Yingang Xue

Non-point source (NPS) pollution has emerged as a critical environmental issue, significantly impacting water quality and ecosystem health at the watershed scale. The identification of critical periods (CPs) and critical source areas (CSAs) is fundamental for formulating effective watershed management strategies. However, the identification of effective management measures remains challenging, primarily due to the complex interplay between diverse pollution sources and dynamic environmental factors. To address this challenge, this study proposes an integrated framework that synergistically combines the Soil and Water Assessment Tool (SWAT) model, the eXtreme Gradient Boosting (XGBoost) machine learning algorithm, and the SHapley Additive exPlanations (SHAP) approach. The framework aims to quantitatively analyze the driving factors responsible for the formation of CSAs of NPS pollution in small watersheds during CPs. SWAT simulated nutrient loads, identifying CPs and CSAs via load-time and load-area curves. XGBoost modeled factor relationships, and SHAP quantified each driver's contribution. Applied to a small watershed, results showed CPs (months 2, 6, 7) contributed 59% of total nitrogen (TN) and 65% of total phosphorus (TP) loads. Within CSAs, 56.2-66.2% of TN/TP loads originated from just 35.2-36.8% of the area. Fertilizer application amount (mean |SHAP|= 1.91) and the proportion of cultivated land (mean |SHAP|= 0.52) were identified as the predominant drivers governing the formation of CSAs. Operationally, the identified thresholds (e.g., runoff 30 mm, fertilizer 100 kg/ha) serve as objective tipping points that trigger the implementation of targeted best management practices (BMPs). Despite limitations in the temporal scope of monitoring data and potential model parameter uncertainties, this framework provides a robust scientific basis and a novel methodology for precision watershed management.

Bisphenol A (BPA) is a persistent environmental contaminant requiring effective removal strategies. Biofilms offer advantages over conventional activated sludge for refractory compound degradation, yet the specific microorganisms and mechanisms driving BPA removal in biofilms remain poorly understood. This study employed an integrated approach, combining ¹³C-DNA stable isotope probing (SIP) and metagenomics to identify BPA-assimilating microorganisms and elucidate their metabolic pathways in biofilms. Two moving bed biofilm reactors (MBBRs) were operated at contrasting BPA concentrations (500 μg/L and 10 mg/L) to enrich distinct microbial communities. Using DNA-SIP, we revealed differences in assimilating bacteria across diverse concentrations of BPA-enriched biofilms. Simultaneously, we reconstructed the genomes of these assimilating bacteria, dissecting the functional genes essential to the degradation process and identifying significant gene variations among different assimilating bacteria. By integrating these gene functions, we constructed the BPA metabolic pathway, which surprisingly comprised genes from various assimilating bacteria. This research significantly advances our understanding of BPA-assimilating bacteria within biofilms and provides valuable insights for refining biofilm technologies aimed at BPA removal from wastewater.

Tetracycline (TC), commonly utilized in medicine and aquaculture, frequently enters aquatic environments, raising ecological concerns. This study examined TC-contaminated wastewater treated through ultraviolet (UV), potassium persulfate (PS), and combined UV/PS disinfection processes. The degradation of TC followed pseudo-first-order kinetics, with removal efficiency ranked as UV/PS > UV > PS. High-performance liquid chromatography–mass spectrometry (HPLC-MS) identified 20 disinfection byproducts (DBPs) across all processes. Based on the identified intermediates, the degradation pathways of TC under different disinfection processes (UV, PS, and UV/PS) were elucidated. Using the ECOSAR program, both acute and chronic aquatic toxicities of TC and its DBPs were predicted. The biological effects on Chlorella were also investigated. DBPs from UV and PS treatments inhibited algal growth, reducing it by 4.8–9.4% relative to the control. Conversely, DBPs formed under UV/PS disinfection stimulated growth, increasing rates by 3.4–6.6%. To counteract oxidative stress from TC and its DBPs, Chlorella enhanced superoxide dismutase (SOD) and catalase (CAT) activities. These findings highlight that while TC degradation occurs efficiently, the nature of DBPs and their ecological impacts vary significantly depending on the disinfection method. Overall, the UV/PS process not only improved TC removal but also reduced harmful effects on microalgal growth compared with UV or PS alone.

Reducing the generation of excess sludge and achieving resource recovery are crucial for enhancing the economic efficiency and environmental sustainability of wastewater treatment plants (WWTPs). This study utilizes ultrasonic cavitation technology to transform organic matter into excess sludge to achieve sludge reduction and carbon source recovery. To this end, we systematically investigated the effects of various ultrasonic cavitation conditions on sludge reduction, organic matter conversion, and denitrification efficiency. The results showed that the optimal sludge reduction effect occurs at an original mixed liquid suspended solids (MLSS) of 10 g/L, under neutral and non-aerated conditions, reaching 15.07%. Ultrasonic cavitation treatment significantly enhanced the conversion efficiency of organic matter in the sludge, greatly increasing the concentration of organic matter in the supernatant, with soluble chemical oxygen demand (SCOD) maintained around 900 mg/L, thereby significantly improving the denitrification process. Furthermore, through magnetic-nanoparticle mediated isolation (MMI) and metagenomic sequencing analysis, the dominant denitrifying bacteria and their functional genes that utilize organic matter in the supernatant of ultrasonically treated sludge as a carbon source were identified. Finally, long-term pilot-scale operations further validated the practical application potential of ultrasonic cavitation technology for excess sludge reduction and resource utilization.

Tetrabromobisphenol A bis (2-hydroxyethyl) ether (TBBPA-DHEE), a derivative of TBBPA, has been frequently detected in the environment. In this study, the median lethal concentration (LC₅₀) of TBBPA-DHEE at 96 h post-fertilization (hpf) was 1.573 mg/L. Based on the reported environmental concentrations, we investigated the effects of TBBPA-DHEE on the nervous system of zebrafish embryos following exposure to varying concentrations (0, 20, 100, and 500 μg/L) for 4 to 144 hpf. Our results indicated that exposure to 100 μg/L at 144 hpf led to behavioral abnormalities in zebrafish. Furthermore, exposure to TBBPA-DHEE inhibited the development of the central nervous system and motor neurons in zebrafish. Real-time polymerase chain reaction (PCR) analysis revealed that exposure to TBBPA-DHEE significantly downregulated the expression levels of neurodevelopmental genes (shha, syn2a, elavl3, gfap, and gap43). Additionally, TBBPA-DHEE increased oxidative stress in zebrafish. Transcriptomic analysis demonstrated that exposure to TBBPA-DHEE affected the signaling pathways involved in neurodevelopment. Overall, this study demonstrated that TBBPA-DHEE may disrupt the early development of the nervous system, leading to abnormal motor behavior in zebrafish larvae, and provided novel insights into the potential mechanisms of TBBPA-DHEE neurotoxicity.

Bisphenol A (BPA), an endocrine disruptor widely used in industrial production, is found in various environmental sources. Despite numerous reports on BPA degradation and removal, the details remain unclear. This paper aims to address this gap by providing a comprehensive review of BPA degradation methods, focusing on biological, physical, and chemical treatments and the factors that affect the degradation of BPA. Firstly, the paper uses VOSviewer software (version 1.6.15) to map out the literature on BPA degradation published in the past 20 years, which reveals the trends and research focus in this field. Next, the advantages and limitations of different BPA degradation methods are discussed. Overall, this review highlights the importance of BPA degradation to protect the environment and human health. The paper provides significant insights for researchers and policymakers to develop better approaches for BPA degradation and removal.