Turbulent transfer of sulphur dioxide to a wheat crop

Fluxes of sulphur dioxide to wheat were measured over two growing seasons. The deposition velocity, v g , depended primarily on affinities of surfaces for SO 2 and varied from less than 0.1 to about 1.5cms −1 . Stomata were an important sink, and diurnal changes in stomatal resistance accounted for most of the variation in v g when leaves were green and dry. When leaves were wet with dew, v g was generally large, irrespective of the physiological state of vegetation. A resistance analogue of transfer to the canopy agrees well with published work and is used to estimate seasonal uptake of SO 2 by the crop, showing that 30% of the sulphur content of the crop at harvest was probably supplied by absorption of SO 2 through stomata.