Since 1993, systemic insecticides such as neonicotinoids have been extensively applied in Japanese rice farming, leading to contamination of surface waters. These chemicals may infiltrate groundwater, which serves as a source of tap water, yet data on their occurrence in Japan remained unclear. This study investigated the contamination of neonicotinoids and their metabolites, sulfoxaflor, and triflumezopyrim in surface water and groundwater of Hii River and tap water in Izumo City, Shimane Prefecture, Japan. Monthly sampling over one year followed by the liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis showed that all water types contained at least three compounds. Mean concentration ratios across surface water, groundwater, deep groundwater, and tap water were approximately 10:8:4:1, indicating that deeper depth and water treatment may reduce concentrations. Dinotefuran showed a 100% detection with concentrations far exceeding other compounds, particularly in summer months during the rice-growing season, reaching 225 ng/L in surface water. Its two metabolites were also present throughout all environmental water compartments. The findings emphasize that systemic insecticides could persist in deep groundwater up to 20 meters, leading to their occurrence in tap water.

In this study, modified cationic cassava peel starch grafted with 3-chloro-2-hydroxpropyl trimethyl ammonium chloride (ME.St-g-CatCHP) flocculant was developed by etherification with 0.95 degrees of substitution (DS). The flocculation performance of ME.St-g-CatCHP was compared with a conventional starch (ME.St) flocculant in removing chemical oxygen demand (COD). The results showed that dosage, pH and settling time significantly affected the flocculation performance (p-value < 0.05). The ME.St-g-CatCHP demonstrated a better flocculation performance to achieve 88.63% removal efficiency with optimum conditions obtained at pH 7, dosage 360 mg/L, 29 mins settling time, 278 rpm within 1 min of rapid mixing and 31 rpm within 53 mins of slow mixing. Response Surface Methodology was applied to optimize ME.St-g-CatCHP quadratic model showed that R² = 0.98 and adjusted R² = 0.83. Charge neutralization played a dominant role in the flocculation process by ME.St-g-CatCHP due to strong positive polyelectrolyte across the whole pH range between pH 2 and 11. While bridging mechanisms could be the main contributor to the flocculation process by ME.St during the slow adsorption process. The findings supported that modified ME.St-g-CatCHP increased the COD removal efficiency from 74% to 88% removal efficiency compared to ME.St, and shortened the settling period from 107 to 29 mins.

In this study, a Bi₂MoO₆/g-C₃N₄ heterojunction photocatalyst was successfully synthesized via a hydrothermal method combined with thermal treatment to enhance visible-light-driven photocatalytic performance. Integration of Bi₂MoO₆ and g-C₃N₄ was designed to exploit the synergistic effect between the two semiconductors, aiming to improve light absorption and suppress the recombination of photogenerated electron–hole pairs. The synthesized materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and ultraviolet-visible diffuse reflectance spectroscopy analysis (UV–Vis DRS) of spectroscopy to evaluate their structural, morphological, and optical properties. The photocatalytic activity of the Bi₂MoO₆/g-C₃N₄ composite was assessed through the degradation of ciprofloxacin (CIP), a widely used and environmentally persistent antibiotic, under visible light irradiation. Results revealed that the Bi₂MoO₆/g-C₃N₄ composite exhibited significantly enhanced degradation efficiency compared to the individual components, along with excellent stability and reusability. The improved photocatalytic performance was attributed to the effective charge separation and extended light absorption range facilitated by the heterojunction structure. This study demonstrates the potential of Bi₂MoO₆/g-C₃N₄ as an efficient visible-light-responsive photocatalyst for treating antibiotic-contaminated wastewater, contributing to the development of sustainable water purification technologies.

The widespread presence of per- and polyfluoroalkyl substances (PFASs) in aquatic environments poses significant risks to aquatic food webs. As primary consumers, benthic animals not only transfer energy through food chains but also facilitate PFASs accumulation across trophic levels. This study investigated PFASs contamination across river sections and tidal flats with whole watershed in a river of Japan and the dual regulation of organic matters and ω-3 polyunsaturated fatty acids (PUFAs) on the bioaccumulation of PFASs in benthic animals. Elevated PFASs concentrations were observed in water (5.61 ng L⁻¹) and sediments (0.85 ng g⁻¹) from areas near pollution sources, while the highest PFASs levels in benthic animals were detected in organic-rich tidal flats (210.19 ng g⁻¹). Since benthic animals primarily derive their food from sediments, sediment organic matter content not only influences PFASs distribution but also enhances PFASs accumulation in these organisms. Concurrently, short-chain PFASs exhibited higher bioaccumulation factors (BAFs) in benthic organisms. Benthic animals are affected by their feeding habits and have a relatively high content of ω-3 PUFAs, which may have a potential impact on the bioaccumulation of PFASs. Therefore, increased attention should be directed toward organic-rich riverine zones and the health of aquatic ecosystems. This study provided a theoretical foundation for understanding PFAS trophic transfer dynamics and assessing ecological risks in watersheds.