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Abstract

This study presents a stepwise concept to assess the in situ microbial mineralization of petroleum hydrocarbons (PHC) in aquifers. A new graphical method based on stable carbon isotope ratios (delta 13C) was developed to verify the origin of dissolved inorganic carbon (DIC). The concept and the isotope method were applied to an aquifer in Student, Switzerland, in which more than 34,000 liters of heating oil were accidentally released. Chemical analyses of ground water revealed that in this aquifer locally, anaerobic conditions prevailed, and that PHC mineralization was linked to the consumption of oxidants such as O2, NO3-, and SO4(2-) and the production of reduced species such as Fe2+, Mn2+, H2S and CH4. However, alkalinity and DIC balances showed a quantitative disagreement in the link between oxidant consumption and DIC production, indicating that chemical data alone may not be a reliable assessment tool. delta 13C ratios in DIC have been used before for bioremediation assessment, but results were reported to be negatively influenced by methanogenesis. Using the new graphical method to display delta 13C data, it was possible to identify anomalies found in methanogenic monitoring wells. It could be shown that 88% of the DIC produced in the contaminated aquifer originated from microbial PHC mineralization. Thus, the new graphical method to display delta 13C ratios appears to be a useful tool for the assessment of microbial hydrocarbon mineralization in a complex environment.

CO2 Inflow and Elements Desorption Prior to a Seismic Sequence, Amatrice‐Norcia 2016, Italy

“…A preseismic and coseismic elemental contribution from bituminous-asphaltic and/or hydrothermal fluids was hypothesized (Barberio et al, 2017). However, neither additional trace elements (e.g., Ba, Ni, and Mn) nor salinity and oxygen-hydrogen stable isotope ratio changes-which should be a consequence of hydrocarbon decomposition (Bolliger et al, 1999;Tissot & WeIte, 1984) and fluid mixing, respectively-were detected (Barberio et al, 2017). The possible cause of the anomalies must explain the steady characteristics of groundwater flow and the simultaneous increase of selected trace elements.…”

Carbon Isotope Fractionation in the Reductive Dehalogenation of Carbon Tetrachloride at Iron (Hydr)Oxide and Iron Sulfide Minerals

“…Quantification of in situ degradation at contaminated sites often suffers from the inability to establish reasonable mass balances based on concentration data from a limited number of sampling wells. Recently, compound-specific isotope analysis (CSIA) has evolved into a useful tool to gain additional information on the fate of groundwater contaminants ( − ) because during irreversible chemical reactions (i.e., the cleavage or formation of chemical bonds) a shift between the isotope ratios of the contaminant and its degradation product(s) may occur known as kinetic isotope fractionation. In the reductive transformation of the priority groundwater pollutant carbon tetrachloride (CCl 4 ), for example, an initial electron transfer has been shown to be directly concerted with the cleavage of a C−Cl bond ().…”

Recovery of in-situ methanotrophic activity following acetylene inhibition

“…Methane has been previously detected in groundwater of monitoring wells PS3, 4 and 5, all located within the contaminant source area at this site (Bolliger et al 1999;Bolliger et al 2000) (Fig. 1a).…”