Total OH reactivity measurement in a BVOC dominated temperate forest during a summer campaign, 2014

Abstract A total OH reactivity measurement was conducted in coniferous forest located in Wakayama prefecture, Japan, during the summer of 2014. The average total OH reactivity, measured using a laser-induced pump and probe technique was 7.1 s −1 . The measured OH reactivity was comparable with other coniferous and temperate forest measurements and much lower than that of tropical forests. OH reactivity varied diurnally and showed moderate linear correlation with temperature ( r 2  = 0.66) and light ( r 2  = 0.53). Monoterpene emitters, Cryptomeria japonica and Chamaecyparis obutsa , are the dominant tree species in this forest. Although clean air from the sea was predominant, the beginning of the campaign was influenced by transported anthropogenic pollutants and consequently a higher average OH reactivity of 9.8 s −1 with high missing sinks of 37.3% was determined. Cleaner conditions, along with cooler day-time temperatures during in the second half of the campaign resulted in a lower average OH reactivity of 6.0 s −1 with a lower missing OH reactivity of 21.5%. Monoterpenes, isoprene, acetaldehyde were the dominant contributors to the total OH reactivity, accounting for 23.7%, 17.0% and 14.5%, respectively.