Temperature dependence of carbon kinetic isotope effect for the oxidation reaction of ethane by hydroxyl radicals under atmospherically relevant conditions: experimental and theoretical studies

Ethane is the second most abundant hydrocarbon in the atmosphere, after methane, impacting on air quality, human health and climate. A quantification of its effects requires accurate knowledge of sources, processes along transport, and sinks. Carbon stable isotopic ratio investigations, complementarily to concentration measurements, were demonstrated to give more insight in source apportionment and atmospheric processing of organic compounds. Yet, apportionment of atmospheric ethane sources, processing and sinks by using the 13C isotopic composition (δ13C) requires accurate knowledge of the stable carbon kinetic isotope effect (KIE) of its atmospheric degradation through oxidation by hydroxyl (OH) radicals. Moreover, the interpretation of tropospheric ambient data should account for the temperature dependence of KIE, since the tropospheric temperatures can vary extremely, over the range of 180-320 K.