Antibiotics have been widely used in human and veterinary medicine to both treat and prevent disease. Due to their high water solubility and low bioavailability, many antibiotic residues have been found in aquatic environments. Fish are an indispensable link between the environmental pollution and human health. However, the chronic effects of environmental concentrations of antibiotics in fish have not been thoroughly investigated. Sulfamethoxazole (SMX) and oxytetracycline (OTC) are frequently detected in aquatic environments. In this study, zebrafish were exposed to SMX (260 ng/L) and OTC (420 ng/L) for a six-week period. Results indicated that exposure to antibiotics did not influence weight gain of fish but increased the metabolic rate and caused higher mortality when treated fish were challenged with Aeromonas hydrophila. Furthermore, exposure to antibiotics in water resulted in a significant decrease in intestinal goblet cell numbers, alkaline phosphatase (AKP), acid phosphatase (ACP) activities, and the anti-oxidant response while there was a significant increase in expression of inflammatory factors. Antibiotic exposure also disturbed the intestinal microbiota in the OTC-exposed group. Our results indicated that environmental antibiotic concentrations can impair the gut health of zebrafish. The potential health risk of antibiotic residues in water should be evaluated in the future.

In this study, the accumulation and toxicity effect of 1–7 μM of Hg was determined during 24–72 h on two strains of Chlamydomonas reinhardtii, CC-125 and CC-503 as a cell wall-deficient mutant, by monitoring the growth rate and the maximum quantum yield of Photosystem II. In addition, the level of extracytoplasmic polyphosphates (polyP related to the cell wall) was determined to understand the polyP physiological role in Hg-treated algal cells. The results showed that the polyP level was higher in the strain CC-125 compared to CC-503. When algal cells were exposed to 1 and 3 μM of Hg, the accumulation of Hg was correlated with the degradation of polyP for both strains. These results suggested that the degradation of polyP participated in the sequestration of Hg. In fact, this mechanism might explain at 72 h the recovery of the polyP level, the efficiency of maximum PSII quantum yield, the low inhibition of growth rate, and the low accumulated Hg in algal biomass. Under the effect of 5 and 7 μM of Hg, the degradation of polyP was complete and could not be recovered, which was caused by a high accumulation and toxicity of Hg already at 24 h. Our results demonstrated that the change of polyP level was correlated with the accumulation and effect of Hg on algal cells during 24–72 h, which can be used as a biomarker of Hg toxicity. Therefore, this study suggested that extracytoplasmic polyP in C. reinhardtii contributed to the cellular tolerance for Hg.

The present experiment was conducted to explicate the genotoxic effects of profenofos, an organophosphate insecticide, on the erythrocytes of silver barb (Barbonymus gonionotus). Silver barb were exposed to a solution of 10% and 50% of lethal concentrations (LC₅₀) of profenofos as sub-lethal concentrations at different days (1, 7, 15, and 30 d), along with a control (0% profenofos). Subsequent recovery patterns were assessed allowing the fish exposed to profenofos free water for the same period that they were exposed to profenofos. Our results revealed that with the progression of time and concentration, fish exposed to profenofos showed significantly (p < .05) higher level of erythrocytic nuclear abnormalities (ENA) such as micronuclei, bi-nuclei, degenerated nuclei, notched nuclei, nuclear bridge and nuclear buds, as well as erythrocytic cellular abnormalities (ECA) such as echinocytic, elongated, fusion, spindle, tear-drop and twin shaped cells. After exposure, the silver barb recovered spontaneously, and the abnormal erythrocytic parameters were normalized with a concentration- and duration-dependent fashion. Therefore, these abnormalities and their recovery can be used to assess the toxic levels of pesticides on aquatic organisms. There is great potential to use this technique as in vivo to predict susceptibility of aquatic animals to environmental pollution.

Antifouling biocides in surface sediments and gastropod tissues were assessed for the first time along coastal areas of Panama under the influence of maritime activities, including one of the world's busiest shipping zones: the Panama Canal. Imposex incidence was also evaluated in five muricid species distributed along six coastal areas of Panama. This TBT-related biological alteration was detected in three species, including the first report in Purpura panama. Levels of organotins (TBT, DBT, and MBT) in gastropod tissues and surficial sediments ranged from <5 to 104 ng Sn g⁻¹ and <1–149 ng Sn g⁻¹, respectively. In addition, fresh TBT inputs were observed in areas considered as moderate to highly contaminated mainly by inputs from fishing and leisure boats. Regarding booster biocides, TCMTB and dichlofluanid were not detected in any sample, while irgarol 1051, diuron and DCOIT levels ranged from <0.08 to 2.8 ng g⁻¹, <0.75–14.1 ng g⁻¹, and <0.38–81.6 ng g⁻¹, respectively. The highest level of TBT (149 ng Sn g⁻¹) and irgarol 1051 (2.8 ng g⁻¹), as well as relevant level of DCOIT (5.7 ng g⁻¹), were detected in a marina used by recreational boats. Additionally, relatively high diuron values (14.1 ng g⁻¹) were also detected in the Panama Canal associate to a commercial port. DCOIT concentrations were associated with the presence of antifouling paint particles in sediments obtained nearby shipyard or boat maintenance sites. The highest levels of TBT, irgarol 1051, and diuron exceeded international sediment quality guidelines indicating that toxic effects could be expected in coastal areas of Panama. Thus, the simultaneous impacts produced by new and old generations of antifouling paints highlight a serious environmental issue in Panamanian coastal areas.

Understanding of the interaction of graphene with natural polysaccharides (e.g., alginate) is crucial to elucidate its environmental fate. We investigated the impact of alginate on the agglomeration and stability of ¹⁴C-labeled few-layer graphene (FLG) in varying concentrations of monovalent (NaCl) and divalent (CaCl₂) electrolytes. Enhanced agglomeration occurred at high CaCl₂ concentrations (≥5 mM) due to the alginate gel networks formation in the presence of Ca²⁺. FLG enmeshed within extended alginate gel networks was observed under transmission electron microscope and atomic force microscope. However, background Na⁺ competition for binding sites with Ca²⁺ at the alginate surfaces shielded the gelation of alginate. FLG was readily dispersed by alginate under environmentally relevant ionic strength conditions (i.e., <200 mM Na⁺ and <5 mM Ca²⁺). In comparison with the bare FLG, the slow sedimentation of the alginate-stabilized FLG (158 μg/L) caused continuous exposure of this nanomaterial to freshwater snails, which ingested 1.9 times more FLG through filter-feeding within 72 h. Moreover, surface modification of FLG by alginate significantly increased the whole-body and intestinal levels of FLG, but reduced the internalization of FLG to the intestinal epithelial cells. These findings indicate that alginate will act as a stabilizing agent controlling the transport of FLG in aqueous systems. This study also provides the first evidence that interaction of graphene with natural polysaccharides affected the uptake of FLG in the snails, which may alter the fate of FLG in aquatic environments.

To elucidate the sorption affinity of biochars for neonicotinoid pesticides and the influence of biochar structure on sorption mechanisms therein, 24 biochar samples were obtained by pyrolyzing maize straw and pig manure at pyrolyzing temperatures (PTs) of 200–700 °C and by further deashing them using acids, and the sorption of three typical neonicotinoids, imidacloprid, clothianidin and thiacloprid on untreated and acid-deashed biochars were evaluated. All the biochar samples could efficiently adsorb the three neonicotinoids and multiple mechanisms were involved in sorption. With the increasing PTs, hydrophobic partition sorption increased, but had a declined contribution to the total sorption as revealed by a dual-mode model. Besides hydrophobic partition, specific interactions like cation-π electron donor acceptor (EDA) interactions (only for protonated IMI and CLO) and hydrogen bond and contributed much to the sorption on low-PT (≤500 °C) biochars, while the sorption on those high-PT (>500 °C) biochars mainly depended on pore-filling strengthened by cation-π and p/π-π EDA interactions. Thiacloprid showed stronger sorption on untreated biochars compared to imidacloprid and clothianidin, due to its greater ability to form hydrogen bond and hydrophobic interactions. Acid-deashing treatments increased the relative percentage contents of organic carbon, bulk O, aromaticity and O-containing functional groups, surface area and pore volume of biochars. The ash can bind neonicotinoids by specific interactions but played a negative role in the whole sorption on high-PT biochars by covering the inner sorption sites of organic moieties and blocking the micropores in biochars. The results acquired in the present study will help us to get deep insight in the comprehensive sorption mechanisms of polar pesticides on biochar and the effects of biochar structure.

Environmental contamination of the Arctic has widely been used as a worldwide pollution marker. Various classes of organic pollutants such as pesticides, personal care products, PAHs, flame retardants, biomass burning markers, and many others emerging contaminants have been regularly detected in Arctic samples. Although numerous papers have been published reporting data from the Canadian, Danish, and Norwegian Arctic regions, the environmental situation in Russian Arctic remains mostly underreported. Snow analysis is known to be used for monitoring air pollution in the regions with cold climate in both short-term and long-term studies. This paper presents the results of a nontargeted study on the semivolatile organic compounds detected and identified in snow samples collected at the Russian Artic Archipelago Novaya Zemlya in June 2016. Gas chromatography coupled to a high-resolution time-of-flight mass spectrometer enabled the simultaneous detection and quantification of a variety of pollutants including those from the US Environmental Protection Agency (EPA) priority pollutants list, emerging contaminants (plasticizers, flame retardants-only detection), as well as the identification of novel Arctic organic pollutants, (e.g., fatty acid amides and polyoxyalkanes). The possible sources of these novel pollutants are also discussed.GC-HRMS enabled the detection and identification of emerging contaminants and novel organic pollutants in the Arctic, e.g., fatty amides and polyoxyalkanes.

The contamination of agricultural crops by polycyclic aromatic hydrocarbons (PAHs) has drawn considerable attention due to their carcinogenicity, mutagenicity, and toxicity. However, the uptake process of PAHs in plant roots has not been clearly understood. In this work, we first study the radial uptake of phenanthrene in hydroculture wheat roots by vacuum-infiltration-centrifugation method. The concentration-dependent kinetics of apoplastic and symplastic uptake at phenanthrene concentrations of 0–6.72 μM for 4 h can be described with the Langmuir and Michaelis-Menten equations, respectively; whereas, their time-dependent kinetics at 5.60 μM phenanthrene for 36 h follow the Elovich equation. The apoplastic and symplastic uptake increases with temperature of 15–35 °C. The apparent Arrhenius activation energies for apoplastic and symplastic uptake are 77.5 and 9.39 KJ mol⁻¹, respectively. The symplastic uptake accounts for over 55% of total phenanthrene uptake, suggesting that symplast is the dominant pathway for wheat root phenanthrene uptake. Larger volume of symplast in roots and lower activation energy lead to the greater contribution of symplast to total uptake of phenanthrene. Our results provide not only novel insights into the mechanisms on the uptake of PAHs by plant roots, but also the help to optimize strategies for crop safety and phytoremediation of PAH-contaminated soil/water.

Several studies have indicated the presence of contaminants in Alpine aquatic ecosystems. Even if measured concentrations are far below those that cause acute effects, continuous exposure to sub-lethal concentrations may have detrimental effects on the aquatic species present in these remote environments. This may lead to a cascade of indirect effects at higher levels of the ecological hierarchy (i.e., the community). To improve the determination of ecologically relevant risk endpoints, behavioural alterations in organisms due to pollutants are increasingly studied in ecotoxicology. In fact, behaviour links physiological function with ecological processes, and can be very sensitive to environmental stimuli and chemical exposure. This is the first study on behavioural alteration in a wild population of an Alpine species. In the present study, a video tracking system was standardized and subsequently used to identify contaminant-induced behavioural alterations in Diamesa zernyi larvae (Diptera, Chironomidae). Diamesa zernyi larvae, collected in an Italian Alpine stream (Rio Presena, Trentino Region), were acclimated for 24 h and successively exposed to several aquatic contaminants (pesticides: chlorpyrifos, metolachlor, boscalid, captan; pharmaceuticals: ibuprofen, furosemide, trimethoprim) at concentrations corresponding to their Lowest Observed Effect Concentration (LOEC). After 24, 48, 72, and 96 h of exposure, changes in the distance moved, the average speed, and the frequency of body bends were taken to reflect contaminant- and time-dependent effects on larval behaviour. In general, metolachlor, captan, and trimethoprim tended to reduce all the endpoints under consideration, whereas chlorpyrifos, boscalid, ibuprofen, and furosemide seemed to increase the distances moved by the larvae. This could be related to the different mechanisms of action of the investigated chemicals. Independently of the contaminant, after 72 h a general slowing down of all the behavioural activities occurred. Finally, we propose a behavioural stress indicator to compare the overall behavioural effects induced by the various contaminants.