Chunsheng Liu

Low carbon-to-nitrogen (C/N) municipal wastewater often limits heterotrophic denitrification and increases external carbon addition. This study evaluated an exogenous denitrifying bioaugmentation (DEN) strategy for improving nitrogen removal per unit of external carbon added. The screened inoculant reached approximately 2.5 × 10⁹ CFU/mL, and maximum nitrate and nitrite reduction rates of 307.42 and 215.42 g N/(m³ h), respectively, were achieved by the selected isolates. Among the tested carbon sources, the highest denitrification rate was obtained with sodium acetate. Across wastewater samples from six municipal wastewater treatment plants (WWTPs), the apparent C/N requirement was reduced from 2.79–9.41 to 1.92–5.20 by DEN addition, corresponding to a 21–55% decrease in chemical oxygen demand (COD) required per unit total nitrogen (TN) removed. During full-scale validation at a 24,000 m³/d WWTP, effluent TN was maintained at approximately 10 mg/L through startup and adaptive maintenance dosing, while specific denitrification rate (SDNR) was increased by approximately 2.3-fold. Activated-sludge community restructuring was indicated by 16S rRNA sequencing, with an increase in the relative abundance of Pseudomonadota from 18.4% to 27.6% after dosing. Based on external carbon-source expenditure, the specific external carbon-source cost per unit TN removed decreased from 0.036 to 0.011 Chinese Yuan (CNY)/(t water·mg TN), corresponding to a 69.4% reduction in this cost indicator. Overall, DEN bioaugmentation was shown to be a practical engineering tool for carbon-efficient nitrogen removal from low-C/N municipal wastewater.

Recently, increasing attention has been focused on the intergenerational toxicity of environmental contaminants. Tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) is a widely detected contaminant in aquatic environments, but its paternally mediated intergenerational toxicity in vertebrates has remained insufficiently elucidated. In this study, zebrafish at 50 days postfertilization (dpf) were exposed to environmentally relevant concentrations (55, 550, and 5500 ng/L) of TDCIPP for 150 days. Following exposure, the males were paired with unexposed females, and cardiotoxicity and hepatotoxicity were assessed in the offspring larvae. It was found that TDCIPP accumulated in F0 testes but not in the offspring embryos. Furthermore, paternal exposure to TDCIPP led to an increased heart rate, abnormal cardiac morphology, and significantly elevated ventricular wall thickness in the offspring zebrafish. Additionally, lipid metabolism disorders, abnormal liver morphology, and functional impairment were also observed in the offspring. Moreover, paternal exposure to TDCIPP down-regulated the expression of the hepcidin antimicrobial peptide gene (hamp) in the offspring larvae, leading to iron overload, which might contribute to the observed cardiotoxicity and lipid metabolism disorders in the offspring, as well as the subsequent development of hepatotoxicity. Furthermore, the up-regulation of miR-184 in F0 testes and offspring larvae accounted for the suppression of hamp expression following paternal exposure to TDCIPP. Our findings reveal that paternal exposure to TDCIPP induces up-regulation of miR-184 in F0 testes, and this overexpressed microRNA can be transmitted to the offspring, subsequently inhibiting hamp expression, leading to iron overload and consequently contributing to cardiotoxicity and hepatotoxicity in the offspring.

Phthalate esters (PAEs), ubiquitous plastic additives, have emerged as persistent contaminants in aquatic ecosystems, yet their propagation from molecular initiating events to ecosystem-level collapse remains poorly integrated. This review synthesizes current knowledge on the source-to-sink dynamics of PAEs, revealing a critical paradox in their bioaccumulation patterns: unlike classical persistent organic pollutants, high molecular weight PAEs exhibit distinct trophic dilution rather than biomagnification along food webs, driven by metabolic biotransformation in higher trophic organisms. Despite this dilution, PAEs trigger a bottom-up toxicity cascade. Driven by molecular initiating events, PAEs induce a range of adverse effects at the individual level, including immunotoxicity, neurotoxicity, endocrine disruption, metabolic dysfunction, and trans-trophic oxidative stress. Crucially, prolonged exposure drives epigenetic reprogramming, which reduces reproductive output, thereby threatening long-term population recruitment. These individual and population deficits could escalate into higher ecological consequences, specifically by diminishing benthic biological control over phytoplankton, dampening energy transfer efficiency, and simplifying community structure, thereby posing a potential threat to primary productivity and aquatic ecosystem sustainability. Despite recent advances, critical knowledge gaps remain, particularly regarding their cascading impacts on ecosystem services, as well as synergistic interactions between PAEs and other contaminants. In order to validate laboratory results with actual ecological risk assessments, future research should incorporate multi-scale models and quantitative adverse outcome Pathways as well as their synergistic interactions between PAEs and other contaminants, and advanced in vitro systems such as organoids. Resolving these issues is essential to reducing the risks that PAEs pose to aquatic environments.

Low concentrations of chemicals are widespread in the environment, but exploration of the effects of their chronic exposures on animal life span in the wild is limited. Field investigations showed that fish populations of lake skygazer ( Culter dabryi ) with chronic low-dose chlorpyrifos loads had shortened telomeres and truncated age structures. Laboratory experiments confirmed that chronic low-dose chlorpyrifos exposure induced telomere degradation and reduced survival in a dose- and physiological age–dependent manner, whereas acute high-dose exposure did not. Together, these studies provide evidence that chronic low-level chlorpyrifos exposure reduces life span and population viability in a wild fish by accelerating physiological aging. Given the pervasive presence of low pesticide concentrations in the environment and the conserved mechanisms of aging across vertebrates, these findings raise concerns that even low doses of pesticides may pose long-term risks to longevity.

1,2-Bis (2,4,6-tribromophenoxy) ethane (BTBPE) has been increasingly detected in environmental and biota samples, primarily accumulating in the liver. However, the mechanism underlying BTBPE-induced metabolic dysregulation remains unclear. In this study, molecular docking and microscale thermophoresis assays indicated that BTBPE binds to zebrafish liver X receptor α (LXRα). Subsequently, zebrafish embryos were exposed to BTBPE, an LXR antagonist (GSK2033), or coexposed to BTBPE with an LXR agonist (GW3965) for 120 h postfertilization (hpf). The results showed that BTBPE induced reduction in body weight and lipid levels, likely via inhibition of the LXR signaling pathway. Exposure of adult female zebrafish to environmentally relevant concentrations of BTBPE (0.01-10 μg/L) for 28 days induced developmental toxicity, evidenced by decreases in body weight, growth rate, and fat accumulation. Metabolomic analysis revealed that BTBPE-induced alterations in liver metabolites were primarily associated with LXR-mediated lipid metabolic pathways such as glycerophospholipid metabolism and primary bile acid biosynthesis. Additionally, BTBPE impaired the physical barrier and induced inflammation, resulting in gut microbiota dysbiosis, which is potentially linked to LXR activation. These effects were validated through the alterations of multiple biomarkers at various levels. Overall, our results suggest that BTBPE disrupts lipid metabolism and gut function via the LXR-mediated pathway.

Abnormal development and mortality in early life stages pose significant threats to the growth and continuation of fish populations. Tris(2,4-di-tert-butylphenyl) phosphate (TDtBPP) is a novel organophosphate ester contaminant detected in natural waters. However, the potential effects of maternal exposure to TDtBPP on the early development of offspring embryos in fish remain unknown. Here, 30-day-old zebrafish were exposed to TDtBPP at 0, 50, 500, or 5000 ng/L for 180 days, and the exposed females were spawned with unexposed males. TDtBPP accumulation was detected in offspring embryos, accompanied by an increased malformation rate and mortality. The developmental abnormality of offspring embryos was identified to originate from the gastrula stage. Furthermore, based on transcriptome analysis, the down-regulation of RHO family interacting cell polarization regulator 2 gene (ripor2) was considered as a key toxic event, and this was confirmed in the subsequent knockdown experiment. Moreover, molecular docking studies and forkhead box O1 (foxO1) transcription factor inhibitor (AS1842856) exposure experiments demonstrated that the blockade of foxO1 transcriptional regulation was responsible for the decreased expression of ripor2. The results of this study demonstrated that the occurrence of developmental malformation and mortality in zebrafish offspring embryos following maternal TDtBPP exposure were triggered by the blockade of foxO1 transcriptional regulation and the consequent down-regulation of ripor2.

As a novel organophosphate ester (NOPE), tris­(2,4-ditert-butylphenyl) phosphate (TDtBPP) has attracted significant attention due to its unexpectedly high detection in natural environments. However, the ecological toxic effects of environmentally relevant concentrations of TDtBPP in organisms remain entirely unknown. In this study, 1 month old zebrafish were exposed to 0, 50, 500, or 5000 ng/L TDtBPP for 150 days, and the reproductive toxicity in male fish was evaluated. Results demonstrated that TDtBPP exposure significantly inhibited the maturation of spermatozoa and thus decreased spermatogenesis. Furthermore, abnormal sperm morphology and decreased sperm motility were also observed. The decrease in sperm quantity and quality eventually resulted in the declining fecundity. Moreover, TDtBPP exposure downregulated the expression of hsd3b1 in vivo and in vitro and subsequently inhibited the synthesis of androgens in zebrafish testes and Leydig cells. This inhibition of androgen synthesis appeared to be responsible for the observed reproductive toxicity in male fish. Molecular docking and dual-luciferase reporter gene experiments elucidated that TDtBPP inhibited the promotion of vitamin D on hsd3b1 transcription by the vitamin D receptor and thus downregulated the expression of hsd3b1. Our findings provide first time evidence that TDtBPP poses a risk to male fish reproduction at environmentally relevant levels.

Amines are widespread environmental pollutants that may pose health risks. Specifically, the N-dealkylation of amines mediated by cytochrome P450 enzymes (P450) could influence their metabolic transformation safety. However, conventional experimental and computational chemistry methods make it difficult to conduct high-throughput screening of N-dealkylation of emerging amine contaminants. Machine learning has been widely used to identify sources of environmental pollutants and predict their toxicity. However, its application in screening critical biotransformation pathways for organic pollutants has been rarely reported. In this study, we first constructed a large dataset comprising 286 emerging amine pollutants through a thorough search of databases and literature. Then, we applied four machine learning methods—random forest, gradient boosting decision tree, extreme gradient boosting, and multi-layer perceptron—to develop binary classification models for N-dealkylation. These models were based on seven carefully selected molecular descriptors that represent reactivity-fit and structural-fit. Among the predictive models, the extreme gradient boosting shows the highest prediction accuracy of 81.0%. The SlogP_VSA2 descriptor is the primary factor influencing predictions of N-dealkylation metabolism. Then an ensemble model was generated that uses a consensus strategy to integrate three different algorithms, whose performance is generally better than any single algorithm, with an accuracy rate of 86.2%. Therefore, the classification model developed in this work can provide methodological support for the high-throughput screening of N-dealkylation of amine pollutants.

Pesticides have been frequently detected in global freshwater ecosystems, but attempts to document changes in population dynamics of organisms upon exposure to pesticides, establish a causal relationship between exposure and population effects, and identify the key toxic events within individuals under natural field conditions remain rare. Here, we used a field survey, a reciprocal cross-transplant experiment, and a laboratory toxicity experiment to build a compelling case that exposure to the insecticide chlorpyrifos was responsible for differences in snail (Bellamya aeruginosa) densities in eastern (ELL) and western basins of Liangzi Lake in China. Our field survey and reciprocal cross-transplant experiment revealed significant differences in snail densities, juvenile percentage, survival, and relative telomere length (RTL) in the two basins. The insecticide chlorpyrifos detected in snail tissues was negatively correlated with snail densities, the percentage of juvenile snails, and RTL and had an extremely high risk quotient in ELL. In the laboratory experiment, tissue concentrations of chlorpyrifos detected in ELL were associated with reduced RTL and increased juvenile mortality in B. aeruginosa. These results support the hypothesis that chlorpyrifos exposure in ELL reduced the density of snails by reducing juvenile survival and, consequently, recruitment to the adult population.