Diurnal variability, photochemical production and loss processes of hydrogen peroxide in the boundary layer over Europe

摘要: Hydrogen peroxide (H2O2) plays a significant role in the oxidizing capacity of atmosphere. It is an efficient oxidant liquid phase and serves as temporary reservoir for hydroxyl radical (OH), most important agent gas phase. Due to its high solubility, removal H2O2 due wet dry deposition efficient, being sink HOx (OH+HO2) radicals. In continental boundary layer, budget controlled by photochemistry, transport processes. Here we use situ observations account chemical source mechanisms study interplay between these The data were obtained during five groundbased field campaigns across Europe from 2008 2014 bring together boreal forest, two mountainous sites Germany, coastal Spain Cyprus. Most took place summer, while measurements south-west early winter. Diel variations are strongly site-dependent indicate altitude dependence. While boundarylayer mixing ratios at low-level show classical diel cycles with lowest values morning maxima around local noon, profiles reversed on nocturnal residual layer free troposphere. concentration hydrogen largely governed main precursor, hydroperoxy (HO2), shows anti-correlation nitrogen oxides (NOx ) that remove HO2. A calculation indicates all campaigns, noontime photochemical production rate through selfreaction HO2 radicals was much larger than loss reaction OH photolysis, dominant mechanism. Estimated velocities varied approximately 1 6 cm s-1, relatively observed day forested regions, indicating enhanced uptake vegetation. order reproduce change sunrise midday, variable contribution (10 %-100 %) required balance net loss. Transport likely related entrainment above growth morning. © Author(s) 2019.