Table 3.

Advantages and disadvantages of dynamic and passive methods to collect volatile organic compounds (VOCs) in belowground environments.

Method to collect belowground VOCs	Advantages	Disadvantages	After sampling/pre-analysis process
Dynamic sampling (Tholl et al., 2021) Gas chromatography–mass spectrometry (GC-MS), Pull/push–pull systems (Adsorbent traps, Trapping Super-Q)	➢Separate sampling and analysis times ➢Controlled collection and pre-concentration of VOCs ➢Quantitative and qualitative analyses ➢Repeatable sample analysis ➢Application of miniature devices (e.g., Super-Q trap)	➢High Cost ➢More challenging to apply in the field or other places ➢Sampling requires equipment (pumps, flow meters, charcoal filters, VOC traps) ➢Use of organic solvents in solvent elution and liquid injection	➢Method collects volatile mixtures, need to future step to distinguish original VOCs ➢Trap>>elute traps with solvents for liquid injection or use thermal desorption of traps>>GC-MS or Gas Chromatography–Time-of-Flight Mass Spectrometry (GCxGC-Tof MS) analysis
Passive sampling (Tholl et al., 2021) GC-MS, SPME, Polytetrafluoroethylene (PTFE) tubing	➢Low cost ➢Miniature sampling devices, sensitive, cost effective ➢No consumption of organic solvents, clear spectrum of VOCs without solvent background interference ➢Sampling is a snapshot of the VOC current state rather than for a time interval	➢Separate sampling and analysis times ➢One-time only sample analysis due to thermal desorption (SPME) ➢Limited quantitative analysis ➢Adsorbent preference for analytes	➢Method collects volatile mixtures>> directly measure with thermal desorption of fibers or tubing>>GC-MS or GCxGC-Tof MS analysis