Soil Gas Sampling Solutions

Significance of the Topic

Soil gas sampling is a critical tool in environmental monitoring, vapor intrusion assessment, and remediation planning. Accurate characterization of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) in soil gas informs risk evaluation for indoor air quality, groundwater protection, and regulatory compliance.

Study Goals and Overview

This document presents a turnkey approach for collecting representative soil gas samples across five zones—from sub-slab beneath structures to the vadose zone. It introduces an integrated sampling train (“Chameleon”) and supporting probe, chamber, and shroud systems designed to maximize sample integrity and flexibility.

Methodology and Instrumentation

• Sampling Train Design: Inert Silonite™-coated stainless steel minimizes adsorption and carryover. Custom-machined flow paths reduce dead volume and potential leaks.
• Flow Control and Vacuum Monitoring: Replaceable critical-orifice flow controls enable rates from 10 to 200 cc/min. Integrated down-hole vacuum gauges verify that soil gas equilibrium is undisturbed.
• Sub-Slab and Vapor Intrusion: The Slab-Tight™ sampler uses a triple mechanical seal (dual O-rings and water dam) to isolate beneath-slab gas.
• Surface Flux Measurement: Enclosed flux chambers (3 L or 7.5 L) collect equilibrated vapors for rapid site screening without drilling.
• Shallow Probe Sampling: The Accu-Probe 5 ft unit employs a fixed drill bit and removable plastic sleeve to maintain a clean, direct sampling inlet.
• Deep Vadose Zone and Well Monitoring: Adaptable Micro-QT™ fittings connect the Chameleon to permanent well tubing for deep-zone sampling.
• Tracer Gas Shroud: Magnetic latch shrouds allow helium or butane leak verification of the entire train using an ultrasonic speed-of-sound helium analyzer.
• Indoor Air Quality: The CS1200E time-integrated canister sampler captures ambient VOCs from one hour to one month at controlled low flows.
• SVOC Sampling: Thermal-desorption Sorbent Pens™ collect PCBs, diesel range organics, and other SVOCs, compatible with active train sampling.

Main Findings and Discussion

The Chameleon system outperforms passive or pump-driven tube methods by eliminating batteries, reducing sample handling steps, and preserving compound recovery across wide concentration ranges. Inert flow paths and pre-shipment vacuum testing assure field integrity. Combined with targeted accessories, the solution addresses diverse site conditions while minimizing cross-contamination.

Practical Benefits and Applications

• Universal applicability for indoor air, sub-slab, surface flux, shallow probe, and deep-zone sampling.
• Streamlined field operations: no grout mess, simple probe installation, and rapid chamber placement.
• Enhanced data quality: controlled flow rates maintain phase equilibrium and reduce sampling biases.
• Modular design: interchangeable inlets/outlets and optional vacuum gauges adapt to existing well hardware.

Future Trends and Potential Applications

Advances may include integration of real-time sensors for continuous VOC monitoring, miniaturized portable chromatography modules for field screening, and data-driven adaptive sampling guided by remote sensing. Emerging low-flow automation will expand temporal resolution for indoor and subsurface studies.

Conclusion

The integrated soil gas sampling solution described here enhances accuracy, efficiency, and versatility across environmental monitoring scenarios. By combining inert materials, configurable flow control, and leak-verified assemblies, this approach sets a new standard for representative gas sampling.

Used Instrumentation

• Chameleon Soil Gas Sampling Train with Silonite™ coating
• Accu-Probe 5 ft Soil Gas Probe
• Slab-Tight™ Sub-slab Sampler
• Surface Flux Chambers (3 L, 7.5 L)
• Micro-QT™ fittings and Silonite™ MiniCans (600 mL–1.4 L)
• Helium Tracer Gas Shrouds and SG-He Analyzer
• CS1200E Time-Integrated Canister Sampler
• Sorbent Pens™ for SVOCs

Reference

No formal literature references were provided in the source document.