A downhole passive sampling system to avoid bias and error from groundwater sample handling

Area of Science:

• Environmental Science
• Hydrogeology
• Analytical Chemistry

Background:

• Traditional groundwater sampling methods can introduce bias and errors through sample handling and exposure.
• Well purging, often required, can alter in-situ conditions and generate disposal concerns.

Purpose of the Study:

• To introduce and evaluate a new downhole groundwater sampler designed to reduce bias and error.
• To assess the performance of the In Situ Sealed (ISS) sampler against conventional techniques.

Main Methods:

• The "In Situ Sealed" (ISS) device utilizes double end-opening bottles set in an open position for flow-through equilibration.
• Bottles are triggered to close downhole, enabling passive, non-purge sampling and sealed sample retrieval.
• Six field studies compared ISS sampling with traditional methods for various groundwater constituents.

Main Results:

• ISS sampling typically yielded higher volatile organic compound (VOC) concentrations compared to traditional methods.
• ISS results for arsenic showed less bias than both filtered and unfiltered purge samples.
• Inorganic constituents demonstrated parity between ISS and traditional sampling methods.

Conclusions:

• The ISS sampler is a versatile tool that enhances reproducibility and avoids low VOC recovery bias.
• This passive, non-purge sampling method simplifies procedures and eliminates purge water disposal issues.
• The ISS sampler offers a more accurate and reliable approach for groundwater quality assessment.