Chloride Methylation by Plant Pectin: An Efficient Environmentally Significant Process

Abstract

Atmospheric chloromethane (CH 3 Cl) plays an important role in stratospheric ozone destruction, but many uncertainties exist regarding the strengths of its sources and sinks and particularly regarding the processes generating this naturally occurring gas. Evidence is presented here that CH 3 Cl is produced in many terrestrial environments by a common mechanism. Abiotic conversion of chloride to CH 3 Cl occurs readily in plant material, with the widespread plant component pectin acting as a methyl donor. Significant CH 3 Cl emissions from senescent and dead leaves were observed at ambient temperatures; those emissions rose dramatically when temperatures increased. This ubiquitous process acting in terrestrial ecosystems and during biomass burning could contribute the bulk of atmospheric CH 3 Cl.