Narrabeen Lagoon is recognized as an Intermittently Closed and Open Lake or Lagoon (ICOLL) and is the largest coastal lagoon (2.2 km²) in the Sydney metropolitan region. The catchment (53 km²) supports five major river systems, and land use comprises of 56% residential, 42% parkland and 2% light industry, commercial, hospital and education. An initial screening environmental assessment was undertaken using sedimentary metals to determine the magnitude of anthropogenic change and level of ecological risk posed by these contaminants. Results illustrated an unusual example of an estuary significantly influenced by human-induced change, but exhibiting minimal ecological risk. This anomaly was due to high anthropogenic metal concentrations in the fine fraction of surficial sediment, which was considerably diluted by abundant metal-poor coarse material resulting in reduced adverse ecological impact for total sediment. Predictive modelling to 2020 suggested that Pb concentrations will decline and Cu and Zn levels will increase slightly. Modelling of river discharge and analyses of fluvial sedimentary metals suggested stormwater derived from the most urbanized catchments and a major roadway combined with poor flushing explained surficial sediment metal distributions in the lagoon.

This study reports the efficiency of a synthesized eco-friendly geopolymer (7.5 wt% of coal fly ash incorporated into its composition) as an adsorbent for the removal of Cu(II) from an aqueous solution and a real water matrix. The results obtained were compared with a commercial natural zeolite used as an adsorbent of toxic metals in Brazil. The effect of the operating conditions on the adsorption kinetics and equilibrium were studied in a finite bath and in a fixed bed column. The adsorption kinetics curves obey the pseudo-first-order model for both materials. The geopolymer presented higher adsorption capacity than zeolite, and values for the qₘₐₓ_gₑₒ/qₘₐₓ_zₑₒ ratio were 1.13, 1.92, and 2.56 at temperatures of 25, 40, and 55 °C, respectively. The isotherms obtained in the thermodynamic study are favorable and spontaneous adsorption process. The adsorption processes are endothermic. The geopolymer showed higher adsorption efficiency than the zeolite in a fixed-bed column, and even with the presence of substances in the natural water sample, the Cu(II) removal capacity of the geopolymer is 3–4 times higher than that of the zeolite. A cost analysis was also performed, the geopolymer was found to be a more economical adsorbent than the commercial zeolite.

Synthetic dyes, generally resistant, toxic and carcinogenic presents a substantial risk to the environment and health of human. The present study was aimed to decolourize a dye mixture (Evans blue and brilliant green) by selected bacterial strains cultivated at different growth conditions (e.g. unmodified, correction of pH value and supplementation with nutrients). The bacterial strains used as pure and mixed cultures include facultative anaerobes Aeromonas hydrophila (Abs37), Citrobacter sp. (Cbs50) and obligatory aerobe Pseudomonas putida (Pzr3). The efficiency of removal of all successive doses of dye mixture (4–5 doses, total load 170–200 mg/l) was tested in static conditions in fed-batch bioreactors. The modification of bacteria growth conditions influenced on decolourization efficiency: most advantageous was pH value correction combined with nutrient supplementation then pH correction alone and nutrient supplementation (final removal results 95.6–100%, 92.9–100% and 89.1–97.2%, respectively). The mixed bacterial cultures removed the total load of dyes with higher efficiency than pure strains (final removal 95.2–100% and 84.0–98.2%, respectively). The best results were obtained for the mixture of facultative anaerobe Citrobacter sp. and obligatory aerobe Pseudomonas putida which removed the highest load of dye mixture (200 mg/l introduced at five doses) in the shortest time (288 h), while the others pure and mixed cultures needed 425–529 h for removal four doses of dye mixture (total load 170 mg/l). The zoo- and phytotoxicity decreased after these processes (from V class of toxicity (extremely toxic) even to II class (low toxicity)). The main mechanisms of decolourization was biotransformation/biodegradation, supported by sorption.

Based on the quasi-natural experiment of the establishment of the Yangtze River economic belt, this paper uses a difference-in-difference-in-differences model (DDD) to test the impact of regional integration on transboundary pollution. The results show that regional integration can significantly reduce transboundary water pollution. Regional integration reduces chemical oxygen demand (COD) by 0.357, ammonia nitrogen content (NH₃-N) by 0.155, and dissolved oxygen content (DO) by 0.088 in the downstream of the provincial boundary. And regional integration has a long-term inhibitory effect on transboundary pollution. The heterogeneity results show that the regional integration has a stronger inhibition effect on the transboundary pollution of the middle and lower reaches of the Yangtze River economic belt and the tributaries. At the government level, regional integration can reduce transboundary pollution by strengthening the government’s environmental regulation and collaborative governance. At the industry level, it can inhibit transboundary pollution by promoting industrial structure optimization and green technology innovation. At the market level, regional integration can promote market competition to reduce transboundary pollution and expand market scale to intensify transboundary pollution. At the society level, regional integration can intensify transboundary pollution by promoting population agglomeration and effectively alleviate transboundary pollution by enhancing public environmental supervision.

Soil fungi have been widely studied, but the effects of heavy metal contamination at various levels as well as the abundance and diversity of heavy metal tolerant fungi in the contaminated paddy soils are still unknown. The purpose of this study is to analyze the adaptability of fungi at different levels of heavy metal contamination to identify species that have strong adaptability to heavy metals. In this research, the technology of high-throughput sequencing was applied to study fungal communities in severe level (SL), moderate level (ML), light level (LL), and clean level (CL) for soil samples polluted by heavy metal, as well as to analyze the relations between environmental variables and fungal communities. The spearman analysis showed that 6 dominant fungal phyla and 18 dominant fungal genera were significantly correlated with these environmental variables. The α-diversity indexes of the soil fungal community from SL, ML, and CL were, mostly, drastically higher than the LL samples (p < 0.05). Meanwhile, Ascomycota, the main fungal phylum, was spotted to yield a strong tolerance towards heavy metals, especially in ML. The most dominant genera of tolerant fungi in this area, which are Aspergillus, Penicillium, and Fusarium, could absorb and transport the heavy metals with the help of nutrients under certain heavy metal contamination levels. Therefore, this study indicated that some fungi, which have strong biodegradability on heavy metals, can reduce toxicity of heavy metals and create a proper soil environment to grow food crops. Graphical abstract

The bio-resource utilization of sewage sludge is presented by preparation of novel waste sludge–doped graphite carbon nitride (g-C₃N₄) photocatalyst. The sludge flocs which constitute bacteria and organic substances served as a pore-forming framework in the catalyst, while the inorganic fractions including those transition metals and crustal metals can function as dopants for sludge-based g-C₃N₄ composite. The physicochemical properties of as-prepared catalyst were well analyzed by multiple characterizations. The composite catalyst showed higher surface area (50 m²/g) and more mesoporous structures (8.9 × 10⁻² cm³/g) as compared with pristine g-C₃N₄ (8.4 m²/g and 6.6 × 10⁻² cm³/g, respectively). The photoelectrochemical results showed that introduced sewage sludge impurities lowered down the photocarriers recombination efficiency and enhanced more efficient electron-hole separation by about 100 times. The photocatalytic activity was tested by degradation of typical dye Eriochrome Black T (EBT). The optimal sample improved removal of EBT by 56% in 90 min under ultraviolet irradiation (λ = 254 nm). According to the results of main metal ion leaching concentration and reuse tests, the composite catalyst exhibited excellent stability and repeatability.

The occurrence, seasonal variation, and environmental impact of five widely used parabens, methyl-(MeP), ethyl-(EtP), n-propyl-(n-PrP), n-butyl-(n-BuP), and benzyl-(BzP) parabens, were investigated in a municipal wastewater treatment plant (WWTP) located in Guangzhou, China, for 1 year. The concentrations of ∑₅parabens in the influent and the effluent were 94.2–957 and 0.89–14.7 ng L⁻¹, respectively. The influent paraben concentrations in autumn were significantly lower than in winter, spring, and summer, and the concentrations were generally higher in spring. The removal efficiencies of ∑₅parabens in the dissolved phase were over 96%, with high efficiencies in MeP, EtP, and n-PrP. Risk assessment indicated that parabens in the effluent were not likely to pose an environmental risk to aquatic ecosystems. The present study indicates that the treatment processes employed in full-scale WWTPs are effective at removing parabens and highlights the possibility of utilizing WWTPs for restoring water quality in riverine and coastal regions heavily impacted by paraben contamination.

Urea, being a nitrogen fertilizer, is crucial for plant growth but when excessively provided (above biuret 2% levels specified by the World Health Organization), plant characteristics are deeply affected. A real-time sensor to check the presence of excess urea in plants is therefore necessary. Towards this goal, a manganese oxide–reduced graphene oxide composite was synthesized by modified Hummer’s method and precipitation techniques, which was subsequently used as a nano-interface to immobilize urease enzyme for specific detection of urea. The synthesized nanocomposite helped in shuttling of electrons between the redox species and in enhanced electron transfer rate due to their high surface area, vindicated by their structural and morphological characterization using X-ray diffractometer (XRD), scanning electron microscope (SEM), and X-ray photoelectron spectrometer (XPS), and electrochemical characterization using cyclic voltammetry and amperometry, respectively. The fabricated biosensor for urea exhibited a linear range of 5–100 μM with a sensitivity of 9.7 × 10⁻³ μA μM⁻¹, limit of detection of 14.693 μM, and a response time of 118 s.

Single-stage autotrophic nitrogen removal offers advantages of low energy and carbon consumptions. Based on previous work about a novel composite membrane aerated biofilm (CMAB), two microbial entrapping patterns (mixed and stratified patterns) were evaluated for their applicability to artificially regulate the spatial distribution of distinct microbial aggregates for single-stage autotrophic nitrogen removal. Experimental results showed that the stratified pattern caused little accumulation of NO₂⁻ and NO₃⁻, which leads to a superior nitrogen removal performance compared with the mixed pattern. Candidatus Kuenenia was found to be the major anammox bacterium in the gel film of the mixed pattern and the outer film of the stratified pattern. In contrast, Nitrosomonas, as a representative genus of ammonia-oxidizing bacteria, was substantially enriched in the inner film of the stratified pattern and the gel film of the mixed pattern. Finally, modeling results further confirmed the advantages of the stratified pattern with respect to the formation of rational microbial and nutrient profiles in gel films. The ratio of partial nitrification and anammox film thicknesses should remain below 3:2 to obtain a high fraction of anammox bacteria and to avoid NO₂⁻ accumulation. Increasing O₂ surface loading does not affect microbial profiles, but can greatly promote the TN removal performance only in the stratified pattern. Overall, the stratified pattern should be employed to achieve optimal microbial profiles and nitrogen removal efficiency.

Aerosol acidity (pH), one of key properties of fine-mode particulate (PM₂.₅), depends largely on nitrate and sulfate in particle. The mass contribution of nitrate relative to sulfate in PM₂.₅ has tended to increase in many regions globally, but how this change affects aerosol pH remains in debate. In this way, we measured PM₂.₅ ionic species and oxygen isotopic composition of nitrate in the eastern China, and predicted aerosol pH using the ISORROPIA-II model. When nitrate to sulfate molar ratio increases and thus PM₂.₅ is gradually enriched in ammonium nitrate (NH₄NO₃), aerosol pH tends to increase. The oxidation of nitrogen dioxide (NO₂) by hydroxyl radical is responsible for most of nitrate formation (generally above 60%). These indicate that nitrate formation through gas-to-particle conversion involving ammonia and nitric acid results in increasing aerosol pH with increasing molar ratio of nitrate to sulfate. Conversely, aerosol pH is expected to decrease with increasing relative abundance of nitrate as ammonia emissions are lowered. Our research concludes that it should be considered to reduce aerosol NH₄NO₃ by reducing the precursors of nitric oxide and ammonia emissions, to substantially improve the air quality (i.e., reduce PM₂.₅ levels and potential nitrate deposition) in China.