Methyl chloride and C2–C5 hydrocarbon emissions from dry leaf litter and their dependence on temperature

Abstract

Emissions of methyl chloride and several C2–C5 hydrocarbons from dry leaf litter at temperatures in the range 20–100 °C are reported for different plant species. The emission rates of ethane, ethene, propane, propene, n-pentane and methyl chloride increased with temperature. Hydrocarbon emission rates up to 0.88 ng gdw−1 h−1 were measured at 20 °C, while methyl chloride emission rates between 0.03 and 0.85 ng gdw−1 h−1 were observed at this temperature. At 70 °C emission rates increased up to 650 ng gdw−1 h−1 for C2–C5 hydrocarbons and up to 18 μg gdw−1 h−1 for methyl chloride. The Arrhenius relation can be used to describe the temperature dependence of methyl chloride emissions, while for hydrocarbon emissions deviations from this relation were observed. The emissions were not due to enzymatic activity, which was indicated by emission rates that continuously increased with increasing temperature, and activation energies higher than 50 kJ mol−1. At constant temperature, the emission rate of both methyl chloride and hydrocarbons from dry leaf litter decreased in time. At high temperatures (80–100 °C) this was noticeable on a timescale of hours, while at low temperatures (20–30 °C) the decrease was very slow and only visible on a timescale of months. Emission of methyl chloride from leaf litter might be significant for its global budget, while temperature induced hydrocarbon emissions from leaf litter are likely insignificant.