Field Test Study Conducted in Association with The University of Waterloo
Note the very good correlation coefficients (R-squared) with both polyethylene diffusion bags and low-flow purge sampling.
The linear trendline slope of less than 1 for both low-flow and PDBs indicates a consistent pattern of slightly higher results for Snap Samples. A 1:1 trendline would indicate a direct 1:1 correlation. These results show about a 1.1:1 ratio across wide concentration ranges.
T-test statistics show that these results are significant at the 95% confidence level.
This site is a TCE release site with consituents limited to TCE, cis-1,2 DCE, trans-1,2, DCE and VC. Seven wells were sampled, but one well had high concentrations probably associated with NAPL. Pumped results from this well were inconsistent with the other wells and may indicate entrainment of sorbed NAPL on particulates in the pumped sample. This well was excluded from the data plot. The remaining 6 downgradient plume wells with only dissolved constituents showed very good correlation between the Snap Sampler and low flow (R-squared coefficient greater than 0.99). The Snap Sampler in this case showed somewhat higher average VOC concentrations compared to the baseline sampling method (slope of the best fit line y=1.15). This difference is most like attributed to avoidance of surface bottle filling with the Snap Sampler.
