Contamination by polycyclic aromatic hydrocarbons in the Jiulong River Estuary and Western Xiamen Sea, China

Spatial heterogeneity, sediment-water exchange, and diffusion mechanisms of organophosphate esters from river to coastal aquatic system in a typical economic circle of northern China

Organophosphate esters (OPEs) have proven to be pervasive in aquatic environments globally. However, understanding their partitioning behavior and mechanisms at the sediment-water interface remains limited. This study elucidated the spatial heterogeneity, interfacial exchange, and diffusion mechanisms of 14 OPEs (∑14OPEs) from river to coastal aquatic system. The transport tendencies of OPEs at the sediment-water interface were quantitatively assessed using fugacity methods. The total ∑14OPEs concentrations in water and sediments ranged from 154 ng/L to 528 ng/L and 2.41 ng/g dry weight (dw) to 230 ng/g dw, respectively. This result indicated a descending spatial tendency with moderate variability. OPE distribution was primarily influenced by temperature, pH, and dissolved oxygen levels. As the carbon atom number increased, alkyl and chlorinated OPEs transitioned from diffusion towards the aqueous phase to equilibrium. In contrast, aryl OPEs and triphenylphosphine oxide, which had equivalent carbon atom counts, maintained equilibrium throughout. Diffusion trends of individual OPE congener at the sediment-water interface varied at the same total organic carbon contents (foc). As the foc increased, the fugacity fraction values for all OPE homologs showed a declining trend. The distinct molecular structure of each OPE monomer might lead to unique diffusive behaviors at the sediment-water interface. Higher soot carbon content had a more pronounced effect on the distribution patterns of OPEs. The sediment-water distribution of OPEs was primarily influenced by total organic carbon, sediment particle size, dry density, and moisture content. OPEs displayed the highest sensitivity to fluctuations in ammonium and dissolved organic carbon. This study holds significant scientific and theoretical implications for elucidating the interfacial transport and driving forces of OPEs and comprehending their fate and endogenous release in aquatic ecosystems.

Air-sea exchange of PAHs in the Taiwan Strait: Seasonal dynamics and regulation mechanisms revealed by machine learning approach

In this study, to understand the seasonal dynamics of air-sea exchange and its regulation mechanisms, we investigated polycyclic aromatic hydrocarbons (PAHs) at the air-sea interface in the western Taiwan Strait in combination with measurements and machine learning (ML) predictions. For 3-ring PAHs and most of 4- to 6-ring, volatilization and deposition fluxes were observed, respectively. Seasonal variations in air-sea exchange flux suggest the influence of monsoon transitions. Results of interpretable ML approach (XGBoost) indicated that volatilization of 3-ring PAHs was significantly controlled by dissolved PAH concentrations (contributed 24.0 %), and the gaseous deposition of 4- to 6-ring PAHs was related to more contaminated air masses originating from North China during the northeast monsoon. Henry's law constant emerged as a secondary factor, influencing the intensity of air-sea exchange, particularly for low molecular weight PAHs. Among environmental parameters, notably high wind speed emerges as the primary factor and biological pump's depletion of PAHs in surface seawater amplifies the gaseous deposition process. The distinct dynamics of exchanges at the air-water interface for PAHs in the western TWS can be attributed to variations in primary emission intensities, biological activity, and the inconsistent pathways of long-range atmospheric transport, particularly within the context of the monsoon transition.

PAHs and hopanes in the surface sediments of Qatar coast and their ecological risks: Comparison with regional and global coastal regions

The distribution, characteristics, sources and ecological risks of polycyclic aromatic hydrocarbons (PAHs) and hopanes in the surface sediments collected along the Qatar coast were investigated. Concentration of ∑14PAHs and hopanes ranged between 0.076 and 7.04 ng g-1 (mean: 2.60 ng g-1), 100 and 700 ng g-1 (mean: 205 ng g-1), respectively. Sediment samples were dominated by high molecular weight PAHs composition (4-6 rings). Diagnostic ratios of PAH concentrations showed both petrogenic and pyrogenic origins of PAHs, with a higher percentage of pyrogenic sources. The ecological risk levels of PAHs were estimated using sediment quality guidelines (SQG), mean probable effect level quotient values (PEL-Q), carcinogenic toxic equivalent quantity (TEQ), and risk quotient (RQ) evaluation methods. The calculated TEQ values (0.00012-0.85 ng g-1) were lesser than those in other locations around the globe, and were also within the safe level (600 ng g-1) suggested by the Canadian soil quality guidelines.

AHR-mediated DNA damage contributes to BaP-induced cardiac malformations in zebrafish

Benzo[a]pyrene (BaP) is a representative polycyclic aromatic hydrocarbon widely present in the environment. We previously reported that the aryl hydrocarbon receptor (AHR) mediates BaP-induced apoptosis and cardiac malformations in zebrafish embryos, but the underlying molecular mechanisms were unclear. Since BaP is a mutagenetic compound, we hypothesize that BaP induces apoptosis and heart defects via AHR-mediated DNA damage. In this study, zebrafish embryos were exposed to BaP at a concentration of 0.1 μM from 2 to 72 h post fertilization, either with or without inhibitors/agonists. AHR activity and levels of reactive oxygen species (ROS) were examined under a fluorescence microscope. mRNA expression levels were quantified by qPCR. DNA damage and apoptosis were detected by immunofluorescence. Our findings revealed that BaP exposure significantly increased BPDE-DNA adducts, mitochondrial damage, apoptosis and heart defects in zebrafish embryos. These effects were counteracted by inhibiting AHR/cyp1a1 using pharmaceutical inhibitors or genetic knockdown. Furthermore, we observed that spironolactone, an antagonist of nucleotide excision repair (NER), significantly enhanced BaP-induced BPDE-DNA adducts, mitochondrial damage, apoptosis and heart malformation rates. Conversely, SRT1720, a SIRT1 agonist, reduced the adverse effects of BaP. Supplementation with spironolactone also enhanced γ-H2AX signals in the heart of zebrafish embryos exposed to BaP. Additional experiments demonstrated that BaP suppressed the expression of SIRT1. We further established that AHR, when activated by BaP, directly inhibited SIRT1 transcription, leading to downregulation of XPC and XPA, which are essential NER genes involved in the recognition and verification steps of the NER process. Taken together, our results indicate that AHR mediates BaP-induced DNA damage in the heart of zebrafish embryos by inducing BPDE-DNA adduct formation via the AHR/Cyp1a1 signalling pathway, as well as suppressing NER via AHR-mediated inhibition of SIRT1.

Genomic insights into the adaptation of Synechococcus to the coastal environment on Xiamen

Synechococcus are widely distributed in the global ocean, from the pelagic zone to coastal waters. However, little is known about Synechococcus in coastal seawater due to limitations in isolation and culture conditions. In this study, a combination of metagenomic sequencing technology, flow cytometry sorting, and multiple displacement amplification was used to investigate Synechococcus in the coastal seawater of Xiamen Island. The results revealed 18 clades of Synechococcus and diverse metabolic genes that appear to contribute to their adaptation to the coastal environment. Intriguingly, some metabolic genes related to the metabolism of carbohydrates, energy, nucleotides, and amino acids were found in 89 prophage regions that were detected in 16,258 Synechococcus sequences. The detected metabolic genes can enable prophages to contribute to the adaptation of Synechococcus hosts to the coastal marine environment. The detection of prophages also suggests that the cyanophages have infected Synechococcus. On the other hand, the identification of 773 genes associated with antiviral defense systems indicates that Synechococcus in Xiamen have evolved genetic traits in response to cyanophage infection. Studying the community diversity and functional genes of Synechococcus provides insights into their role in environmental adaptation and marine ecosystems.

Occurrence, source estimation, and risk assessment of Polycyclic Aromatic Hydrocarbons in coastal seawaters from the Quintero Industrial Complex (Valparaíso, Chile)

In the 1960s, the Quintero industrial complex was inaugurated in Chile. This began a history of dramatic anthropogenic impacts on the Chilean coast. Among the known, we could mention high atmospheric emissions of chemicals due to combustion processes and frequent oil spills. For this reason, we surveyed the concentrations of fifteen EPA_PAHs in the surface coastal waters of the Quintero Bay area in 2015. The levels found are in the range of the highest levels when reviewing the literature (0.97 μg L^-1 up to 9.84 μg L^-1). The highest levels were found in the vicinity of the industrial complex and decreased in the other two zones. The concentration of individual compounds significantly exceeds the levels recommended by the EPA (Environmental Protection Agency) and the EU water framework directive (WFD). The risk estimations revealed that PAH concentrations represent high-risk for wildlife. Molecular ratios of PAHs were used to identify the possible sources, being these were mainly of pyrogenic origin, agreeing with an origin in the combustion of wood, coal, grass, and fossil fuels. This study contributes to the first data for surface water in a country's highly impacted industrial coastal area.

AHR-mediated m6A RNA methylation contributes to PM2.5-induced cardiac malformations in zebrafish larvae

A growing body of evidence indicates that ambient fine particle matter (PM_2.5) exposure inhibits heart development, but the underlying mechanisms remain elusive. We hypothesized that m⁶A RNA methylation plays an important role in the cardiac developmental toxicity of PM_2.5. In this study, we demonstrated that extractable organic matter (EOM) from PM2.5 significantly decreased global m⁶A RNA methylation levels in the heart of zebrafish larvae, which were restored by the methyl donor, betaine. Betaine also attenuated EOM-induced ROS overgeneration, mitochondrial damage, apoptosis and heart defects. Furthermore, we found that the aryl hydrocarbon receptor (AHR), which was activated by EOM_, directly repressed the transcription of methyltransferases mettl14 and mettl3. EOM also induced genome-wide m⁶A RNA methylation changes, which led us to focus more on the aberrant m⁶A methylation changes that were subsequently alleviated by the AHR inhibitor, CH223191. In addition, we found that the expression levels of traf4a and bbc3, two apoptosis related genes, were upregulated by EOM but restored to control levels by the forced expression of mettl14. Moreover, knockdown of either traf4a or bbc3 attenuated EOM-induced ROS overproduction and apoptosis. In conclusion, our results indicate that PM_2.5 induces m⁶A RNA methylation changes via AHR-mediated mettl14 downregulation, which upregulates traf4a and bbc3, leading to apoptosis and cardiac malformations.

Sex-specific thyroid disruption caused by phenanthrene in adult zebrafish (Danio rerio)

Polycyclic aromatic hydrocarbons (PAHs) are well-known contaminants with widespread distribution in environment and food. Phenanthrene is one of the most abundant PAHs in food and aquatic environment and generates reproductive and developmental toxicity in zebrafish. Nonetheless, whether phenanthrene caused sex-specific thyroid disruption in adult zebrafish is unclear. To determine this, adult zebrafish (male and female) were treated with phenanthrene (0, 0.85, 8.5, and 85 μg/L) for 60 days. After the treatment period, we assessed the concentrations of thyroid hormones (THs) and expression levels of genes in the hypothalamic-pituitary-thyroid (HPT) axis. The results showed that phenanthrene exposure can lead to thyroid disruption in both male and female zebrafish. Exposure to phenanthrene dramatically reduced the levels of L-thyroxine (T4) and L-triiodothyronine (T3) in both male and female zebrafish, with a similar trend in both. However, the genes expression profiles of hypothalamic-pituitary-thyroid (HPT) axis were sex-specific. In all, the present study demonstrated that phenanthrene exposure could result in sex-specific thyroid disruption in adult zebrafish.

Soil nutrient distribution and plant nutrient status in a mangrove stand adjacent to an aquaculture farm

The marine aquaculture industry has caused a suite of adverse environmental consequences, including offshore eutrophication. However, little is known about the extent to which aquaculture effluents affect nearby wetland ecosystems. We carried out a field experiment in a mangrove stand located between two effluent-receiving creeks to estimate the extent to which marine aquaculture affects the soil nutrient distribution and plant nutrient status of adjacent mangroves. Carbon (C), nitrogen (N), and phosphorus (P) contents and C isotopic signatures were determined seasonally in creeks, pore water, surface soils, and in the leaves of the dominant mangrove species Kandelia obovata. The creeks exhibited nutrient enrichment (2.44 mg N L^-1 and 0.09 mg P L^-1 on average). The soils had N (from 1.40 to 2.70 g kg^-1) and P (from 0.58 to 2.76 g kg^-1) much greater than those of pristine mangrove forests. Combined analyses of the N:P ratio, nutrient resorption efficiency, and proficiency indicated that soil P met plant demands, but plants in most plots showed N limitation, suggesting that soil nutrient accumulation did not fundamentally impact the plant nutrient status. Collectively, this case study shows that marine aquaculture farms can affect adjacent mangrove stands even though their effluents are not directly discharged into the mangrove stands, but mangrove forests may have substantial buffering capabilities for long-term nutrient loading.

Desorption of polycyclic aromatic hydrocarbons from polyethylene microplastics in two morphologically different digestive tracts of marine teleosts: Gastric red seabream (Pagrus major) and agastric mummichog (Fundulus heteroclitus)

In this study, we elucidated the desorption potency of polycyclic aromatic hydrocarbons (PAHs) sorbed on microplastics (MP; polyethylene) in the digestive tract of two fish species: gastric red seabream and agastric mummichog. In our in vitro assay system using the real gut sample of unexposed fish, the digestive tract was firstly removed from the fish and divided into three parts. Then, MP that had previously been sorbed with 16 PAHs were incubated with extracts of the gut contents or tissue with buffer or only a buffer. The desorption potency of PAHs was individually assessed for gut contents and tissue, which revealed that PAH desorption from MP was elevated in extracts of the gut contents compared with that in the buffer alone for both fish species. PAH desorption potency was the highest in the midgut for gastric red seabream and in the foregut for agastric mummichog, which indicates that PAH desorption from MP varies among different parts of the digestive tract and among fish with distinct gut morphology. In the midgut contents of red seabream and foregut contents of mummichog, the desorption fraction was 5.6% and 8.1% of the total PAHs sorbed on MP, respectively. The desorption fraction enhancement achieved by adding gut contents extracts tended to be greater with an increase in the n-octanol/water partition ratio, suggesting that enhancement of the desorption fraction in the digestive tract depends on the physicochemical properties of PAHs. Thus, morphological differences in digestive tracts and PAH properties should be considered when evaluating the effect of MP vector on pollutant exposure in fish.

Phenanthrene stress response and phytoremediation potential of free-floating fern Azolla filiculoides Lam

In this study, the potential of Azolla filiculoides, a freshwater fern species, on phenanthrene phytoremediation and biodegradation was investigated. Furthermore, the effect of phenanthrene on growth performance, photosynthetic activity and biosynthesis, and accumulation of secondary metabolites of A. filiculodes were evaluated. Plants were grown in a nitrogen-free Hoagland and exposed to different phenanthrene concentrations (0, 1, 5, and 10 mg/L). Exposure to 10 mg/L phenanthrene caused a significant reduction (42%) in Azolla filiculoides growth compared to control on day 14. The photosynthetic pigment content of A. filiculoides treated with 1 and 5 mg/L was almost the same as the control, while 10 mg/L phenanthrene was significantly reduced. In comparison to unplanted controls, the biodegradation percentages obtained from the planted growth medium were found to be 88, 69, and 60%, respectively, for the application of 1, 5, and 10 mg/L phenanthrene. Data on plant growth, photosynthetic pigments, secondary metabolite contents, and biodegradation percentages indicated the tolerance level and the effective phytoremediation potential of A. filiculoides for phenanthrene was <10 mg/L. The results indicated that A. filiculoides is highly effective in phytoremediation of low concentrations of phenanthrene pollution in a short time.

Stimulatory and inhibitory effects of phenanthrene on physiological performance of Chlorella vulgaris and Skeletonema costatum

The effects of polycyclic aromatic hydrocarbons on phytoplankton have been extensively documented, but there is limited knowledge about the physiological responses of marine primary producers to phenanthrene at environmentally relevant levels. Here, we investigated the toxicity of phenanthrene (0, 1, and 5 or 10 μg L⁻¹) to the physiological performance of two cosmopolitan phytoplankton species: the green alga Chlorella vulgaris and bloom-forming diatom Skeletonema costatum. The specific growth rates of both species were remarkably inhibited at both low (1 μg L⁻¹) and high phenanthrene concentrations (5 or 10 μg L⁻¹), while their tolerance to phenanthrene differed. At the highest phenanthrene concentration (10 μg L⁻¹), the growth of C. vulgaris was inhibited by 69%, and no growth was observed for S. costatum cells. The superoxide dismutase activity of both species was enhanced at high phenanthrene concentration, and increased activity of catalase was only observed at high phenanthrene concentration in C. vulgaris. Interestingly, the low phenanthrene concentration stimulated the photosynthetic and relative electron transport rates of S. costatum, whereas hormetic effects were not found for growth. Based on our results, phenanthrene could be detrimental to these two species at a environmentally relevant level, while different tolerance levels were detected.

Predicting the total PAHs concentrations in sediments from selected congeners using a multiple linear relationship

In this study, we observed that four congeners, including naphthalene (Nap), acenaphthylene (Acy), phenanthrene (Phe), and benz(a)anthracene (BaA), are the characteristic congeners for predicting the emission and the sediment concentrations of polycyclic aromatic hydrocarbons (PAHs). A novel multiple relationship of the total PAHs concentrations (C_∑PAHs) in sediments with the concentrations of four congeners was established (p < 0.01, R² = 0.95) using published data over the past 30 years. Moreover, the multiple linear relationship of the total PAHs emission factors with the emission factors of four congeners was also established (p < 0.01, R² = 0.99). Interestingly, the ratio of multicomponents coefficient from the multiple linear relationship in sediments to that from the multiple linear relationship in emission sources correlated positively with octanol–water partition coefficient (logK_ow) (p < 0.01, R² = 0.88) of the four PAHs congeners. Therefore, a novel model was established to predict C_ΣPAHs in sediments using the emissions and logK_ow of the four characteristic PAHs congeners. The percent sample deviation between calculated C_∑PAHs and their observed values was 54%, suggesting the established model can accurately predict C_ΣPAHs in sediments.

Microplastics increase the accumulation of phenanthrene in the ovaries of marine medaka (Oryzias melastigma) and its transgenerational toxicity

Microplastics (MPs) are considered to exacerbate the impacts of hydrophobic organic pollutants on aquatic organisms through the carrier function, but whether MPs affect the transgenerational toxicity of pollutants is unclear. This study exposed adult female marine medaka to phenanthrene (Phe)-adsorbed MPs for 60 days to investigate the effects of MPs on the bioaccumulation, reproductive and transgenerational toxicity of Phe. Compared to Phe alone, co-exposure to Phe and 200 μg/L MPs significantly increased Phe bioaccumulation in the intestines and ovaries. Phe alone and Phe combined with MPs disrupted the regulation of the hypothalamus-pituitary-gonadal axis, and reduced vitellogenin levels and reproductive capacity of female fish. In particular, co-exposure to 200 μg/L MPs and Phe increased the rate of follicular atresia, inhibited ovarian maturity, and aggravated reproductive toxicity. Notably, maternal uptake of Phe could be transferred to the offspring, and embryonic accumulation increased with the concentrations of MPs. Moreover, MPs aggravated Phe-induced bradycardia in embryos, suggesting that MPs exacerbated the transgenerational toxicity of Phe. These findings reveal that the growing number of MPs in the ocean might amplify the adverse effects of organic pollutants on the health and population stability of marine fishes, and this problem merits more attention.

Long-Term Exposure to Phenanthrene Induced Gene Expressions and Enzyme Activities of Cyprinus carpio below the Safe Concentration

Phenanthrene (PHE) is a typical compound biomagnified in the food chain which endangers human health and generally accumulates from marine life. It has been listed as one of the 16 priority PAHs evaluated in toxicology. In order to evaluate the changes of CYP1A GST mRNA expression and EROD GST enzyme activity in carp exposed to lower than safe concentrations of PHE. Long-term exposure of carp to PHE at lower than safe concentrations for up to 25 days. The mRNA expression level and cytochrome P450 (CYP1A/EROD (7-Ethoxylesorufin O-deethylase)) and glutathione S-transferase (GST) activity were measured in carp liver and brain tissue. The results showed that PHE stress induced low-concentration induction and high-concentration inhibition of CYP1A expression and EROD enzyme activity in the liver and brain of carp. In both two organs, GST enzyme activity was also induced. However, the expression of GST mRNA was first induced and then inhibited, after the 15th day. These results indicate that long-term exposure to PHE at lower than safe concentrations still poses a potential threat to carp’s oxidase system and gene expression.

Spatial distribution, source identification and ecological risk assessment of POPs and heavy metals in lake sediments of Istanbul, Turkey

Istanbul needs to be protected and constantly monitored water resources due to its increasing population and the decrease in precipitation. This study aims to comprehensively reveal surface sediments collected from reservoirs that supply water to Istanbul concerning POPs (PAHs, PCBs, and OCPs) and heavy metals; to identify possible sources of PAHs, and conduct their ecological risk assessment. Pollution indices in this study were used as contamination degree (CD) contamination factor (CF), geoaccumulation index (I_geo), pollution load index (PLI) and Sediment Quality Guidelines (SQGs). Total PAH concentrations of surface sediments at the sampling points ranged from 46.29 ng/g (A7) to 403.9 ng/g (A15). Benzo(b)fluoranthene (5.647-59.42 ng/g), Pyrene (3.625-83.10 ng/g), Fluoranthene (3.363-66.48 ng/g), Phenanthrene (3.115-52.48 ng/g), Chrysene (3.532-43.98 ng/g), Naphthalene (6.606-36.20 ng/g), Benzo(g,h,i)perylene (3.316-41.73 ng/g) and Indeno(1,2,3-c,d)pyrene (3.453-38.84 ng/g) are the dominant PAH compounds. PAH pollution may be caused by the village-town settlements near the dam and the O7-D020 highway. Total OCP concentration ranged from 2.233 ng/g (A12) to 7.337 ng/g (A1), while total PCB concentration ranged from 0.246 ng/g (A13) to 3.708 ng/g (A1). The lowest total OCP and PCB concentrations were found in surface sediments taken from Kazandere, Papuçdere and Alibey Dam lakes. DDT p,p (0.072-5.177 ng/g) has the highest concentration among all sediment samples. While the most dominant OCP compounds in the samples were DDT p,p, DDE p,p and DDD p,p, HCH alpha, HCH beta, respectively, PCB 153, 138 and 180 were the highest detected PCB congeners in the same samples. Total heavy metal concentration varied from 77,812 mg/kg to 267,072 mg/kg. According to PAH diagnostic analysis, the surface sediments of Terkos, Büyükçekmece, Elmalı, Darlık, Sazlıdere, Alibey and Ömerli Dams were polluted by petrogenic sources, while the surface sediments of Kazandere and Papuçdere Dams were affected by pyrogenic sources. None of the levels of POPs in the samples exceeded the ERM values. Slight and moderate contamination of heavy metals, such as Pb and Zn, were present in most of the sampling points according to CD, CF, PLI and I_geo values. The quality criteria of heavy metals showed that almost all of the sampling points had Cd, Pb and Hg concentrations below the ERL values. The Ni concentrations at most of the sampling points significantly exceeded the ERM values. The concentrations of As, Cr, Cu and especially Ni and Zn exhibit a significant toxic risk to aquatic organisms to sediment quality criteria.

Thyroid disruption and growth inhibition of zebrafish embryos/larvae by phenanthrene treatment at environmentally relevant concentrations

Phenanthrene induces reproductive and developmental toxicity in fish, but whether it can disrupt the thyroid hormone balance and inhibit growth had not been determined to date. In this study, zebrafish embryos were exposed to phenanthrene (0, 0.1, 1, 10 and 100 μg/L) for 7 days. The results of this experiment demonstrated that phenanthrene induced thyroid disruption and growth inhibition in zebrafish larvae. Phenanthrene significantly decreased the concentration of l-thyroxine (T4) but increased that of 3,5,3'-l-triiodothyronine (T3). The expression of genes related to the hypothalamic-pituitary-thyroid (HPT) axis was altered in zebrafish larvae exposed to phenanthrene. Moreover, phenanthrene exposure significantly increased the malformation rate and significantly reduced the survival rate and the body length of zebrafish larvae. Furthermore, phenanthrene significantly decreased the concentrations of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Changes observed in gene expression patterns further support the hypothesis that these effects may be related to alterations along the GH/IGF-1 axis. In conclusion, our study indicated that exposure to phenanthrene at concentrations as low as 0.1 μg/L resulted in thyroid disruption and growth inhibition in zebrafish larvae. Therefore, the estimation of phenanthrene levels in the aquatic environment needs to be revisited.

Comprehensive insights into the occurrence, source, distribution and risk assessment of polycyclic aromatic hydrocarbons in a large drinking reservoir system

The resource, environment, and ecological value of drinking reservoirs have received widespread concerns due to the pollution of persistent organic pollutants such as polycyclic aromatic hydrocarbons (PAHs). Therefore, we comprehensively studied the occurrence, source, distribution, and risk assessment of representative PAHs in Fengshuba Reservoir (FSBR) (large drinking reservoir, China). The total concentrations of 16 USEPA PAHs in the water phase, porewater phase, sediment phase, and soil phase were in ranges of 109.72-393.19 ng/L, 5.75-35.15 μg/L, 364.4-743.71 μg/kg, and 367.81-639.89 μg/kg, respectively. The naphthalene (Nap) was the dominant PAHs in the water phase, while it was Nap and phenanthrene (Phe) in porewater, sediment, and soil phase. The main sources of PAHs in FSBR were biomass combustion. Redundancy analysis indicated that the NTU, NO₂^-, NH₄⁺, Chl-α, and IC were the dominant factors influencing the PAH distribution in water phase, and the PAHs in sediment phase was affected by T and NO₃^-. Pseudo-partitioning coefficients indicated that the PAHs in the porewater phase were more likely to migrate to the sediment phase. Risk assessment indicated that the PAHs both in the water and sediment phases were generally in a low-risk state, while the PAHs in the soil phase were in a moderate-risk state, and the Nap was in a high-risk state, and exposure to the PAHs in FSBR through drinking and skin exposure had little impact on consumers' health. In summary, Nap could be used as a key indicator to evaluate the existence and potential risk of PAHs in FSBR.

Ship navigation disturbance alters multiphase distribution of perfluoroalkyl acids and increases their ecological risk in waterways

As a global persistent organic pollutant, perfluoroalkyl acids (PFAAs) have aroused great public concern. However, little is known regarding the effect of ship navigation disturbance on the transport and fate of PFAAs in inland waterways developed regions. In the present study, overlying water, pore water, suspended particulate matter (SPM), and sediment were collected from waterways (WWs), non-navigable channels (NCs), and ports (PTs) in Taihu Lake Basin. The results revealed that the total concentrations of PFAAs (ΣPFAAs) in WWs, NCs, and PTs varied considerably in different media. In overlying water, the mean ΣPFAAs in WWs were the highest, while those of NCs were relatively higher in the remaining three media. A comparison of PFAA distribution coefficients revealed that the values in NCs were generally higher than those of WWs and PTs, suggesting the critical role of ship navigation in PFAA transport. Furthermore, a structural equation model was applied to estimate direct and indirect effects of environmental factors on PFAA partitioning behavior. The results revealed that ship traffic volume (STV) exerted indirect effects on PFAA distribution between solid and dissolved phases by influencing dissolved oxygen, total suspended solid concentration, clay and sand contents, and median diameter. PFAAs were more readily to be released into overlying water from pore water than in sediment, and the ΣPFAAs carried per gram of SPM decreased with an increase in STV. Ecological risk assessment and Monte Carlo simulation results revealed that ship navigation could exert adverse effects on aquatic organisms, making the average probability of RQ_mix values to exceed corresponding risk values in WWs, which were 1.3-2-fold higher than in NCs. The present study provides crucial information for simulating the environmental behaviors of PFAAs under the influence of ship navigation and is significant for the integration of inland water transport development and aquatic environmental protection.

Sublethal Effect Concentrations for Nonpolar Narcosis in the Zebrafish Embryo

Nonpolar narcosis, also known as baseline toxicity, has been described as the minimal toxicity that an organic chemical may elicit based on its lipophilicity. Although lethal effects of narcosis-inducing chemicals (NICs) have been thoroughly investigated, knowledge of sublethal effects is still very limited. We investigated the effects of 3 well-known NICs (phenanthrene, 1,3,5-trichlorobenzene, and pentachlorobenzene) on a variety of organismal endpoints (malformations, swim bladder inflation, respiration, heart rate, swimming activity, and turning angles), which can be plausibly linked to narcosis in zebrafish embryos. Baseline toxicity recorded as mortality is typically observed in similar exposure ranges in a wide variety of species including fish, corresponding to a chemical activity range between 0.01 and 0.1. In the present study, we found that sublethal effects occurred at concentrations approximately 5 times below lethal concentrations. Altered swimming activity and impaired swim bladder inflation were the most sensitive endpoints occurring at exposure levels below the generally accepted threshold for baseline toxicity for 2 out of 3 compounds. Overall, most effective exposure levels across the sublethal endpoints and compounds did fall within the range typically associated with baseline toxicity, and deviations were generally limited to a factor 10. Although there could be benefit in adding sublethal endpoints to toxicity tests, such as the fish embryo acute toxicity (FET) test, based on the present sublethal endpoints and available evidence from our and other studies, the underestimation of toxicity as a result of the sole assessment of mortality as an endpoint in an FET test may be limited for narcosis. Environ Toxicol Chem 2021;40:2802-2812. © 2021 SETAC.

Baseline distributions and sources of polycyclic aromatic hydrocarbons (PAHs) in reef-associated sediments of Vembar group of Islands, Gulf of Mannar, India

The study aims to investigate the source and concentration of PAH fractions in the reef sediments of the Vembar group of Islands, Gulf of Mannar, India. The concentration of PAHs ranged from 0.36 to 15.98 ng/g. The reef environment was less contaminated with low-molecular-weight PAH fractions. The accumulation of the LMW-PAH fraction was very less, whereas the HMW fraction was derived from pyrolytic sources. The level of low and high molecular weight PAHs was lower than the level of Effective Range Median (ERM) and Effective Range Low (ERL).The calculated total TEQ value ranged from ND to 10.24 ng/g in the reef sediments.

Acute and chronic toxicity of microcystin-LR and phenanthrene alone or in combination to the cladoceran (Daphnia magna)

Hazardous substances, such as microcystin-LR (MC-LR) and phenanthrene (Phe) are ubiquitous co-contaminants in eutrophic freshwaters, which cause harms to aquatic organisms. However, the risks associated with the co-exposure of aquatic biota to these two chemicals in the environment have received little attention. In this study, the single and mixture toxic effects of MC-LR and Phe mixtures were investigated in Daphnia magna after acute and chronic exposure. Acute tests showed that the median effective concentrations (48 h) for MC-LR, Phe and their mixtures were 13.46, 0.57 and 8.84 mg/L, respectively. Mixture toxicity prediction results indicated that the independent action model was more applicable than the concentration addition model. Moreover, combination index method suggested that the mixture toxicity was concentration dependent. Synergism was elicited at low concentrations of MC-LR and Phe exposure (≤4.04 + 0.17 mg/L), whereas antagonistic or additive effects were induced at higher concentrations. The involved mechanism of antagonism was presumably attributable to the protective effects of detoxification genes activated by high concentrations of MC-LR in mixtures. Additionally, chronic results also showed that exposure to a MC-LR and Phe mixture at low concentrations (≤50 +2 μg/L) resulted in greater toxic effects on D. magna life history than either chemical acting alone. The significant inhibition on detoxification genes and increased accumulation of MC-LR could be accounted for their synergistic toxic effects on D. magna. Our findings revealed the exacerbated ecological hazard of MC-LR and Phe at environmental concentrations (≤50 +2 μg/L), and provided new insights to the potential toxic mechanisms of MC-LR and Phe in aquatic animals.

The state of persistent organic pollutants in South African estuaries: A review of environmental exposure and sources

The long-term health of many South African estuaries is impacted by pollutants entering these systems through industrial and agricultural runoff, sewage outfalls, contaminated storm water drainage, flows from informal settlements, and plastic materials in marine debris. Uncontrolled inputs combined with poor environmental management often result in elevated levels of persistent organic pollutants (POPs) in affected estuaries. Data on POPs research from 1960 to 2020 were analysed in terms of their sources, environmental investigations, and health implications. The outcome showed polychlorinated biphenyls (PCBs) and per- and poly-fluoroalkyl sulphonates (PFASs) to exceed the US EPA health advisory levels for drinking water. Concentration of organochlorine pesticides (OCPs) in water were below the WHO limits, while those in fish tissues from most estuaries were found to be below the US FDA limits. Although environmental compartments in some estuaries (e.g. Rooiels and uMngeni estuaries) seem to be less contaminated relative to other marine systems around the world, many others were polluted and critically modified (e.g. Durban Bay, Swartkops, Sundays, and Buffalo systems). Due to inconsistent monitoring methods coupled with limited data availability, temporal trends were unclear. Of the 290 estuaries in South Africa, 65 were prioritised and recommended for POPs evaluation based on their pollution sources, and a monitoring strategy was defined in terms of sampling. Government policies to curb marine pollution need to be enforced to prevent chronic contamination that leads to water quality deterioration and loss of ecosystem services.

Biological responses and toxicopathic effects elicited in Solea senegalensis juveniles by waterborne exposure to benzo[a]pyrene

Polycyclic aromatic hydrocarbons (PAHs) are priority contaminants in coastal and estuarine ecosystems under anthropogenic pressure. Although PAHs tend to accumulate in the sediment, toxicity for benthic flat fish such as soles may be caused by PAHs released from the sediment to the water column. Within this context, the present investigation aims at recognizing toxicopathic effects elicited after waterborne exposure to benzo[a]pyrene B[a]P, a model individual PAH compound, in juvenile Solea senegalensis. Sole juveniles were exposed to various concentrations of waterborne B[a]P for 3 and 7 days. Brain, liver, gills and gonad were the target tissues selected to determine biochemical and lysosomal biomarkers, and histopathology. Biological responses and toxicopathic effects were consistent with B[a]P concentration and exposure time. From day 3, hepatic catalase inhibition indicated potential oxidative effects of B[a]P. At day 7, contaminant exposure produced hepatic glutathione-S-transferase induction at low concentrations and inhibition at higher levels, evidencing a bell-shaped response. A clear gradient in lysosomal membrane destabilisation was observed in relation with B[a]P concentrations. Histopathological lesions were more frequent at day 7 and at higher contaminant levels. It seems that environmentally relevant waterborne concentrations of B[a]P (1000 ng/l) would suffice to cause toxicopathic effects on sole juveniles in relatively short exposure times. In agreement, the Integrative Biological Response index (IBR/n) indicated a dose-dependent decline in health condition upon exposure to B[a]P (IBR/n_HighB[a]P > IBR/n_MidB[a]P > IBR/n_LowB[a]P > IBR/n_DMSO > IBR/n_Control). Overall, changes in antioxidant enzymes activity, lysosomal biomarkers and gill and liver histopathology are responsive early-warning signs of health disturbance in sole juveniles exposed to waterborne PAHs.

Compound-specific radiocarbon reveals sources and land-sea transport of polycyclic aromatic hydrocarbons in an urban estuary

As typical chemical indicators of the Anthropocene, polycyclic aromatic hydrocarbons (PAHs) and their environmental behavior in urban estuaries can reveal the influence of anthropogenic activities on coastal zones worldwide. In contrast to conventional approaches based on concentration datasets, we provide a compound-specific radiocarbon (¹⁴C) perspective to quantitatively evaluate the sources and land‒sea transport of PAHs in an estuarine‒coastal surficial sedimentary system impacted by anthropogenic activities and coastal currents. Compound-specific ¹⁴C of PAHs and their ¹⁴C end-member mixing models showed that 67-73% of fluoranthene and pyrene and 76-80% of five- and six-ring PAHs in the Jiulong River Estuary (JRE, China) originated from fossil fuels (e.g., coal, oil spill, and petroleum-related emissions). In the adjacent Western Taiwan Strait (WTS), the contributions of fossil fuel to these PAH groups were higher at 74-79% and 84-87%, respectively. Furthermore, as a significant biomarker for source allocation of terrigenous organic matter, perylene, a typical five-ring PAH, and its land‒sea transport from the basin through the JRE and finally to the WTS was quantitatively evaluated based on the ¹⁴C transport models. In the JRE, fluvial erosions and anthropogenic emissions affected the ¹⁴C signature of perylene (Δ¹⁴C_perylene, -535 ± 5‰) with contributions of > 38% and < 62%, respectively. From the JRE to the WTS, the decreased Δ¹⁴C_perylene (-735 ± 4‰) could be attributed to the long‒range transport of "ocean current-driven" perylene (-919 ± 53‰) with a contribution of 53 ± 8%. This compound-specific ¹⁴C approach and PAH transport model help provide a valuable reference for accurately quantifying land‒sea transport and burial of organic pollutants in estuarine‒coastal sedimentary systems.

Nonlinear partition of nonionic organic compounds into humus-like substance humificated from lignin

Nonlinear sorption of nonionic organic compounds (NOCs) by soil organic matter (SOM) is a significant behaviour that affecting their distribution, transport and fate in the environment. Sorption of typical NOCs, including phenols, anilines, nitrobenzenes and polycyclic aromatic hydrocarbons (PAHs) by Lig48, a humus-like substance humificated from lignin (the principal component of plant precursors of SOM), is nonlinear and without desorption hysteresis, and interpreted by nonlinear partition mechanism in this study. The positively linear relationship between sorption capacity and water solubility of NOCs is a distinguish characteristic for their nonlinear partition into Lig48. Moreover, the nonlinear partition capacity of NOCs is mainly dependent on the aromaticity of humus-like substances with a positively linear relationship, while the nonlinear partition affinity is mainly dependent on the polarity of humus-like substances with a negatively linear relationship. Competition between phenols, anilines, nitrobenzenes and PAHs was observed for their nonlinear partition into Lig48. In addition to van der Waals force, specific interactions, i.e., hydrogen-bonding and π-π interactions are responsible for the nonlinear partitioning of NOCs into humus-like substances including Lig48. These novel observations are helpful for understanding the nonlinear sorption of NOCs by SOM and elucidating the migration and transport of NOCs in the environment.

Fire Suppression Agents Combined with Gasoline in Aquatic Ecosystems: A Mixture Approach

Fire suppression agents are recommended for extinguishing fires by flammable liquids and frequently end in water bodies, combined with the fuels. There is a lack of toxicity information on these commercial formulations and the effects of mixtures of fire suppression agents and fuels. The aim of the present study was to evaluate the toxic effects of different fire suppression agents, the gasoline water-soluble fraction (GWSF), and mixtures of each fire suppression agent and GWSF. Individual tests were performed with Daphnia similis and Artemia sp.; the most toxic fire suppression agents to D. similis and Artemia sp. were F-500®, Cold Fire®, Agefoam®, and Kidde Sintex® 1%; the GWSF was the least toxic. The concentration addition model was used to predict the mixture effects and evaluate synergism/antagonism, dose ratio dependence, and dose level dependence. Cold Fire with GWSF showed dose level deviation to D. similis, marked mainly by synergism; for Artemia sp., the dose ratio pattern was predicted, with a synergistic response mainly by Cold Fire. Agefoam and GWSF behaved additively for D. similis and dose ratio for Artemia sp., with synergism being caused by Agefoam. Kidde Sintex 1% with GWSF were dose ratio for both organisms, with Kidde Sintex 1% being responsible for synergism. Our results show that some mixtures of fire suppression agents and GWSF may cause toxicity to aquatic organisms, posing risk in a real environmental scenario, such as a major fire combat. Environ Toxicol Chem 2021;40:767-779. © 2020 SETAC.

Effects of pyrene and benzo[a]pyrene on the reproduction and newborn morphology and behavior of the freshwater planarian Girardia tigrina

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants of aquatic ecosystems. Because they are persistent, there is great potential for chronic toxicity to aquatic species, and the evaluation of reproductive effects is fundamental. In this context, planarians are interesting experimental animals, since they can be sensitive to environmental pollutants, and a wide range of reproductive-related endpoints can be assessed. In this work we evaluated fecundity (number of cocoons), fertility (number of newborns), newborn anomalies, adult weight, regenerative abilities and PAH-residues in tissues of the freshwater planarian Girardia tigrina, exposed to either pyrene or benzo[a]pyrene (B[a]P). Pyrene reduced planarian fecundity and fertility at 18.75 μg L^-1 and 75.00 μg L^-1, while B[a]P reduced planarian fecundity at the 37.50 μg L^-1 treatment, which was accompanied by a 33.7% reduction in fertility. Cocoons were kept in clean media and newborns were evaluated for behavioral and morphological anomalies. Many of the newborns resulting from the B[a]P experiment revealed behavioral anomalies, such as spasms and uncoordinated movements. These behavioral anomalies were observed in 12.9% and 38.2% of newborns resulting from the exposure of adult planarians to 9.38 μg L^-1 and 37.50 μg L^-1 of B[a]P, respectively. This study is the first report on the effects of PAHs in freshwater planarians' sexual reproduction and a decreased reproductive output was evidenced. Moreover, the exposure of adults to B[a]P lead to defects in newborns, raising concern on the possible long-term consequences of these compounds for natural planarian populations.

Immune toxicity of phenanthrene and its combined effects of white spot syndrome virus on the survival of kuruma shrimp (Penaeus Japonicus)

Shrimp inhabiting coasts that are frequented by humans are exposed to various pollutants. Additionally, viral infections that cause serious damage to shrimp populations have been observed in these environments. The present study sought to evaluate the immunotoxic effects of phenanthrene (Phe), a pollutant detected in coastal environments, on kuruma shrimp (Penaeus japonicus). We further examined the survival of shrimp following combined exposure to Phe (30 or 300 μg/L) and white spot syndrome virus (WSSV). Results show that exposure to Phe for seven days decreased immune system-related parameters, including total hemocyte count and phenoloxidase activity in hemolymph (p < 0.05). However, these effects were not detected after three days of exposure. Moreover, a combined exposure assay revealed that shrimp mortality increased following exposure to 300 μg/L Phe and infection with WSSV. The number of WSSV gene copies was also observed to increase in these co-exposed shrimp. Taken together, these results indicate that long-term Phe exposure impairs the immune system of P. japonicus, resulting in fatal proliferation of WSSV. Hence, considering that combined exposure to Phe and WSSV leads to increased mortality of shrimp, it is imperative that the detrimental effects elicited by multiple stresses be considered, and controlled, in areas inhabited by kuruma shrimp.

Seasonal dynamics of polycyclic aromatic hydrocarbons between water and sediment in a tide-dominated estuary and ecological risks for estuary management

Understanding the transportation of polycyclic aromatic hydrocarbons (PAHs) across the water-sediment interface can help researchers to partition their sources while being particularly important for managing PAH input. This study fully explored the PAH dynamics between water and sediment in a tide-dominated estuary. The monthly concentration of ΣPAHs in sediments ranged from 325.47 to 1098.49 ng/g (dry weight), while that in water varied from 154.00 to 725.80 ng/L. The PAH levels found in the present study were relatively high in comparison with other estuarine systems worldwide. The high-molecular-weight PAHs were more readily redissolved from sediment to water, while the low-molecular-weight PAHs were mostly in an unsaturated state with diffusion occurring from water to sediment. The seasonal differences of ΣPAHs were significant and were largely controlled by the changes in sediment properties, marine currents, and water temperature. The diagnostic ratios revealed that predominant sources of PAHs were pyrogenic processes and petrogenic inputs.

The intergenerational toxic effects on offspring of medaka fish Oryzias melastigma from parental benzo[a]pyrene exposure via interference of the circadian rhythm

Benzo[a]pyrene (BaP), a widely existed polycyclic aromatic hydrocarbon pollutant in aquatic environment, has toxic effects on marine animals and their generations, but the intergenerational immunotoxic mechanism underlying has not been clearly understood. In the study, the offspring of marine medaka (oryzias melastigma) which were exposed to 0.5 μg L^-1 BaP suffered from circadian rhythm oscillation disorders and severe DNA damage. Many clock-associated genes like per1 were significantly modulated in offspring, both per1 and p53 were significantly inhibited that altered the progression of cell cycle and inhibited DNA repair, which possibly resulted in the increased mortality of offspring. The hypermethylation of the per1 promotor and abnormal levels of N⁶-methyladenosine (m⁶A) suggested that the underlying mechanism was probably related to the epigenetic modification. Moreover, the offspring from paternal BaP exposure had more severe DNA damage and a higher degree of hypermethylation than those from maternal exposure. F1 larvae from BaP-exposed parents were more sensitive to BaP exposure, showing that the expression of immune and metabolism-related genes were significantly up-regulated. Taken together, the parental toxicity induced by BaP could be passed to F1 generation and the mechanism underlying was probably associated with a characteristic circadian rhythm disorder.

Retene, pyrene and phenanthrene cause distinct molecular-level changes in the cardiac tissue of rainbow trout (Oncorhynchus mykiss) larvae, part 2 - Proteomics and metabolomics

Polycyclic aromatic hydrocarbons (PAHs) are global contaminants of concern. Despite several decades of research, their mechanisms of toxicity are not very well understood. Early life stages of fish are particularly sensitive with the developing cardiac tissue being a main target of PAHs toxicity. The mechanisms of cardiotoxicity of the three widespread model polycyclic aromatic hydrocarbons (PAHs) retene, pyrene and phenanthrene were explored in rainbow trout (Oncorhynchus mykiss) early life stages. Newly hatched larvae were exposed to sublethal doses of each individual PAH causing no detectable morphometric alterations. Changes in the cardiac proteome and metabolome were assessed after 7 or 14 days of exposure to each PAH. Phase I and II enzymes regulated by the aryl hydrocarbon receptor were significantly induced by all PAHs, with retene being the most potent compound. Retene significantly altered the level of several proteins involved in key cardiac functions such as muscle contraction, cellular tight junctions or calcium homeostasis. Those findings were quite consistent with previous reports regarding the effects of retene on the cardiac transcriptome. Significant changes in proteins linked to iron and heme metabolism were observed following exposure to pyrene. While phenanthrene also altered the levels of several proteins in the cardiac tissue, no clear mechanisms or pathways could be highlighted. Due to high variability between samples, very few significant changes were detected in the cardiac metabolome overall. Slight but significant changes were still observed for pyrene and phenanthrene, suggesting possible effects on several energetic or signaling pathways. This study shows that early exposure to different PAHs can alter the expression of key proteins involved in the cardiac function, which could potentially affect negatively the fitness of the larvae and later of the juvenile fish.

Zebrafish (Danio rerio) as an excellent vertebrate model for the development, reproductive, cardiovascular, and neural and ocular development toxicity study of hazardous chemicals

In the past decades, the type of chemicals has gradually increased all over the world, and many of these chemicals may have a potentially toxic effect on human health. The zebrafish, as an excellent vertebrate model, is increasingly used for assessing chemical toxicity and safety. This review summarizes the efficacy of zebrafish as a model for the study of developmental toxicity, reproductive toxicity, cardiovascular toxicity, neurodevelopmental toxicity, and ocular developmental toxicity of hazardous chemicals, and the transgenic zebrafish as biosensors are used to detect the environmental pollutants.

Retene, pyrene and phenanthrene cause distinct molecular-level changes in the cardiac tissue of rainbow trout (Oncorhynchus mykiss) larvae, part 1 - Transcriptomics

Polycyclic aromatic hydrocarbons (PAHs) are contaminants of concern that impact every sphere of the environment. Despite several decades of research, their mechanisms of toxicity are still poorly understood. This study explores the mechanisms of cardiotoxicity of the three widespread model PAHs retene, pyrene and phenanthrene in the rainbow trout (Oncorhynchus mykiss) early life stages. Newly hatched larvae were exposed to each individual compound at sublethal doses causing no significant increase in the prevalence of deformities. Changes in the cardiac transcriptome were assessed after 1, 3, 7 and 14 days of exposure using custom Salmo salar microarrays. The highest number of differentially expressed genes was observed after 1 or 3 days of exposure, and retene was the most potent compound in that regard. Over-representation analyses suggested that genes related to cardiac ion channels, calcium homeostasis and muscle contraction (actin binding, troponin and myosin complexes) were especially targeted by retene. Pyrene was also able to alter similar myosin-related genes, but at a different timing and in an opposite direction, suggesting compound-specific mechanisms of toxicity. Pyrene and to a lesser extent phenanthrene were altering key genes linked to the respiratory electron transport chain and to oxygen and iron metabolism. Overall, phenanthrene was not very potent in inducing changes in the cardiac transcriptome despite being apparently metabolized at a slower rate than retene and pyrene. The present study shows that exposure to different PAHs during the first few days of the swim-up stage can alter the expression of key genes involved into the cardiac development and function, which could potentially affect negatively the fitness of the larvae in the long term.

Polycyclic Aromatic Hydrocarbons: Occurrence, Electroanalysis, Challenges, and Future Outlooks

The past several decades have seen increasing concern regarding the wide distribution of polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Primary toxicological data show PAHs' persistent characteristics and possible toxicity effects. Because of this pressing global issue, electroanalytical methods have been introduced. These methods are effective for PAH determination in environmental waters, even outclassing sophisticated analytical techniques such as chromatography, conventional spectrophotometry, fluorescence, and capillary electrophoresis. Herein, the literature published on PAHs is reviewed and discussed with special regard to PAH occurrence. Moreover, the recent developments in electrochemical sensors for PAH determination and the challenges and future outlooks in this field, are also presented.

Polycyclic aromatic hydrocarbons (PAHs) and putative PAH-degrading bacteria in Galveston Bay, TX (USA), following Hurricane Harvey (2017)

Hurricane Harvey was the wettest hurricane in US history bringing record rainfall and widespread flooding in Houston, TX. The resulting storm- and floodwaters largely emptied into the Galveston Bay. Surface water was collected from 10 stations during five cruises to investigate the concentrations and sources of 16 priority polycyclic aromatic hydrocarbons (PAHs), and relative abundances of PAH-degrading bacteria. Highest PAH levels (102-167 ng/L) were detected during the first sampling event, decreasing to 36-69 ng/L within a week. Four sites had elevated concentrations of carcinogenic benzo[a]pyrene that exceeded the Texas Standard for Surface Water threshold. The highest relative abundances of known PAH-degrading bacteria Burkholderiaceae, Comamonadaceae, and Sphingomonadales were detected during the first and second sampling events. PAH origins were about 60% pyrogenic, 2% petrogenic, and the remainder of mixed sources. This study improves our understanding on the fate, source, and distributions of PAHs in Galveston Bay after an extreme flooding event.

Teratogenic effects of environmentally relevant concentrations of phenanthrene on the early development of marine medaka (Oryzia melastigma)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in marine environments and have arouse great concern since they pose adverse effects to marine ecosystem. To determine the potential impacts of environmentally relevant PAHs on early life stages of marine fish, this study exposed embryos of marine medaka (Oryzias melastigma) to 0, 2, 10, 50, and 250 μg/L of phenanthrene (Phe), one of the most abundant PAHs. The results demonstrated that Phe exposure decreased hatching rates, delayed hatching time of embryos, and increased deformity rate of newly-hatched larvae. Exposure to 10 and 50 μg/L Phe decreased the survival rate of marine medaka larvae at 28 days post-fertilization (dpf), and no embryo successfully hatched in 250 μg/L Phe exposure group. Morphology results showed that 10, 50, and 250 μg/L Phe exposure significantly retarded the development of embryos, and 2, 10, and 50 μg/L caused yolk sac edema and pericardial edema in newly-hatched larvae, indicating that low concentrations of Phe could induce developmental cardiac toxicity. Furthermore, the changes in the expression of heart development-related genes were determined, and the results showed that Phe-induced cardiac malformation might be related with fgf8, bmp4, smyd1, ATPase and gata4 genes. Overall, environmentally relevant PAHs could disrupt heart morphogenesis and hatching process of marine medaka, which might have profound consequences for sustainability of fish population.

Polycyclic Aromatic Hydrocarbons in the Estuaries of Two Rivers of the Sea of Japan

The seasonal polycyclic aromatic hydrocarbon (PAH) variability was studied in the estuaries of the Partizanskaya River and the Tumen River, the largest transboundary river of the Sea of Japan. The PAH levels were generally low over the year; however, the PAH concentrations increased according to one of two seasonal trends, which were either an increase in PAHs during the cold period, influenced by heating, or a PAH enrichment during the wet period due to higher run-off inputs. The major PAH source was the combustion of fossil fuels and biomass, but a minor input of petrogenic PAHs in some seasons was observed. Higher PAH concentrations were observed in fresh and brackish water compared to the saline waters in the Tumen River estuary, while the PAH concentrations in both types of water were similar in the Partizanskaya River estuary, suggesting different pathways of PAH input into the estuaries. The annual riverine PAH mass flux amounted to 0.028 t/year and 2.5 t/year for the Partizanskaya River and the Tumen River, respectively. The riverine PAH contribution to the coastal water of the Sea of Japan depends on the river discharge rather than the PAH level in the river water.

Multicompartment occurrence and partitioning of alternative and legacy per- and polyfluoroalkyl substances in an impacted river in China

Per- and polyfluoroalkyl substances (PFASs) are emerging global environmental contaminants. Exploring the occurrence and environmental behavior of PFASs in the aquatic environment is a key step in solving global fluorine chemical pollution problems. In this study, surface water, pore water, and sediment were collected from the main tributary and the middle and lower reaches of the Daling River, adjacent to the Fuxin fluorochemical manufacturing facilities in Liaoning Province in China, to elucidate the occurrence and partition behavior of PFASs. The total concentrations of PFASs ranged from 48.4 to 4578 ng/L in the overlying water, from 173 to 9952 ng/L in the pore water, and from 2.16 to 40.3 ng/g dw in the sediment fraction. Generally, perfluorobutanoic acid (PFBA) and perfluorobutane sulfonate (PFBS) were the predominant congeners in the samples, with the mean relative content fractions being almost consistently >40% in the dissolved phase and >25% in the sediment. Hexafluoropropylene oxide dimer acid (HFPO-DA) and chlorinated polyfluorinated ether sulfonic acid (6:2 Cl-PFESA) were detected, albeit at low levels. In addition, the detection frequency and the contribution of legacy long-chain PFASs in sediment were higher than those in the overlying water and pore water. Except for perfluorohexane sulfonate (PFHxS), the concentrations of the alternative PFASs in the pore water were higher than in the overlying water. The organic carbon fraction was a more important controlling factor for PFAS sediment levels than cations content. As with legacy long-chain PFASs, HFPO-DA and 6:2 Cl-PFESA tended to partition into the solid phase, whereas short-chain PFASs were readily distributed in the aqueous phase. Such research results will be helpful in modeling the transport and fate of PFASs released by point sources into coastal waters through rivers and in developing effective risk assessment and management strategies for the control of PFAS pollution.

Spatiotemporal distribution, source, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the urbanized semi-enclosed Jiaozhou Bay, China

Coastal contamination by polycyclic aromatic hydrocarbons (PAHs) is a worldwide issue. Nevertheless, the spatiotemporal distribution of PAHs in the urbanized semi-enclosed bays in China remains relatively uncharacterized. Here we present measurements of 15 priority PAHs in the water and sediment of the Jiaozhou Bay, as well the assessment of their spatiotemporal distribution, sources and ecological risk. The total PAH (ΣPAH) concentrations ranged from 23.6 to 86.2 ng L ^-1 in the water and from 37.7 to 290.9 ng g^-1 in the sediment. The average ΣPAH concentration in the water was significantly higher in the winter (52.8 ng L ^-1) than in the spring (30.4 ng L ^-1) (α = 0.05 level). Average concentration of phenanthrene in the water was 8.9 ng L^-1 in the spring and 15.7 ng L^-1 in the winter and the highest of PAHs, contributing about 29.4% to ΣPAHs. Compared with three-ring PAHs, four- and five-ring PAHs were more tended to accumulate in the sediment, and the partitioning into sediment was influenced by the water salinity. The spatial distribution of ΣPAH concentrations in the water were controlled by water exchange capability. Organic matter content and sediment texture played important roles in determining the spatial distribution of ΣPAHs in the sediment. Molecular diagnostic ratio analysis indicated that pyrogenic source was the main source for PAHs in the Bay. Specifically, the positive matrix factorization (PMF) model indicated that vehicle emission, biomass combustion, coal combustion, and petrogenic sources contributed for 41.6, 20.2, 20, and 18.2% of ΣPAHs, respectively. The risk assessment by sediment quality guidelines suggested that adverse biological effects are expected to occur rarely in the sediment.

Tidal variability of polycyclic aromatic hydrocarbons and organophosphate esters in the coastal seawater of Dalian, China

We investigated the tidal variability of polycyclic aromatic hydrocarbons (PAHs) and organophosphate esters (OPEs) in water dissolved phase from a coastal area of Dalian, China, as well as their air-water exchange trends. The concentrations of PAHs and OPEs in water were in the range of 50.5-74.7 ng/L and 21.6-61.5 ng/L, respectively. Phenanthrene (PHE) was the dominant congener followed by fluorene (FLU) for PAHs, while tris(2-chloroisopropyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP) dominated for OPEs. PAHs in coastal water showed a tidal variability, but not for OPEs, which may due to the influence of occasional wastewater discharges of OPEs. The source apportionments using principle component analysis and positive matrix factorization suggested that PAHs in the coastal water mainly came from oil spill from ships, coal combustion, and petroleum combustion, while OPEs were derived from diverse sources. The fugacity fractions (ff) suggested that ACY, ACE, FLU, PHE, TCEP, and TPHP volatilized from water into air, while TNBP, TCIPP, and TDCIPP deposited from air into water, and FLA, PYR, BaA, CHR, and EHDPP reached equilibrium. The ff values varied slightly with tidal circle, but the variations were not enough to alter the air-water exchange directions of those compounds. Although the influences of tide on the air-water exchange of PAHs and OPEs were limited, tide still played an important role on the transports and diffusions of those chemicals in the coastal water, which requires further studies.

Long-Term Exposure to Benzo[a]Pyrene Affects Sexual Differentiation and Embryos Toxicity in Three Generations of Marine Medaka (Oryzias Melastigma)

Benzo[a]pyrene (BaP) is a common environmental disrupting chemical that can cause endocrine disorders in organisms. However, the continued interference effects of BaP on multi-generation fish needs further research. In this study, we performed different periods (G1F1-3, G2F2-3, G3F3) of BaP exposure on marine medaka. We determined the embryo toxicity, and analyzed relative reproductive genes (ERα, cyp19a and vtg1) to predict the sexual differentiation of marine medaka. The results showed that high concentrations of BaP (200 μg·L⁻¹) significantly delayed the hatching time of embryos. Moreover, medium/high concentrations of BaP (20 and 200 μg·L⁻¹) prolonged the sexual maturity time of marine medaka. The relative gene expression of ERα, cyp19a and vtg1 were measured at 5 d_pf of embryos. We found that BaP had significantly inhibited the expression of the genes related to female fish development. Consequently, there were more males in the offspring sex ratio at BaP exposure. Overall, BaP can cause embryonic toxicity and abnormal sexual differentiation, while the expression of related reproductive genes can effectively indicate the sex ratio.

Polyaromatic hydrocarbons in pollution: a heart-breaking matter

Air pollution is associated with detrimental effects on human health, including decreased cardiovascular function. However, the causative mechanisms behind these effects have yet to be fully elucidated. Here we review the current epidemiological, clinical and experimental evidence linking pollution with cardiovascular dysfunction. Our focus is on particulate matter (PM) and the associated low molecular weight polycyclic aromatic hydrocarbons (PAHs) as key mediators of cardiotoxicity. We begin by reviewing the growing epidemiological evidence linking air pollution to cardiovascular dysfunction in humans. We next address the pollution-based cardiotoxic mechanisms first identified in fish following the release of large quantities of PAHs into the marine environment from point oil spills (e.g. Deepwater Horizon). We finish by discussing the current state of mechanistic knowledge linking PM and PAH exposure to mammalian cardiovascular patho-physiologies such as atherosclerosis, cardiac hypertrophy, arrhythmias, contractile dysfunction and the underlying alterations in gene regulation. Our aim is to show conservation of toxicant pathways and cellular targets across vertebrate hearts to allow a broad framework of the global problem of cardiotoxic pollution to be established. AhR; Aryl hydrocarbon receptor. Dark lines indicate topics discussed in this review. Grey lines indicate topics reviewed elsewhere.

Ultrasensitive detection of polycyclic aromatic hydrocarbons in coastal and harbor water using GC-APLI-MS

Polycyclic aromatic hydrocarbons (PAH) are a group of ubiquitous environmental pollutants among which some compounds show carcinogenic properties. The emission of PAH from anthropogenic and natural sources to the aquatic environment demands monitoring. In this study, ten different surface water samples were collected and analyzed for 48 different PAH compounds by gas chromatography-atmospheric-pressure-laser-ionization coupled to mass spectrometry (GC-APLI-MS) after liquid-liquid extraction. Results varied from 9.22 ng/L for fluoranthene in harbor water to 0.01 ng/L for 4-methylchrysene in Rhine river water. Overall low PAH concentrations were found in the samples. Toxic equivalent (TEQ) calculations were used to assess the potential environmental impact of the analyzed compounds. The results showed higher concentrations and TEQ for the samples from harbors in comparison to riverine and estuarine sampling locations. Suspected target analysis indicated the occurrence of alkylated PAH in the surface water samples.

Identification of gnrh2 and gnrh3 and their expression during brood pouch growth and short-term benzo(a)pyrene exposure in lined seahorse (Hippocampus erectus)

Gonadotropin-releasing hormones (GnRH) regulate gonadal growth of teleosts. Benzo(a)pyrene (BaP) functions as a reproductive endocrine disruptor. Furthermore, endocrine regulation on brood pouch growth of Syngnathidaes is elusive. To better understand the role of GnRH in brood pouch growth and effects of BaP on reproductive endocrine in lined seahorse (Hippocampus erectus), gnrh2 and gnrh3 genes were identified. Results showed that lined seahorse GnRH2 and GnRH3 precursors included the conservative tripartite structure and their transcripts highly expressed in brain as other teleosts. Expression profiles of gnrh2 and gnrh3 transcripts were detected during brood pouch growth. Results indicated that brain gnrh2 transcripts remarkably increased at the middle-stage and late-stage of brood pouch growth, while brain gnrh3 transcripts significantly raised at the early-stage and middle-stage. These suggested that GnRH2 and GnRH3 regulated brood pouch growth at different stages. Short-term BaP exposure in lined seahorse was performed. Transcripts of gnrh2 and gnrh3 remarkably increased in females and males exposed to BaP. Besides, plasma 17-beta estradiol (E2) levels presented a reduced trend during female fish exposed to BaP. This revealed that BaP functioned as anti-estrogenic effects and it may result in high expression of gnrh mRNA. However, plasma 11-ketone testosterone (11-KT) levels showed an increased trend during male fish exposed to BaP. Taken together, these indicated interesting results of BaP on reproduction in each sex of seahorse. These observations contribute to provide novel information of regulation on brood pouch growth and effects of BaP on reproductive endocrine in Syngnathidaes.

Seasonal variation and spatial transport of polycyclic aromatic hydrocarbons in water of the subtropical Jiulong River watershed and estuary, Southeast China

Riverine runoff is one of the most important pathways of pollutants entering the oceans. To study the seasonal variations, spatial transports, sources and mass fluxes of polycyclic aromatic hydrocarbons (PAHs) from the subtropical Jiulong River watershed to estuary, water samples were collected in wet and dry seasons. PAH concentrations showed significant temporal-spatial variations (ANOVA, p < 0.05). In the watershed, PAH concentrations in wet season (48.6 ± 18.2 ng L^-1) were significantly lower than in dry season (90.3 ± 18.5 ng L^-1). In contrast, estuarine PAH concentrations in wet season (67.1 ± 24.6 ng L^-1) were significantly higher than in dry season (27.4 ± 10.6 ng L^-1) (p < 0.0001). The spatial variations of PAH concentrations in wet and dry seasons reflected positive and restricted transport processes occurred in the river. These findings might be subjected to seasonal changes in precipitation, water discharge, hydrodynamic conditions, and human activities. The compositional patterns of PAHs illustrated that fluorene and phenanthrene were the dominant compounds in the watershed, while phenanthrene was predominant in the estuary. Source analysis by molecular diagnostic ratios and PMF model indicated that fossil fuel and biomass combustion and petroleum both contributed to the presence of PAHs, and the high contributions of pyrogenic PAHs might be related to urban rainstorm runoff in winter and atmospheric inputs in winter. Although the estimated flux of PAHs from watershed to estuary was about 676 kg yr^-1 with a low level by comparing the data obtained in the worldwide, continue concern of PAHs in the Jiulong River is recommended due to the intense human activities.

Chronic exposure to environmental concentrations of phenanthrene impairs zebrafish reproduction

Phenanthrene (PHE) is a tricyclic polycyclic aromatic hydrocarbon which distributed extensively in the aquatic environment. However, the knowledge about its impact on fish reproduction is still limited, particularly under a chronic exposure regime. In this study, we exposed zebrafish (Danio rerio) embryos to environmentally relevant concentrations (0.2, 1.0, and 5.0 μg/L) of PHE for 4 months and assessed the impact on reproduction. The results demonstrated that egg production was decreased in fish exposed to PHE, with a significant reduction at 5.0 μg/L. The exposure significantly decreased the circulating concentrations of estradiol (E2) and testosterone (T) in female fish or E2 in male fish. In addition, plasma vitellogenin levels were significantly inhibited after PHE exposure in female fish. The transcription of hypothalamic-pituitary-gonadal (HPG) axis related genes (GnRH2, FSHβ, LHβ, 17β-HSD, CYP11A1, and CYP19a) were significantly altered in a sex-specific manner. In addition, embryos derived from exposed parents exhibited increased malformation and decreased hatching success in the F1 generation. Taken together, these results demonstrate that chronic exposure to environmentally relevant concentration of PHE could cause adverse effects on reproduction and impair the development of offspring, ultimately leading to fish population decline in aquatic environment.

Benzo[a]pyrene (BaP) exposure generates persistent reactive oxygen species (ROS) to inhibit the NF-κB pathway in medaka (Oryzias melastigma)

Benzo[a]pyrene (BaP), a common environmental pollutant, can modulate the immune-associated signal pathway NF-κB, which is one of the critical signal pathways involved in various immune responses. BaP exposure usually generates reactive oxygen species (ROS), but whether ROS are predominantly involved in the modulation mechanism of the NF-κB pathway has not been clearly understood. In this study, an in vivo examination of Oryzias melastigma demonstrated that BaP exposure led to a down-regulation of the NF-κB pathway and increased levels of ROS. Conversely, in vitro results using the medaka liver cell line DIT-29 and a widely applied H₂O₂ method showed the opposite: up-regulation of the NF-κB pathway. However, the down-regulation of NF-κB upon BaP exposure in vitro was inhibited by the addition of a ROS inhibitor, indicating ROS are involved in the modulation of NF-κB. The discrepancy between in vivo and in vitro results of ROS impacts on NF-κB activation might be related to the concentration and persistence of ROS. Using a modified luminol detection system, BaP was found to generate sustained physiological concentrations of ROS for 24 h, while an H₂O₂ bolus generated ROS for less than 30 min. Furthermore, a steady-state sub-micromolar H₂O₂ system (H₂O₂ss) was developed in parallel as a positive control of ROS, by which H₂O₂ could be maintained for 24 h. Comparative evaluation using H₂O₂, H₂O₂ss and BaP exposures on the medaka cell line with pGL4.32 demonstrated that the persistent physiological concentrations of ROS generated upon BaP exposure or treatment with H₂O₂ss inhibited the NF-κB pathway, but direct H₂O₂ exposure had the opposite effect. Moreover, a western-blot assay and EMSA detection further confirmed the modulation of the NF-κB pathway in DIT-29. Taken together, this study shows that BaP exposure inhibits the NF-κB pathway by generating sustained physiological concentrations of ROS.