated and more recent data will be presented, as well as a comparison with calculated OH reactivity from measured individual species. ACKNOWLEDGEMENTS

This work was supported by Academy of Finland (Academy Research Fellowship No. 275608). The authors acknowledge Juuso Raine for technical support. REFERENCES

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