Bioaccumulation and toxicokinetics of polycyclic aromatic compounds and metals in giant floater mussels (Pyganodon grandis) exposed to a simulated diluted bitumen spill

Cigarette butt leachates induce alterations in gene expression and damage in health status of tropical oysters

Cigarette butts (CB) are among the most frequent debris in marine litter collected in coastal areas. They are potential sources of chemical contamination by leaching process, posing risks to biota. This study aimed to evaluate the short-term impacts of CB leachates on the oyster Crassostrea brasiliana. The animals were exposed in the laboratory to different leached dilutions and assessed for bioaccumulation of polycyclic aromatic hydrocarbons (PAHs), their general health status by neutral red retention time (NRRT), and variation in expression of genes related to xenobiotic biotransformation. The results showed that CB leachates at very low dilutions impaired the general health status of oysters, with significant reductions in NRRT at 24 h (dilution 0.1 %), and that persisted at 96 h (dilution 0.01 %). Therefore, a single cigarette butt was able to make toxic 250 l of seawater after 24 h release, and 2500 l after 96hs. The gene expression indicated a decrease in gill transcripts (CYP2-like, GSTΩ, and HSP70) of C. brasiliana exposed for 24 h, with no marked trend at 96 h. Despite the low PAHs bioaccumulation, the damages observed in lysosomal membranes followed by the decreased expression of key genes involved in xenobiotic biotransformation, and the protection of protein stability, represent evidence of early effects caused by cigarette residues on marine organisms from tropical environments.

Effects of water-accommodated fractions of crude oil on detoxification and antioxidant mechanisms in Ruditapes philippinarum

To assess the impact of crude oil pollution on Manila clams (Ruditapes philippinarum), we analyzed the effects of exposure to water-accommodated fraction (WAF) at different concentrations (nominal TPH concentrations of 0.5, 1.0 and 3.0 mg/L), including survival rate, histopathology observation and antioxidant enzyme detection. Results demonstrated that the activities of antioxidant enzymes-Catalase (CAT), Superoxide dismutase (SOD), Glutathione peroxidase (GSH-PX) and Malondialdehyde (MDA) in Manila clams was significantly elevated in 3.0 mg/L WAF group compared with the control group (P < 0.05). In addition, RNA-seq was performed to analyze clam hepatopancreas tissue in 0 d (control group, CG), 7 d (exposure group, O7d), 15 d (exposure group, O15d) after the exposure to WAF (3 mg/L) and recovery in clean water for 7 d after 15 d WAF exposure (recovery group, R7d). The results showed that a total of 129 differentially expressed genes (DEGs) were detected in the O7d vs CG group, 123 DEGs were detected in the O15d vs CG group, and 2113 DEGs were detected in the R7d vs CG group. Of these genes, the expression of cytochrome P450 2J2 (6.30-fold), bile salt sulfotransferase (8.06-fold), multidrug resistance-associated protein 1 (8.17-fold) was significantly induced at 15 d under the WAF exposure. DEGs were significantly enriched in pathways such as cysteine and methionine metabolism, as well as glycine, serine and threonine metabolism. Furthermore, eight DEGs, including metabolism-related genes (ABCC1, ABCG2, SULT2A1, CYP2J2), ion transport genes (SLC39a14, RFT2), an immune-related gene (Gvin1), and a cellular structure and signal regulatory gene (Ank3) were selected for qRT-PCR analysis. The results confirmed that DEG expression levels were consistent with RNA-seq findings. This study provides crucial molecular insights into the adaptive responses and recovery processes of marine bivalves in response to oil pollution, thereby contributing a scientific foundation for evaluating and monitoring marine environmental pollution.

Rapid screening of shellfish tainting from oil spills using an antibody-based biosensor

Tainting of shellfish by polyaromatic hydrocarbons (PAHs) following an oil spill poses possible health risks as well as socioeconomic impacts. Traditional screening approaches for evaluating PAH contamination have limitations that can prevent timely, objective spill response decisions. The objective of this study was to investigate the relationship between PAH concentrations measured in the oyster, Crassostrea virginica, interstitial fluid using a rapid antibody-based biosensor method, with PAH concentrations in oyster tissues determined using conventional gas chromatography-mass spectrometry analysis. To accomplish this objective, bioconcentration tests were performed to simulate oil spill exposures using a crude and heavy fuel oil containing different PAH compositions. This design allowed both the PAH concentration and composition in water and, subsequently, accumulated by oysters to be varied over time. Oysters sampled during uptake and depuration phases were analyzed using biosensor and conventional analysis methods to generate comparative data. Results indicated that biosensor measurements of oysters captured the kinetics of PAH accumulation during uptake and depuration phases. Further, significant positive correlations were observed between biosensor interstitial fluid and lipid-normalized PAH tissue concentrations. However, quantitative predictions appear to be modulated by the contamination source and target analyte list for tissue analysis. Thus, the biosensor can be applied for rapidly evaluating relative PAH contamination between biota samples and offers a promising new analytical tool for oil spill monitoring and fisheries management contexts. A generic model was also developed from study and literature data to predict PAH half-lives from bivalve tissues. These predictions can help inform field monitoring of shellfish and estimate recovery times required to achieve pre-spill conditions.

Occurrence, characterization, and ecological risk analysis of petroleum hydrocarbons in water and sediments following large-scale field simulated oil spills at the experimental lakes area, Northwestern Ontario, Canada

This study assessed the impact of on-site field-simulated oil spills at the International Institute for Sustainable Development-Experimental Lakes Area (IISD-ELA) on a freshwater boreal lake. Low total petroleum hydrocarbons (TPH) values were obtained in water and sediments from the locations without direct oil loading across the 6-year monitoring program. Biogenic n-alkanes and pyrogenic polycyclic aromatic hydrocarbons (PAHs) were predominant pre- and post-spill. No petroleum biomarkers were detected in the water, but trace levels appeared in a few sediments. Most TPH and PAH levels were within acceptable limits set by the Canadian Council of Ministers of the Environment (CCME) and Ontario regulations, though some PAHs exceeded guidelines. However, the frequency of exceedances did not change significantly before and after the spill. These results suggest that the spilled oil was contained effectively during the experiment period, and the environment recovered to near-background levels afterward with appropriate precautions and remediation operations.

Aquatic life criteria of hydrothermal liquefaction wastewater via ecotoxicity test and modeling

Wastewater resulting from hydrothermal liquefaction (HTL-AP) of biowaste is gaining attention as an emerging hazardous material. However, there is a lack of specific and systematic ecotoxicity studies on HTL-AP. This study addresses this gap by conducting acute toxicity tests on HTL-AP using typical aquatic species and integrating these results with predicted toxicity values from interspecies correlation estimation models to establish aquatic life criteria. HTL-AP exhibited significant toxicity with LC50 of 956.12-3645.4 mg/L, but demonstrated moderate toxicity compared to common freshwater pollutants like commercial microbicides, personal care products, and insect repellents. The resulting hazardous concentration for 5 % of species (HC5), the criterion maximum concentration, and the short-term water quality criteria for aquatic were 506.0, 253.0, and 168.7 mg/L, respectively. Notably, certain organisms like Misgurnus anguillicaudatus and Cipangopaludina chinensis showed high tolerance to HTL-AP, likely due to their metabolic capabilities on HTL-AP components. The significant decrease in HC5 values for some HTL-AP substances compared to pure compounds could indicate the synergistic inhibition effects among HTL-AP compositions. Furthermore, according to the established criteria, HTL-AP required significantly less diluted water (13 t) than carbendazim (1009 t) to achieve biosafety, indicating a safer release. This research establishes a preliminary water quality criterion for HTL-AP, offering a valuable reference for risk assessment and prediction in the utilization of HTL-AP within environmental contexts.

The assessment of bioavailability and environmental risk of dissolved and particulate polycyclic aromatic hydrocarbons in the seawater of typical bays

The pollution of dissolved and particulate polycyclic aromatic hydrocarbons (PAHs) in coastal waters has been increasing in recent decades. However, limited research has been conducted on the characteristics of dissolved and particulate PAHs in seawater and their associated risk assessment. Here, we focused on the bioavailability and environmental risk of PAHs in four typical bays of Shandong Province, China, and used scallop Chlamys farreri and clam Mactra veneriformis as sentinel species. The results revealed that dissolved PAHs tended to bioaccumulate in scallop C. farreri, and their ecological risk exhibited a significant correlation with the health risk of bioaccumulated PAHs and the bioeffect of screened biomarkers in scallop. Conversely, particulate PAHs demonstrated a higher bioaccumulation potential in the clam M. veneriformis, showing a stronger correlation between their ecological risk, health risk, and bioeffect in clams. This study provides the first elucidation of the connection between the ecological risk, health risk, and bioeffect of PAHs. Furthermore, based on the better correlation of health risk and bioeffect caused by PAHs with total PAHs in seawater, we propose that the clam M. veneriformis is a more suitable sentinel species for assessing environmental risk in typical bays of Shandong Province.

Chemical Weathering Patterns of Diluted Bitumen Spilled into Freshwater Limnocorrals

Due to the sudden nature of oil spills, few controlled studies have documented how oil weathers immediately following accidental release into a natural lake environment. Here, we evaluated the weathering patterns of Cold Lake Winter Blend, a diluted bitumen (dilbit) product, by performing a series of controlled spills into limnocorrals installed in a freshwater lake in Northern Ontario, Canada. Using a regression-based design, we added seven different dilbit volumes, ranging from 1.5 to 180 L, resulting in oil-to-water ratios between 1:71,000 (v/v) and 1:500 (v/v). We monitored changes in the composition of various petroleum hydrocarbons (PHCs), including n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and oil biomarkers in dilbit over time, as it naturally weathered for 70 days. Depletion rate constants (k_D) of n-alkanes and PAHs ranged from 0.0009 to 0.41 d^-1 and 0.0008 to 0.38 d^-1, respectively. There was no significant relationship between k_D and spill volume, suggesting that spill size did not influence the depletion of petroleum hydrocarbons from the slick. Diagnostic ratios calculated from concentrations of n-alkanes, isoprenoids, and PAHs indicated that evaporation and photooxidation were major processes contributing to dilbit weathering, whereas dissolution and biodegradation were less important. These results demonstrate the usefulness of large scale field studies carried out under realistic environmental conditions to elucidate the role of different weathering processes following a dilbit spill.