Determination of Microbial Carbon Sources and Cycling during Remediation of Petroleum Hydrocarbon Impacted Soil Using Natural Abundance ¹⁴C Analysis of PLFA

Abstract

In a petroleum impacted land-farm soil in Sarnia, Ontario, compound-specific natural abundance radiocarbon analysis identified biodegradation by the soil microbial community as a major pathway for hydrocarbon removal in a novel remediation system. During remediation of contaminated soils by a plant growth promoting rhizobacteria enhanced phytoremediation system (PEPS), the measured Delta(14)C of phospholipid fatty acid (PLFA) biomarkers ranged from -793 per thousand to -897 per thousand, directly demonstrating microbial uptake and utilization of petroleum hydrocarbons (Delta(14)C(PHC) = -1000 per thousand). Isotopic mass balance indicated that more than 80% of microbial PLFA carbon was derived from petroleum hydrocarbons (PHC) and a maximum of 20% was obtained from metabolism of more modern carbon sources. These PLFA from the contaminated soils were the most (14)C-depleted biomarkers ever measured for an in situ environmental system, and this study demonstrated that the microbial community in this soil was subsisting primarily on petroleum hydrocarbons. In contrast, the microbial community in a nearby uncontaminated control soil maintained a more modern Delta(14)C signature than total organic carbon (Delta(14)C(PLFA) = +36 per thousand to -147 per thousand, Delta(14)C(TOC) = -148 per thousand), indicating preferential consumption of the most modern plant-derived fraction of soil organic carbon. Measurements of delta(13)C and Delta(14)C of soil CO(2) additionally demonstrated that mineralization of PHC contributed to soil CO(2) at the contaminated site. The CO(2) in the uncontaminated control soil exhibited substantially more modern Delta(14)C values, and lower soil CO(2) concentrations than the contaminated soils, suggesting increased rates of soil respiration in the contaminated soils. In combination, these results demonstrated that biodegradation in the soil microbial community was a primary pathway of petroleum hydrocarbon removal in the PEPS system. This study highlights the power of natural abundance radiocarbon for determining microbial carbon sources and identifying biodegradation pathways in complex remediation systems.

Advection of surface-derived organic carbon fuels microbial reduction in Bangladesh groundwater

“…Compound-specific radiocarbon analysis of cellular biomass can be compared with the radiocarbon content of different OC sources that have a unique radiocarbon signature to provide a direct measure of carbon substrate utilization in the environment (15)(16)(17)(18)(19)(20)(21). For example, this method has been used to document the preference of microbes for degradation of petroleum hydrocarbons and utilization of organic matter derived from shale weathering.…”

Microbe‐Assisted Phytoremediation of Petroleum Impacted Soil

“…Further experiments definitively showed that the PHC were degraded in situ in the rhizosphere and that biodegradation by the microbial community in PHC-impacted soils is a major pathway for PHC removal by PEPS [128,136]. Further experiments definitively showed that the PHC were degraded in situ in the rhizosphere and that biodegradation by the microbial community in PHC-impacted soils is a major pathway for PHC removal by PEPS [128,136].…”

“…This provides multiple benefits: it eliminates ecological risk; and PGPR isolated from specific PHC-contaminated soils are PHC tolerant and are often PHC degraders, using PHC as their source of carbon in the nutrient-poor soils [136]. This strategy also facilitates native habitat reconstruction/reclamation following remediation.…”

“…Although it has been definitively shown that PHC are degraded in soils during PEPS treatment [128,136], accumulation of BOC can confound the results of standard PHC analytical methods. This issue was discussed in Section 16.1.3.…”

The relative contribution of methanotrophs to microbial communities and carbon cycling in soil overlying a coal-bed methane seep

“…CBM) into biomass and organic carbon pools. Carbon-14 values are readily corrected for kinetic isotope fractionation effects by a d 13 C value-based normalization (Stuiver & Polach, 1977) and have been successfully used to trace the incorporation of fossil carbon by microorganisms in a variety of environments (Petsch et al, 2001;Pearson et al, 2005;Slater et al, 2005Slater et al, , 2006Wakeham et al, 2006;Ahad et al, 2010;Cowie et al, 2010;. We used a dual carbon isotope approach, in combination with compound-specific biomarker and 16s rDNA techniques, to characterize methanotroph and nonmethanotroph populations in soil overlying a natural coal-bed methane (CBM) seep.…”