BIOGENIC VOLATILE ORGANOIODINE AND ORGANOBROMINE COMPOUNDS RELEASED FROM POLAR MACROALGAE

During September 1992 three different species of macroalgae (Laminaria saccharina, Desmarestia aculeata and Fucus distichus) were collected on Spitsbergen. These macroalgae were cultivated in incubation vessels on Spitsbergen under polar conditions and the releasing rates of volatile organoiodine and organobromine compounds were determined by using a purge and trap system for the isolation of the compounds followed by a gas chromatographic separation with an electron capture detection. Using this method the releasing rates of CH3I, CH2ClI, CH3CH2CH2I, CH3CHICH3, CH2I2, CHBrCl2, CHBr2Cl, CH2Br2, and CHBr3 were determined. The three species of macroalgae showed distinct differences in the releasing rates for the various substances. Laminaria saccharina was found to produce the highest amounts of bromoform and dibromomethane with average releasing rates of about 72 and 8 ng per g of alga (wet weight) and day, respectively. This species also showed the highest releasing rate for diiodomethane with about 4 ng g-1 d-1, whereas the average releasing rates for methyl iodide, 1-propyl iodide, and 2-propyl iodide were highest for Fucus distichus with 0.8, 0.15, and 0.8 ng g-1 d-1, respectively. These results show that macroalgae are responsible for part of the total production of volatile iodinated and brominated organic substances in the polar coastal seawater and therefore for their corresponding atmospheric concentration, which plays an important role in atmospheric chemistry. In addition, it could be shown that every species of macroalgae has its own releasing pattern of iodinated compounds, which can possibly be used in the future for source identification.