Photo-Enhanced Oil Toxicity to Alcid Immune Function.

Oil spills are devastating to seabirds, causing high levels of mortality and toxic physiological effects, especially to immune function. Sunlight exposure can further enhance the toxicity of oil to marine species by generating photodegradation products. Photo-enhanced oil toxicity to marine birds has not been studied. Therefore, the goal of the present study was to investigate the toxicity and photo-enhanced toxicity of oil to lymphocyte proliferation, macrophage phagocytosis, and reactive oxygen species production in three alcid species, common murres (Uria aalge), tufted puffins (Fratercula cirrhata), and horned puffins (Fratercula corniculata). Intrinsic factors (species, age, and sex) had a more significant effect on lymphocyte proliferation than exposure to oil or photoactivated oil. Macrophage phagocytosis was significantly reduced in oil and photoactivated oil treatments, whereas hydrogen peroxide production was significantly increased. Interestingly, nonphotoactivated oil stimulated significantly more hydrogen peroxide than photoactivated oil. The results suggest that alcid immune function could be variably influenced during an oil spill depending on the species, sex, and age of the bird as well as the season and level of sunlight exposure. Environ Toxicol Chem 2023;42:2701-2711. © 2023 SETAC.

Photochemical mobilization of dissolved hydrocarbon oxidation products from petroleum contaminated soil into a shallow aquifer activate human nuclear receptors.

Elevated non-volatile dissolved organic carbon (NVDOC) concentrations in groundwater (GW) monitoring wells under oil-contaminated hydrophobic soils originating from a pipeline rupture at the National Crude Oil Spill & Natural Attenuation Research Site near Bemidji, MN are documented. We hypothesized the elevated NVDOC is comprised of water-soluble photooxidation products transported from the surface to the aquifer. We use field and laboratory samples in combination with complementary analytical methods to test this hypothesis and determine the biological response to these products. Observations from optical spectroscopy and ultrahigh-resolution mass spectrometry reveal a significant correlation between the chemical composition of NVDOC leached from photochemically weathered soils and GW monitoring wells with high NVDOC concentrations measured in the aquifer beneath the contaminated soil. Conversely, the chemical composition from the uncontaminated soil photoleachate matches the NVDOC observed in the uncontaminated wells. Contaminated GW and photodissolution leachates from contaminated soil activated biological targets indicative of xenobiotic metabolism and exhibited potential for adverse effects. Newly formed hydrocarbon oxidation products (HOPs) from fresh oil could be distinguished from those downgradient. This study illustrates another pathway for dissolved HOPs to infiltrate GW and potentially affect human health and the environment.

Dissolved organic matter production from herder application and in-situ burning of crude oil at high latitudes: Bioavailable molecular composition patterns and microbial community diversity effects.

Chemical herders and in-situ burning (ISB) are designed to mitigate the effects that oil spills may have on the high latitude marine environment. Little information exists on the water solubilization of petroleum residues stemming from chemically herded ISB and whether these bioavailable compounds have measurable impacts on marine biota. In this experiment, we investigated the effects of Siltech OP40 and crude oil ISB on a) petroleum-derived dissolved organic matter (DOMHC) composition and b) seawater microbial community diversity over 28 days at 4 °C in aquarium-scale mesocosms. Ultra-high resolution mass spectrometry and fluorescence spectroscopy revealed increases in aromaticity over time, with ISB and ISB+OP40 samples having higher % aromatic classes in the initial incubation periods. ISB+OP40 contained a nearly 12-fold increase in the number of DOMHC formulae relative to those before ISB. 16S rRNA gene sequencing identified differences in microbial alpha diversity between seawater, ISB, OP40, and ISB+OP40. Microbial betadiversity shifts were observed that correlated strongly with aromatic/condensed relative abundance and incubation time. Proteobacteria, specifically from the genera Marinomonas and Perlucidibaca experienced -22 and +24 log2-fold changes in ISB+OP40 vs. seawater, respectively. These findings provide an important opportunity to advance our understanding of chemical herders and ISB in the high latitude marine environment.

Hydrocarbons to carboxyl-rich alicyclic molecules: A continuum model to describe biodegradation of petroleum-derived dissolved organic matter in contaminated groundwater plumes.

Relationships between dissolved organic matter (DOM) reactivity and chemical composition in a groundwater plume containing petroleum-derived DOM (DOMHC) were examined by quantitative and qualitative measurements to determine the source and chemical composition of the compounds that persist downgradient. Samples were collected from a transect down the core of the plume in the direction of groundwater flow. An exponential decrease in dissolved organic carbon concentration resulting from biodegradation along the transect correlated with a continuous shift in fluorescent DOMHC from shorter to longer wavelengths. Moreover, ultrahigh resolution mass spectrometry showed a shift from low molecular weight (MW) aliphatic, reduced compounds to high MW, unsaturated (alicyclic/aromatic), high oxygen compounds that are consistent with carboxyl-rich alicyclic molecules. The degree of condensed aromaticity increased downgradient, indicating that compounds with larger, conjugated aromatic core structures were less susceptible to biodegradation. Nuclear magnetic resonance spectroscopy showed a decrease in alkyl (particularly methyl) and an increase in aromatic/olefinic structural motifs. Collectively, data obtained from the combination of these complementary analytical techniques indicated that changes in the DOMHC composition of a groundwater plume are gradual, as relatively low molecular weight (MW), reduced, aliphatic compounds from the oil source were selectively degraded and high MW, alicyclic/aromatic, oxidized compounds persisted.

Barium ion adduct mass spectrometry to identify carboxylic acid photoproducts from crude oil-water systems under solar irradiation.

Petroleum derived dissolved organic matter (DOMHC) samples were successfully cationized with barium, revealing many [M-H + Ba]+ peaks in both dark and simulated sunlight treatments. The DOMHC samples generated after light exposure exhibited a greater number of [M-H + Ba]+ peaks compared to the dark control. Multiple [M-H + Ba]+ peaks were investigated in the irradiated DOMHC using low resolution MS/MS in order to confirm the presence of diagnostic fragment ions, m/z 139, 155 and 196 in each treatment. Due to the high complexity of the bariated DOMHC mixture, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS/MS) was employed to obtain molecular level information for both irradiated and dark treatments. The irradiated DOMHC treatments had more bariated oxygenated species over a wide range of H/C and O/C when compared to the dark controls. Doubly bariated species were also observed in DOMHC, which provides evidence that photochemistry transforms DOMHC to even more complex mixtures with multiple oxygenations per molecule. This study provides evidence that barium adduct mass spectrometry can be successfully applied to DOMHC screening for the presence of COOHs, both in dark samples and solar irradiated samples. Furthermore, direct evidence and molecular composition of aqueous phase crude oil photoproducts is provided by this technique.

DOC export is exceeded by C fixation in May Creek: A late-successional watershed of the Copper River Basin, Alaska.

Understanding the entirety of basin-scale C cycling (DOC fluxes and CO2 exchanges) are central to a holistic perspective of boreal forest biogeochemistry today. Shifts in the timing and magnitude of dissolved organic carbon (DOC) delivery in streams and eventually into oceans can be expected, while simultaneously CO2 emission may exceed CO2 fixation, leading to forests becoming stronger CO2 sources than sinks amplifying rising trace gases in the atmosphere. At May Creek, a representative late-successional boreal forest watershed at the headwaters of the Copper River Basin, Alaska, we quantified the seasonality of DOC flux and landscape-scale CO2 exchange (eddy covariance) over two seasonal cycles. We deployed in situ fDOM and conductivity sensors, performed campaign sampling for water quality (DOC and water isotopes), and used fluorescence spectroscopy to ascertain DOC character. Simultaneously, we quantified net CO2 exchange using a 100 ft eddy covariance tower. Results indicate DOC exports were pulse-driven and mediated by precipitation events. Both frequency and magnitude of pulse-driven DOC events diminished as the seasonal thaw depth deepened, with inputs from terrestrial sources becoming major contributors to the DOC pool with decreasing snowmelt contribution to the hydrograph. A three-component parallel factorial analysis (PARAFAC) model indicated DOC liberated in late-season may be bioavailable (tyrosine-like). Combining Net Ecosystem Exchange (NEE) measurements indicate that the May Creek watershed fixes 142-220 g C m-2 yr-1 and only 0.40-0.57 g C m-2 yr-1 is leached out as DOC. Thus, the May Creek watershed and similar mature spruce forest dominated watersheds in the Copper River Basin are currently large ecosystem C sinks and exceeding C conservative. An understanding of DOC fluxes from Gulf of Alaska watersheds is important for characterizing future climate change-induced seasonal shifts.

Molecular-Level Composition and Acute Toxicity of Photosolubilized Petrogenic Carbon.

To examine the molecular-level composition and acute toxicity per unit carbon of the petroleum-derived dissolved organic matter (DOMHC) produced via photo-oxidation, heavy and light oils were irradiated over seawater with simulated sunlight. Increases in dissolved organic carbon concentrations as a function of time were associated with changes in the DOMHC composition and acute toxicity per unit carbon. Parallel factor analysis showed that the fluorescent dissolved organic matter (FDOM) composition produced from the heavy oil became more blue-shifted over time, while the light oil produced a mixture of blue- and red-shifted components similar to FDOM signatures. Ultrahigh-resolution mass spectrometry reveals that the composition of the DOMHC produced from both heavy and light oils was initially relatively reduced, with low O/C. With time, the composition of the DOMHC produced from the heavy oil shifted to unsaturated, high-oxygen compounds, while that produced from the light oil comprised a range of high O/C aliphatic, unsaturated, and aromatic compounds. Microtox assays suggest that the DOMHC initially produced is the most toxic (62% inhibition); however, after 24 h, a rapid decrease in toxicity decreased linearly to 0% inhibition for the heavy DOMHC and 12% inhibition for the light DOMHC at extended exposure periods.

Examining Natural Attenuation and Acute Toxicity of Petroleum-Derived Dissolved Organic Matter with Optical Spectroscopy.

Groundwater samples containing petroleum-derived dissolved organic matter (DOMHC) originating from the north oil body within the National Crude Oil Spill Fate and Natural Attenuation Research Site near Bemidji, MN, USA were analyzed by optical spectroscopic techniques (i.e., absorbance and fluorescence) to assess relationships that can be used to examine natural attenuation and toxicity of DOMHC in contaminated groundwater. A strong correlation between the concentration of dissolved organic carbon (DOC) and absorbance at 254 nm ( a254) along a transect of the DOMHC plume indicates that a254 can be used to quantitatively assess natural attenuation of DOMHC. Fluorescence components, identified by parallel factor (PARAFAC) analysis, show that the composition of the DOMHC beneath and adjacent to the oil body is dominated by aliphatic, low O/C compounds ("protein-like" fluorescence) and that the composition gradually evolves to aromatic, high O/C compounds ("humic-/fulvic-like" fluorescence) as a function of distance downgradient from the oil body. Finally, a direct, positive correlation between optical properties and Microtox acute toxicity assays demonstrates the utility of these combined techniques in assessing the spatial and temporal natural attenuation and toxicity of the DOMHC in petroleum-impacted groundwater systems.

Impact of Photooxidation and Biodegradation on the Fate of Oil Spilled During the Deepwater Horizon Incident: Advanced Stages of Weathering.

While the biogeochemical forces influencing the weathering of spilled oil have been investigated for decades, the environmental fate and effects of "oxyhydrocarbons" in sand patties deposited on beaches are not well-known. We collected sand patties deposited in the swash zone on Gulf of Mexico beaches following the Deepwater Horizon oil spill. When sand patties were exposed to simulated sunlight, a larger concentration of dissolved organic carbon was leached into seawater than the corresponding dark controls. This result was consistent with the general ease of movement of seawater through the sand patties as shown with a 35SO42- radiotracer. Ultrahigh-resolution mass spectrometry, as well as optical measurements revealed that the chemical composition of dissolved organic matter (DOM) leached from the sand patties under dark and irradiated conditions were substantially different, but neither had a significant inhibitory influence on the endogenous rate of aerobic or anaerobic microbial respiratory activity. Rather, the dissolved organic photooxidation products stimulated significantly more microbial O2 consumption (113 ± 4 µM) than either the dark (78 ± 2 µM) controls or the endogenous (38 µM ± 4) forms of DOM. The changes in the DOM quality and quantity were consistent with biodegradation as an explanation for the differences. These results confirm that sand patties undergo a gradual dissolution of DOM in both the dark and in the light, but photooxidation accelerates the production of water-soluble polar organic compounds that are relatively more amenable to aerobic biodegradation. As such, these processes represent previously unrecognized advanced weathering stages that are important in the ultimate transformation of spilled crude oil.

Sunlight creates oxygenated species in water-soluble fractions of Deepwater Horizon oil.

In order to assess the impact of sunlight on oil fate, Macondo well oil from the Deepwater Horizon (DWH) rig was mixed with pure water and irradiated with simulated sunlight. After irradiation, the water-soluble organics (WSO) from the dark and irradiated samples were extracted and characterized by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Liquid-liquid extraction yielded two fractions from dark and irradiated water/oil mixtures: acidic WSOs (negative-ion electrospray (ESI)), and base/neutral WSOs (positive-ion ESI) coupled to FT-ICR MS to catalog molecular-level transformations that occur to Macondo-derived WSOs after solar irradiation. Such direct measure of oil phototransformation has not been previously reported. The most abundant heteroatom class detected in the irradiated WSO acid fractions correspond to molecules that contain five oxygens (O5), while the most abundant acids in the dark samples contain two oxygen atoms per molecule (O2). Higher-order oxygen classes (O5-O9) were abundant in the irradiated samples, but <1.5% relative abundance in the dark sample. The increased abundance of higher-order oxygen classes in the irradiated samples relative to the dark samples indicates that photooxidized components of the Macondo crude oil become water-soluble after irradiation. The base/neutral fraction showed decreased abundance of pyridinic nitrogen (N1) concurrent with an increased abundance of N1Ox classes after irradiation. The predominance of higher-order oxygen classes indicates that multiple photochemical pathways exist that result in oxidation of petroleum compounds.