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Comparison of Radiocarbon‐ and Background Location‐Corrections on Soil‐Gas CO 2 Flux‐Based NSZD Rate Measurements at Petroleum Impacted Sites
Author(s) -
Zimbron Julio A.
Publication year - 2022
Publication title -
groundwater monitoring and remediation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 47
eISSN - 1745-6592
pISSN - 1069-3629
DOI - 10.1111/gwmr.12538
Subject(s) - flux (metallurgy) , environmental science , carbon fibers , radiocarbon dating , fraction (chemistry) , soil gas , fossil fuel , natural gas , petroleum , soil science , soil water , chemistry , environmental chemistry , atmospheric sciences , geology , materials science , composite material , paleontology , organic chemistry , composite number
The measurement of contaminant natural source zone depletion (NSZD) rates has become an important tool to manage petroleum contaminated sites. Most NSZD rate measurement methods rely on a balance on the biodegradation by‐products (either carbon or heat). Carbon balance‐based methods stoichiometrically convert measured soil‐gas CO 2 flux related to contaminant degradation to equivalent contaminant mass loses. CO 2 flux‐based methods require separating the fraction of the total CO 2 flux produced by NSZD from the fraction of CO 2 flux produced by natural soil processes (due to modern carbon turnover). Two method corrections are available to distinguish the nature of the measured CO 2 flux: (1) The background location correction subtracts a measurement from an unimpacted location from measurements collected at impacted locations, and (2) a location‐specific radiocarbon ( 14 C) analysis that differentiates the modern and old carbon fractions of each total CO 2 measurement. This work evaluates both correction approaches using 36 measurements at impacted locations from five sites. The 14 C‐corrected data shows that the magnitude and variability of the modern carbon‐related fraction (noise) and the NSZD related fossil fuel signal are similar, suggesting a location‐specific correction is more valid. Only one sparsely vegetated arid site showed close agreement between both corrections ( 14 C‐ and background location). These results highlight the strong effect of the correction method used on NSZD rate measurements, and the importance of considering data quality on the subsequent data management process.