A Study at a Large Oil Spill in an Urban Site in the Northeast USA Demonstrates the Use of Radiocarbon Analysis to Accurately Measure NSZD Rates

A study was initiated in 2016 to investigate NSZD, based on CO₂ fluxes at the surface, as part of a remediation project at a large oil spill in the Northeast U.S.

This study included four seasonal NSZD rate measurements to determine temporal variability. Measurements were conducted at multiple locations, representing a variety of subsurface conditions. Besides that, the study took into consideration atmospheric pressure, temperature, and rain data for potential correlations with measured CO₂ fluxes.

The study used E-Flux CO₂ traps and the dynamic closed chamber (DCC) method to measure NSZD rates. While the results of both techniques on total CO₂ fluxes were in general agreement, it was the ¹⁴C analysis of the E-Flux CO₂ traps that ultimately enabled a precise quantification of NSZD rates.

The study highlighted the importance of NSZD for LNAPL remediation. “NSZD is not only occurring across the Site, but also occurring at a magnitude that will be an important contribution to LNAPL degradation/removal as other remedial technologies reach their limits of efficient operation”.

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