Biodegradation of crude oil into nonvolatile organic acids in a contaminated aquifer near Bemidji, Minnesota

K. A. Thorn; G. R. Aiken

doi:10.1016/s0146-6380(98)00167-3

Home/Archive/USGS

USGS · 70185269

Biodegradation of crude oil into nonvolatile organic acids in a contaminated aquifer near Bemidji, Minnesota

K. A. Thorn·G. R. Aiken

View original source ↗Export metadata ↓

Abstract

As the result of a pipeline burst, a body of light aliphatic crude oil floats atop the groundwater in a shallow sand and gravel aquifer in a remote area outside Bemidji, Minnesota. Biodegradation has resulted in the formation of a plume of DOC downgradient from the oil body. Groundwater has also been contaminated in an area known as the spray zone, from vertical infiltration of DOC resulting from biodegradation of crude oil in the overlying unsaturated zone. The majority of DOC in the contaminated groundwater is in the form of nonvolatile organic acids (NVOA's) which represent the partial oxidation products of the crude oil constituents. The NVOA's have been classified into three fractions according to their isolation on XAD resins: hydrophobic neutrals (HPO-N), hydrophobic acids (HPO-A) and hydrophilic acids (HPI-A). These fractions of NVOA's were isolated from a well downgradient from the oil body (well 530; DOC=21 mg C/l), from a well in the spray zone (well 603; DOC=15 mg C/l) and from an uncontaminated well upgradient of the oil body where the naturally occurring DOC is 2.9 mg C/l (well 310). The three sets of NVOA's were characterized by elemental analyses, molecular weight determinations, 14 C ages and liquid phase 1 H and 13 C NMR. The crude oil and the saturate, aromatic, resin and asphaltene fractions of the crude oil were similarly analyzed by elemental analysis and NMR. The NVOA's from the contaminated wells were clearly distinguishable from the naturally occurring groundwater DOC. Based upon molecular weights, sulfur contents, aromaticities and the presence of methyl groups bonded to aromatic rings, the characterization data suggests that the NVOA's originate from the C 18 or greater alkylaromatic, naphthenoaromatic and sulfur-containing constituents of the crude oil, including possibly the resins and asphaltenes.

Explore related subjects

Organic Geochemistry Article

Source-reported bounding extent: 47.342545069660225° to 47.589494110887394° latitude; -94.998779296875° to -94.6966552734375° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

K. A. Thorn, G. R. Aiken. 1998. Biodegradation of crude oil into nonvolatile organic acids in a contaminated aquifer near Bemidji, Minnesota. https://doi.org/10.1016/s0146-6380(98)00167-3

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Evidence for a biological origin of uranium-rich carbon masses within the Ediacaran Salt Range Formation of Pakistan

Thucholites are unique organic structures found in igneous and sedimentary rocks composed of a U-C-rich interior enclosed by an organic outer shell. Their formation and occurrence have perplexed scientists for over 100 years. Typically, thucholites are sparse in sedimentary rocks but where found in abundance, they may be the result of rapid paleoecological disruptions, e.g., volcanic ashfall. Here, we evaluated thucholites from the Ediacaran Salt Range Formation of the Indus Basin in Pakistan using field emission scanning electron microscopy (FESEM) and nanoscale secondary ion mass spectroscopy (NanoSIMS) to propose a two-stage mechanism for thucholite development. NanoSIMS results suggest organic matter in thucholite cores formed by biological fractionation (represented by the presence of lighter 13 C/ 12 C and 34 S/ 32 S) while the outer organic mantle formed via radiolysis-induced polymerization. FESEM elemental analysis confirms compositional differences between the two thucholite components (core and mantle), further implying their contrasting origins. Dimensional comparison of thucholite cores and their U-bearing mineral morphologies to ancient and modern U-biomineralized microbes suggests that the thucholite cores formed from metal-biological interactions. The presence of volcanogenic biotite, alkali feldspar, and clay spherules (interpreted as devitrified volcanic glass) with thucholite suggests that the thucholite cores in the Salt Range Formation are biological responses to rapid paleoenvironmental change from volcanic eruption which preserved the fossilized morphologies of Proterozoic microorganisms.

Salt Range↗

USGS2026

Metalloporphyrins in the Eagle Ford Shale

Using Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), Zheng et al. (2018, Energy & Fuels 32, 10382) reported abundant iron and vanadyl porphyrins and minor amounts of gallium and nickel porphyrins in asphaltenes extracted from a single lower Eagle Ford Shale sample. This finding is most unusual as iron and gallium porphyrins have been previously found only in coal. In this study, petroporphyrins in samples of the Eagle Ford Shale previously studied by French et al. (2020, Marine Petrol. Geol. 118, 104459), were examined using atmospheric pressure photoionization (APPI) FT-ICR-MS. Vanadyl porphyrins (N4VO) dominated the asphaltenes in thermally immature (VRo < 0.56%) samples decreasing in relative abundance with increasing maturity. Only minor amounts of nickel porphyrins were detected in the immature and early oil samples. The distribution of the vanadyl porphyrins is comparable to those reported for marine oils at varying levels of maturity. Immature samples contained porphyrins that were predominantly deoxophylloerythroetio- (DPEP: DBE = 18) and di- deoxophylloerythroetio (di-DPEP: DBE = 19) porphyrins, while ETIO- (DBE = 17), rhodo- (DBE = 20, 21, and 22) and higher condensed (DBE ≥ 23) porphyrins increased with increasing maturity. The vanadyl porphyrins included species with additional one to three oxygen atoms (N4VOx, x= 1 to 4) and one sulfur atom with one to two oxygen atoms (S1N4VOx, x=1 to 3). The degree of additional oxygen and sulfur atoms is consistent with O/C and Sorg/C of associated kerogen. No iron or gallium porphyrins were detected, showing that they are not a ubiquitous feature of the Eagle Ford. We hypothesize that the previously reported iron and gallium porphyrins (Zheng et al., 2018) were present because the specific sample that was analyzed in detail was from the early onset of the Cenomanian–Turonian oceanic anoxic event (OAE-2) in contrast to the samples investigated in this study that are primarily from the lower part of the Eagle Ford pre-dating OAE-2. Submarine volcanism, associated with eruption of large igneous provinces, occurred pre-OAE-2, injecting iron and other inorganic nutrients, giving rise to algal blooms and the acidification of the seawater. At the onset of OAE-2, boreal water masses flowed into the southern Western Interior Seaway, shifting the water column to more oxygenated conditions. Low pH-high Eh (oxic) conditions enhance the availability of iron and gallium such that these events abruptly changed the seawater chemistry, specifically enriching iron and gallium relative to vanadium and nickel. These pH-Eh conditions are similar to the depositional conditions associated with coals, which are known to contain iron and gallium porphyrins, suggesting similar conditions resulted in iron and gallium metalation of porphyrins in the marine setting of the Western Interior Seaway.

Texas↗

USGS2025

Validation of the U37K' paleotemperature proxy in the South Brazilian Bight from core-top sediments

The paleothermometer based on the alkenone unsaturation index ( U 37 K ′ "> U37K′ ) is often used to reconstruct past sea surface temperatures (SST). In the SW Atlantic Ocean, however, a limited understanding of the seasonal and depth distribution of coccolithophores, which generates the U 37 K ′ "> U37K′ signal preserved in ocean sediments, hinders accurate estimates of past regional SSTs. We analyzed 45 core-top sediment samples from the continental shelf of the South Brazilian Bight (SBB, 23 °S to 28 °S) to assess regional spatial U 37 K ′ "> U37K′ -SST gradients and improve SST estimates. The U 37 K ′ "> U37K′ data were converted to SST using six published paleotemperature equations and compared to modern observational SST data from the World Ocean Atlas (2018) data set. Data indicate that the U 37 K ′ "> U37K′ signal is produced during the austral summer and autumn when regional episodic upwelling events occur over the inner-shelf and the nutricline shoals at the slope. Our analysis of core-top data shows that SST estimates derived from most calibration equations closely align with modern observed temperatures but are skewed toward warmer months associated with upwelling-derived nutrients. Our findings underscore the importance of considering regional and seasonal biases to improve the accuracy of paleotemperature reconstructions. Understanding the factors influencing the SBB U 37 K ′ "> U37K′ signal enables a more meaningful comparison between regional paleoceanographic studies, improving our understanding of past changes in the SW Atlantic Ocean and our ability to predict regional SST response to ongoing and future warming.

South Brazilian Bight↗