Production of methylated mercury and lead by polar macroalgae — A significant natural source for atmospheric heavy metals in clean room compartments

During August and September 1995 samples of different species of macroalgae were collected from the Kongsfjord on Spitsbergen. These macroalgae were cultivated in incubation vessels under polar conditions and the releasing rates of methylated heavy metal compounds for mercury, lead and cadmium were determined. The analysis of monomethyl and dimethyl mercury was carried out by a gas chromatographic system with atomic fluorescence detection after conversion of monomethyl mercury into the volatile methylethyl mercury compound. A differential pulse anodic stripping voltammetric method was used for the determination of trimethyl lead and monomethyl cadmium, respectively. The different species of macroalgae showed distinct differences in the releasing rate of the various methylated heavy metals. Laminaria saccharina, for example, was found to produce monomethyl mercury, dimethyl mercury and trimethyl lead but no monomethyl cadmium. Fucus distichus released only the two methylated mercury compounds, whereas Desmarestia aculeata showed only production of dimethyl mercury. The releasing rates of ten different types of macroalgae were determined to be in the range of up to 13 pg for methylated mercury and of up to 110 pg for trimethyl lead per gram of wet alga and day by allowing incubation times of 1–5 days. Because permethylated heavy metal compounds show high volatility as well as low solubility in ocean water, they are easily emitted into the atmosphere. If therefore follows from the results of this work that macroalgae can significantly contribute to the atmospheric heavy metal content, especially of mercury by the production of dimethyl mercury, in the clean room compartments of the polar regions.