Global uptake of carbonyl sulfide (COS) by terrestrial vegetation: Estimates corrected by deposition velocities normalized to the uptake of carbon dioxide (CO 2 )

Abstract. COS uptake by trees, as observed under dark/light changes and under application of the plant hormone abscisic acid, exhibited a strong correlation with the CO2 assimilation rate and the stomatal conductance. As the uptake of COS occurred exclusively through the stomata we compared experimentally derived and re-evaluated deposition velocities (Vd for COS and CO2). We show that Vd of COS is generally significantly larger than that of CO2. We therefore introduced this attribute into a new global estimate of COS fluxes into vegetation. The global COS uptake by vegetation as estimated by the new model ranges between 0.69-1.40 Tg a-1, based on the Net Primary Productivity (NPP). Taking into account Gross Primary Productivity (GPP) the deposition estimate ranges between 1.37-2.81 Tg a-1 (0.73-1.50 Tg S a-1). We believe that in order to obtain accurate and reliable global NPP-based estimates for the COS flux into vegetation, the different deposition velocities of COS and CO2 must be taken into account.