Methodologies for Trace Chemical Sampling and Analysis of Snow, Water and Soil in Support of the WWMPP: Summary and Lessons Learned

The Desert Research Institute (DRI) is one of the pioneers in performing trace chemical analyses of snow for the dual purposes of: 1) validation of weather modification efforts (by verifying that silver iodide levels above natural background values are present in snow) and 2) ensuring that the quantities of silver iodide introduced into the environment through cloud seeding activities are, in accordance with best practices, of such a low concentration so as not to pose a significant environmental hazard.

For the last five seasons of the WWMPP, DRI has conducted snow, water and, for the last two years, soil sampling campaigns for the dual purposes noted above. In particular, physical sampling of snow and the resultant trace chemical analysis were hoped to be able to provide additional physical-chemical validation to the Randomized Statistical Experiment in the Medicine Bow and Sierra Madre ranges of southern Wyoming. Sampling of snow involved two different approaches: 1) Very high temporal resolution sampling at specific locations within the expected RSE target areas while, and shortly after, seeding events were in progress; 2) vertical profile sampling of snow columns at periodic intervals during the winter season at more sites within the target areas.

This talk will focus on the methodologies, and changes in those methodologies, that occurred within the five-year period that sampling and trace chemical analysis were performed. Although much of the talk will focus on the snow sampling approaches noted in the preceding paragraph, we will also discuss the water and soil sampling and analysis methods that were performed primarily to ensure that harmful levels of silver were not being introduced into the environment by cloud seeding. Although relevant results relating to changes in methodologies will be referenced, companion papers will provide the principal results of the trace chemical analysis.