Influence of aquatic colloids on the bioaccumulation and biological effects of diclofenac in zebrafish (Danio rerio)

Molecular-level insights into dissolved organic matter and its variations of the full-scale processes in a typical petrochemical wastewater treatment plant

Petrochemical wastewater (PCWW) treatment poses challenges due to its unique and complex dissolved organic matter (DOM) composition, originating from various industrial processes. Despite the addition of advanced treatment units in PCWW treatment plants to meet discharge standards, the mechanisms of molecular-level sights into DOM reactivity of the upgraded full-scale processes including multiple biological treatments and advanced treatment remain unclear. Herein, we employ water quality indexes, spectra, molecular weight (MW) distribution, and Fourier transform ion cyclotron resonance mass spectrometry to systematically characterize DOM in a typical PCWW treatment plant including influent, micro-oxygen hydrolysis acidification (MOHA), anaerobic/oxic (AO), and micro-flocculation sand filtration-catalytic ozonation (MFSF-CO). Influent DOM is dominated by tryptophan-like and soluble microbial products with MW fractions 〈 1 kDa and 〉 100 kDa, and CHO with lignin and aliphatic/protein structures. MOHA effectively degrades macromolecular CHO (10.86 %) and CHON (5.24 %) compounds via deamination and nitrogen reduction, while AO removes CHOS compounds with MW < 10 kDa by desulfurization, revealing distinct DOM conversion mechanisms. MFSF-CO transforms unsaturated components to less aromatic and more saturated DOM through oxygen addition reactions and shows high CHOS and CHONS reactivity via desulfurization and deamination reactions, respectively. Moreover, the correlation among multiple parameters suggests UV254 combined with AImod as a simple monitoring indicator of DOM to access the chemical composition. The study provides molecular-level insights into DOM for the contribution to the improvement and optimization of the upgraded processes in PCWW.

Effects of natural nanoparticles on the acute toxicity, chronic effect, and oxidative stress response of phenicol antibiotics in Daphnia magna

Natural nanoparticles (NNP) are ubiquitous in natural water and can interact with other contaminants, causing ecotoxic effects on aquatic nontarget organisms. However, the impact of NNPs on the ecotoxicity of antibiotics remains largely unknown. This work investigated the acute toxicity, chronic effect, and oxidative response and damage in Daphnia magna co-exposed to phenicol antibiotics (chloramphenicol, thiamphenicol) and different concentrations of NNPs (10 mg/L: environmentally relevant concentration; 100 mg/L: a high concentration that caused no apparent immobilization in D. magna). The results showed that the acute toxicity of chloramphenicol was increased by 10 mg/L NNPs but decreased by 100 mg/L NNPs; both concentrations of NNPs increased and decreased acute toxicities of thiamphenicol and chloramphenicol + thiamphenicol treatments, respectively. After long-term exposure, phenicol antibiotics (1 μg/L) and NNP (10 mg/L) mixtures in environmentally relevant concentrations significantly affected the reproduction of D. magna but did not influence their growth. The catalase activity, reduced glutathione level, and malonaldehyde content in D. magna also varied with the NNPs concentrations. Notably, the lowest concentration of thiamphenicol and chloramphenicol + thiamphenicol combined with NNPs significantly increased the malondialdehyde content in D. magna compared with the control, indicating membrane lipid peroxidation occurred in daphnids. This study suggests that the toxic effects of contaminants and NNPs on aquatic organisms should be considered thoroughly to avoid underestimating the hazard of these pollutants in the actual aquatic environment.

Natural colloids at environmentally relevant concentrations affect the absorption and removal of benzophenone-3 in zebrafish

Aquatic natural colloids are closely related to the environmental behavior of pollutants, which may affect their bioavailability in aquatic organisms. This study explored the potential mechanisms of the natural colloids at environmentally relevant concentrations affecting the bioaccumulation process of benzophenone-3 (BP3) in zebrafish (Danio rerio). The results of kinetic model fitting showed that the natural colloids decreased the uptake and loss rate of BP3 by zebrafish but prolonged the time to reach the cumulative equilibrium, eventually resulting in a higher cumulative concentration in zebrafish. According to the tissue concentration at equilibrium and the results of toxicokinetic analysis, the presence of high molecular colloids could enhance the bioaccumulation of freely dissolved BP3 due to its high desorption rate with BP3 in the intestines of fish, increasing the freely dissolved BP3 concentrations to which zebrafish were exposed. Both natural colloids and BP3 could enhance the cell permeability of zebrafish, which allowed colloid-bound BP3 to directly enter the fish and accumulate in its muscle. Besides, although both natural colloids and BP3 could cause the metabolic disorders in adult zebrafish, they affected the physiological and biochemical activities of zebrafish through different pathways. The disturbance of glutathione metabolism in zebrafish induced by natural colloids may be the reason for the diminished ability of zebrafish to clear and transform BP3 in the mixture system. The carrier effect of natural colloids and reduced clearance ability of zebrafish eventually increased the bioaccumulation of BP3 in zebrafish. This study highlights the significance of natural colloids at environmentally relevant concentrations on the biological effects of emerging contaminants in actual waters, however, natural colloids are always ignored in most field investigation of pollutants, which would ultimately lead to an underestimation of the true ecological risk of pollutants.

Reaction of spring barley seedlings and H. incongruens crustaceans to the presence of acetylsalicylic acid in soil

Acetylsalicylic acid (ASA) is one of the more commonly used analgesic, antipyretic, and anti-inflammatory as well as anticoagulant drugs available in the OTC (over the counter) segment. Due to the considerable use of this drug, an attempt was made to determine the effect of ASA on the crustacean Heterocypris incongruens and the monocotyledonous plant spring barley. The tested compounds were introduced into soil in which these organisms "lived". The study showed that ASA had an adverse effect on seed germination potential as well as a negative effect on spring barley growth; however, and photosynthetic pigments content was observed only at the highest concentrations of the studied compounds. ASA did not cause oxidative stress in plants but did also cause disturbances in the growth of H. incongruens, without causing their mortality. As a result, ASA may have certain negative effects on both crustaceans and monocots.

Evaluation of the Acute Effects and Oxidative Stress Responses of Phenicol Antibiotics and Suspended Particles in Daphnia magna

Suspended particles (SP) exist widely in various water systems and are able to adsorb other pollutants in water, producing ecotoxic effects on aquatic nontarget species. Until now, however, few studies have focused on the effects of SP on antibiotics. Therefore, the present study investigated the effects of the mixtures of SP and phenicol antibiotics (chloramphenicol [CAP], thiamphenicol [TAP]) on acute toxicity and oxidative stress responses in Daphnia magna. The results indicated that the acute toxicity of phenicol antibiotics in D. magna was increased when combined with SP. Besides, the immobilization of daphnids caused by phenicol drugs in the presence of 10 mg/L of SP was more intense than that with 200 mg/L of SP. Furthermore, the impact of SP with diverse concentrations on the activity of catalase and the level of reduced glutathione in D. magna was different. Notably, almost all CAP + TAP + SP treatments markedly increased malondialdehyde content in D. magna, causing potential cellular oxidative damage in D. magna. In summary, the present study provides insights into the toxic effects of phenicol antibiotic and SP mixtures on aquatic organisms. Environ Toxicol Chem 2021;40:2463-2473. © 2021 SETAC.

Multimedia distribution and trophic transfer of PPCPs in the middle and lower reaches of the Yarlung Zangbo River

The increasing human presence is having an impact on plateau ecosystems, but the special environment and lack of data make it difficult to assess the real ecological risks of pharmaceutical and personal care products (PPCPs) in the river of plateau. The occurrence, distribution and trophic transfer of nineteen PPCPs were investigated in the middle and lower reaches of the Yarlung Zangbo River on the Tibetan Plateau. All the targeted PPCPs were detected in filtrated water, and seventeen PPCPs were detected in the colloid, sediment and suspended particulate matter (SPM). The distribution coefficients of colloid-infiltration water (IFW) were 1-2 orders of magnitude larger than those in the SPM-IFW, which were 1-2 orders of magnitude greater than those in the sediment-IFW. Colloids are sinks for PPCPs with up to 78.55% of the water being in the colloidal phase, in which important factors such as protein and protein-like substances are found. PPCPs in the rivers of the plateau showed high bioaccumulation ability. The fugacity-based bioaccumulation model was established and revealed that the fish in the Tibetan Plateau ingested PPCPs mainly through water instead of food and excreted them mainly through metabolism. In addition, the trophic dilution effect in the food web was observed with trophic magnification factors ranging from 0.06 to 0.22. The positive correlation between the K_d in the colloid-IFW and the bioaccumulation factors implied that natural colloids can not only regulate the behaviour of PPCPs in the environment, but also play an important role in bioaccumulation, which may affect the scientific nature of biological risk assessment.