High-latitude invasion and environmental adaptability of the freshwater mussel Limnoperna fortunei in Beijing, China.

The invasive freshwater mussel Limnoperna fortunei (Dunker, 1857) has spread widely throughout Asia and South America, especially via interbasin water diversion and navigation. The middle route of the South-to-North Water Transfer Project (SNWTP), whose terminal is Beijing, has diverted more than 60 billion m3 of water from the Yangtze River Basin to Northern China since December 2014. L. fortunei has spread north to Beijing along the SNWTP, biofouling its channels and tunnels. To determine the status of L. fortunei's invasion in Beijing, we systematically inspected the water bodies receiving southern water, including all branches of the SNWTP, water treatment plants, lakes, reservoirs, and rivers. We measured the densities of adults and veligers of L. fortunei and conducted eDNA analyses of water samples. A generalized linear model and canonical correspondence analysis were adopted to investigate the correlations between environmental (e.g., water temperature, conductivity, pH, total nitrogen, and phosphorus) and biological (e.g., chlorophyll a, plankton density, and community composition) variables and the densities of adults and veligers of L. fortunei. Water temperature is the most important factor in determining the densities of D-shaped and pediveliger veligers, with explanatory variable contributions of 56.2% and 43.9%, respectively. The pH affects the densities of D-shaped, umbonated, and pediveliger veligers. The density of plantigrade veligers is negatively correlated with the conductivity and positively correlated with the concentration of chlorophyll a. Canonical correspondence analysis shows a weak correlation between the dominant phytoplankton taxa and the density of veligers. The densities of D-shaped, umbonated, and pediveliger veligers are positively correlated with the density of small phytoplankton (12.54 ± 4.33 µm), and the density of plantigrade veligers is positively correlated with the density of large (16.12 ± 5.96 µm) phytoplankton. The density of planktonic veligers is well correlated with local abiotic variables, and that of plantigrade veligers is less correlated with local abiotic variables. This finding implies that controlling early-stage veligers by altering water temperature, pH, and food size might effectively control the establishment of further L. fortunei colonies.

Decoding Adverse Effects of Organic Contaminants in the Aquatic Environment: A Meta-analysis of Species Sensitivity, Hazard Prediction, and Ecological Risk Assessment.

Aquatic organisms in the environment are frequently exposed to a variety of organic chemicals, while these biological species may show different sensitivities to different chemical groups present in the environment. This study evaluated species sensitivity, hazards, and risks of six classes of organic chemicals in the aquatic environment. None of the taxonomic groups were the most sensitive or tolerant to all chemicals, as one group sensitive to one class of chemicals might possess adaptations to other chemical groups. Polychlorinated biphenyls were generally the most toxic chemical group, followed by polybrominated diphenyl ethers, polycyclic aromatic hydrocarbons, and pharmaceuticals and personal care products, while per- and polyfluoroalkyl substances and phthalate esters were the less toxic chemical groups. The hazard of organic chemicals was closely related to their physicochemical properties, including hydrophobicity and molecular weight. It was shown that 20% of the evaluated chemicals exhibited medium or high ecological risks with the worst-case scenario in the Pearl River Estuary. This novel work represented a comprehensive comparison of chemical hazards and species sensitivity among different classes of organic chemicals, and the reported results herein have provided scientific evidence for ecological risk assessment and water quality management to protect aquatic ecosystems against organic chemicals.

Genome-Centric Metagenomics Insights into the Plastisphere-Driven Natural Degradation Characteristics and Mechanism of Biodegradable Plastics in Aquatic Environments.

Biodegradable plastics (BPs) are pervasively available as alternatives to traditional plastics, but their natural degradation characteristics and microbial-driven degradation mechanisms are poorly understood, especially in aquatic environments, the primary sink of plastic debris. Herein, the three-month dynamic degradation process of BPs (the copolymer of poly(butylene adipate-co-terephthalate) and polylactic acid (PLA) (PBAT/PLA) and single PLA) in a natural aquatic environment was investigated, with nonbiodegradable plastics polyvinyl chloride, polypropylene, and polystyrene as controls. PBAT/PLA showed the weight loss of 47.4% at 50 days and severe fragmentation within two months, but no significant decay for other plastics. The significant increase in the specific surface area and roughness and the weakening of hydrophobicity within the first month promoted microbial attachment to the PBAT/PLA surface. Then, a complete microbial succession occurred, including biofilm formation, maturation, and dispersion. Metagenomic analysis indicated that plastispheres selectively enriched degraders. Based on the functional genes involved in BPs degradation, a total of 16 high-quality metagenome-assembled genomes of degraders (mainly Burkholderiaceae) were recovered from the PBAT/PLA plastisphere. These microbes showed the greatest degrading potential at the biofilm maturation stage and executed the functions by PLA_depolymerase, polyesterase, hydrolase, and esterase. These findings will enhance understanding of BPs' environmental behavior and microbial roles on plastic degradation.

Combined pollution of tetracyclines and microplastics in the aquatic environment: insights into the occurrence, interaction mechanisms and effects.

Tetracyclines, a widely used class of antibiotics, and synthetic plastic products are both prevalent in the environment. When released into water bodies, these pollutants can pose significant risks due to their daily influx into aquatic ecosystems. Microplastics can adsorb tetracyclines, acting as a transport vector that enhances their impact on aquatic species. Understanding the co-exposure effects of microplastics and tetracyclines is crucial. This review comprehensively examines the occurrence and distribution of microplastics and tetracyclines across various environmental contexts. The interactions between these two contaminants are primarily driven by electrostatic interactions, hydrophobic effects, hydrogen bonding, π-π interactions, and others. Factors such as the presence of heavy metals, ions, and dissolved organic matter can influence the adsorption and desorption of tetracyclines onto microplastics. The stability of microplastic-tetracycline complexes is highly dependent on pH conditions. The combined pollution tetracyclines and microplastics leads to negative impacts on marine species. Future research should focus on understanding the adsorption behavior of tetracyclines on microplastics and developing effective treatment techniques for these contaminants in aquatic environments.

Occurrence and characterization of plasmid-encoded qnr genes in quinolone-resistant bacteria across diverse aquatic environments in southern Ontario.

Antimicrobial resistance is an ever-increasing threat. The widespread usage of ciprofloxacin has led to the manifestation of resistance due to chromosomal mutations or the acquisition of plasmid-mediated quinolone resistance (PMQR) traits. Some particular PMQR traits, qnr genes, have been identified globally in clinical and environmental isolates. This study aimed to determine the prevalence of ciprofloxacin-resistant bacteria in aquatic environments in southern Ontario and investigate the extent of dissemination of ciprofloxacin resistance traits among the bacterial communities. We surveyed the prevalence of plasmid encoding qnr genes using a multiplex PCR assay of associated PMQR genes, qnrA, qnrB, and qnrS, on 202 isolates. Despite the absence of significant impacts on minimum inhibitory concentration levels, the presence of qnr genes correlates with heightened resistance to quinolones and nalidixic acid in some isolates. Taxonomic analysis highlights distinct differences in the composition and diversity of ciprofloxacin-sensitive (CipS) and ciprofloxacin-resistant (CipR) populations, with Proteobacteria dominating both groups. Importantly, CipR populations exhibit lower genetic diversity but higher prevalence of multiple antibiotic resistances, suggesting co-selection mechanisms. Co-occurrence analysis highlights significant associations between ciprofloxacin resistance and other antibiotic resistances, implicating complex genetic linkages. The results of our study signified the critical role of environmental monitoring in public health.

Effects of biochar on the manganese enrichment and oxidation by a microalga Scenedesmus quadricauda in the aquatic environment.

Microalgae play a significant impact in the biogeochemical cycle of Mn(II) in the aquatic ecosystem. Meanwhile, the inflow of biochar into the water bodies is bound to impact the aquatic organisms. However, the influence of biochar on the manganese transformation in algae-rich water has not drawn much attention. Thus, we studied the effects of rice straw biochar on manganese enrichment and oxidation by a common type of algae in freshwater (Scenedesmus quadricauda). The results showed that Mn(II) was absorbed intracellularly and adsorbed extracellularly by active algal cells. A significant portion of enriched Mn(II) was oxidized to amorphous precipitates MnO2, MnOOH, and Mn2O3. Moreover, the extracellular bound Mn(II) content in the coexistent system of algae and biochar increased compared with the pure Scenedesmus quadricauda system. Nevertheless, the intracellular Mn content was continually lowered as the biochar dose rose from an initial 0.2 to 2.0 g·L-1, suggesting that Mn assimilation of the cell was suppressed. It was calculated that the total enrichment ability of Scenedesmus quadricauda in the algae-biochar coexistent system was 0.31- 15.32 mg Mn/g biomass, more than that in the pure algae system. More importantly, with biochar in the algae system, the amount of generated MnOx increased, and more Mn(II) was oxidized into highly-charged Mn(IV). This was probably because the biochar could relieve the stress of massive Mn(II) on algae and support the MnOx precipitates. In brief, moderate biochar promoted the Mn(II) accumulation by algal cells and its oxidation activity. This study offers deeper insight into the bioconversion of Mn(II) by algae and the potential impact of biochar application to the aquatic system.

Fluoroquinolone antibiotics in the aquatic environment: environmental distribution, the research status and eco-toxicity.

The increasing presence of fluoroquinolone (FQ) antibiotics in aquatic environments is a growing concern due to their widespread use, negatively impacting aquatic organisms. This paper provides an overview of the environmental distribution, sources, fate, and both single and mixed toxicity of FQ antibiotics in aquatic environments. It also examines the accumulation of FQ antibiotics in aquatic organisms and their transfer into the human body through the food chain. The study identifies critical factors such as metabolism characteristics, physiochemical characteristics, light, temperature, dissolved oxygen, and environmental compatibility that influence the presence of FQ antibiotics in aquatic environments. Mixed pollutants of FQ antibiotics pose significant risks to the ecological environment. Additionally, the paper critically discusses advanced treatment technologies designed to remove FQ antibiotics from wastewater, focusing on advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs). The discussion also includes the benefits and limitations of these technologies in degrading FQ antibiotics in wastewater treatment plants. The paper concludes by proposing new approaches for regulating and controlling FQ antibiotics to aid in the development of ecological protection measures.

A nanogold sensor test for tire wear chemicals based on the plasmon ruler approach.

The release of tire wear substances in the environment is raising concerns about potential impacts on aquatic ecosystems. The purpose of this study was to develop a quick and inexpensive screening test for the following tire wear substances: 6-phenylphenyldiamine quinone (6-PPD quinone), hexamethoxymethylmelamine (HMMM), 1-3-diphenylguanidine (1,3-DPG), and melamine. A dual strategy consisting of nanogold (nAu) signal intensity and the plasmonic ruler principle was used based on the spectral shift from the unaggregated free-form nAu from 525 nm to aggregated nAu at higher wavelengths. The shift in resonance corresponded to the relative sizes of the tire wear substances at the surface of nAu: 6-PPD (560 nm), HMMM (590 nm), 1,3-DPG (620 nm), and melamine (660 nm) in a concentration-dependent manner. When present in mixtures, a large indiscriminate band between 550 and 660 nm with a maximum corresponding to the mean intermolecular distance of 0.43 nm from the tested individual substances suggests that all compounds indiscriminately interacted at the surface of nAu. An internal calibration methodology was developed for mixtures and biological extracts from mussels and biofilms and revealed a proportional increase in absorbance at the corresponding resonance line for each test compound. Application of this simple and quick methodology revealed the increased presence of melamine and HMMM compounds in mussels and biofilms collected at urban sites (downstream city, road runoffs), respectively. The data also showed that treated municipal effluent decreased somewhat melamine levels in mussels.

Interaction between Haematococcus pluvialis microalgae and lead nitrate: lead adsorption from water.

Our study aims to investigate the response of the unicellular alga, Haematococcus pluvialis, to the toxicity of lead and propose a low-cost, highly efficient biological adsorbent for the purification of wastewater and lead-contaminated water. The first part examines the effects of lead toxicity on certain physiological indicators of this alga. In the second part, the potential of this alga in lead removal and its adsorption capacity was assessed. The alga was cultivated in a BG11 medium and treated with lead nitrate concentrations of 10, 50, and 200 mg/L during its exponential growth. The results showed that with an increase in lead concentration up to 200 mg/L, the growth rate, chlorophyll a, chlorophyll b, carotenoid and total protein content decreased, while malondialdehyde (MDA) content increased. The astaxanthin content slightly increased at the 10 mg/L but decreased at the 200 mg/L treatment. Maximum lead adsorption was observed at 98.69% under optimal conditions, including a pH of 6, an adsorbent dose of 1 g/L, a lead concentration of 25 mg/L, a temperature of 25 °C, and an exposure time of 120 min. The results of this study demonstrate that Haematococcus pluvialis has the potential for effective lead removal from aquatic environments.

While the influence of heavy metals on certain algae species has been explored, research on the impact of lead on Haematococcus pluvialis­a microalga of significant interest for astaxanthin production­remains uncharted territory. Therefore, understanding the impact of this heavy metal and the alga's metal absorption capabilities has profound implications for biotechnology and bioremediation applications. This study promotes H. pluvialis as an economically viable lead absorbent suitable for both industrial and domestic purposes.

Visualization and characterisation of microplastics in aquatic environment using a home-built micro-Raman spectroscopic set up.

Microplastics (MP) which are tiny plastic particles of sizes range from 1 µm (µm) to 5 mm (mm), have become a growing cause of concern due to their widespread presence in the environment and their potential impacts on ecosystems and human health. Marine organisms have the potential to consume microplastics, which could lead to physical injuries, blockages, or the transfer of harmful substances up the food chain. Humans may indirectly consume microplastics through contaminated seafood and water, although the complete scope of health risks is currently under investigation. An essential step in gaining a comprehensive understanding of microplastic pollution in waterbodies is the identification of microplastics, which is also crucial for further development of effective environmental regulations to address its adverse impacts. Majority of the researchers are accomplishing it globally using commercial platforms based on Raman spectroscopy. However, the development of indigenous Raman systems, which can enable microplastic identification, particularly in developing nations, is the need of the hour due to the outrageous cost of commercial platforms. In the current study, a custom-designed micro-Raman spectroscopy system was developed to detect and characterize microplastics from waterbodies. The developed system enabled visualization, size measurement and characterization of microplastics. Experimental parameters were fine-tuned, and a standardized Raman database was established for each type of plastic. This system exhibited high resolution which was capable of analysing microparticles of size up to 5 µm. Principal component analysis was carried out on the experimental Raman data, demonstrating good classification amongst different kinds of plastics. The performance of the developed system in analysing real samples was evaluated through experiments conducted on water samples obtained from the shore of Malpe Beach in Udupi district. The results revealed the presence of polyethylene and polyethylene terephthalate in the samples, along with the detection of pigments like copper phthalocyanine and indigo blue.

Microbiome and network analysis reveal potential mechanisms underlying Carassius auratus diseases: The interactions between critical environmental and microbial factors.

Despite the rapid development of research on aquatic environment microbiota, limited attention has been paid to exploring the complex interactions between microbial communities and aquatic environments. Particularly, the mechanisms underlying fish diseases based on such dynamic interactions remain unknown. This study aimed to address the gap by conducting microbiome and co-occurrence network analyses on the typical freshwater aquaculture systems. High-throughput 16S rRNA gene sequencing results revealed significant differences in the microbiota between the disease and healthy groups. Notably, disease mortality varied consistently with the gradient of relative abundance of Proteobacteria (intestine, R2 = 0.46, p < 0.05) and Cyanobacteria (gill, R2 = 0.67, p < 0.01), indicating their potential use as diagnostic criteria. Furthermore, the elevated hepatosomatic index, NO3-N, COD and TC (sediment) were directly correlated with diseases (r > 0.54, p < 0.01). Mean concentrations of NO3-N, COD and TC were elevated by 78.87%, 25.63% and 44.2%, respectively, in ponds where diseases occurred. Quantitative analysis (qPCR) revealed that Aeromonas sobria infected hosts through a potential pathway of "sediment (4.4 × 105 copy number/g)-water (1.1 × 103 copy number/mL)-intestine (1.2 × 106 copy number/g)". Similarly, the potential route for Aeromonas veronii was sediment (4.9 × 106 copy number/g) to gill (5.1 × 105 copy number/g). Additionally, the complexity of microbial networks in the intestine, water, and sediment was significantly lower in the disease group, although no similar phenomenon was observed in the gill microbial network. In summary, these findings reveal that elevated concentrations of crucial environmental factors disrupt the linkages within microbiota, fostering the growth of opportunistic bacteria capable of colonizing fish gut or gills. This offers new insights into potential mechanisms by which environmental factors cause disease in fish.

Exploring the advantages and limitations of degradation for various biodegradable micro-bioplastic in aquatic environments.

Biodegradable plastics are being the substitute for synthetic plastics and widely been used in order to combat plastic pollution. Yet not all biodegradable plastics are degradable especially when it does not meet its favourable conditions, and also when it comes to aquatic environments. Therefore, this review is intended to highlight the types of various biodegradable plastic synthesized and commercialised and identify the limitations and advantages of these micro-bioplastics or residual bioplastic upon degradation in various aquatic environments. This review paper highlights on biodegradable plastic, degradation of biodegradable plastic in aquatic environments, application of biodegradable plastic, polylactic acid (PLA), Polyhydroxyalkanoates (PHA), Polysaccharide derivatives, Poly (amino acid), polycaprolactone (PCL), polybutylene succinate (PBS), polybutylene adipate terephthalate (PBA/T), limitations and advantages of biodegradable plastic degradation in aquatic environment. There is no limit on the period for literature search as this field is continuously being studied and there is no wide range of studies. Biodegradable plastic that is commercially available has its own advantages and limitations respectively upon degradation in both freshwater and marine environments. There is a growing demand for bioplastic as an alternative to synthetic plastic which causes plastic waste pollution. Thus, it is crucial to understand the biodegradation of biodegradable plastic in depth especially in aquatic environments. Moreover, there are also very few studies investigating the degradation and migration of micro-bioplastics in aquatic environments.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water and edible fish species of Karun River, Ahvaz, Iran: spatial distribution, human health, and ecological risk assessment.

Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are environmental contaminants with unfavorable impacts on human health and nature. This study aimed to determine the PFOA and PFOS concentration in water and fish samples from Karun, the largest river in Iran. According to the results, the PFOA and PFOS in water samples were 5.81-69.26 ng/L and not detected (n.d.)-35.12 ng/L, respectively. The dry season displayed higher concentrations in water samples than in the wet season. The maximum PFOS concentration measured was related to Barbus barbules sp. (27.89 ng/g). The human health risk assessment indicated minor risks (hazard ratio, HR < 1) from PFOA and PFOS through consuming contaminated drinking water and fish. Only HR value of PFOS in downstream area exceeded slightly 1.0, indicating potential health risk due to consumption of the river fish. Considering the average PFASs concentration, the risk quotients (RQs) showed low ecological risk.

A review of microplastics in wastewater treatment plants in Türkiye: Characteristics, removal efficiency, mitigation strategies for microplastic pollution and future perspective.

The effluent of WWTPs is an important source of microplastics (MP) for the aquatic environment. In this review study, MPs in wastewater treatment plants (WWTP) in Türkiye and their removal from WWTPs are reviewed for the first time. First, MP characteristics in the influent and effluent of WWTPs in Türkiye are discussed. In the next section, the abundance of MPs in the influent and effluent of WWTPs in Türkiye and the MP removal efficiency of WWTPs in Türkiye are evaluated. Then, the results of studies on MP abundance and characteristics in Türkiye's aquatic environments are presented and suggestions are made to reduce MPs released from WWTPs into the receiving environments. Strategies for reducing MPs released to the receiving environment from WWTPs of Türkiye are summarized. In the last section, research gaps regarding MPs in WWTPs in Türkiye are identified and suggestions are made for future studies. This review paper provides a comprehensive assessment of the abundance, dominant characteristics, and removal of MPs in WWTPs in Türkiye, as well as the current status and deficiencies in Türkiye. Therefore, this review can serve as a scientific guide to improve the MP removal efficiency of WWTPs in Türkiye.

An improved method for isotopic and quantitative analysis of dissolved organic carbon in natural water samples.

A wet chemical oxidation (WCO) method has been widely used to obtain the dissolved organic carbon (DOC) content and carbon isotope (δ13CDOC) ratios. However, it is sometimes difficult to get high precision results because not enough CO2 was oxidized from the natural water samples with low DOC concentrations. This improvement primarily aims to increase the water sample volume, improve the removal rate of dissolved inorganic carbon (DIC), and minimize the blank DOC from the standard solution. Following the improved procedure, the δ13C ratios of standardized DOC solutions were consistent with their actual values, and their differences were less than 0.2‰. The improved method demonstrated good accuracy and stability when applied to natural water samples with DOC concentrations ≥0.5 mg L-1, with the precisions of DOC concentrations and δ13C ratios were better than 0.07 mg L-1 and 0.1‰, respectively. More importantly, this method saved much pre-treatment time and realized batch processing of water samples to obtain their DOC contents and isotope ratios.

Advances in perfluoro-alkylated compounds (PFAS) detection in seafood and marine environments: A comprehensive review on analytical techniques and global regulations.

Per- and poly-fluoroalkyl substances (PFAS) are persistent organic pollutants that severely threaten the environment and human health due to their distinct chemical composition, extensive production, widespread distribution, bioaccumulation in nature, and long-term persistence. This review focuses on the occurrence and sources of PFAS in seafood, with a particular emphasis on advanced detection methods viz. nanoparticle-based, biosensor-based, and metal-organic frameworks-based, and mass spectrometric techniques. The challenges associated with these advanced detection technologies are also discussed. Recent research and regulatory updates about PFAS, including hazardous and potential health effects, epidemiological studies, and various risk assessment models, have been reviewed. In addition, the need for global monitoring programs and regulations on PFAS are critically reviewed by underscoring their crucial role in protecting human health and the environment. Further, approaches for reducing PFAS in seafood are highlighted with future innovative remediation directions. Although advanced PFAS analytical methods are available, selectivity, sample preparation, and sensitivity are still significant challenges associated with detection of PFAS in seafood matrices.  Moreover, crucial research gaps and solutions to essential concerns are critically explored in this review.

Design and application of a novel culturing chip (cChip) for culturing the uncultured aquatic microorganisms.

Culturing uncultured microorganisms is an important aspect of microbiology. Once cultured, these microorganisms can be a source of useful antibiotics, enzymes etc. In this study, we have designed a novel culturing chip (cChip) to facilitate the growth of uncultured aquatic bacterial community by concentrating the samples. cChip was optimized for microbial growth using known bacteria in the laboratory as a pre-experiment. Then microorganisms from a freshwater lake were concentrated and inoculated, before putting the inoculated cChip in a simulated lake environment and further sub-culturing on laboratory media. High-throughput sequencing and traditional culturing were also performed for comparison. These three methods were able to detect 265 genera of microorganisms in the sample, of which 78.87% were detected by high-throughput sequencing, 30.94% by cChip, while only 6.42% were obtained by traditional culture. Moreover, all microorganisms obtained by traditional culture were also cultured using the cChip. A total of 45 new strains were isolated from the cChip, and their 16S rRNA gene sequences were 91.35% to 98.7% similar to their closest relatives according to NCBI GenBank database. We conclude that the design and simple operation of cChip can improve the culture efficiency of traditional culture by almost 5 times. To the best of our knowledge, this is the first report comparing a novel culturing method with high-throughput sequencing data and traditional culturing of the same samples.

Using a Multi-isotope Approach and Isotope Mixing Models to Trace and Quantify Phosphorus Sources in the Tuojiang River, Southwest China.

Identifying phosphorus (P) sources is critical for solving eutrophication and controlling P in aquatic environments. Phosphate oxygen isotopes (δ18Op) have been used to trace P sources. However, the application of this method has been greatly restricted due to δ18OP values from the potential source having wide and overlapping ranges. In this research, P sources were traced by combining δ18Op with multiple stable isotopes of nitrogen (δ15N), hydrogen (δD), and dissolved inorganic carbon (δ13C). Then, a Bayesian-based Stable Isotope Analysis in R (SIAR) model and IsoSource model were used to estimate the proportional contributions of the potential sources in the Tuojiang River. δ18Op was not in equilibrium with ambient water, and statistically significant differences in the δ18Op values were found between the potential sources, indicating that δ18Op can be used to trace the P sources. δ15N, δD, and δ13C could assist δ18Op in identifying the main sources of P. The SIAR and IsoSource models suggested that industrial and domestic sewage was the largest contributor, followed by phosphate rock and phosphogypsum and agricultural sewage. The uncertainty of the calculation results of the SIAR model was lower than that of the IsoSource model. These findings provide new insights into tracing P sources using multiple stable isotopes in watersheds.

Deep-Learning-Based Automated Tracking and Counting of Living Plankton in Natural Aquatic Environments.

Plankton are widely distributed in the aquatic environment and serve as an indicator of water quality. Monitoring the spatiotemporal variation in plankton is an efficient approach to forewarning environmental risks. However, conventional microscopy counting is time-consuming and laborious, hindering the application of plankton statistics for environmental monitoring. In this work, an automated video-oriented plankton tracking workflow (AVPTW) based on deep learning is proposed for continuous monitoring of living plankton abundance in aquatic environments. With automatic video acquisition, background calibration, detection, tracking, correction, and statistics, various types of moving zooplankton and phytoplankton were counted at a time scale. The accuracy of AVPTW was validated with conventional counting via microscopy. Since AVPTW is only sensitive to mobile plankton, the temperature- and wastewater-discharge-induced plankton population variations were monitored online, demonstrating the sensitivity of AVPTW to environmental changes. The robustness of AVPTW was also confirmed with natural water samples from a contaminated river and an uncontaminated lake. Notably, automated workflows are essential for generating large amounts of data, which are a prerequisite for available data set construction and subsequent data mining. Furthermore, data-driven approaches based on deep learning pave a novel way for long-term online environmental monitoring and elucidating the correlation underlying environmental indicators. This work provides a replicable paradigm to combine imaging devices with deep-learning algorithms for environmental monitoring.

Effect of Mass Fraction on Leaching Kinetics of Hydrophobic Ultraviolet Stabilizers in Low-Density Polyethylene.

The leaching kinetics of five hydrophobic ultraviolet (UV) stabilizers from low-density polyethylene (LDPE) (micro)fibers into water was evaluated in this study, with variation of the mass fraction (ω = 0.1-2.0 wt %) of the stabilizers. A one-dimensional convection-diffusion model for a cylindrical geometry, requiring partitioning between the LDPE fibers and water (KLDPEw) and the internal diffusion coefficients (DLDPE), was used to evaluate the leaching process and the leaching half-life of the target UV stabilizers at ω < 0.5 wt % (Case I). Diffusion through the aqueous boundary layer is the rate-determining step, and the leaching half-life is predicted to be very long (a few months to years) under unaffected conditions. When the UV stabilizers are supersaturated within LDPE fibers (i.e., ω > 0.5 wt %, Case II), the possible formation of a surficial crystal layer of the additives on the LDPE fiber extends the time scale for leaching compared to that in Case I due to the requirement of overcoming the crystallization energy. This study provides a fundamental understanding of the leaching profiles of plastic additives for assessing their potential chemical risks in aquatic environments; further studies under the relevant environmental conditions are required.