Sediment Toxicity Research Articles

Integrated Chemical and Ecotoxicological Assessment of Metal Contamination in the Andong Watershed: Identifying Key Toxicants and Ecological Risks

This study employed an integrated field monitoring approach, combining chemical analysis and ecotoxicity testing of multiple environmental matrices—water, sediment, and sediment elutriates—to comprehensively assess the environmental health of the Andong watershed, located near a Zn smelter and mining area. The primary objectives were to evaluate the extent of metal contamination, identify key toxicants contributing to ecological degradation, and trace the sources of these pollutants. Our findings revealed severe metal contamination and significant ecotoxicological effects both in proximity to and downstream from industrial sites. Specifically, Cd, Zn, and Pb were strongly linked to the smelter, while Hg, Ni, Cu, and As were predominantly associated with mining activities in the tributaries. To further assess toxicity of field-collected sediment and their elutriates, a logistic regression analysis was employed to estimate benchmark values for distinguishing between toxic and non-toxic samples, using the sum of toxic units for sediment elutriates and the mean probable effect level (PEL) quotient for sediment toxicity. These models demonstrated greater predictive accuracy than conventional benchmarks for determining toxicity thresholds. Our results highlight that integrating chemical and ecotoxicological monitoring with site-specific concentration–response relationships enhances the precision of ecological risk assessments, facilitating more accurate identification of key toxicants driving mixture toxicity in complex, pollution-impacted aquatic ecosystems.

Assessment of recent lake sediment conditions in the conterminous U.S.

This study provides the largest sediment quality assessment of lakes in the conterminous United States (U.S.). A variety of lakes (n = 1005) were selected based on the randomized, probabilistic sampling design of the broader 2017 National Lakes Assessment study. Surficial sediment samples (0–5 cm) were collected at one representative site (generally the deepest point) for each lake (n = 969). The samples were analyzed for 16 metal(loid)s, 25 polycyclic aromatic hydrocarbons (PAHs), 53 polychlorinated biphenyl (PCB) congeners, 27 legacy pesticides and metabolites, total organic carbon, and grain size. Metal(loid)s and PAHs were widely distributed due to natural and potential anthropogenic sources, with regional variations observed for lakes in the nine ecoregions encompassing the U.S. Most sites did not have detectable PCB congeners or legacy pesticides. An integrative chemical index of mean probable effect concentration quotients, composed of seven metal(loid)s and ƩPAH13, was used to assess sediment quality for the estimated population of 224,916 lakes in the conterminous U.S. Nationally, 26.5 % (CI of 20–33 %) of lakes were in good condition (corresponding to predicted low incidences of toxicity to benthic organisms), 69.3 % (CI of 63–76 %) of lakes were in fair condition, and 1.8 % (CI of 0.6–3 %) of lakes were in poor condition (corresponding to predicted high incidences of sediment toxicity). Unweighted metal(loid) and ƩPAH13 concentrations were compared to lake, watershed, and land use data. Deeper lakes were significantly more contaminated (or naturally enriched) with As, Cd, Cu, Pb, Hg, Zn, and ƩPAH13 than shallow lakes. Lakes at lower elevation were also associated with more contamination (or natural enrichment) of As, Cr, Pb, Hg, Ni, Zn, and ƩPAH13 than higher elevation lakes. Greater contamination was associated with watersheds containing larger percentages of developed land. This study demonstrates an approach which can be used by others to assess sediment quality in their jurisdictions.

Exploring the temporal toxicity signature: A baseline evaluation of the heavy metal concentration in estuarine core sediments in the coastal region of cauvery delta, bay of bengal.

Globally, the concentration of heavy metals and sediment toxicity analysis are significant liabilities to aquatic environments. This scrutiny outlines the sediment textures, heavy metals and toxicity status associated with environmental pollution indices in the core sediment of the Cauvery and Vettar estuaries, East coast of India. The impact of rapid industrialization, urbanization, harbour activities and agricultural activities influences on the twain estuary is a significant concern to designate the environment. The contamination status of the sediments affects the potential biodiversity, ecological risks and human health. A total of two core sediments were recovered from the Cauvery and Vettar estuaries in March 2023 to decipher the environmental pollution status. Meticulous observation of the textural studies underscores the prevalence of sand content in Cauvery, and Vettar sediments consist of predominate clay content and minor silt contents. Furthermore, the organic matter is augmented in the Vettar River due to the higher input of waste disposal, seaweeds and algae due to the surrounding landmass. Twain core sediments argue that heavy metal concentration is decreasing in order as Fe > Zn > Ni > Pb > Cu > Cr by using portable X-ray fluorescence (pXRF) spectrometry. Remarkable results of environmental pollution indices such as Igeo, Ef, Cf, Cd and mCd state very highly polluted, extreme enrichments, high contamination and very high degree of contamination. Furthermore, the potential ecological risk indices such as PLI, SQGs, and PERI argue polluted, medium to high toxicity and moderate adverse ecological risk to the estuarine regions. Statistical analysis of the heavy metal affirms the enrichment of Fe metals may derive from lithogenic and/or anthropogenic influences, and the other studied metals such as Cu, Ni, Zn, Pb and Cr may be influenced by the anthropogenic activities in the aspect of point and non-point pollution sources. This could result from both estuaries undergoing higher pollution, in which the Vettar estuary is a considerable environmental risk zone compared to the Cauvery river due to the impact of industrial effluents and rapid urbanization activities. This finding underscores the urgent need for enhanced estuarine sediment quality study and comprehensive assessment of sediment toxicity, regulating the beneficial acumen for the government to follow the suitable remediation on the embellish policy of river and marine environments.

Novel chitosan-enhanced alkali-activated material for remediation of zinc-contaminated coastal mudflat sediment

Sustainable utilization and development for contaminated mudflat sites face dual challenges associated with contaminant enrichment and engineering diseases, impacting ecological quality and coastal construction. Commonly used cement has limitations in ensuring geo-environmental engineering performances for polluted sediments. This study investigates a solidification/stabilization approach using novel chitosan-enhanced alkali-activated material (CTS-AAM) to remediate highly concentrated zinc-contaminated sediments. Results exhibit that the compressive strength and water stability of sediments are remarkably improved by CTS-AAM, satisfying engineering service even under long-term immersion and zinc accumulation. Significant improvements dependent on curing period and CTS-AAM dosage also reflect in the resistance to deformation of remediated sediments, maintaining low-compressibility states due to the enhancement of structural yield stress. The leaching toxicity of remediated sediments meets Zn ≤ 5.0 mg/L, as zinc primarily distributes to the residual fraction associated with low mobility. The bidirectional enhancement of toxic sediment is attributed to the generation of hydrates with cementitious and pore-filling effects through hydration reactions. Simultaneously, chitosan with hydrated gels and ettringite collectively form gel networks and compact skeleton structures within sediments, as well as immobilize Zn through comprehensive physical encapsulation, chemical binding, and chelation. This study provides a feasible strategy for future projects involving remediation and utilization of mudflats.

Developing a dynamic energy budget model to project potential effects of deep-sea mining plumes on the Atlantic deep-sea mussel, Bathymodiolus azoricus

Due to the consistent lack of Environmental Risk Assessment (ERA) for deep-sea mining scenarios, the potential impacts of this industry on marine ecosystems remain largely unknown. In order to fill this gap, a Dynamic Energy Budget (DEB) model was developed to study the consequences of toxic sediment plumes derived from deep-sea mining on the energy budget of the Atlantic deep-sea mussel, Bathymodiolus azoricus. Model calibration was based on environmental conditions observed at the Menez Gwen (MG) vent field (Mid-Atlantic Ridge- MAR), assuming a B. azoricus lifespan of 10 years and a maximum shell length of 119 mm. Scenario simulations were conducted to mimic the effects of increased concentrations of toxic sediment plumes on mussel filtration rates, the absorption of reduced substrates by their endosymbionts, and the energetic costs associated with metal toxicity. Data were sourced from B. azoricus and, when necessary, from proxy species. One disturbance scenario (EF1) incorporated measured rates and realistic parameters, while the other (EF2) was intentionally designed to encompass cumulative effects and uncertainties, representing a potential worst-case scenario. Both disturbance scenarios were initiated at three different timings (0, 1200 and 2400 days) to accommodate the mining effects at different stages of the mussels' life cycle. Results indicate that B. azoricus is significantly impacted by toxic sediment plumes, particularly during earlier life stages, potentially leading to severe growth impairment and mortality. These results were integrated into a food web model of the MG vent field, revealing that disruptions to the energetic balance of the vent mussel have widespread consequences for the entire ecosystem. Overall, we argue that this numerical framework offers a valuable tool for conducting ERA and Environmental Impact Assessments (EIA) in the context of industrial deep-sea mining.

Acute and chronic toxicity of rare earth elements-enriched sediments from a prospective mining area: Effects on life history traits, behavioural and physiological responses of Gammarus fossarum (Crustacea Amphipoda)

Rare earth elements (REE) have an essential role and growing importance in the world's economy. They are attracting interest from society, policymakers, and scientists. The rapidly growing global demand for REE in several strategic industrial and agricultural sectors led many countries to consider the (re)-opening of mining activities for REE extraction. Hence, their increasing use led to the disruption of their biogeochemical cycles with anthropic abnormalities already observed in aquatic ecosystems. Nonetheless, REE remain less studied, and their mechanisms of toxicity actions are not fully understood. As amphipods, Gammarus fossarum represent an important part of the aquatic macroinvertebrate assemblage and are generally used in ecotoxicological studies for their high ecological relevance. However, their use for the study of REE effects has been rather limited so far. The current study aims to assess the potential effects of two naturally REE-enriched sediments (N2 and B4) on G. fossarum. Effects on life history traits, behavioural and physiological responses have been evaluated. Exposing G. fossarum males for 72h to sediments N2 and B4 led to a decrease in haemolymph osmolality and locomotion while an increase in ventilatory activity was observed. Exposing G. fossarum pre-copula pairs with females at the same reproductive stage to the naturally REE-enriched sediments, for one moult cycle duration (∼30 days) showed that sediment B4 led to i) a significant uptake of REE, ii) a significant decrease in the proportion of females with oocytes and iii) a significant reduction in the total number of juveniles. The physicochemical analyses of sediments showed that B4 contains the highest amount of REE with a higher proportion of light REE. The present study gives the first insights into the potential toxicity of REE on G. fossarum as they may have deleterious effects on G. fossarum population's dynamics, which may alter the functioning of aquatic ecosystems.

The sediment of a river having ‘’good ecological status” turned out to be toxic to midge Chironomus riparius larvae: Implication for environmental monitoring?

Globally, monitoring of the surface waters is largely limited to the physico-chemical analysis of water in rivers and lakes. Sediment state in the aquatic systems including sediment chemical content or the structure and diversity of benthic communities or ecotoxicological studies with natural sediments remains largely overlooked by the monitoring programs. Hence we assessed the potential toxicity of three riverine sediments on the life-cycle traits (emergence and reproduction) of midge Chironomus riparius via an ecotoxicological testing method over two generations (according to OECD test 233 guidelines). In addition, the riverine sediments were spiked with polyamide (nylon) microplastic particles (1 g kg−1) to analyze an additive effect of microplastic on the sediment toxicity. As model river systems, three rivers (Karchaghbyur, Gavaraget, Argichi) in the Lake Sevan basin (Armenia) were selected. Results of ecotoxicity testing were compared with the indices of water quality (derived from the physico-chemical analysis) and the indices of the ecological status of the rivers (derived from the analysis of benthic communities). The results of testing demonstrated an unexpectedly low emergence of midges after the first generation exposed to the sediment of the river having ‘’good ecological status’’ - the Argichi. Sediments of the Karchaghbyur and Gavaraget rivers impeded the emergence and reproduction of midges after the second generation. An addition of polyamide particles to the sediments did not significantly affect the life-cycle traits of C. riparius indicating the primary effect of the sediments’ condition. The discrepancy of biotesting result with that of the other two methods (which indicated ‘’average water quality’’ and “good ecological status”) underlies the importance of designing more comprehensive monitoring programs for better assessment and protection of aquatic systems and resources.

A Comprehensive Review on Heavy Metal Toxicity in Coastal Sediments

Abstract Heavy metal toxicity is becoming a growing environmental concern worldwide. The estuary’s surface waters and sediments are finally being transported to the coastal areas. During this transportation, the water and sediments carry numerous elements. The essential elements like nutrition are nitrates, phosphates, silicates, and sulphates, which are required for aquatic life, and non-essential elements contribute to pollution. The input of these essential and non-essential elements is being contributed by nature and anthropogenic activities. Due to the increase in urbanization and anthropogenic activities like agricultural, industrial, thermal power plants, dye factories, inland fisheries, small and significant scale industries, as well as recreational activities, are the sources of heavy metal toxicity. The toxic heavy metals, including mercury, cadmium, chromium, and lead, are leading to biological toxicity. Environmental standards are being modified due to increasing concerns. However, naturally occurring heavy metals and metalloids are drawn from parent rocks and absorbed by aquatic organisms, such as benthic organisms, which fix some heavy metal ions. Flora and fauna also absorb these ions, reducing their concentration. However, due to climatic factors like temperature and pH, these metal ions get adsorbed on the surface of the sediments. During hydrodynamic forces, they get released back into the water and vary seasonally.

Degradation Kinetics of Antifouling Biocides in Sediment During the Spiking Equilibrium Phase

The new generation of antifouling biocides, as well as other emerging contaminants, has not yet been included in sediment quality guidelines or present standard protocols for sediment spiking. Most of these biocides have short half-lives in water, but little information is available regarding their degradation in sediments. Thus, there is a need to establish a reliable duration of the equilibrium phase for sediment spiking prior to sediment toxicity testing to determine the actual exposure concentrations during ecotoxicological tests. This study aimed to evaluate the degradation of DCOIT, Irgarol, Diuron, and Dichlofluanid during a spiking equilibrium phase of 24 h at three different time intervals (0, 6, and 24 h) and concentrations (10, 100, and 1000 ng g-1), by applying kinetic degradation models. The models presented a better fit for the 1000 ng g-1 treatments, in which the half-lives of DCOIT and Diuron were < 5 h, Dichlofluanid < 2 h, and Irgarol < 6h. Our results also indicate that, except for Dichlofluanid, the degradation rates of the other antifouling biocides were reduced dramatically after 6 h of equilibrium. Therefore, an equilibrium phase of 24 h (or greater than 6 h) was considered viable for sediment spiking. Our findings provide valuable information to guide future sediment toxicity tests using these compounds.

Effect of PCBs on Production Characteristics and Fucoxanthin / Fatty Acid Content of Cylindrotheca closterium (Ehrenberg) Reimann et Lewin Diatom Enrichment Culture

Background: Since the mid-20th century, polychlorinated biphenyls (PCBs) have emerged as one of the foremost anthropogenic organic pollutants in aquatic environments. Microphytobenthic algae of the genus Cylindrotheca have been recurrently employed in laboratory experiments to assess sediment toxicity. Recently, a novel strain of benthic diatoms belonging to the genus Cylindrotheca has been identified and characterized from PCB-contaminated sediments in the coastal region of Sevastopol Bay (Black Sea). This species of algae has high biomass productivity, the ability to synthesize fucoxanthin, and a variety of fatty acids. Cylindrotheca closterium is capable of metabolizing organic pollutants in bottom sediments. Objective: The objective of the study was to investigate the effects of PCBs on the growth patterns and physiological responses of C. closterium through a 9-day experiment, subjecting the microalgae to varying concentrations of PCBs ranging from 0.0003 to 100 mg/L. Results: The experiments revealed that C. closterium could grow in environments containing concentrations of PCBs ranging from 0.0003 to 10 mg/L, indicating its resilience to moderate levels of PCB exposure. Additionally, adaptive biochemical processes were observed in C. closterium under PCB exposure. Notably, on the sixth day of the experiment, the culture transitioned into a stationary growth phase, accompanied by significant increases in total lipid content by 1.6 times and fucoxanthin by 4.6 times compared to the control. However, a pronounced decrease in culture growth was observed at a PCB concentration of 100 mg/L, coinciding with reductions in total lipid and fucoxanthin content, suggesting a tolerance threshold of C. closterium between 10 and 100 mg/L PCB concentrations. Furthermore, alterations in the fatty acid profile of C. closterium were noted, characterized by a decrease in polyene content and an increase in monoene fatty acids, under PCB exposure. Conclusion: The study underscores the resilience of C. closterium to moderate PCB concentrations and highlights the complex physiological responses and adaptive mechanisms initiated in response to PCB exposure. The findings contribute to understanding the toxic effects of PCBs on C. closterium and provide insights into potential mechanisms underlying these effects.

Ecological risk assessment of heavy metals (Pb, Cd, Cr, Ni, Zn, Fe) and metalloid (As) in surface sediment of Anzali International Wetland, Iran

ABSTRACT This study aimed to assess the metal concentration, mobility, bioavailability, ecological risk, and toxicity in the surface sediment of Anzali International Wetland. Contamination and ecological risk were evaluated using parameters such as Global Contamination Factors (GCF), Risk Assessment Code (RAC), Toxic Unit (TU), sum of Toxic Units (ΣTUs), Toxic Risk Index (TRI), ecological risk (ER), Risk Index (RI), and modified Hazard Quotients (MHQ). Heavy metal mean concentrations (mean ± SD) ranked as follows: Zn (95.46 ± 20.71) > Cr (19.79 ± 2.79) > Ni (18.49 ± 5.23) > Pb (13.97 ± 3.20) > As (6.45 ± 1.87) > Cd (0.90 ± 0.34). Cd exhibited high mobility and bioavailability, while Cr, Pb, Zn, Ni, and As mainly existed in residual fractions, indicating low bioavailability and minimal ecological risk. Ecological risk assessment identified “moderate” to “considerable” risk potential for Cd at specific sites. The Risk Index categorized Anzali sediment as having “low” to “moderate” risk potential (150 < RI < 300). Values of RI, ΣTUs, and MHQ suggested low to moderate risk potential and low toxicity in the sediment. Global Contamination Factor (GCF) values indicated high contamination (12.53 to 79.11). Recommendations include installing effective sewage treatment plants and promoting proper agricultural practices to mitigate metal toxicity in Anzali Wetland and also protect human and environmental health.

Reducing baseline toxicity in fishery product-related sediments from land to sea: Region-specific solutions are required

Eastern China is a major producer of fishery products (including inland aquaculture, coastal mariculture, and coastal fishing products). The quality of the products is affected by hydrophobic organic contaminants (HOCs) in the sediments. Based on in-vitro luminescent bacterial assay, the baseline toxicity (BEQBio) of 56 common HOCs were assessed in the present study. Specifically, the BEQBio of sediments declined from land (31–400 mg/kg) to sea (9.1–270 mg/kg). However, the toxicity contribution explained by the HOCs increased gradually from land (0.70 %) to sea (10 %) using Iceberg Modeling. In the inland pond, current use HOCs (pyrethroid pesticide (PEs), organic tin (OTCs), and antibiotic) exhibited considerable concentrations, although their toxicity contribution was very small (0.076 %), thus more regulations on the use of HOCs should be proposed and further screening is needed to confirm the major toxicants. In coastal mariculture area, the toxicity contribution of current use HOCs further declined (0.010 %), whereas environmental background HOCs, such as polycyclic aromatic hydrocarbons (PAHs), became increasingly significant, with the contribution ratio increasing from 0.37 % to 2.4 %. To minimize the negative impacts of PAHs, optimization of energy structure in transportation and coastal industry is required. In the coastal fishing area, the phased-out persistent organic pollutants (POPs) remained a major concern, in terms of both concentration and toxicity contribution. The phased-out POPs explained 7.0 % of the toxic effects of the sediments from the coastal fishing area, due to historical residue, industrial emissions, and their high toxicities. For this reason, it is critical to improve the relevant emission regulations and standards, so as to eventually reduce the unintentional discharges of POPs.

Metal-contaminated sediment toxicity in a highly impacted Neotropical river: Insights from zebrafish embryo toxicity assays

The Fundão dam collapse was one of the largest mining-related disasters globally. It resulted in the release of mining tailings containing heavy metals, which contaminated the Doce River in southeastern Brazil. This study assessed the effects of acute exposure of Danio rerio embryos to sediments contaminated by mine tailings six years after the Fundão dam collapse. The study sites included P2, P3, and P4 in the upper Doce River, as well as site P1 on the Piranga River, an uncontaminated river. Sediment samples were analyzed for 10 metals/metalloid by atomic absorption spectrometry. In the assays, embryos were exposed to sediment from P1–P4 sites, and uncontaminated quartz was used as control sediment. Various biomarkers were applied to assess biological responses, and the integrated biomarker response (IBR) index was calculated for each site. Sediment samples revealed elevated levels of As, Cr, Cu, Hg, and Ni beyond Brazilian legislation limits. At 96-h exposure, embryo mortality rates exceeded 20% in P1, P2, and P3, higher than the control and P4 (p < 0.0001). Hatching rates ranged from 60 to 80% in P1, P2, and P3, lower than the control and P4 (p < 0.001). Larvae exposed to P2 sediment (closest to the Fundão dam) exhibited skeletal, physiological, and sensory malformations. Neurotoxicity was indicated by increased acetylcholinesterase activity and reduced spontaneous movements in embryos exposed to Doce River sediment. Contamination also increased metallothionein and heat shock protein 70 levels, along with changes in cell proliferation and apoptosis. Principal component analysis showed a good correlation between metals/metalloid in the sediment and larval morphometric endpoints. The IBR index highlighted suitable biomarkers for monitoring metal contamination in fish embryos. Overall, our findings suggest that sediment toxicity following the Fundão dam failure may compromise the sustainability of fish communities in the Doce River.

Incorporation of sediment- and soil-specific aspects in the Criteria for Reporting and Evaluating Ecotoxicity Data (CRED).

In environmental risk assessment either for registration purposes or for retrospective assessments of monitoring data, the hazard assessment is predominantly based on effect data from ecotoxicity studies. Most regulatory frameworks require studies used for risk assessment to be evaluated for reliability and relevance. Historically, the Klimisch methodology was used in many regulatory procedures where reliability needed to be evaluated. More recently, the Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) have been developed for aquatic ecotoxicity studies, providing more detailed guidance on the evaluation and reporting of not only the reliability but also the relevance of a scientific study. Here, we discuss the application of the CRED methodology for assessing sediment and soil ecotoxicity studies, addressing important sediment- and soil-specific criteria that should be included as part of the CRED evaluation system. We also provide detailed recommendations for the design and reporting of sediment and soil toxicity studies that can be used by scientists and researchers wishing to contribute ecotoxicological data for effect assessments carried out within regulatory frameworks. Integr Environ Assess Manag 2024;20:2162-2174. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Developing a protocol whole sediment toxicity testing with the polychaete Armandia agilis

Sediments constitute a key compartment of coastal and marine ecosystems. They also constitute the ultimate sink for most of the chemical substances and a source of contamination to the benthic fauna. In this study, we aimed to develop a protocol for acute toxicity tests using the polychaete Armandia agilis as a model species. To achieve that, we evaluated the species tolerance to the salinity of overlying water (in the presence and absence of sediment), the tolerance to sediments with different particle sizes, the sensitivity to reference substances (potassium dichromate – K2Cr2O7, zinc sulfate – ZnSO4; and Sodium Dodecyl Sulfate - SDS), and the responses to clean and contaminated sediments. The species survives in several latitudes on the American coast (North Carolina, Gulf of Mexico, and South-Southeast of Brazil) in different haline conditions (above 20) in typically sandy textures. In Ilhabela (SE Brazil), the species was available throughout the year. The LC50-48h values calculated to the K2Cr2O7, ZnSO4, and SDS, were 20.94 (33.38-14.04); 4.25 (7.66-2.98); 4.90 (6.59-3.84) mg L-1 respectively; thus A. agilis can be considered as sensitive as other benthic organisms. The responses of A. agilis to environmental sediments were similar to those exhibited by the amphipod Tiburonella viscana, showing that this polychaete is responsive to contaminated sediments. Armandia agilis can be considered a promising organism to be used in sediment toxicity tests.

Ecotoxicology of sediment in the estuary of the Jundiaí and Potengi Rivers in Natal-RN, Brazil, by using Leptocheirus plumulosus as test-organism

The estuary of the Potengi and Jundiaí Rivers is situated on the coast of the state of Rio Grande do Norte, Brazil, and has a record of contamination by metals and organic contaminants. However, there are few studies regarding the toxic effects of pollution on the aquatic organisms from this area. The objective was to assess the quality of sediments from the Jundiaí and Potengi Rivers, by the use of toxicity tests with the amphipod Leptocheirus plumulosus. The sediments were collected from 4 sites, in 4 different months along 2011. After data analysis, it was possible to observe that the sediments collected close to the most populated areas of Macaíba and Natal (P1 and P3) were toxic. Sediment from the Station 4 did not show toxicity in any of the months studied, despite its urban location near the port of Natal. This result might be related to a low level of organic matter and greater tidal influence, which affect the dilution of the contaminants at this area and can reduce the sediment toxicity. No relationship between rainfall and environmental toxicity was observed.

Deep Learning Bridged Bioactivity, Structure, and GC-HRMS-Readable Evidence to Decipher Nontarget Toxicants in Sediments.

Identifying causative toxicants in mixtures is critical, but this task is challenging when mixtures contain multiple chemical classes. Effect-based methods are used to complement chemical analyses to identify toxicants, yet conventional bioassays typically rely on an apical and/or single endpoint, providing limited diagnostic potential to guide chemical prioritization. We proposed an event-driven taxonomy framework for mixture risk assessment that relied on high-throughput screening bioassays and toxicant identification integrated by deep learning. In this work, the framework was evaluated using chemical mixtures in sediments eliciting aryl-hydrocarbon receptor activation and oxidative stress response. Mixture prediction using target analysis explained <10% of observed sediment bioactivity. To identify additional contaminants, two deep learning models were developed to predict fingerprints of a pool of bioactive substances (event driver fingerprint, EDFP) and convert these candidates to MS-readable information (event driver ion, EDION) for nontarget analysis. Two libraries with 121 and 118 fingerprints were established, and 247 bioactive compounds were identified at confidence level 2 or 3 in sediment extract using GC-qToF-MS. Among them, 12 toxicants were analytically confirmed using reference standards. Collectively, we present a "bioactivity-signature-toxicant" strategy to deconvolute mixtures and to connect patchy data sets and guide nontarget analysis for diverse chemicals that elicit the same bioactivity.

Oil and gas platforms degrade benthic invertebrate diversity and food web structure

Oil and gas exploitation introduces toxic contaminants such as hydrocarbons and heavy metals to the surrounding sediment, resulting in deleterious impacts on marine benthic communities. This study combines benthic monitoring data over a 30-year period in the North Sea with dietary information on >1400 taxa to quantify the effects of active oil and gas platforms on benthic food webs using a multiple before-after control-impact experiment. Contamination from oil and gas platforms caused declines in benthic food web complexity, community abundance, and biodiversity. Fewer trophic interactions and increased connectance indicated that the community became dominated by generalists adapting to alternative resources, leading to simpler but more connected food webs in contaminated environments. Decreased mean body mass, shorter food chains, and the dominance of small detritivores such as Capitella capitata near to structures suggested a disproportionate loss of larger organisms from higher trophic levels. These patterns were associated with concentrations of hydrocarbons and heavy metals that exceed OSPAR's guideline thresholds of sediment toxicity. This study provides new evidence to better quantify and manage the environmental consequences of oil and gas exploitation at sea.

Sediment Toxicity Tests: A Critical Review of Their use in Environmental Regulations.

Sediments are an integral component of aquatic systems, linking multiple water uses, functions, and services. Contamination of sediments by chemicals is a worldwide problem, with many jurisdictions trying to prevent future pollution (prospective) and manage existing contamination (retrospective). The present review assesses the implementation of sediment toxicity testing in environmental regulations globally. Currently, the incorporation of sediment toxicity testing in regulations is most common in the European Union (EU), North America, and Australasian regions, with some expansion in Asia and non-EU Europe. Employing sediment toxicity testing in prospective assessments (i.e., before chemicals are allowed on the market) is most advanced and harmonized with pesticides. In the retrospective assessment of environmental risks (i.e., chemicals already contaminating sediments), regulatory sediment toxicity testing practices are applied inconsistently on the global scale. International harmonization of sediment toxicity tests is considered an asset and has been successful through the widespread adoption and deployment of Organisation for Economic Co-operation and Development guidelines. On the other hand, retrospective sediment assessments benefit from incorporating regional species and protocols. Currently used toxicity testing species are diverse, with temperate species being applied most often, whereas test protocols are insufficiently flexible to appropriately address the range of environmental contaminants, including nanomaterials, highly hydrophobic contaminants, and ionized chemicals. The ever-increasing and -changing pressures placed on aquatic resources are a challenge for protection and management efforts, calling for continuous sediment toxicity test method improvement to insure effective use in regulatory frameworks. Future developments should focus on including more subtle and specific toxicity endpoints (e.g., incorporating bioavailability-based in vitro tests) and genomic techniques, extending sediment toxicity testing from single to multispecies approaches, and providing a better link with ecological protection goals. Environ Toxicol Chem 2024;43:1697-1716. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Sediment pesticide contamination and toxicity in an agricultural tailwater recovery system

ABSTRACT Tailwater recovery system (TWR) sediment quality in Mississippi, USA, was evaluated seasonally within the storage reservoir and drainage ditch system from 2016 to 2019 for pesticide contamination, effects and bioavailability to Hyalella azteca (Saussure). Sediment bioassays (28-day) measured H. azteca survival and growth and tissue residue risks from sediment pesticide exposure. Sediment pesticide contamination comprised six current-use herbicides, three current-use insecticides, three legacy insecticides and one metabolite (p,p’-DDE). Sediment clomazone, bifenthrin and ΣDDT concentrations were greatest in drainage ditch sites during summer and fall. H. azteca tissue pesticide residues comprised three current-use herbicides and insecticides, as well as two legacy insecticides. Tissue residue clomazone, Ζ-cypermethrin and ΣDDT concentrations were greatest in drainage ditch sites during fall and winter. H. azteca survival and growth varied seasonally and spatially with lowest survival during fall and winter and lowest survival in the storage reservoir relative to drainage ditch sites during winter. Growth decreased during winter and spring with lowest growth in drainage ditches relative to the storage reservoir during spring. Patterns of associated survival and growth with tissue pesticide residues indicate increased risk during fall in TWR and where system water flows mobilise sediment pesticides increasing the risk of ecological impairment.