Bioavailability-based assessment of aryl hydrocarbon receptor-mediated activity in Lake Tai Basin from Eastern China

An application of waste algae biochar in aquaculture water to remove co-existed cadmium and PAHs and the corresponding mechanism

Water quality in aquaculture farms is highly related to the quality of aquaculture products and the connected environment. Cadmium (Cd²⁺) and polycyclic aromatic hydrocarbons (PAHs) are two of the most common pollutants in the aquaculture water, while biochar derived from waste algae (Enteromorpha prolifera), namely BE, was applied in farms ponds to improve water quality. Firstly, the adverse environmental impact of BE was minor, while the concentrations of the heavy metal (Cd²⁺ in the present study) and PAHs (FLU, PHE, FLT and PYR) were removed with efficiencies of 49%, 88%, 90%, 91% and 88%, respectively. The ecological risk values (RQs) were reduced subsequently with a rate of 58 ± 11%. After dosing BE, the ecological risk values in all the studied ponds were lower than 1, indicating no ecological risk in the corresponding aquaculture environment. The sorption capacities (q_m) of BE were 15, 12, 6.3, 0.41, 0.29 and 0.56 mg·g^-1 for Cd²⁺, FLU, PHE, FLT, PYR and BaP, respectively. The sorption capacities were acceptable compared with those derived from other types of biomass. The removal mechanisms were partition (PAHs), complexation (Cd²⁺), π-π interaction (Cd²⁺ and PAHs), precipitation (Cd²⁺) and ion-exchange (Cd²⁺). Practically and theoretically, the algae biochar is applicable in the aquaculture environment, where Cd²⁺ and PAHs co-exist.

Effect-directed analysis for revealing aryl hydrocarbon receptor agonists in sediment samples from an electronic waste recycling town in China

Exposure to electronic and electrical waste (e-waste) has been related to a few adverse health effects. In this study, sediment samples from an e-waste recycling town in China were collected, and aryl hydrocarbon receptor (AhR) agonists in the samples were identified using an effect-directed analysis (EDA) strategy. The CBG2.8D cell line reporter gene bioassay was used as a toxicity test, while suspect screening against chemical databases was performed for potential AhR agonist identification where both gas chromatography- and liquid chromatography-high resolution mass spectrometry analyses were run. When the original sample extract showed high AhR-mediated activity, sample fractionation was performed, and fractions exhibiting high bioactivity were chemically analyzed again to reveal the corresponding AhR agonists. In total, 23 AhR agonists were identified, including 14 commonly known ones and 9 new ones. Benzo [k]fluoranthene and 6-nitrochrysene were the dominant AhR agonists, covering 16-71% and 2.7-12%, respectively, of the AhR activation effects measured in the parent extracts. The newly identified AhR-active chemicals combined explained 0.13-0.20% of the parent extracts' effects, with 7,12-dimethylbenz [a]anthracene and 8,9,11-trimethylbenz [a]anthracene being the major contributors. A diagnostic isomer ratio analysis of polycyclic aromatic hydrocarbons suggested that the major source of AhR agonists identified in these e-waste related sediment samples were probably petroleum product combustion and biomass combustion. In the future, for a more comprehensive AhR agonist investigation, in-house chemical synthesis and purification, and, when necessary, a secondary sample fractionation, would be beneficial.

Applicability of Equilibrium Sampling in Informing Tissue Residues and Dietary Risks of Legacy and Current-Use Organic Chemicals in Aquaculture

Equilibrium sampling based on silicone polydimethylsiloxane (PDMS) has been used to determine the concentrations of freely dissolved hydrophobic organic compounds (HOCs) and assess the thermodynamic potentials for bioaccumulation of these compounds in the aquatic environment. This allows the use of PDMS-based sampling techniques in assisting conventional sampling and extraction methods for the determination of the concentrations of HOCs in aquaculture products. The present study is an ex situ demonstration of how well PDMS can inform the tissue residues and dietary risks of legacy or current-use organic chemicals in aquaculture species from farm ponds in eastern China. For legacy contaminants such as polybrominated diphenyl ethers (PBDEs, n = 10), good agreement between the predicted concentrations based on PDMS and the measured lipid-normalized concentrations was observed for 60% of the studied biota, including both pelagic and benthic species. For pesticides currently used, such as pyrethroid (PE) (n = 4) and organophosphate pesticides (OPPs, n = 7), the measured tissue residues were consistently higher than those predicted by PDMS, possibly caused by the continuous input from the surroundings. For the organochlorine pesticides (OCPs, n = 5), the only detected chemical was also underestimated. Adjusted by ingestion rates of aquaculture products and toxicology data, the target hazard quotients of these chemicals predicted from PDMS were generally comparable to those derived from measured concentrations in tissue because of the predominance of PBDEs. Overall, PDMS-based equilibrium sampling offered an alternative approach for the prediction of tissue residues and dietary risks of PBDEs. Moreover, it should be applied with caution for PEs, OPPs, and OCPs. Improving the application of PDMS for these chemicals in farm ponds warrants future study. Environ Toxicol Chem 2021;40:79-87. © 2020 SETAC.

Bioavailable Environmental Pollutant Patterns in Sediments from Passive Equilibrium Sampling

Sediment-associated risks depend on the bioavailable fraction of organic chemicals and cannot be comprehended by their total concentrations. The present study investigated contamination patterns of bioavailable chemicals in sediments from various sites around the globe by using passive equilibrium sampling. The extracts had been characterized previously for mixture effects by in vitro reporter gene assays and were in this study analyzed using gas chromatography-high resolution mass spectrometry for 121 chemicals including both legacy and emerging contaminants. The spatial distribution of the detected chemicals revealed distinct contamination patterns among sampling sites. We identified compounds in common at the different sites but most contaminant mixtures were site-specific. The mixture effects of the detected chemicals were predicted with a mixture toxicity model from effect concentrations of bioactive single chemicals and detected concentrations, applying a joint model for concentration addition and independent action. The predicted mixture effects were dominated by polycyclic aromatic hydrocarbons, and among the chemicals with available effect data, 17% elicited oxidative stress response and 18% activated the arylhydrocarbon receptor. Except for two sites in Sweden, where 11 and 38% of the observed oxidative stress response were explained by the detected chemicals, less than 10% of effects in both biological end points were explained. These results provide a comprehensive investigation of bioavailable contamination patterns of sediments and may serve as an example of employing passive equilibrium sampling as a monitoring technique to integrate the risk of bioavailable sediment-associated chemicals in aquatic environments.

Mixture Risk Drivers in Freshwater Sediments and Their Bioavailability Determined Using Passive Equilibrium Sampling

The identification of mixture risk drivers is a great challenge for sediment assessment, especially when taking bioavailability into consideration. The bioavailable portion, which comprises the organic contaminants in pore water and the ones bound to organic carbon, was accessed by equilibrium partitioning to polydimethylsiloxane (PDMS). The exhaustive solvent and PDMS extracts were toxicologically characterized with a battery of in vitro reporter gene assays and chemically analyzed with liquid and gas chromatography coupled to high-resolution mass spectrometry. The bioavailable fractions of mixture effects and individual chemicals were mostly lower than 0.1, indicating that more than 90% of the substances are strongly bound and would not pose an immediate risk but could potentially be remobilized in the long term. Despite 655 organic chemicals analyzed, only 0.1-28% of the observed biological effects was explained by the detected compounds in whole sediments, while 0.009-3.3% was explained by bioavailable chemicals. The mixture effects were not only dominated by legacy pollutants (e.g., polycyclic aromatic hydrocarbons (PAHs) in the bioassay for activation of the aryl-hydrocarbon receptor (AhR) and oxidative stress response (AREc32)) but also by present-use chemicals (e.g., plastic additives for binding to the peroxisome proliferator-activated receptor γ (PPARγ)), with different fingerprints between whole sediments and bioavailable extracts. Our results highlight the necessity to involve different bioassays with diverse effect profiles and broader selection of contaminants along with bioavailability for the risk assessment of chemical mixtures in sediments.

Magnetic activated carbon (MAC) mitigates contaminant bioavailability in farm pond sediment and dietary risks in aquaculture products

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) are among the contaminants of concern in aquaculture ponds due to their frequent detection and high bioaccumulation in aquatic products and hence high dietary risks to human beings. In this study, magnetic activated carbon (MAC) was added as a stabilization and removal adsorbent to native pond sediment with known contamination of HMs and PAHs to reduce the tissue residues and dietary risks of HMs and PAHs in a model aquaculture species (Venerupis philippinarum) in the course of a 28-day bioaccumulation experiment. Meanwhile, passive sampling techniques based on diffusive gradient in thin films (DGT) and polydimethylsiloxane (PDMS) were applied to sense the bioavailable fraction of HMs and PAHs in sediment during the stabilization process. The results showed that 3% dosage of MAC to sediment achieved the most cost-effective stabilization for HMs and PAHs. A remarkable decrease was observed with the tissue residues of HMs and PAHs in V. philippinarum (28-47% for HMs and ~76% for ∑PAHs), which was quantitatively linked to the decline in their bioavailable concentrations in sediment pore water (31-46% for HMs and ~76% for ∑PAHs). Consequently, the target hazard quotients (THQs) posed by HMs and incremental lifetime cancer risks (ILCRs) by PAHs in V. philippinarum were reduced by 38% and 46%, respectively. Along with the magnetic recovery of ~70% MAC from the sediment, HMs (4.8-13%) and PAHs (2-60%) can be effectively removed. We further established a multi-domain equilibrium sorption model that was able to predict the optimal amendment of MAC for quantitative mitigation of bioavailable PAHs in sediment pore water within a certain range of MAC dosage. Future studies are warranted to explore the applicability domain of MAC for in situ remediation in aquaculture ponds to ensure the quality of farming organisms or to serve other purposes in aquatic systems.

Reduced bioavailability and ecological risks of polycyclic aromatic hydrocarbons in Yangshan port of East China Sea: Remediation effectiveness in the transition from construction to operation

To assess the remediation effectiveness of ecological restoration in the transition period from construction to operation of Yangshan Port, the largest deepwater port of East China Sea, we employed equilibrium passive sampling and partitioning theory to assess the changing bioavailability and flux of polycyclic aromatic hydrocarbons (PAHs) in relation to bioaccumulation and ecological risks in marine organisms. Due to the ecological restoration efforts, both the bulk and bioavailable concentrations of PAHs in sediment and surface seawater samples decreased dramatically after the port entered the operation phase, as compared with those reported during the last construction phase. PAH concentrations in the marine organisms also showed a dramatic decline, and corresponded to the change in the freely dissolved fractions of PAHs in sediment/surface water according to their thermodynamic potential for bioaccumulation. While trophic magnification of ΣPAHs was observed in the pelagic communities, concentrations of PAHs in benthic species were relatively consistent across multiple trophic levels, and were generally higher than those in pelagic species. The differing bioaccumulation between benthic and pelagic species may be related to the habitat-specific bioavailability of PAHs and the prey-predator relations among different species. The incremental lifetime cancer risks (ILCR) of PAHs in marine organisms also dropped by nearly three orders of magnitude, and were lower than the guideline (1 × 10^-6) proposed by the U.S. EPA, except for several species at higher trophic levels. Overall, our study highlights an integrated use of passive sampling and equilibrium partitioning theory as a robust tool that can be applied to assess the effectiveness of ecological remediation in the port environment with quantitative, mechanistic insights from bioavailability to bioaccumulation.

State of the art and future challenges for polycyclic aromatic hydrocarbons is sediments: sources, fate, bioavailability and remediation techniques

Polycyclic aromatic hydrocarbons (PAHs) are amongst the most abundant contaminants found in the aquatic environment. Due to their toxicity and carcinogenicity, their sources, fate, behaviour, and cleanup techniques have been widely investigated in the last several decades. When entering the sediment-water system, PAH fate is determined by particular PAH and sediment physico-chemical properties. Most of the PAHs will be associated with fine-grained, organic-rich, sediment material. This makes sediment an ultimate sink for these pollutants. This association results in sediment contamination, and in this manner, sediments represent a permanent source of water pollution from which benthic organisms may accumulate toxic compounds, predominantly in lipid-rich tissues. A tendency for biomagnification can result in critical body burdens in higher trophic species. In recent years, researchers have developed numerous methods for measuring bioavailable fractions (chemical methods, non-exhaustive extraction, and biomimetic methods), as valuable tools in a risk-based approach for remediation or management of contaminated sites. Contaminated sediments pose challenging cleanup and management problems, as conventional environmental dredging techniques are invasive, expensive, and sometimes ineffective or hard to apply to large and diverse sediment sites. Recent studies have shown that a combination of strategies including in situ approaches is likely to provide the most effective long-term solution for dealing with contaminated sediments. Such in situ approaches include, but are not limited to: bioaugmentation, biostimulation, phytoremediation, electrokinetic remediation, surfactant addition and application of different sorbent amendments (carbon-rich such as activated carbon and biochar) that can reduce exposure and limit the redistribution of contaminants in the environment.

Anthropogenic PAHs in lake sediments: a literature review (2002-2018)

Lake sediments are an important reservoir for toxic and hydrophobic polycyclic aromatic hydrocarbons (PAHs). Monitoring of PAHs in sediment is helpful to understand pollution mechanisms and anthropogenic activities. This study reviews studies of PAHs in lake sediments published during 2002-2018. The studies' findings are analyzed, distributions of PAHs in lake sediments are summarized, and the applicability of lake sediments for tracking changes in PAH emission sources is emphasized. Lake sediments heavily polluted with PAHs are distributed in China, Egypt, the USA, and some urban lakes in Africa. The high levels of PAHs are predominantly associated with human activities such as anthropogenic combustion, petroleum industries, road traffic, and socioeconomic factors. However, the concentrations of sedimentary PAHs in most lakes were below the international guideline values.

Emerging investigator series: effect-based characterization of mixtures of environmental pollutants in diverse sediments

This study investigated whether cell-based bioassays were suitable to characterize profiles of mixture effects of hydrophobic pollutants in multiple sediments covering remote Arctic and tropical sites to highly populated sites in Europe and Australia. The total contamination was determined after total solvent extraction and the bioavailable contamination after silicone-based passive equilibrium sampling. In addition to cytotoxicity, we observed specific responses in cell-based reporter gene bioassays: activation of metabolic enzymes (arylhydrocarbon receptor: AhR, peroxisome proliferator activated receptor gamma: PPARγ) and adaptive stress responses (oxidative stress response: AREc32). No mixture effects were found for effects on the estrogen, androgen, progesterone and glucocorticoid receptors, or they were masked by cytotoxicity. The bioanalytical equivalent concentrations (BEQ) spanned several orders of magnitude for each bioassay. The bioavailable BEQs (passive equilibrium sampling) typically were 10-100 times and up to 420 times lower than the total BEQ (solvent extraction) for the AhR and AREc32 assays, indicating that the readily desorbing fraction of the bioactive chemicals was substantially lower than the fraction bound strongly to the sediment sorptive phases. Contrarily, the bioavailable BEQ in the PPARγ assay was within a factor of five of the total BEQ. We identified several hotspots of contamination in Europe and established background contamination levels in the Arctic and Australia.

Using Multiple Discriminant Analysis for the Assignment of Initial Water Entitlements at River Basin-Level under the Strictest Water Resources Management System Constraints in China

From the perspective of system science, in China, an assignment system of initial water entitlements at the river basin-level can be divided into two subsystems, namely the assignment subsystem of initial water entitlements at the province-level and government reserved water at the river basin-level. Under the new backdrop of implementing the strictest water resources management system (SWRMS), we propose a novel methodological framework for addressing the in-coordination of pre-allocation plans between two subsystems for Lake Tai Basin, China. First, considering total water use, pollutant discharge and water use efficiency, we establish several criteria for the discriminant analysis of pre-allocation plans. Whilst based on these criteria, we built a comprehensive discriminant criterion to further verify coupling and coordination of pre-allocation plans between two subsystems. Second, according to uncoordinated or less coordinated situations, we propose adjusted strategies to decide the direction (increase or decrease) of the adjustment for pre-allocation plans of two subsystems. Third, taking coupling and coordination as optimal objectives, and considering total water use, total pollutant discharge and water use efficiency as constraints, we built an adjusted decision-making model for the assignment of initial water entitlements of the basin. Finally, the results of this novel discriminant analysis methodology that were applied to the Lake Tai Basin show that under the water frequency of 75%, in the planning year 2030, Jiangsu Province is assigned the most initial water entitlements at the province-level, followed by Shanghai and Zhejiang Province. In this paper, results are generally in accordance with pilot plans released by China’s Ministry of Water Resources. Apart from pilot plans, our findings also show the assignment plans for government reserved water at the river basin-level, which is coordinated and coupled with assignment plans for initial water entitlements at the province-level. The novel methodological framework of this paper can also be applied as a reference to other similar river basin.

Safety and quality of the green tide algal species Ulva prolifera for option of human consumption: A nutrition and contamination study

This study sampled U. prolifera and surface seawater from the same locations where green tide broke out in the southern Yellow Sea, in both the year 2016 and 2017. The revealed nutritive components of U. prolifera samples characterized U. prolifera as a high-protein, high-Fe, high ratio of unsaturated lipid acids and low-fat seaweed food, with an ideal ratio of essential and nonessential amino acids. The concentrations and health risk assessment of major micropollutants (heavy metals, pesticides and polycyclic aromatic hydrocarbon (PAHs)) in U. prolifera were also analyzed, respectively. The results showed that the Target Hazard Quotient values of five heavy metals (<1.0 × 10^-1) and the total hazard index of 13 pesticides (<1.5 × 10^-8) were lower than the unity, respectively, and the incremental lifetime cancer risk values of PAHs (<7.4 × 10^-7) were lower than the USEPA limit (1.0 × 10^-6). It suggested that consuming U. prolifera is safe as a food-source option, with PAHs causing relatively higher risks. PAHs from the sites closer to the shore were also found more originated from pyrolysis. We further confirmed the PAH congeners were partly in equilibrium between seawater and U. prolifera. It suggested the possibility that the food safety-risk turned to be above the USEPA limit was not high regardless of the sample collecting time. However, the sources of PAHs and their contributions to the accumulation in U. prolifera need further investigation. This study favored that U. prolifera of the green tide from the southern Yellow Sea has a potential for a nutritious-food production.

In situ microbiota distinguished primary anthropogenic stressor in freshwater sediments

Conventional assessment and evaluation of sediment quality are based on laboratory-based ecotoxicological and chemical measurements with lack of concern for ecological relevance. Microbiotas in sediment are responsive to pollutants and can be used as alternative ecological indicators of sediment pollutants; however, the linkage between the microbial ecology and ecotoxicological endpoints in response to sediment contamination has been poorly evaluated. Here, in situ microbiotas from the Three Gorges Reservoir (TGR) area of the Yangtze River were characterized by DNA metabarcoding approaches, and then, changes of in situ microbiotas were compared with the ecotoxicological endpoint, aryl hydrocarbon receptor (AhR) mediated activity, and level of polycyclic aromatic hydrocarbons (PAHs) in sediments. PAHs and organic pollutant mixtures mediating AhR activity had different effects on the structures of microbiotas. Specifically, Shannon indices of protistan communities were negatively correlated with the levels of AhR mediated activity and PAHs. The sediment AhR activity was positively correlated with the relative abundance of prokaryotic Acetobacteraceae, but had a negative correlation with protistan Oxytrichidae. Furthermore, a quantitative classification model was built to predict the level of AhR activity based on the relative abundances of Acetobacteraceae and Oxytrichidae. These results suggested that in situ Protista communities could provide a useful tool for monitoring and assessing ecological stressors. The observed responses of microbial community provided supplementary evidence to support that the AhR-active pollutants, such as PAHs, were the primary stressors of the aquatic community in TGR area.

Equilibrium sampling informs tissue residue and sediment remediation for pyrethroid insecticides in mariculture: A laboratory demonstration

Mariculture product safety in relation to sediment quality has attracted increasing attention because of the accumulation of potentially hazardous chemicals, including pyrethroid insecticides, in sediment. Passive sampling has been widely used to assess the bioavailability of sediment-associated hydrophobic organic contaminants and predict their body residue in benthic organisms. Therefore, in this study, we introduced polydimethylsiloxane (PDMS) polymer as a biomimetic "chemometer" for freely-dissolved concentrations (C_free) to assess the efficacy of different carbon sorbents in reducing the bioavailability of pyrethroids in the process of sediment remediation. Black carbon (BC)-based materials (e.g., charcoal, biochar, and activated carbon) showed the advantageous sorption capacity over humic substance-based peat soil based on both C_free and tissue residue in exposed clams. Of the tested BC-type materials, biochar appeared to be an ideal one in the remediation of pyrethroid-contaminated sediment. The predictive value of the PDMS chemometer approach to informing tissue residue was confirmed by a good agreement between the measured lipid-normalized concentrations of pyrethroids in clams and the lipid-based equilibrium concentrations calculated from C_free via lipid-water partition coefficients. The quantitative inter-compartmental relationship underlying the laboratory system of sediment-pore water-PDMS-biota was also cross-validated by a mechanistically-based bioaccumulation model, thus confirming the validity of C_free as a predictive intermediate to alert for tissue residue and guide sediment remediation. The present study revealed a great promise of sensing C_free by polymer-based equilibrium sampling in predicting tissue residue of chemicals applied in mariculture against regulatory guidelines, and, in turn, informing remediation measures when needs arise. In situ demonstration is warranted in the future to ascertain the field applicability of this approach in real mariculture systems.

Extraction techniques using isopropanol and Tenax to characterize polycyclic aromatic hydrocarbons bioavailability in sediment

Polycyclic aromatic hydrocarbon (PAH)-degrading bacterium strain J1-q (Sphingomonas pseudosanguinis strain J1-q) was isolated from Yangtze River surface sediment in the downtown area of Chongqing in a previous study. Isopropanol and Tenax extraction techniques were used to characterize the bioavailability of target PAH compounds. Phenanthrene (Phe) and fluoranthene (Fluo) were the target PAHs due to their significant background concentrations in surface sediment samples. Isopropanol solutions at concentrations of 50-100% and residual Phe and Fluo concentrations in sediment were correlated, with R² values of 0.9846 and 0.9649, respectively. The quantities of the Phe and Fluo fractions extracted for 3days with isopropanol from sediment were closely related with the corresponding quantities of PAHs degraded by bacterial strain J1-q when the extracting concentrations were 55% and 80%, respectively. The quantity of Phe extracted by Tenax agreed with the total quantity biodegraded when the Tenax: sediment mass ratio was 0.25 and the target PAHs were degraded for 30d, whereas the extracted quantity of Fluo accounted for 93.30% of the total quantity biodegraded by the bacterium. The triphasic model was appropriate to simulate the consecutive Phe and Fluo extraction process using Tenax at various Tenax: sediment ratios, and all simulated correlation coefficients were >0.9151. A 24-h extraction period was adequate to estimate the rapidly desorbing fractions when they were extracted with Tenax. Isopropanol extraction was preferable to characterize Phe and Fluo bioavailability under the experimental conditions, whereas Tenax extraction was useful to predict bioavailability of the two target PAHs with particular selectivity.

In vitro toxicity assessment of sediment samples from Huangpu River and Suzhou River, Shanghai, China

Sediments are the ultimate sink for many toxic organic contaminants released into aquatic environment. The present study evaluated the toxicity effect of 13 surface sediment samples from Huangpu River and Suzhou River, East China using two-hybrid yeast bioassays for estrogenic and thyroidal effects and H4IIE rat hepatoma cell bioassay for ethoxyresorufin O-deethylase (EROD) activity. Toxicity was expressed as 17β-estradiol equivalent (E2-EQ), 3,3',5-triiodothyronine equivalent (T3-EQ), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) equivalent (TEQ). At the same time, the causality between the observed EROD activity and concentrations of polycyclic aromatic hydrocarbons (PAHs) was examined. The results showed that the total estrogenic effects in sediments ranged from 0.06 to 1.21 μg E2-EQ kg(-1) dry weight (dw), the thyroidal effects ranged from 4.68 to 69.9 μg T3-EQ kg(-1) dw, and significantly positive correlations were found between lgT3-EQs and lgE2-EQs. The AhR agonist effects varied from 26.5 to 148.3 ng TEQ kg(-1) dw. Chemical analysis-derived TEQs contributed by PAHs ranged from 13.8 to 66.0 ng kg(-1) dw accounting for 27.2-109.9 % with mean of 48.9 % of TEQbio, indicating that PAHs made important contributions to the EROD effects of sediment extracts from the two rivers. The present study would provide meaningful information for further analysis and risk evaluation for organic pollutants in Huangpu River and Suzhou River.