MEASUREMENT OF MERCURY DEPOSITION USING PASSIVE SAMPLERS BASED ON THE SWEDISH (IVL)-DESIGN

The Swedish Environmental Research Institute (IVL) in 1988 developed a passive sampler for collecting wetfall and some dryfall, which they have been using successfully in a network configuration for the past 4 years. The IVL, utilizing dean handling and analysis techniques (to avoid mercury contamination), has demonstrated that (for the locations being monitored) this modified bulk sampler can provide data comparable to wetfall-only sampling and integrated event sampling. It has been generally agreed that modified bulk sampling (such as the IVL sampler) was equivalent to wet-only sampling in areas not subject to large amounts of locally resuspended soil. Wisconsin has replicated the IVL sampler (with some modifications and enhancements) and conducted a study of the feasibility of deploying a network of these passive modified bulk samplers. Triplicate samples were collected-on one purchased IVL and two Wisconsin-fabricated samplers-and analyzed for 17 weeks between mid-June and early October 1993. Comparison of rainfall volume in the IVL samplers versus the NADP Belfort rain gage (or the NADP Aerochem Metrics sampler) showed an average collection efficiency of 97% overall (with a few outliers). The average mercury concentration for all samples was 20.6 ngl(-)1 with the median at 17.1 ngl(-1). The median weekly deposition rate of 0.226 mu gm(-2) yielded an extrapolated annual rate of 11.8 mu gm(-2) comparable to other reported data for the region. This paper presents details of the modified sampler, the results of the monitoring study, as well as some analysis of data.