Sampling of Glacial Snow for Pesticide Analysis on the High Plateau Glacier of Mount Logan

Résumé

Recently there have been a number of attempts to determine the presence of pollutants in remote areas of the world. The snow of glaciers is a particularly interesting subject for such work, since it contains a record of past years as well as the present. ... Such pollutants are transported by the atmosphere, and it is especially interesting to know if they are present in precipitation that forms at high altitude. As part of the Ice Field Ranges Research Project (IRRP) of 1970, we undertook the study of another common pollutant, the pesticide DDT. Here we report on our attempt to develop techniques for taking snow samples at high altitude in locations where work had to be done under adverse conditions, and with simple equipment. Samples were taken at an elevation of 5,364 metres on Mount Logan, Yukon Territory, Canada. ... The work was performed at temperatures below -20°C, and often in high winds. At this elevation the effects of hypoxia are quite marked .... when unpacked in the field, quantities of an oily material were found on the [new SIPRE snow] auger. It was not practical to achieve a thorough cleaning under field conditions, but as much of the material as possible was removed by using Coleman Fuel - a highly refined non-leaded gasoline designed for camp stoves. Provision of suitable sample containers was an important aspect of the preparations. Two-gallon wide-mouth Nalgene jugs were used on the glacier. The mouth was large enough so that the snow core could slide into the jug directly from the auger without intermediate handling. As long as the samples remained frozen, they could be stored in plastic. However, since liquid water slowly leaches material from the jugs, the samples were transferred to glass jars as soon as they melted. ... A special effort was made in the precleaning of both jars and jugs because of the low levels of pesticide expected. ... Precautions were taken to avoid contamination during sample collection. The first few samples were discarded in the hope of removing any residual contamination from the auger. During the sampling process the auger was never touched by bare hands or gloves. The only surface which came into contact with the samples before their arrival at the laboratory were the auger and the precleaned jugs and jars. At the end of the work, one sample was deliberately mishandled as a control. It subsequently showed no contamination from either polychlorinated biphenyls (PCBs) or DDT. Nineteen samples were taken at depths of from 1 to 15 metres. The DDT analysis was carried out ... using a gas chromatographic technique .... DDT was not detected in any of the samples. In seven of the samples the lower limit of detectibility for DDT was 5 nanograms per liter. Due to interference, apparently from PCBs, 10 to 50 ng/l of DDT could have been present in the remaining samples and not have been detected by this method. It is suggestive that the samples showing no PCB contamination were the last ones taken. It is likely that the PCB contamination came from the oily material originally on the auger, and that the remnant of this was removed during the early part of the drilling. On the basis of these results it seems that sampling of glacial snow for trace organic pollutants is feasible, even when samples must be taken under unfavourable conditions with primitive techniques. It is of paramount importance to preclean every surface that will come into contact with the sample, both sampling tools, and sample containers. ...