Performance Monitoring

Groundwater concentrations represent conditions at a particular location and time. They can vary because of groundwater flow, recharge, pumping, dilution, plume movement, and sampling variability.

A declining concentration therefore does not necessarily prove that contaminant mass has been destroyed.

A stronger performance-monitoring program can combine concentration data with biological, isotopic, geochemical, and mass-flux measurements to evaluate not only whether concentrations are changing, but why they are changing.

Compound-Specific Isotope Analysis measures changes in the isotopic composition of individual contaminants.

Because many degradation reactions preferentially transform molecules containing lighter isotopes, the remaining contaminant can become enriched in heavier isotopes as degradation proceeds.

This makes CSIA a valuable line of evidence for distinguishing contaminant destruction from concentration reductions caused primarily by dilution, dispersion, or other physical processes.

CSIA can be used to evaluate natural attenuation, demonstrate remedy performance, distinguish degradation mechanisms, and support remediation optimization and closure strategies.

Conventional groundwater samples primarily measure concentration. iFLUX passive samplers measure groundwater flux and contaminant mass flux over a deployment period.

This provides information about both groundwater movement and the amount of contaminant mass moving through a defined area.

Mass-flux information can identify preferential transport pathways, quantify contaminant loading, improve conceptual site models, optimize amendment placement, and evaluate whether remediation is actually reducing contaminant mass discharge.

IsoFLUX combines iFLUX contaminant mass-flux measurements with Compound-Specific Isotope Analysis.

The two measurements answer complementary questions: mass flux indicates how much contaminant is moving through the aquifer, while CSIA provides evidence about whether degradation is occurring.

Together, these data can help distinguish contaminant destruction from dilution, quantify reductions in mass discharge, evaluate natural attenuation or active remediation, and provide multiple independent lines of evidence to support remedial decisions and site closure.