Integrated sampling and analytical approach for common groundwater dissolved gases

Area of Science:

• Environmental Science
• Analytical Chemistry
• Geochemistry

Background:

• Conventional methods for dissolved gas analysis in groundwater can be complex and prone to errors.
• Existing techniques often involve multiple steps, increasing the risk of sample alteration and bias.

Purpose of the Study:

• To introduce and validate a novel passive gas diffusion sampler (PGDS) for streamlined dissolved gas analysis.
• To develop an integrated sampling and gas chromatography (GC) method for accurate quantification of dissolved gases.

Main Methods:

• A novel passive gas diffusion sampler (PGDS) with a 4.5 mL internal volume was designed for direct injection into a GC.
• Dissolved gases were separated using parallel Rt-Molsieve 5A and Rt-Q-PLOT columns.
• Quantification was performed using a pulse discharge helium ionization detector (PD-HID).

Main Results:

• The PGDS method demonstrated a large, dynamic sampling range with a single, small-volume injection.
• The integrated sampling and GC analysis showed reduced systematic bias compared to conventional techniques.
• Incorporating total dissolved gas pressure measurements with the PGDS improved the accuracy of dissolved gas concentrations.

Conclusions:

• The novel PGDS offers a simplified, accurate, and less biased approach for dissolved gas analysis in groundwater.
• Routine use of this method can enhance understanding of groundwater chemical and biological processes.
• This technique improves the accuracy of chemical mass balance calculations in hydrogeological studies.