Versatile direct push profiler for the investigation of volatile compounds near the water table

The collection of representative samples of dissolved volatile compounds requires particular care to ensure that degassing does not occur during sampling, particularly for sites where the water table is deep. Furthermore, the investigation of physical and chemical processes involving volatile components can be enhanced by collecting vadose zone gas samples above the water table and collecting water samples very close to the water table. Here we describe the design and operation of a direct push profiler that allows the collection of gas and water samples from one hole. The profiler is capable of collecting water samples close to the water table and preserves the integrity of the samples collected from below deep water tables with respect to volatile compounds. The versatility of the profiler is due to the incorporation of a small-diameter bladder pump into the tip of a Waterloo profiler. Laboratory testing shows that samples collected from 10 cm below the water table and at 9 m depth below ground surface show no signs of degassing. Field measurements made at a petroleum spill site near Bemidji, Minnesota, provide a comparison of profiler results to samples collected from an existing well cluster, demonstrating the ability of the profiler to obtain representative samples under field conditions. Furthermore, the field tests demonstrate the utility of the direct push profiler in terms of obtaining high-resolution, high-quality data through the vadose zone and into the upper few meters of the aquifer.