Dearomatization drives complexity generation in freshwater organic matter.

Dissolved organic matter (DOM) is one of the most complex, dynamic and abundant sources of organic carbon, but its chemical reactivity remains uncertain1-3. Greater insights into DOM structural features could facilitate understanding its synthesis, turnover and processing in the global carbon cycle4,5. Here we use complementary multiplicity-edited 13C nuclear magnetic resonance (NMR) spectra to quantify key substructures assembling the carbon skeletons of DOM from four main Amazon rivers and two mid-size Swedish boreal lakes. We find that one type of reaction mechanism, oxidative dearomatization (ODA), widely used in organic synthetic chemistry to create natural product scaffolds6-10, is probably a key driver for generating structural diversity during processing of DOM that are rich in suitable polyphenolic precursor molecules. Our data suggest a high abundance of tetrahedral quaternary carbons bound to one oxygen and three carbon atoms (OCqC3 units). These units are rare in common biomolecules but could be readily produced by ODA of lignin-derived and tannin-derived polyphenols. Tautomerization of (poly)phenols by ODA creates non-planar cyclohexadienones, which are subject to immediate and parallel cycloadditions. This combination leads to a proliferation of structural diversity of DOM compounds from early stages of DOM processing, with an increase in oxygenated aliphatic structures. Overall, we propose that ODA is a key reaction mechanism for complexity acceleration in the processing of DOM molecules, creation of new oxygenated aliphatic molecules and that it could be prevalent in nature.

Plastic debris in lakes and reservoirs.

Plastic debris is thought to be widespread in freshwater ecosystems globally1. However, a lack of comprehensive and comparable data makes rigorous assessment of its distribution challenging2,3. Here we present a standardized cross-national survey that assesses the abundance and type of plastic debris (>250 µm) in freshwater ecosystems. We sample surface waters of 38 lakes and reservoirs, distributed across gradients of geographical position and limnological attributes, with the aim to identify factors associated with an increased observation of plastics. We find plastic debris in all studied lakes and reservoirs, suggesting that these ecosystems play a key role in the plastic-pollution cycle. Our results indicate that two types of lakes are particularly vulnerable to plastic contamination: lakes and reservoirs in densely populated and urbanized areas and large lakes and reservoirs with elevated deposition areas, long water-retention times and high levels of anthropogenic influence. Plastic concentrations vary widely among lakes; in the most polluted, concentrations reach or even exceed those reported in the subtropical oceanic gyres, marine areas collecting large amounts of debris4. Our findings highlight the importance of including lakes and reservoirs when addressing plastic pollution, in the context of pollution management and for the continued provision of lake ecosystem services.

Size Distributions of Microplastics in the St Louis Estuary and Western Lake Superior.

Identifying the sources and fate of microplastics in natural systems has garnered a great deal of attention because of their implications for ecosystem health. This work characterizes the size fraction, morphology, color, and polymer composition of microplastics in western Lake Superior and its adjacent harbor sampled in August and September 2021. The results reveal that the overall microplastic counts are similar, with the harbor stations ranging from 0.62 to 3.32 microplastics per liter and the lake stations ranged from 0.83 to 1.4 microplastics per liter. However, meaningful differences between the sample locations can be seen in the size fraction trends and polymer composition. Namely, the harbor samples had relatively larger amounts of the largest size fraction and more diversity of polymer types, which can be attributed to the urbanized activity and shorter water residence time. Power law size distribution modeling reveals deviations that help in the understanding of potential sources and removal mechanisms, although it significantly underpredicts microplastic counts for smaller-sized particles (5-45 µm), as determined by comparison with concurrently collected microplastic samples enumerated by Nile Red staining and flow cytometry.

Unveiling microplastics pollution in a subtropical rural recreational lake: A novel insight.

While global attention has been primarily focused on the occurrence and persistence of microplastics (MP) in urban lakes, relatively little attention has been paid to the problem of MP pollution in rural recreational lakes. This pioneering study aims to shed light on MP size, composition, abundance, spatial distribution, and contributing factors in a rural recreational lake, 'Nikli Lake' in Kishoreganj, Bangladesh. Using density separation, MPs were extracted from 30 water and 30 sediment samples taken from ten different locations in the lake. Subsequent characterization was carried out using a combination of techniques, including a stereomicroscope, Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM). The results showed a significant prevalence of MPs in all samples, with an average amount of 109.667 ± 10.892 pieces/kg3 (dw) in the sediment and 98.167 ± 12.849 pieces/m3 in the water. Small MPs (<0.5 mm), fragments and transparent colored particles formed the majority, accounting for 80.2%, 64.5% and 55.3% in water and 78.9%, 66.4% and 64.3% in sediment, respectively. In line with global trends, polypropylene (PP) (53%) and polyethylene (PE) (43%) emerged as the predominant polymers within the MPs. MP contents in water and sediment showed positive correlations with outflow, while they correlated negatively with inflow and lake depth (p > 0.05). Local activities such as the discharge of domestic sewage, fishing waste and agricultural runoff significantly influence the distribution of polypropylene. Assessment of pollution factor, pollution risk index and pollution load index values at the sampling sites confirmed the presence of MPs, with values above 1. This study is a baseline database that provides a comprehensive understanding of MP pollution in the freshwater ecosystem of Bangladesh, particularly in a rural recreational lake. A crucial next step is to explore ecotoxicological mechanisms, legislative measures and future research challenges triggered by MP pollution.

Microplastics increase the microbial functional potential of greenhouse gas emissions and water pollution in a freshwater lake: A metagenomic study.

Aquatic ecosystems are being increasingly polluted by microplastics (MPs), which calls for an understanding of how MPs affect microbially driven biogenic element cycling in water environments. A 28-day incubation experiment was conducted using freshwater lake water added with three polymer types of MPs (i.e., polyethylene, polypropylene, polystyrene) separately or in combination at a concentration of 1 items/L. The effects of various MPs on microbial communities and functional genes related to carbon, nitrogen, phosphorus, and sulfur cycling were analyzed using metagenomics. Results showed that Sphingomonas and Novosphingobium, which were indicator taxa (genus level) in the polyethylene treatment group, made the largest functional contribution to biogenic element cycling. Following the addition of MPs, the relative abundances of genes related to methane oxidation (e.g., hdrD, frhB, accAB) and denitrification (napABC, nirK, norB) increased. These changes were accompanied by increased relative abundances of genes involved in organic phosphorus mineralization (e.g., phoAD) and sulfate reduction (cysHIJ), as well as decreased relative abundances of genes involved in phosphate transport (phnCDE) and the SOX system. Findings of this study underscore that MPs, especially polyethylene, increase the potential of greenhouse gas emissions (CO2, N2O) and water pollution (PO43-, H2S) in freshwater lakes at the functional gene level.

Community structure, environmental conditions and anthropogenic pressure on the habitat of the European endemic aquatic plant Luronium natans (L.) Raf.

Luronium natans (L.) Raf. is a European endemic species and is becoming increasingly rare and endangered in most countries. This study aimed to compare the community structure and environmental conditions of shallow and deep-water habitats of Luronium, and related anthropogenic influences. A total of 21 Luronium lake habitats were surveyed at Pomerania Lakeland (NW Poland). Luronium occurs mainly with other isoetids, as well as bryophytes, specifically Sphagnum denticulatum. It can also be found in oligotrophic lakes at a depth of 1.0 ± 0.6 m and in water with a large pH range (4.52 - 8.76), as well having a low conductivity (38.3 ± 20.9 µS cm-1; 19.0 - 106.1) and calcium concentration (3.9 ± 2.4 mg dm-3; 1.6 - 11,7).The largest Luronium cover occurs at a depth of 1.5 m (44.8 ± 35.3%), but occasionally as deep as 3.5 m. In the depth gradient, the structure of underwater vegetation and environmental conditions exhibit obvious changes, which presents a clear distinction between shallow and deep-water habitats of Luronium. The differences mainly pertain to the abundances of Isoëtes lacustris and Elodea canadensis in the community, as well as environmental factors, such as water calcium, nitrogen and phosphorus concentrations, PAR, conductivity, and water color.Compared to other isoetids, Luronium usually occurs in habitats with intermediate features, which are characterized by values between the typical, but deep-water, Isoëtes and shallow water Lobelia and Littorella. However, Luronium clearly prefers waters with higher temperatures (23.8 ± 2.7 °C), which are thus less oxygenated (96.6 ± 20.0%). In terms of pH, conductivity, and calcium concentration, Luronium occurs in waters having slightly lower values compared to other isoetids. Therefore, Luronium is a species that significantly expands the diversity of habitat number 3110 in the Natura 2000 network. Therefore, it can be considered as an indicator species of lobelia lakes.An increased anthropogenic pressure primarily results in an increased water conductivity and a decreased water transparency. Consequently, Luronium increasingly inhabits shallower waters that are more oxygenated. Moreover, Luronium abundance is decreasing, while the abundances of species comprising underwater communities are also decreasing, e.g., S. denticulatum and I. lacustris, with a concurrent increase in Myriophyllum alterniflorum and E. canadensis cover.

FT-ICR-MS combined with fluorescent spectroscopy reveals the driving mechanism of the spatial variation in molecular composition of DOM in 22 plateau lakes.

Dissolved organic matter (DOM) is the largest carbon pool and directly affects the biogeochemistry in lakes. In the current study, fourier transform ion cyclotron mass spectrometry (FT-ICR-MS) combined with fluorescent spectroscopy was used to assess the molecular composition and driving mechanism of DOM in 22 plateau lakes in Mongolia Plateau Lakes Region (MLR), Qinghai Plateau Lakes Region (QLR) and Tibet Plateau Lakes Region (TLR) of China. The limnic dissolved organic carbon (DOC) content ranged from 3.93 to 280.8 mg L-1 and the values in MLR and TLR were significantly higher than that in QLR. The content of lignin was the highest in each lake and showed a gradually decreasing trend from MLR to TLR. Random forest model and structural equation model implied that altitude played an important role in lignin degradation while the contents of total nitrogen (TN) and chlorophyll a (Chl-a) have a great influence on the increase of DOM Shannon index. Our results also suggested that the inspissation of DOC and the promoted endogenous DOM production caused by the inspissation of nutrient resulted in a positive relationship between limnic DOC content and limnic factors such as salinity, alkalinity and nutrient concentration. From MLR to QLR and TLR, the molecular weight and the number of double bonds gradually decreased but the humification index (HIX) also decreased. In addition, from the MLR to the TLR, the proportion of lignin gradually decreased, while the proportion of lipid gradually increased. Both above results suggested that photodegradation was dominated in lakes of TLR, while microbial degradation was dominated in lakes of MLR.

Occurrence and sources of microplastics in dust of the Ebinur lake Basin, northwest China.

Currently, there is a lack of studies on microplastic pollution in mountain terrains and foothills areas in Northwest China and Central Asia. Here, we collected monthly dusts samples for one year and we studied the distribution, pollution levels, and sources of microplastics in atmospheric dust fall in the Ebinur Lake Basin in Northwest China. Results showed that the average content of dust microplastic on construction land was 28.61 ± 1.13 mg/kg, followed by farmland (20.25 ± 1.56 mg/kg), forest (19.52 ± 1.06 mg/kg), and deserts (8.08 ± 0.56 mg/kg). Regarding different land use types, atmospheric dust reduction dominated on farmland (58.64%), followed by urban area (26.65%), forest (9.76%), and desert (4.95%). Regarding the shape of microplastics, the order of occurrence in dust was film (46.85%) > fiber (35.15%) > foam(12.35%) > fragment (5.65%). In this study, four colors of microplastics were found in dust, and white accounted for the largest proportion (52.15%), followed by transparent (18.65%), black (19.45%), and green (9.75%). The main components of film microplastics in atmospheric dustfall in the Ebinur Lake Basin were PE and PP, and their sources were mainly plastic products in daily life, plastic industrial packaging materials from urban enterprises, broken plastic woven bags, and PET mostly from fabric fragment emissions. The abundance of microplastics in dust was correlated with atmospheric dust pH, EC, and total salt content. The contents of seven heavy metals (Cu, Ni, Cd, Pb, Cr, Mn, and Co) adsorbed by microplastics were also correlated with pH, EC, and total salt content. Our results represent a reference for microplastics pollution prevention in mountain terrains and foothills areas in northwest China and Central Asia.

Changes in Water Chemistry Associated with Rainstorm Events Increase Carbon Emissions from the Inflowing River Mouth of a Major Drinking Water Reservoir.

Large reservoirs are hotspots for carbon emissions, and the continued input and decomposition of terrestrial dissolved organic matter (DOM) from upstream catchments is an important source of carbon emissions. Rainstorm events can cause a surge in DOM input; however, periodic sampling often fails to fully capture the impact of these discrete rainstorm events on carbon emissions. We conducted a set of frequent observations prior to and following a rainstorm event in a major reservoir Lake Qiandao (China; 580 km2) from June to July 2021 to investigate how rainstorms alter water chemistry and CO2 and CH4 emissions. We found that the mean CO2 efflux (FCO2) (13.2 ± 9.3 mmol m-2 d-1) and CH4 efflux (FCH4) (0.12 ± 0.02 mmol m-2 d-1) in the postrainstorm campaign were significantly higher than those in the prerainstorm campaign (-3.8 ± 3.0 and +0.06 ± 0.02 mmol m-2 d-1, respectively). FCO2 and FCH4 increased with increasing nitrogen and phosphorus levels, elevated DOM absorption (a350), specific UV absorbance SUVA254, and terrestrial humic-like fluorescence. Furthermore, FCO2 and FCH4 decreased with increasing chlorophyll-a (Chl-a), dissolved oxygen (DO), and pH. A five-day laboratory anoxic bioincubation experiment further revealed a depletion of terrestrial-DOM concurrent with increased CO2 and CH4 production. We conclude that rainstorms boost the emission of CO2 and CH4 fueled by the surge and decomposition of fresh terrestrially derived biolabile DOM in this and likely many other reservoir's major inflowing river mouths.

Validation and application of diffusive gradient in thin-film (DGT) equipped novel cyclodextrin polymer gels for monitoring endocrine disrupting chemicals (EDCs) and environmental risk assessment in the Taihu lake basin.

Taihu Lake is the most important drinking water source of the major cities in the Yangtze River Delta. The pollution of endocrine disruptors (EDCs)in Taihu Lake has been increasing recently, the accurate determination is an important guide for predicting its health risks and developing appropriate controls. Monitoring organic pollutants in water using the diffusive gradient in thin film technique (DGT) has attracted much attention due to more accuracy and convenience than the grab sampling methods. In this study, a novel cyclodextrin polymer (CDP) synthesized by the simple and green method in water was taken as an adsorbent for the binding gel. Four endocrine-disrupting chemicals (EDCs), bisphenol A (BPA), 17α-ethinylestradiol (EE2), 17ß-estradiol (E2), and estriol (E3), were taken as models to determine the diffusion coefficients (4.68 × 10-6, 3.38 × 10-6, 3.34 × 10-6 and 4.31 × 10-6 cm2/s) and to test the performance of DGT, such as adsorption capacity and deployment time (1-5 day). The assembled CDP-DGT was adopted to determine four EDCs in a simulated water environment (3-9 of pH, 0.001-0.5 M of ionic strength (IS), and dissolved organic matter (DOM) of 0-20 mg/L). The ability of CDP-DGT sampling was verified in the Jiuxiang River and was carried out for a large-scale field application of in situ sampling EDCs in Taihu Lake basin. The results show that the total EDCs concentration range and the estradiol equivalent concentrations (EEQ) in Taihu Lake and its main rivers are 2.78 ng/L to 11.08 ng/L and 2.62 ng/L to 10.91 ng/L, respectively. The risk quotients (RQs) of all sampling sites in the region were greater than 1, indicating that EDCs pose a serious threat to aquatic organisms in the area. Therefore, the monitoring of EDCs in the Taihu Lake basin should be further strengthened.

Vibrational Spectroscopic Analyses and Imaging of the Early Middle Ages Hemp Bast Fibres Recovered from Lake Sediments.

Fourier Transform Infrared (FT-IR) spectroscopy and imaging combined with hierarchical cluster analysis (HCA) was applied to analyse biochemical properties of Early Middle Ages hemp (Cannabis sativa L.) bast fibres collected from lake bottom sediment of lake Slone. The examined plant macrofossil material constitutes residues of the hemp retting process that took place in the 7th-8th century. By comparison of three samples: untreated isolated bast fibres, and fibres incubated overnight at 4 and 37 °C, we were able to mimic the retting conditions. Using FT-IR qualitative and semi-quantitative assessment of the primary polysaccharides content, total protein content, and their spatial distribution was performed within the hemp fibres. The concentration of cellulose remained vastly unchanged, while the concentration of lignin and pectin was the highest in the untreated sample. The spatial distributions of compounds were heterogeneous in the untreated and 4 °C-incubated samples, and homogenous in the specimen processed at 37 °C. Interestingly, a higher amide content was detected in the latter sample indicating the highest degree of enzymatic degradation. In this study, we show that the spectroscopic methods allow for a non-destructive evaluation of biochemical composition of plant fibres without preparation, which can be an appropriate approach for studying ancient plant remains.

Mechanism of biofilm formation on a hydrophobic polytetrafluoroethylene membrane during the purification of surface water using direct contact membrane distillation (DCMD), with especial interest in the feed properties.

The impact of feed water quality on biofilm formation during membrane distillation (MD) was investigated in this study, particularly emphasizing the interrelationship between organics, salts, and microbes. Two types of typical natural surface waters in Nanjing, China, were chosen as feed solutions for long-term MD operation, including the Qinhuai River and Xuanwu Lake. The biofilms that developed under different feed water qualities exhibited distinct Foulant compositions and structures, causing different flux decline trends for the MD system. Accordingly, two typical patterns of biofilm formation were suggested for the MD operation of the two different kinds of surface waters in this study. Organics from a primal feed solution and dead bacteria were the key to the establishment of a biofilm on the membrane, and this needs to be effectively removed from the MD system through pre-treatment and process control strategies. Finally, a feasible strategy for MD biofouling control was suggested.

Comparing microplastics contaminants in (dry and raining) seasons for Ox- Bow Lake in Yenagoa, Nigeria.

The occurrence and distribution of microplastics (MPs) for two seasons (dry and raining) were investigated based on 10 sections of OX- Bow Lake Yenagoa, Nigeria for surface water and sediments. MPs were abundant in colour and dominated by fibrous items. For dry season, Polyethylene terephthalate (PET) and Plasticised polyvinyl chloride (Plasticised PVC) were the predominant MPs; they both account for 72.63% and 10.9% of surface water and sediment samples. The raining season accounted for Plasticised (PVC) 81.5% and low-density polyethylene 4.2% respectively. The raining and dry seasons MPs were characterise by µ-FTIR. Beads and pellets were most common MP shapes in both water and sediment samples for the two seasons. The results showed that there is high presence of MPs in OX -Bow Lake.

Self-contamination from clothing in microplastics research.

Self-contamination should not be underestimated when quantifying microplastics (MPs) in environmental matrices. Standardised and validated methodologies for MP sampling, extraction, and analysis are lacking. The various applications of plastics in our society have made them ubiquitous, even in clothing, rendering MP self-contamination inevitable. In the present study, we sampled lake sediment, snow, and ice, purposefully wearing red overalls composed of cotton; fibres from which we could quantify using Fourier-Transform Infrared Spectroscopy (FTIR), serving as an indication of possible self-contamination from clothes. The suitability of cotton as a representation of MP contamination was also evaluated. For all detected fibres, 25 ± 1%, 20 ± 7%, and 8 ± 6% for snow, ice, and sediment, respectively, originated from sampling attire. These findings demonstrate that self-contamination can play a significant role when quantifying MP pollution, highlighting that sampling conducted to date might have overestimated the presence of MP or even contaminated MP-free samples.

Current research and perspective of microplastics (MPs) in soils (dusts), rivers (lakes), and marine environments in China.

In this study, we first reviewed the current research progress regarding the presence of environmental microplastics (MPs) in environment in China from 2010 to 2019. Results showed that: (1) current research has primarily focused on river and marine environments rather than soils and dusts, mainly located in eastern China, i.e., the Yangtze river, Poyang lake, Dongting lake, Yellow sea, and Bohai sea; (2) the abundance of MPs found in water bodies (sediments) of the rivers in China ranged from 3.9 to 7900 items·m-3 (19.0 × 103-13600.5 × 103 items·km-2), and 20-24300 items·kg-2 (170-5500 × 106 items·km-2) in the sediments, respectively; in lake water the range was 340-8900 items·m-3 (5 × 103-340 × 105 items·km-2) and 8 to 1200 items·m-2/25-300 items·kg-1 in the sediments, respectively; in marine water the range was 0.003-540 items·m-3 (0-380,100 item·km-2) and 1.3-14700 item·kg-1 in the sediments, respectively; in fish, shellfish, and natural planktons from ocean and freshwater, the range was 0-57 items·individuals-1 (0-168 items·g-1); (3) The absorption and toxicological effects of MPs in freshwater and oceans have mainly focused on polyethylene (PE), polypropylene (PP), and polystyrene (PS); (4) the sources of microplastics in soils and dusts primarily come from urban/town activities; for rivers and lakes (estuary), they primarily come from urban activities; for coastal waters, fishing gear and nets, and the maritime activities were the main sources.

Microplastics in waters and soils: Occurrence, analytical methods and ecotoxicological effects.

Microplastics (MPs) are ubiquitous in the environment and more abundant in the marine environment. Consequently, increasing focus has been put on MPs in oceans and seas, while little importance has been attached to their presence in freshwaters and soils. Therefore, this paper aimed to provide a comprehensive review of the occurrence, analysis and ecotoxicology of MPs. The abundance and distribution of MPs in several typical freshwater systems of China were summarized. It suggested that the surface water of Poyang Lake contained the highest concentration of 34 items/L MPs among all the 8 freshwater systems, and the content of MPs in sediments were higher than that of the surface water. Net-based zooplankton sampling methods are the most frequently utilized sampling methods for MPs, and density separation, elutriation and digestion are three major pretreatment methods. Fourier transform infrared spectroscopy, Raman spectroscopy and pyrolysis-gas chromatography coupled to mass spectrometry are often used to identify the polymer types of MPs. Besides, MPs might damage the digestive tract of various organisms and negatively inhibit their growth, feeding and reproduction. The ways of human exposure to MPs are by ingestion, inhalation and dermal exposure, digestive and respiratory system might be adversely influenced. However, potential health risks of MPs to humans are remained insufficiently researched. Overall, by showing the presence of MPs in freshwaters and soils as well as possible ecotoxicological effects on the environment and humans, this paper provided a framework for future research in this field.

Microplastics integrating the zooplanktonic fraction in a saline lake of Argentina: influence of water management.

This study address for the first time in Argentina and the South American continent the effect of water management on the presence of microplastics (MPs) in a shallow lake, assessing their contribution to the zooplankton fraction. Water samples were collected in the lake and its principal affluent, an irrigation channel, from winter 2018 to summer 2019 with a zooplankton net (47 µm). MPs were present in all analyzed samples, with a dominance of fibers, black color, and ≤ 1000 µm range size. MPs concentration was maximum during summer at the lake (180 MPs m-3) while during spring (140 MPs m-3) at the channel. Rotifers and cyclopoids dominated the zooplanktonic fraction at both sites which range sizes (< 200 to 600 µm) included most of the size range found for MPs (50-950 µm). According to our results, the MPs found represents a potential risk for the first levels of the food web. In the lake, the concentration of MPs concerning total zooplankton abundance was higher when the channel was closed. Nevertheless, when the channel was open, the higher concentration in summer matches with the increase of tourism and an extraordinary rainfall. Our results suggest that while the runoff of agro-industrial waste regulates the MPs concentration in the channel, its water management, the touristic activities, and the runoff of MPs from nearby urban settlements regulate the concentration of MPs in the lake. These findings emphasize the need for better treatment of urban and agro-industrial waste that develops near continental aquatic systems, mainly in those where tourism activities are frequent and treatment facilities scarce.

Parallelism of Nutrients and CO2 Dynamics: Evidence Based on Long-Term Data in Taihu Lake.

Inland lakes are important ecosystems for the carbon cycle at both regional and global scales. However, a knowledge gap still exists about the correlations between the partial pressure of CO2 (pCO2) and nutrient dynamics in lakes. In this study, we analysed the long-term dynamics of nutrient and pCO2 in Taihu Lake. Strong spatial heterogeneity was observed with highest nutrient concentrations occurring in the River mouth and significant lower concentrations (p < 0.01) occurring in East Taihu and Other zone. For pCO2, the average values were 1136.81 ± 1240.16 µatm, 433.07 ± 305.45 µatm, and 487.05 ± 414.02 µatm in Rive mouth, East Taihu, and Other zone, respectively. Statistical analysis revealed that pCO2 was significantly and positively related to nutrient (TN: total nitrogen and NH4+: ammonium) concentrations (p < 0.01), but negatively related to Chla (Chlorophyll a) concentrations in River mouth and Other zone (p < 0.01). The parallelism of nutrient concentrations and pCO2 in Taihu Lake highlights the dual effects of external pollution inputs from the surrounding catchment. In addition, progressive mitigation was found for not only nutrients but also pCO2, which was attributed to the previous effort in the environmental protections in Taihu Lake basin. Our results also suggest the importance of long-term monitoring for the future assessment of anthropogenic impacts on nutrient and CO2 dynamics in freshwater lakes.

Molecularly imprinted polymer coating on metal-organic frameworks for solid-phase extraction of fluoroquinolones from water.

In this work, a novel surface molecularly imprinted polymer with high adsorption capacity, high adsorption rate, and high selectivity for fluoroquinolones was prepared on the surface of UiO-66-NH2 , which is a kind of metal-organic framework. The surface morphology and adsorption properties of this molecularly imprinted polymer were investigated. The maximum adsorption capacity was 99.19 mg/g, and adsorption equilibrium was achieved within 65 s. Combined with reversed-phase high-performance liquid chromatography, the molecularly imprinted polymer was used to selectively enrich, separate and analyze fluoroquinolones present in lake water. The results showed that the recoveries of the four fluoroquinolones were 92.6-100.5%, and the relative standard deviations were 2.9-6.4% (n = 3). The novel molecularly imprinted polymer is an excellent adsorbent and has broad application prospects in the enrichment and separation of trace analytes in complex samples.

Microplastic abundance, distribution and composition in water, sediments, and wild fish from Poyang Lake, China.

Microplastic pollution in global aquatic environments has aroused increasing concern in recent years. In this study, the occurrence of microplastics in multiple environmental compartments was investigated in Poyang Lake, the largest freshwater lake of China. The abundance of microplastics was respectively 5-34 items/L for surface waters, 54-506 items/kg for sediments, and 0-18 items per individual for wild crucians (Carassius auratus). The distribution of microplastics in Poyang Lake varied heterogeneously in space, with the highest abundance being observed in the middle region of the lake for surface waters and in the northern region for sediments. Anthropogenic and topographic factors were speculated to be the major factors affecting the abundance and distribution of microplastics. The majority of the detected microplastics were found with a size of < 0.5 mm, with fibrous and coloured being the predominant characteristics. Polypropylene (PP) and polyethylene (PE) were the major polymer types of the selected plastic particles, indicating that domestic sewage and fishing activities might be the main sources of microplastics in the lake. No significant correlation was observed between microplastic abundance in surface water and sediment samples. Our results demonstrated the wide occurrence of microplastics in water, sediment and biota of the Poyang Lake, which may assist in extending our knowledge regarding microplastics pollution in inland freshwater systems.