Groundwater sampling in karst terranes: passive sampling in comparison to event-driven sampling strategy.

Area of Science:

• Hydrogeology
• Environmental Science
• Geochemistry

Background:

• Karst aquifers are highly susceptible to contamination from surface pollutants due to features like sinkholes and losing streams.
• Traditional water-quality sampling in karst environments is challenging due to complex subsurface flow paths and rapid contaminant transport.
• Event-driven sampling, while effective, is often impractical and costly for routine monitoring.

Purpose of the Study:

• To advocate for the application of passive-sampling strategies in karst aquifers.
• To address the challenges of obtaining representative water-quality samples in complex karst terranes.
• To present passive sampling as a viable alternative to conventional methods.

Main Methods:

• Review and recommendation of passive-sampling methodologies for karst groundwater.
• Analysis of a groundwater tracing investigation in a contaminated karst site.
• Evaluation of tracer recovery data and breakthrough curves to infer flow characteristics.

Main Results:

• Groundwater tracing confirmed connectivity between a contaminated site and offsite springs/wells.
• Tracer transport rates were relatively slow (~0.02 m/s), with erratic and spiky breakthrough curves.
• Passive sampling is proposed as an effective strategy for representative karst groundwater sampling.

Conclusions:

• Passive sampling provides a practical and effective approach for monitoring water quality in karst aquifers.
• This methodology is particularly beneficial in complex, folded, and faulted karst systems.
• Implementing passive sampling can overcome limitations associated with traditional and event-driven sampling techniques.