DETERMINATION OF INORGANIC AND ORGANIC TRACES IN THE CLEAN ROOM COMPARTMENT OF ANTARCTICA

The concentration of most elements and of their species as well as of organic compounds in Antarctica is in an extremely low range, normally at the pg g-1 and pptv level or even below. Sensitive and reliable analytical methods must therefore be applied to determine these substances in this remote area. Differential pulse anodic stripping voltammetry, ion chromatography, and gas chromatography with electron capture detection can be used directly in Antarctica under strict contamination control for the determination of some heavy metals, anions, and volatile halogenated hydrocarbons, respectively. Isotope dilution mass spectrometry can be applied in the home laboratory for the calibration and completion of this data. The concentration of most of the heavy metals in Antarctic snow and ice lies in the low pg g-1 range and below. Evidently higher concentrations were only found in hoar-frost samples. It could be shown that even at such a low concentration level lead is partially of anthropogenic, chromium only of terrestrial origin. First indications have been obtained that cadmium is possibly influenced by biological processes in the polar sea. The nitrate content of precipitation in Antarctica agrees with the natural background level of 200-230 ng g-1 found in remote areas of the North and South Atlantic. HNO3 is the most dominant nitrate for-m in the Antarctic atmosphere and can be re-emitted from snow on the surface after its deposition. A natural cycle of nitrate in Antarctica is presented. High enrichment factors for iodine in relation to the chloride concentration have been observed in Antarctic snow compared with the seawater composition. In the Antarctic atmosphere, iodine is preferably associated with the smallest aerosol particles in contrast to chloride which shows the highest concentration in the larger sea salt particles. From this it follows that different types of substances must be responsible for this enrichment effect. HI, I2, HOI, and organoiodine have been identified as volatile iodine species in the atmosphere. Biogenically produced methyl iodide is the most abundant organoiodine compound and, after photodissociation, can act as a natural iodine contaminant in the interior of Antarctica. From these results a natural cycle could also be established for iodine. However, the most dominant biogenic halogenated methane in Antarctica is bromoform with average concentrations of about 6 ng l-1 in the polar surface seawater and 6 pptv in the atmosphere measured during the Antarctic spring. CHBr3 correlates well in its seawater concentration with those of other brominated methanes, e.g. CH2Br2 and CHBrCl2. Under high biological production rates these halogenated methanes can possibly contribute to the greenhouse effect and they will also influence, at least, the tropospheric ozone.