A laboratory and theoretical study on the uptake of sulfur dioxide gas by small water drops containing hydrogen peroxide under laminar and turbulent conditions

Laboratory experiments are described where the uptake of SO2 gas by water drops containing H2O2 is investigated where the taken up S(IV) is quickly converted to S(VI). During the gas uptake the drops were freely suspended at their terminal velocity by means of the Mainz vertical wind tunnel. Two series of experiments were carried out, one with a laminar air flow in the wind tunnel, one with a turbulent air flow in the wind tunnel. Afterwards, the experimental results were compared against model computations using the so-called fully mixed convective diffusion model. The experimental results for laminar flow conditions showed that the fully mixed convective diffusion model for the uptake of SO2 by water drops is not only applicable to large water drops of millimeter size, as demonstrated in our previous papers, but also to small water drops of some hundreds micron size. Our experimental results for turbulent flow conditions allow, within the experimental error, to conclude that turbulence in the air surrounding falling drops has no measurable effect on the uptake of SO2 by freely falling water drops.