Laboratory study of effects of atmospheric pollutants on ice nucleation activity of bacteria

Abstract

Ice nuclei of some bacterial origin as ice catalysts can initiate ice nucleation at temperatures as warm as –2°C in certain laboratory experiments. The ice nucleation activities of airborne bacteria in the real atmosphere may be different from those experiments. To estimate the impact of typical atmospheric pollutants including monocarboxylic acids (MCAs), dicarboxylic acids (DCAs) and ammonia sulfate on ice nucleation activity of P.syringae pv lachrymans and P.syringae pv.panici, we have conducted some experiments by means of the modified Vali’s droplet freezing testing method in the immersion freezing mode with the mixture of the pure water and the polluted water. Our results show that the ice nucleation activity of bacterial origins can be regulated by such pollutant compounds even though the onset freezing temperatures of water droplets mainly depend on the concentrations of ice nucleation-active bacteria. Atmospheric acids can decrease ice nucleation activity of P.syringae pv lachrymans and P.syringae pv.panici. However, the onset freezing temperatures of water droplets immersed with ice nucleation-active P.syringae pv lachrymans will be enhanced by the low concentration of such atmospheric pollutants.