Articles | Volume 14, issue 23
Research article
15 Dec 2014
Research article |  | 15 Dec 2014

Emission of iodine-containing volatiles by selected microalgae species

U. R. Thorenz, L. J. Carpenter, R.-J. Huang, M. Kundel, J. Bosle, and T. Hoffmann

Abstract. In this study we present the results of an emission study of different phytoplankton samples in aqueous media treated with elevated ozone levels. Halocarbon measurements show that the samples tested released bromoform and different iodocarbons, including iodomethane, iodochloromethane and diiodomethane. Iodide and iodate levels in the liquid phase were representative of concentrations of surface water in a natural environment. Measurement of volatile iodine (I2) emissions from two diatom samples (Mediopyxis helysia and Porosira glacialis) and the background sample (F/2 medium from filtered natural seawater) showed that the quantity of evolved I2 depends on the ozone concentration in the air. This behaviour was assumed to be caused by the oxidation reaction mechanism of iodide with ozone. The I2 emission flux agrees with model calculations at different iodide concentrations. The I2 emission of a natural plankton concentrate sample was, however, very low compared to other samples and showed no dependence on ozone. The reason for this was shown to be the low iodide concentration in the algal suspension, which seems to be the limiting factor in the oxidative formation of I2.

Short summary
Phytoplankton suspensions were treated with high and low ozone levels, and volatile iodine (I2)-containing compounds were measured. Iodocarbon emissions were independent of the ozone level. I2 emission showed a strong dependency on the ozone level in the air as well as on the iodide concentration in the sample suspension. The experiments show that microalgae suspensions are capable of emitting I2 by the reaction of ozone with dissolved iodide at the air-water interface under natural conditions.
Final-revised paper