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

Abstract

[1] 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.

Evidence for iron‐mediated anaerobic methane oxidation in a crude oil‐contaminated aquifer

“…Detailed methods used for obtaining and analyzing these samples are given in Amos et al . () and Amos & Blowes ().…”

“…Samples were analyzed for dissolved gases, including CH 4 , CO 2 , N 2 , and O 2 , along with geochemical parameters, including Fe 2+ , SO 2À 4 , NO À 3 , and carbon isotope ratios in CH 4 and CO 2 . Detailed methods used for obtaining and analyzing these samples are given in Amos et al (2011) and Amos & Blowes (2008).…”

Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding

“…Amos et al . [] also investigated the fate of methane transported from the source zone in the aqueous phase, and Amos and Blowes [] designed a sampler to study the methane attenuation mechanisms. Rasa et al .…”

“…Essaid et al [1995] estimated that 36% of the hydrocarbon degradation in a crude oil plume was by methanogenesis. Methane is an important greenhouse gas and is also explosive, so recent work has examined the fate of methane produced during methanogenic degradation [Amos and Blowes, 2008;Amos et al, 2005;Molins and Mayer, 2007;Rasa et al, 2013]. The production of methane can exceed its aqueous solubility resulting in methane transport through the unsaturated zone in the gas phase [Amos et al, 2005].…”

Fate and transport of petroleum hydrocarbons in the subsurface near Cass Lake, Minnesota

“…2). The first three locations (PP-1 to PP-3) were sampled using a small-diameter downhole bladder pump (Amos and Blowes, 2008). To improve sample recovery a modified push-probe sampling procedure, termed "peristaltic bailing" (Herkelrath and others, 2008), was developed and successfully employed at the next 11 locations (PP-4 to PP-14).…”