The Arctic is subject to long-range atmospheric deposition of globally-distilled semi-volatile organic compounds (SVOCs) that bioaccumulate and biomagnify in lipid-rich food webs. In addition, locally contaminated sites may also contribute SVOCs to the arctic environment. Specifically, Alaska has hundreds of formerly used defense (FUD) sites, many of which are co-located with Alaska Native villages in remote parts of the state. The purpose of this study was to investigate the extent of SVOC contamination on Alaska’s St. Lawrence Island through the analysis of sentinel fish, the ninespine stickleback (Pungitius pungitius), collected from Troutman Lake located within the watershed of an FUD site and adjacent to the Yupik community of Gambell. We measured the concentrations of legacy and emerging SVOCs in 303 fish samples (81 composites), including polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs) and their diester metabolites, and per- and poly-fluoroalkyl substances (PFAS). PBDEs and PCBs were the most abundant SVOC groups found in stickleback with ΣPBDE and ΣPCB median concentrations of 25.8 and 10.9 ng/g ww, respectively, followed by PFAS (median ΣPFAS 7.22 ng/g ww). ΣOPE and ΣOPE metabolite concentrations were lower with median concentrations of 4.97 and 1.18 ng/g ww, respectively. Chemical patterns and distributions based on correlations and comparison with SVOC concentrations in stickleback from other parts of the island suggest strong local sources of PCBs, PBDEs, and PFAS on St. Lawrence Island.

A large amounts of arable land is facing a high risk of hexavalent chromium (Cr(VI)) pollution, which requires remediation using a low toxic agent. In this study, the remediation effect of amorphous iron pyrite (FeS₂₍ₐₘ₎) on Cr(VI) in Cr(VI)-contaminated soil was evaluated by systematically analyzing the variation of the leachability, bioaccessibility, phytotoxicity, and long-term stability of the remediated soil. The effectiveness of FeS₂₍ₐₘ₎ on the leachability was assessed by alkaline digestion and the toxicity characteristic leaching procedure (TCLP); the effect on the bioaccessibility was evaluated via the physiologically based extraction test (PBET) and the Tessier sequential extraction; the effect on the phytotoxicity was assessed via phytotoxicity bioassay (seed germination experiments) based on rape (Brassica napus L.) and cucumber (Cucumis Sativus L.), and the long-term stability of the Cr(VI)-remediated soil was appraised using column tests with groundwater and acid rain as the influents. The results show that FeS₂₍ₐₘ₎, with a stoichiometry of 4× exhibited a high efficiency in the remediation of Cr(VI) and decreased its leachability and bioaccessibility during the 30-day remediation period. In addition, seed germination rate, accumulation and translocation of Cr, and root and shoot elongation of rape and cucumber of remediated soil are not significantly different from those of clean soil, illustrating that FeS₂₍ₐₘ₎ is suitable for remediating Cr(VI) contaminated arable soil. The stabilization of Cr(VI) in contaminated soil using FeS₂₍ₐₘ₎ was maintained for 1575 days. The long-term effectiveness was further confirmed by the increasing amount of free Fe and Mn in the effluent and the decreasing redox potential. In summary, FeS₂₍ₐₘ₎ has an excellent efficiency for the remediation of Cr(VI), demonstrating it is a very promising alternative for use in the contaminated arable soil.

Amendment with sewage sludge or biosolids can increase soil fertility but may also transfer biosolid-borne pollutants to the soil and the possible effects on the soil ecosystem are poorly understood, especially long-term effects. A long-term experiment was therefore established to assess the effects of repeated applications of different types of biosolids (fresh domestic, dried domestic and fresh industrial sludges) in field conditions. Nine years of sludge application led to changes in soil chemical and biological properties and generally contributed little to soil nutrient status. However, soil concentrations of potentially toxic elements (PTEs) were elevated by amendment, especially with industrial biosolids. Soil fauna are usually used to decipher the underlying effects of biosolid applications on the soil ecosystem. Here, collembolans (50.9%), nematodes (41.6%) and enchytraeid worms (7.50%) were collected and differentiated into different ecological and trophic groups and their body lengths and PTE concentrations in the body tissues were investigated. The animals showed different responses to the biosolids at population and individual levels. There were substantial changes in epigeic collembolan communities and bacterivorous nematodes increased significantly after biosolid amendment. Biosolid-borne PTEs were major factors and Redundancy (RDA) analysis indicates that collembolan communities were strongly influenced by zinc (Zn). The three groups of soil animals showed similar trends in accumulation of PTEs in the sequence cadmium (Cd) > Zn > copper (Cu), and the bioaccumulation factor (BAF) values of the PTEs were significantly higher in the industrial sludge treatment than in other two treatments with a similar trend of decreasing body length of nematodes. The results indicate that it is potentially risky to use industrial biosolids in the long term, and different species and ecological groups of collembolans and different trophic groups of nematodes should be examined when assessing soil health.

Mercury (Hg) concentrations in Tilefish (Lopholatilus chamaeleonticeps) have been reported to be one of the highest of all fish species, resulting in advisories that, historically, have recommended zero consumption. The current study assesses Hg bioaccumulation in Tilefish targeted by the commercial fisheries operating off the coast of South Carolina, USA. We provide results for an under-sampled region and explore how life history potentially impacts Hg uptake in Tilefish. Mercury concentration in Tilefish muscle tissue ranged from 0.10 to 0.99 ppm, with a mean of 0.23 ppm (n = 63). The majority of Tilefish samples (95%) were within the “Good Choices” range for consuming at least one serving per week, with 62% being within the range considered best for eating two meals a week”, per suggestion by the US EPA and US FDA (2017). The present study of Tilefish from the western Atlantic further substantiates the importance of monitoring Hg in commercial fish species regionally.

Macrophytes are known to bioaccumulate metals, but a thorough understanding of tolerance strategies and molecular impact of metals in aquatic plants is still lacking. The present study aimed to compare Hg and Cd effects in a representative macrophyte, Elodea nuttallii using physiological endpoints and metabolite profiles in shoots and cytosol.Exposure 24 h to methyl-Hg (30 ng L⁻¹), inorganic Hg (70 ng L⁻¹) and Cd (280 μg L⁻¹) did not affect photosynthesis, or antioxidant enzymes despite the significant accumulation of metals, confirming a sublethal stress level. In shoots, Cd resulted in a higher level of regulation of metabolites than MeHg, while MeHg resulted in the largest number of regulated metabolites and IHg treatment regulated no metabolites significantly. In cytosol, Cd regulated more metabolites than IHg and only arginine, histidine and mannose were reduced by MeHg exposure. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of data suggested that exposure to MeHg resulted in biochemical changes including aminoacyl-tRNA biosynthesis, glycine, serine and threonine metabolism, nitrogen metabolism, arginine and proline metabolism, cyanoamino acid metabolism, while the treatment of Cd stress caused significant variations in aminoacyl-tRNA biosynthesis and branched-chain amino acids pathways. Data supports an impact of MeHg on N homeostasis, while Cd resulted in an osmotic stress-like pattern and IHg had a low impact. Marked differences in the responses to MeHg and IHg exposure were evidenced, supporting different molecular toxicity pathways and main impact of MeHg on non-soluble compartment, while main impact of IHg was on soluble compartment. Metabolomics was used for the first time in this species and proved to be very useful to confirm and complement recent knowledge gained by transcriptomics and proteomics, highlighting the high interest of multi-omics approaches to identify early impact of environmental pollution.

The usages of antibiotics in treating the pathogenic infections could alter the gut microbiome and associated resistome, causing long term adverse impact on human health. In this study, mice were treated with human-simulated regimen 25.0 mg kg⁻¹ of amoxicillin for seven days, and their gut microbiota and resistome were characterized using the 16S rRNA amplicons sequencing and the high-throughput qPCR, respectively. Meanwhile, the flora restorations after individual applications of inulin, Bifidobacterium longum (B. longum), and fecal microbiota transplantation (FMT) were analyzed for up to 35 days. The results revealed the prolonged negative impact of single course AMX exposure on mice gut microbiota and resistome. To be specific, pathobionts of Klebsiella and Escherichia-Shigella were significantly enriched, while prebiotics of Bifidobacterium and Lactobacillus were dramatically depleted. Furthermore, β-lactam resistance genes and efflux resistance genes were obviously enriched after amoxicillin exposure. Compared to B. longum, FMT and inulin were demonstrated to preferably restore the gut microbiota via reconstituting microbial community and stimulating specific prebiotic respectively. Such variation of microbiome caused their distinct alleviations on resistome alteration. Inulin earned the greatest elimination on AMX induced ARG abundance and diversity enrichment. FMT and B. longum caused remove of particular ARGs such as ndm-1, blaPER. Network analysis revealed that most of the ARGs were prone to be harbored by Firmicutes and Proteobacteria. In general, gut resistome shift was partly associated with the changing bacterial community structures and transposase and integron. Taken together, these results demonstrated the profound disruption of gut microbiota and resistome after single-course amoxicillin treatment and different restoration by inulin, B. longum and FMT.

Microplastic (MP) pollution has become an area of increasing concern because MPs accumulate various types of pollutants. Many previous studies have explored the interactions between MPs and hydrophobic pollutants. However, little research has been conducted on hydrophilic pollutants, which are of much higher concentration and ubiquitous in environment. Surfactants cause hydrophobic MPs to become hydrophilic, which may significantly enhance their capacities to adsorb hydrophilic pollutants. This study explored the influence of co-existing surfactants on the adsorption of ionic organic pollutants by MPs, and found that the presence of an ionic surfactant could significantly enhance the capacity of polyvinyl chloride (PVC, 0.2 mm) MPs to adsorb pollutants with opposite charges. The Langmuir methylene blue adsorption capacity of PVC could be increased from 172 to 4417 ppm in the presence of a sodium dodecyl benzene sulfonate surfactant. Nonionic surfactants impeded the adsorption of both cationic and anionic pollutants due to the steric resistance of the hydrophilic polyethelene glycol chains. The electrostatic interaction mechanism dominated the interfacial behaviors of ionic pollutants on surfactant-adsorbed MP interfaces. The effects of the surfactants were further verified using four different model pollutants and six surfactants. The adsorption capacities of real environmental MPs, including PVC, polyethylene (PE), polypropylene (PP), and polystyrene (PS), increased by three to twenty-six times. The adsorption properties of MPs may be determined by the presence of co-existing surfactants, rather than their polymer species or additives.

Aquatic organisms are usually exposed to various co-existing pollutants. However, toxic effects of pesticide mixtures on aquatic organisms and its potential underlying mechanism still remain unclear. The joint effects of fenpropathrin (FEN) and paclobutrazol (PAC) on zebrafish (Danio rerio) using diverse toxicological endpoints were investigated in the current work. Our data exhibited that the 96-h LC₅₀ values of FEN to zebrafish at multiple life phases ranged from 0.0029 (0.0013–0.0042) to 0.16 (0.082–0.23) mg a.i. L⁻¹, which were lower by comparison to PAC ranging from 13.16 (8.564–21.03) to 23.43 (17.94–29.91) mg a.i. L⁻¹. Combination of FEN and PAC displayed synergistic effect on embryonic zebrafish. Activities of T-SOD, Cu/Zn-SOD and CYP450 were remarkably changed in the majority of single and mixture treatments by comparison to the untreated group. The mRNA levels of 17 genes related to oxidative stress, cellular apoptosis, immune system and endocrine system were assessed, and the data suggested that embryonic zebrafish were affected by both single pesticides and their mixtures. Five genes (P53, tsh, ERα, crh and cxcl-clc) showed greater alterations when exposed to pesticide mixtures by comparison to their individual chemicals. Therefore, it is urgently necessary to conduct more studies on mixture toxicities of different pesticides to explore the chemical mixtures with synergistic interactions.

Though invertebrates are one of the largest groups of animal species in the sea and exhibit robust immune and neural responses that are crucial for their health and survival, the potential immunotoxicity and neurotoxicity of the most produced chemical bisphenol A (BPA), especially in conjunction with microplastics (MPs), still remain poorly understood in marine invertebrate species. Therefore, the impacts of exposure to BPA and MPs alone or in combination on a series of immune and neural biomarkers were investigated in the invertebrate bivalve species blood clam (Tegillarca granosa). Evident immunotoxicity as indicated by alterations in hematic indexes was observed after two weeks of exposure to BPA and MPs at environmentally realistic concentrations. The expression of four immune-related genes from the NFκB signaling pathway was also found to be significantly suppressed by the BPA and MP treatment. In addition, exposure to BPA and MPs led to an increase in the in vivo contents of three key neurotransmitters (GABA, DA, and ACh) but a decrease in the expression of genes encoding modulatory enzymes and receptors for these neurotransmitters, implying the evident neurotoxicity of BPA and MPs to blood clam. Furthermore, the results demonstrated that the toxic impacts exerted by BPA were significantly aggravated by the co-presence of MPs, which may be due to interactions between BPA and MPs as well as those between MPs and clam individuals.

Chromium (Cr) is a toxic element among which hexavalent chromium [Cr(VI)] is more toxic than trivalent chromium [Cr(III)]. Chromium can be reduced or oxidized in soil because soil is a complex medium and various soil components affect redox reaction of Cr in soil. Therefore, Cr speciation in hydroponics and soil was compared and Cr uptake and speciation by lettuce grown in the media were evaluated. Higher phytotoxicity was found in Cr(III) spiked soil than in Cr(VI) spiked soil, while Cr toxicity was higher in Cr(VI) treated hydroponics than Cr(III) treated hydroponics. Chromium was mainly accumulated in lettuce roots as Cr(III), and more Cr was translocated from roots to shoots grown in Cr(VI) treated hydroponics than Cr(III) treated hydroponics. Accumulation of Cr in roots grown in Cr(III) treated nutrient solution reduced Fe, K, Ca, Mg, and P uptake in lettuce. Chromium valence state was Cr(III) in lettuce leaves and roots grown in both Cr(III) and Cr(VI) treated hydroponics and soil. Chromium speciation in hydroponically grown lettuce roots was Cr(III) coordinated with 6 oxygens in the first shell and 2 or 4 carbons in the second shell as analyzed by X-ray absorption spectroscopy (XAS), which was similar to chromium acetate. The valence state of Cr in Cr(III) and Cr(VI) treated nutrient solution was not changed, while Cr(VI) was reduced to Cr(III) in Cr(VI) spiked soil by soil organic matter. Spiking of Cr(III) induced reduction of Mn in soil, which resulted in an increase of bioavailable Mn concentration in the Cr(III) spiked soil. Therefore, the increased phytotoxic effect for lettuce in Cr(III) spiked soil can be attributed to the reduction of Mn and subsequent release of Mn(II). For Cr(III) contaminated soil, Mn speciation should be considered, and bioavailable Mn concentration should be monitored although Cr existed as Cr(III) in soil.