Emissions of H2 and CO from leaf litter of Sequoiadendron giganteum, and their dependence on UV radiation and temperature

Senescent and dead plant material releases carbon monoxide (CO), methane and higher hydrocarbons upon heating or irradiation with UV, but emissions of hydrogen (H2) have not been reported. This study investigated whether leaf litter is able to emit H2 and which factors control the possible emissions. In addition, the emission of CO from leaf litter was measured and compared to previous studies. H2 was released from leaf litter of sequoia (Sequoiadendron giganteum) in detectable amounts at temperatures above 45 °C, whereas CO was also emitted at ambient temperature. The emission rates of both H2 and CO increased with temperature according to the Arrhenius relation. UV radiation can induce emissions of both H2 and CO. However, UV induced H2 was only emitted under anoxic conditions, while CO emissions were higher in synthetic air, but strongly reduced in absence of oxygen.