Nanoplastics (NPs) are becoming emerging pollutants of global concern. Understanding the environmental behavior of NPs is crucial for their environmental and human risk assessment. In this study, the aggregation and stability of polystyrene (PS) NPs were investigated under different hydrochemical conditions such as pH, salt type (NaCl, CaCl₂, Na₂SO₄), ionic strength (IS), and natural organic matter (NOM). The critical coagulation concentrations of PS NPs were determined to be 158.7 mM NaCl, 12.2 mM CaCl₂, and 80.0 mM Na₂SO₄. Ca²⁺ was more effective in destabilizing PS NPs, compared to Na⁺, owing to its stronger charge screening effect. In the presence of monovalent ions, NOM reduced aggregation through steric repulsion, whereas in the case of divalent ions, NOM induced aggregation through cation bridging. Initial and long-term stability studies demonstrated that, in waters with high IS and NOM content, NOM was the most significant factor affecting NPs aggregation. PS NPs would be highly suspended in all freshwaters, and even in wastewater, whereas they would aggregate rapidly and deposit in seawater. Finally, a statistical model was established to evaluate the hydrodynamic diameter of NPs in different waters. The results indicated the stability of PS NPs in natural aquatic environments and their potential for long-term transport.

Wastewater containg proteinaceous ossein effluents are problematic to be treated. We studied the possibility to treat ossein effluents with the marine cyanobacterium strain Cylindrospermum stagnale. After optimizing the culture conditions of the bacterium, three different types of ossein effluents were tested: dicalcium phosphate (DCP), high total dissolved solids (HTDS) and low total dissolved (LTDS). The effluents were diluted with sea water at the following ratios 1:1, 2:1 and 3:2. The optimum operating conditions were at 3000 lux light intensity and 37 °C temperature. The highest degradation of ossein effluens by C. stagnale was attained for a dilution ratio of 1:1. However, less diluted ossein effluents reduced the growth of C. stagnale drastically. The degradation was shown by measuring the chlorophyll a content and the dry weight of bacterial cells during a seven-day incubation period degradation. Fourier Transform Infrared Spectroscopy (FT-IR) analysis verified the degradation showing the presence of the degradation products of ossein (i.e. calcium carbonate and calcite) in the culture medium. Lipid composition in fatty acids appeared to be suitable for biofuel production. The results showed that the marine cyanobacterium C. stagnale can be used to treat ossein effluents, and at the same time, to produce biofuel in a sustainable way.

Coastal tourist and industrial cities are most likely to have differential effects on the distance dilution of antibiotic resistance genes (ARGs) in an estuary system. This study used high-throughput fluorescence quantitative polymerase chain reaction to identify sediment ARGs in two typical estuaries of coastal tourist and industrial cities (Xiamen and Taizhou) in China. The distance dilution of ARGs and its relationship with key environmental factors were analysed. The results indicated that along the river inlet towards the sea, the distance dilution effect on ARG abundance in estuary sediments of Taizhou was approximately double that in Xiamen, and the macrolide, lincosamide, and streptogramin B (MLSB) and vancomycin genes were replaced by the fluoroquinolone, quinolone, florfenicol, chloramphenicol, and amphenicol (FCA) and β-lactam genes in Taizhou, whereas β-lactam genes succeeded the MLSB and sul genes in Xiamen. The abundance and number of ARGs and mobile genetic elements (MGEs) were positively correlated with the particle size and total organic carbon (TOC) contents of sediments, whereas they were negatively associated with the oxidation and reduction potential (Eₕ) and pH of sediments, as well as the seawater salinity. The sediment particle size (SPZ) was the dominant physicochemical factor affecting the abundance of ARGs (r = 0.826, p < 0.05) and MGEs (r = 0.850, p < 0.01). These findings suggest that although the distance dilution effect on the ARG abundance of estuary sediments of the industrial city is greater than that of the tourist city, the larger SPZ, higher TOC content, and lower salinity, pH, and Eₕ in estuary regions adjacent to the industrial city can more significantly facilitate the proliferation and propagation of ARGs in the sediments.

The occurrence and spatial distribution of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in seawater and surficial sediment samples (N = 19 and 45, respectively) from the South China Sea (SCS) in 2018 were investigated, and the correlation between BFRs and site parameters (total organic carbon, depth, etc.) were assessed by principal component analysis. The concentration ranges of ΣPBDEs in seawater and sediments were 0.90–4.40 ng/L and 0.52–22.67 ng/g dry weight (dw), respectively, while those of ΣNBFRs were 0.49–37.42 ng/L and 0.78–82.29 ng/g dw, respectively. BDE-209 and decabromodiphenyl ethane were the predominant BFRs, accounting for 38.65% and 36.94% in seawater and 26.71% and 68.42% in sediments, respectively. Notably, tris(2,3-dibromopropyl)isocyanurate and 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, seldomly detected in aquatic matrices worldwide, were detected for the first time in the study area, and their relatively high levels and detection frequencies indicate the ubiquitous application of these NBFRs in the Pearl River Delta. Zhuhai and Jiangmen are the main sources of NBFRs in the SCS. Preliminary risk assessment on NBFRs using hazard quotient indicates low to medium risks to marine organisms at some sites. The occurrence of NBFRs in the SCS highlights the prioritization of more toxicological information on these compounds.

Rare earth elements and yttrium (REY) are critical elements for a wide range of applications and consumer products. Their growing extraction and use can potentially lead to REY and anthropogenic-REY chemical complexes (ACC-REY) being released in the marine environment, causing concern regarding their potential effects on organisms and ecosystems. Here, we critically review the scientific knowledge on REY sources (geogenic and anthropogenic), factors affecting REY distribution and transfer in the marine environment, as well as accumulation in- and effects on marine biota. Further, we aim to draw the attention to research gaps that warrant further scientific attention to assess the potential risk posed by anthropogenic REY release. Geochemical processes affecting REY mobilisation from natural sources and factors affecting their distribution and transfer across marine compartments are well established, featuring a high variability dependent on local conditions. There is, however, a research gap with respect to evaluating the environmental distribution and fate of REY from anthropogenic sources, particularly regarding ACC-REY, which can have a high persistence in seawater. In addition, data on organismal uptake, accumulation, organ distribution and effects are scarce and at best fragmentary. Particularly, the effects of ACC-REY at organismal and community levels are, so far, not sufficiently studied. To assess the potential risks caused by anthropogenic REY release there is an urgent need to i) harmonise data reporting to promote comparability across studies and environmental matrices, ii) conduct research on transport, fate and behaviour of ACC-REY vs geogenic REY iii) deepen the knowledge on bioavailability, accumulation and effects of ACC-REY and REY mixtures at organismal and community level, which is essential for risk assessment of anthropogenic REY in marine ecosystems.

The hydrothermal preparation of o-dianisidine and triazine interlinked porous organic polymer and its successive derivatisation via metal infusion (Ni, Cu) under hydrothermal and calcination conditions (700 °C) to yield pristine (ANIPOP-700) and Ni/Cu decorated porous carbon are described here (Ni-ANIPOP-700 and Cu-ANIPOP-700). To confirm their chemical and morphological properties, the as-prepared materials were methodically analyzed using solid state ¹³C and ¹⁵N NMR, X-ray diffraction, Raman spectroscopy, field emission scanning and high resolution transmission electron microscopic techniques, and x-ray photoelectron spectroscopy. Furthermore, the electrocatalytic activities of these electrocatalysts were thoroughly investigated under standard oxygen evolution (OER) and hydrogen evolution reaction (HER) conditions. The results show that all of the materials demonstrated significant activity in water splitting as well as displayed excellent stability (22 h) in both acidic (HER) and basic conditions (OER). Among the electrocatalysts reported in this study, Ni-ANIPOP-700 exhibited a lower overpotential η₁₀ of 300 mV in basic medium (OER) and 150 mV in acidic medium (HER), as well as a lower Tafel slope of 69 mV/dec (OER) and 181 mV/dec (HER), indicating 30% lower energy requirement for overall water splitting. Gas chromatography was used to examine the electrolyzed products.

Bivalves are useful bioindicators of microplastic contamination in the marine environment for several reasons, such as extensive filter feeding activity, broad geographical distribution, and limited movement capability. This study conducted a nationwide monitoring of microplastic pollution along the Korean coasts using filter-feeding bivalves (including oyster, mussel, and Manila clam) as bioindicators to identify the national contamination level and characteristics of microplastics. Seawater sample was collected from the same sampling stations of oyster and mussel for comparison. Microplastics were widely distributed in both coastal bivalves and waters with mean concentrations of 0.33 ± 0.23 n/g (1.21 ± 0.68 n/individual) in oyster/mussel, 0.43 ± 0.32 n/g (2.19 ± 1.20 n/individual) in Manila clam, and 1400 ± 560 n/m³ in seawater. Despite the lack of significant relationship in the abundance of microplastics, their dominant features such as size, shape, color and polymer type were similar between bivalves and seawater. Fragments (69% for oyster/mussel, 72% for Manila clam, and 77% for seawater), particles smaller than 300 μm (96% for oyster/mussel, 83% for Manila clam, and 84% for seawater) and colorless (79% for oyster/mussel, 85% for Manila clam, 75% for seawater) were the dominant shape, size and color, respectively. The major polymer types were polypropylene, polyethylene, and polyester. The microplastic level in bivalves was relatively high in urbanized areas with a wide diversity of polymer types compared with those in non-urbanized areas, and the proportion of polystyrene in the Korean samples was abundant compared with other regions due to wide use of polystyrene products in Korea. Our result suggests that microplastic contamination is widespread in the Korean coastal environment, and bivalves can reflect the microplastic pollution characteristics of the surrounding waters where they live.

The International Maritime Organization (IMO) has gradually applied stricter regulations on the maximum sulphur content permitted in marine fuels and from January 1, 2020, the global fuel sulphur limit was reduced from 3.5% to 0.5%. An attractive option for shipowners is to install exhaust gas cleaning systems, also known as scrubbers, and continue to use high sulphur fuel oil. In the scrubber, the exhausts are led through a fine spray of water, in which sulphur oxides are easily dissolved. The process results in large volumes of acidic discharge water, but while regulations are focused on sulphur oxides removal and acidification, other pollutants e.g. polycyclic aromatic hydrocarbons, metals and nitrogen oxides can be transferred from the exhausts to the washwater and discharged to the marine environment. The aim of the current study was to investigate how different treatments of scrubber discharge water (1, 3 and 10%) affect a natural Baltic Sea summer microplanktonic community. To resolve potential contribution of acidification from the total effect of the scrubber discharge water, “pH controls” were included where the pH of natural sea water was reduced to match the scrubber treatments. Biological effects (e.g. microplankton species composition, biovolume and primary productivity) and chemical parameters (e.g. pH and alkalinity) were monitored and analysed during 14 days of exposure. Significant effects were observed in the 3% scrubber treatment, with more than 20% increase in total biovolume of microplankton compared to the control group, and an even greater effect in the 10% scrubber treatment. Group-specific impacts were recorded where diatoms, flagellates incertae sedis, chlorophytes and ciliates increased in biovolume with increasing concentrations of scrubber water while no effect was recorded for cyanobacteria. In contrast, these effects was not observed in the “pH controls”, a suggestion that other parameters/stressors in the scrubber water were responsible for the observed effects.

In this study, water and sediment samples from the Jiaozhou Bay and surrounding rivers were collected to analyze the seasonal occurrence and allocation of 12 organophosphate esters (OPEs) and the associated ecological risk. The higher contamination of OPEs in the adjacent rivers indicated the impact of terrestrial input. Tris(1-chloropropan-2-yl) phosphate (TCIPP) was the predominant OPE in the four environmental sample groups investigated. The spatial distribution of OPEs in seawater varied greatly seasonally and was mainly affected by terrestrial input, with OPEs being redistributed under the influence of tidal currents. The partition coefficients (log Kₒc) of the OPEs were calculated, and their strong correlation with the log Kₒw (octanol-water) values suggested that the water-sediment allocation was significantly affected by hydrophobicity. The homologous relationships among the 7 OPEs with detection frequencies greater than 40% were identified by principal component analysis (PCA). The partial least squares regression (PLSR) model explicated that ∑OPEs cycling dynamics and principal controlling factors were dissimilar in the bay versus surrounding rivers. The risk quotient (RQ) faced by typical organisms in seawater and river water indicated that short-term OPEs exposure was safe for green algae, daphnia and fish. The organisms in rivers faced the higher ecological risk of OPEs in spring than in summer and winter. Therefore, the terrestrial transport of OPEs in spring should be controlled.

The high density and viscosity of fuel oil leads to its prolonged persistence in the environment and causes widespread contamination. Dispersants with a low environmental impact are necessary for fuel oil spill remediation. This study aimed to formulate bio-based dispersants by mixing anionic biosurfactant (lipopeptides from Bacillus subtilis GY19) with nonionic oleochemical surfactant (Dehydol LS7TH). The synergistic effect of the anionic-nonionic surfactant mixture produced a Winsor Type III microemulsion, which promoted petroleum mobilization. The hydrophilic-lipophilic deviation (HLD) equations for ionic and nonionic surfactant mixtures were compared, and it was found that the ionic equation was applicable for the calculation of lipopeptides and Dehydol LS7TH concentrations. The best formula contained 6.6% w/v lipopeptides and 11.9% w/v Dehydol LS7TH in seawater, and its dispersion effectiveness for bunker fuels A and C was 92% and 78%, respectively. The application of bio-based dispersants in water sources was optimized by Box-Behnken design. The efficiency of the bio-based dispersant was affected by the dispersant-to-oil ratios (DORs) but not by the water salinity. A suitable range of DORs for different oil contamination levels could be identified from the response surface plot. The dispersed fuel oil was further degraded by adding an oil-degrading bacterial consortium to the chemically enhanced water accommodated fractions (CEWAFs). After 7 days of incubation, the concentration of fuel oil was reduced from 3692 mg/L to 356 mg/L (88% removal efficiency). On the other hand, the abiotic control removed less than 40% fuel oil from the CEWAFs. This bio-based dispersant had an efficiency comparable to that of a commercial dispersant. The process of dispersant formulation and optimization could be applied to other surfactant mixtures.