Mariculture effluents represent a growing anthropogenic perturbation to coastal environments, yet their impacts on dissolved organic matter (DOM) composition and microbially mediated transformation processes remain insufficiently understood. Here, we applied molecular-level DOM analysis combined with microbial community profiling to elucidate DOM biogeochemical behavior in a typical high-density mariculture bay in China. Mariculture effluents substantially increased DOM molecular diversity, yielding up to 1406 unique molecular formulas in tailwater, and introduced abundant nitrogen- and sulfur-containing compounds. Sulfur-containing DOM was markedly enriched in Xiangshan Bay (12.11%) relative to riverine water (7.35%), while inner and mid-bay DOM shared far more molecular formulas with mariculture tailwater than with riverine water. In contrast, outer-bay DOM was dominated by lignin-rich, aromatic compounds associated with the Yangtze River diluted water plume, producing a sharp spatial segregation of DOM sources within the bay. Microbial communities closely mirrored these patterns, showing strong overlap between tailwater and bay waters and enrichment of heterotrophic and sulfur-related pathways. Co-occurrence networks revealed highly connected and modular DOM-microbe interactions in Xiangshan Bay, suggesting potential microbial involvement in sulfur-containing DOM transformation. These results demonstrate that mariculture effluents are closely associated with distinct DOM composition and DOM-microbe coupling patterns, highlighting intensive aquaculture as an important contributor to organic matter transformation in semi-enclosed coastal systems.

Accurate analysis of surface water pollution mechanisms is critical for effective environmental restoration and protection. However, evaluation methods for small watersheds with dense populations and complex pollution sources remain limited. This study integrates partial least squares structural equation modeling (PLS-SEM) with fluorescence fingerprinting data from excitation-emission matrix-parallel factor analysis (EEM-PARAFAC) to investigate nutrient sources in rivers of southeastern China. The findings reveal that land use intensity (LUI) significantly influences pollutant concentrations, but the presence of outliers underscores complex pollution mechanisms. Using EEM-PARAFAC components as mediators, the C5 component, representing sewage-derived substances, was identified as a key driver, fully mediating nitrogen ((3 = 0.953, p < 0.001, VAF = 117.5%) and phosphorus ((3 = 0.921, p < 0.001, VAF = 113.2%) levels. In contrast, agricultural non-point sources (C1 and C2: (3 = -0.270, p > 0.05) had negligible direct effects on nutrient concentrations, emphasizing the need to prioritize domestic sewage control. Additionally, components C1 and C2 exerted strong direct effects on dissolved organic carbon ((3 = 0.495, p < 0.001), surpassing the influence of sewage ((3 = 0.380, p < 0.001). These results demonstrate that the combined use of PLS-SEM and EEM-PARAFAC is a robust approach for identifying pollution sources in data-limited small watersheds, supporting cost-effective aquatic environmental restoration strategies.

Effective management of surface water quality requires a thorough knowledge of the characteristics and contributions of various pollution sources. While stable isotope methods are highly effective for nitrate source tracking, their high cost and operational complexity constrain their routine use in watershed management. This study examined and contrasted the dual stable isotopes (δ15N-NO3 -, δ18O-NO3 -, and the MixSIAR [Bayesian mixing models in R] model) with fluorescence analysis (EEM-PARAFAC [fluorescence excitation-emission matrices coupled with parallel factor analysis]) to trace the origins of nitrate and dissolved organic matter in the Lujiang River, a coastal agriculture-dominated river in southeastern China. Additionally, the feasibility of EEM-PARAFAC as a low-cost complementary tool for nitrate source tracking was assessed. The MixSIAR model identified soil nitrogen (41.0%-49.7%) and fertilizers (29.5%-37.9%) as dominant nitrate sources, pointing to significant nonpoint source pollution. With increasing urbanization, point source pollution from manure and sewage increased from upstream (11.5%) to midstream (13.1%) and downstream (15.3%). EEM-PARAFAC analysis supported these findings, with humic-like components (C1 + C2: 59.31%, 56.85%, and 46.98% in upstream, midstream, and downstream, respectively) showing a strong correlation (r = 0.97) with soil nitrogen contributions identified by MixSIAR. Protein-like components (C5, r = 0.93; C6, r = 0.97) were associated with fertilizers and sewage, respectively, consistent with their increasing downstream contributions, validating EEM-PARAFAC's capacity for cost-effective source discrimination. This study demonstrates that integrating the two methods enhances the understanding of pollutant source dynamics in complex river systems, offering valuable insights for improving water quality and watershed management.

This study investigates urban rivers in Ningbo, a coastal city in southeastern China, to assess how varying levels of sewage infrastructure affect antibiotic contamination and to evaluate an integrated source-tracing framework combining partial least squares structural equation modeling (PLS-SEM) and excitation-emission matrix-parallel factor analysis (EEM-PARAFAC). Antibiotic concentrations ranged from 352.19 ± 151.24-2082.35 ± 865.50 ng·L-1, with substantially higher levels observed in rivers with less complete sewer networks. Dehydrated erythromycin (ETM-H2O) was the dominant antibiotic, accounting for 45-94 % of total concentrations. While PMF attributed pollution to livestock, aquaculture, and pharmaceutical industry sources, these attributions are inconsistent with the actual industrial profile and anthropogenic activities in the region. In contrast, PLS-SEM revealed a strong direct effect of tryptophan-like DOM, indicative of domestic sewage, on both total antibiotics (β = 0.721, p < 0.05) and ETM-H2O (β = 0.789, p < 0.01), identifying sewage leakage as the primary source. Tryptophan-like components also indirectly influenced fluoroquinolones and roxithromycin via phosphorus mediation (β = 0.264 and 0.552, respectively), suggesting additional contributions from manure fertilization in riparian vegetable fields. This study demonstrates the value of coupling DOM fluorescence and path modeling for identifying antibiotic sources in urban waters.

The necessity to eliminate nickel (Ni) from wastewater stems from its environmental and health hazards. To enhance the Ni adsorption capacity, this research applied a copper sulfate–ammonia complex (tetraamminecopper (II) sulfate monohydrate, [Cu(NH3)4]SO4·H2O) as a modifying agent for a Phragmites australis-based activated carbon preparation. The physiochemical properties of powdered activated carbon (PAC) and a modified form ([Cu(NH3)4]-PAC) were examined by measuring their surface areas, analyzing their elemental composition, and using Boehm’s titration method. Batch experiments were conducted to investigate the impact of various factors, such as Ni(II) concentration, contact time, pH, and ionic strength, on its substance adsorption capabilities. Additionally, the adsorption mechanisms of Ni(II) onto activated carbon were elucidated via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The findings indicated that modified activated carbon ([Cu(NH3)4]-PAC) exhibited a lower surface area and total volume than the original activated carbon (PAC). The modification of PAC enhanced its surface’s relative oxygen and nitrogen content, indicating the incorporation of functional groups containing these elements. Furthermore, the modified activated carbon, [Cu(NH3)4]-PAC, exhibited superior adsorption capacity relative to unmodified PAC. Both adsorbents’ adsorption behaviors conformed to the Langmuir model and the pseudo-second-order kinetics model. The Ni(II) removal efficiency of PAC and [Cu(NH3)4]-PAC diminished progressively with rising ionic strength. Modified activated carbon [Cu(NH3)4]-PAC demonstrated notable pH buffering and adaptability. The adsorption mechanism for Ni(II) on activated carbon involves surface complexation, cation exchange, and electrostatic interaction. This research presents a cost-efficient preparation technique for preparing activated carbon with enhanced Ni(II) removal capabilities from wastewater and elucidates its underlying adsorption mechanisms.

Mariculture is a key protein source and economic driver but traditional methods pollute coastal waters, hindering sustainable development. Current research on the ecological impacts of mariculture mainly focuses on specific pollutants and lacks an assessment of the biogeochemical impacts of mariculture discharge. This study examined Xiangshan Bay, a representative intensive mariculture area in China, to explore the impact of mariculture tailwater discharge on water quality, focusing on dissolved organic matter (DOM) and bacterial communities. Based on the fluorescence excitation-emission matrix combined with parallel factor analysis, a characteristic fluorescence component C4 was identified in mariculture tailwater (intensity of 40 +/- 4 %, n = 8), while higher C4 components (47 +/- 3 %, n = 15) were found throughout the bay. Humic-like components from riverine input (C1 + C2: 32 +/- 3 %, n = 15) and protein-like components from domestic sewage (C5: 2 +/- 1 %, n = 15) were significantly lower in the seawater samples, indicating the strong influence of mariculture tailwater on the entire DOM structure of the bay. The bacterial community structure showed a response consistent with DOM, as revealed by nonmetric multidimensional scaling analysis. This showed that bacterial communities in mariculture tailwater and bay water samples clustered together, independent of riverine input. The SourceTracker model indicated that mariculture tailwater (91 +/- 5 %) predominantly contributed to the bacterial community, with minimal contributions from riverine input (< 5 %). Co-occurrence network analysis further showed that under long-term high-intensity mariculture discharge, the C4 component became the core DOM and was closely associated with the bacterial community. The results here demonstrate the profound impact of traditional mariculture on coastal water quality and show that riverine input is not the primary pollution source in this region, providing clear directions for coastal environmental restoration efforts.

断面水质提升与保障是"深入打好污染攻坚战"的重要工作.实际工作中发现断面水质受治污措施、土地利用、气象条件等多因素影响而表现出明显差异,因此水质提升工作需建立在精准分析基础上.本研究以宁波市鄞州区为例,选择位于城区、城乡结合区和农村的7个水质断面为研究对象,分析2018—2020年水质数据的时空变化规律,并采用三维荧光光谱技术对断面污染现状进行快速评价.结果表明鄞州区近年来的治理措施显著降低了断面水体中的化学需氧量、氨氮和总磷浓度,其中以城区断面的改善幅度最大.三类断面主要水质指标浓度上的顺序为:城区断面>城乡断面>>农村断面,表明人类活动强度仍是驱动断面水体质量的主要因素.此外,基于三维荧光光谱的特征峰识别法可快速简便地反映出断面水体污染物组成信息,很好地弥补了常规水质参数对污染源信息的指示不足.本研究表明断面水质提升应充分结合区域特征,利用三维荧光光谱等新型水质参数可有效提升断面水质监管效率.

Here, we studied the shipyard impacts on the distribution of PAHs and PCBs in the semi-enclosed Xiangshan Bay, an important mariculture zone in China. The results showed that the shipyard caused a pollution plume for PAHs but not for PCBs. As characteristic pollutants of oil leakage, the PAHs had concentrations of up to 55.82 ng L-1 in the water, 2235.04 ng g-1 in suspended particulate matter (SPM), and 1489.60 ng g-1 in sediment. The PAHs in water and SPM were dominated by phenanthrene and pyrene that were mostly derived from lubricant and diesel, while those in sediments were dominated by the high-molecular-weight PAHs, such as indeno[1,2,3-c,d]pyrene. In contrast, the PCBs concentrations reached up to 10.17 ng L-1, 79.72 ng g-1, and 124.33 ng g-1 in the seawater, SPM, and sediment samples, respectively, and they did not show spatial patterns affected by the shipyard. Moreover, the health risk assessment indicated that the shipyard discharge caused a substantial PAHs ecological risk to the adjacent and downstream water environment. Therefore, point source discharge in semienclosed bays should be paid close attention to due to the strong pollutant transport effect.

Large quantities of microplastics are found in the East China Sea (ECS), however, the impacts of complicated terrestrial input on the distribution characteristics of microplastics have not been studied. Hence, we aimed to characterize the microplastic distribution in the ECS combined with the fluorescence characteristics of chromophoric dissolved organic matter (CDOM), a sensitive technique to trace terrestrial substances in seawater. The average microplastic abundance in the surface seawater of ECS was 34.73 ± 4.05 items/m3 and sites in the north ECS had a higher microplastic abundance (55.90 ± 2.47 items/m3) than those in the southern region (11.22 ± 4.01 items/m3), due to its proximity to the Yangtze River estuary and Hangzhou Bay. Polyethylene (PE, 44.2 %) was the most abundant microplastic type in the northern region, whereas polyethylene terephthalate (PET, 28.4 %) had a higher proportion in the south ECS. Besides, sites in the north ECS had a higher diversity index of microplastics, suggesting various sources of microplastic pollution. Interestingly, a stronger correlation with the diversity index was found for protein-like component C3 (R2 = 0.56) in northern regions compared to fulvic-like component C1 (R2 = 0.32) and humic-like component C2 (R2 = 0.28), suggesting the significant impact of anthropogenic discharge. Moreover, no correlation between fluorescence components and microplastic diversity index was found in the south ECS, indicating that CDOM can reflect the impact range of terrestrial input on the distribution characteristics of microplastics. This research might be useful in assessing and reducing the impact of terrestrial input on the distribution characteristics of microplastics in the ECS.

The behavior of microplastics in wastewater treatment plants has been investigated, but specific effects of treatment process on microplastics' fate are still unclear due to varied analysis methods and regional differences. In this study, four wastewater treatment plants in Ningbo of southeastern China with different treatment processes were selected to investigate transport and fate of microplastics. Based on number of microplastic particles, fibers and fragments were the main microplastics types in wastewater, while synthetic cellulose represented the largest fraction. The dominance of fibers (76.7%-90.0%) and small particle sizes (<2.0 mm, 62.5%-81.5%) in effluents suggested that they escaped easily from the wastewater treatment plants. The abundance of microplastics particles decreased from 78.0 ± 2.9 items/L in influent to 6.0 ± 2.8 items/L in effluent for anaerobic-anoxic-oxic process, 100.0 ± 3.1 items/L to 4.3 ± 3.4 items/L for sequencing batch reactor activated sludge process, 105.0 ± 5.3 items/L to 3.5 ± 2.6 items/L for cyclic activated sludge technology, 65.0 ± 4.3 items/L to 3.0 ± 1.6 items/L for oxidation ditch process. The microplastics removal capacity of primary and secondary treatment processes for four wastewater treatment plants ranged from 83.7% to 96.3%. Application of different tertiary treatment processes (coagulation/flocculation, membrane related technology and disinfection) enhanced microplastics removal to achieve overall removal rate of 92.3%-96.7%. The removed microplastics from the wastewater treatment plants were mainly transferred to sludge (226.1 ± 95.7-896.0 ± 144.0 items/g dry weight). The biological treatment unit played an important role in microplastics removal with rates varying between 86.9%-95.2%, while tertiary treatment reduced daily microplastics emission 1.4 × 108-2.3 × 108 items/day. This study suggests that proper selection of wastewater treatment unit could significantly reduce the emission number of microplastics, which supports an efficient control strategy of microplastics in wastewater treatment plants.

Recently, the degradation of non-chlorinated organic pollutants in saline pharmaceutical wastewater by SO4˙--based advanced oxidation processes (AOPs) has received widespread attention. However, little is known about the oxidation of chlorinated compounds in SO4˙--based AOPs. This study chose clofibric acid (CA) as a chlorinated pollutant model; the oxidation kinetics and mechanistic pathway were explored in the Co2+/peroxymonosulfate (PMS) system. Notably, a high removal efficiency (81.0%) but low mineralization rate (9.15%) of CA within 120 min were observed at pH 3.0 during Co2+/PMS treatment. Exogenic Cl- had a dual effect (inhibitory then promoting) on CA degradation. Several undesirable chlorinated by-products were formed in the Co2+/PMS system. This demonstrated endogenic chlorine and exogenic Cl- both reacted with SO4˙- to generate chlorine radicals, which participated in the dechlorination and rechlorination of CA and its by-products. Furthermore, SO4˙- was the dominant species responsible for CA degradation at low Cl- concentrations (≤1 mM), whereas Cl2˙- was the predominant radical at [Cl-]0 > 1 mM. A possible degradation pathway of CA was proposed. Our findings suggested that chlorinated compounds in highly saline pharmaceutical wastewater will be more resistant and deserve more attention.

Sunlight plays an important role in the photochemical processes of chromophoric dissolved organic matter (CDOM), which is closely related to water self-purification and primary productivity of healthy aquatic ecosystem health. The fine particles of haze, a widespread air pollutant, absorb natural ultraviolet (UV) irradiation and have an unknown degree of influence on the photochemical transformation of CDOM. Here, an in-situ experiment investigating how the amount and composition of CDOM changes under hazy conditions was conducted in Ningbo, southeastern China, a city that frequently suffers from seasonal haze pollution. The results indicated that haze attenuated UV light under different weather conditions. The UV intensities were reduced from 1124.90 ± 91.58 to 510.26 ± 40.26 μW cm-2 and 748.54 ± 101.68 to 316.32 ± 40.48 μW cm-2 on sunny and cloudy days, respectively; these values approached those on rainy days (186.97 ± 28.58 μW cm-2). Consequently, the loss of dissolved organic carbon during the irradiation test was reduced on hazy days (e.g., from 5.63% to 2.59% on sunny/hazy days). The impact of haze on CDOM photobleaching was further assessed by an excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis. On hazy days, the EEM-PARAFAC components were saved from photobleaching to different degrees; and humic-like substances showed a stronger protective effect from haze than protein-like substances because of their higher photosensitivity. Consequently, haze could cause more terrestrial CDOM to remain in surface water. UV intensity played a critical role in the composition characteristics of CDOM. This study identifies the linkage between atmospheric pollution and water quality and demonstrates that long-term and large-scale haze may adversely influence aquatic ecology through pollutant/nutrient accumulation.

Lateglacial and Holocene summer sea-surface temperature (SST) variability in the northern North Atlantic was reconstructed based on diatom records from two sediment cores from the North Icelandic shelf. The temperature changes are discussed in relation to palaeoceanographic circulation patterns and past climatic changes. Modern diatom data from surface sediments from around Iceland and Southeast and West Greenland, with known modern environmental variables, were used as the basis for the quantitative reconstruction of summer SST. The results show that summer SSTs varied during both the Lateglacial and the Holocene, but the amplitude of SST variations during the Lateglacial was greater than that during the Holocene. No pronounced warm or cool events were recorded on the North Icelandic shelf during the GI-1e to GI-1a events (Bølling-Allerød) and the GS-1 event (Younger Dryas). The changes in SST were possibly caused by major changes in the ocean circulation pattern around Iceland, and by minor variations in the interaction between the cold and warm currents in the region. Comparison of the reconstructed summer SSTs with other marine records from the North Atlantic suggests an antiphase relationship between the oceanic climatic responses off North Iceland and in the eastern North Atlantic during the Lateglacial and the earliest part of the Holocene (the Preboreal).

A challenge for current surface water restoration and management in China is acquiring the source information for complex pollution scenarios in order to develop effective control strategies. As an important part of dissolved organic matter, chromophoric dissolved organic matter (CDOM) contains unique chemical signals related to various pollution sources. Spectral methods such as fluorescence excitation-emission matrices coupled with parallel factor analysis enable rapid and low-cost CDOM characterization for source tracking. In this study, a typical small-sized river flowing through mixed land-use regions in southeastern China, the Lujiang River, was investigated to determine the responses of CDOM to spatiotemporal factors. The effects of land-use patterns were reflected by the fluorescent components of terrestrial and sewage substances. A high and stable proportion of terrestrial-like components (C1 + C2) in each sampling period (i.e., March: 47.6 ± 5.7% and October: 44.3 ± 2.7%) indicated a high input of non-point source (NPS) pollution from both agriculture and urban areas. In addition, the difference in solar radiation intensity induced by climate and air quality changes was also reflected by variability in the photodegradation product component (C3) of terrestrial precursors between October (24.8 ± 2.6%) and March (4.5 ± 2.0%), suggesting that terrestrial components could be a sensitive indicator for NPS pollutant monitoring. Increased sewage impact in downstream regions was reflected by a spike in the tryptophan-like component (C4); temporal variations in C4 (paired t-Test, p < 0.005) also indicated that sewage substances were more prone to removal by microbial activity in warmer seasons. The dynamics of C4 could serve as a good indicator of sewage disposal performance. The results of this study demonstrate that CDOM data have important practical applications for existing water restoration campaigns in southeastern China, as well as substantial potential for routine water quality monitoring.

It is well known that chloride ions could affect the oxidation kinetics and mechanism of contaminant based on SO4•− in the wastewater. Here, the degradation of an organic acid, fumaric acid (FA), was investigated in the presence of chloride (0–300 mM) by the Fe(II)/peroxymonosulfate (Fe(II)/PMS) system. A negative impact of chloride was observed on the rates of FA degradation. The degree of inhibitory effect was higher in Fe(II)/PMS addition order. Some chlorinated byproducts were identified during the FA oxidation process in the presence of Cl− by the ultraperformance liquid chromatography and quadrupole-time of flight mass spectrometer (UPLC-QTOF-MS). With the increasing content of Cl−, an accumulation of adsorbable organic halogen (AOX), an increase in acute toxicity, and an inhibition of mineralization were observed. According to the results of kinetic modeling, the production and transformation of oxidative species were dependent on Cl− dosage and reaction time. SO4•− was supposed to be the main radical for FA degradation with Cl− concentration below 5 mM, whereas Cl2•− was primarily responsible for the depletion of FA at [Cl−] > 5 mM. A possible degradation pathway of FA was discussed. This study reveals the potential environmental risk of organic acid and is necessary to explore useful strategies for ameliorating the treatment of chloride-rich wastewater.

Trace copper ion (Cu(II)) in water and wastewater can trigger peroxymonosulfate (PMS) activation to oxidize organic compounds, but it only works under alkaline conditions. In this work, we found that the presence of chloride could significantly accelerate the oxidation of Acid Orange 7 (AO7) by the Cu(II)/PMS process at a wide pH range (4.0–9.0). The observed pseudo-first-order rate constant k for AO7 oxidation was linearly correlated with the increased Cl− concentration (0–300 mM). An increase in mineralization rate was observed in the presence of Cl−, while the overall mineralization was quite low. Decomposition of PMS facilitated when Cl− concentration or pH value increased. Based on the scavenger experiments and electron paramagnetic resonance (EPR) measurement, the mechanism of Cu(II)-catalyzed PMS oxidation process in the presence of Cl− was proposed as both the radical and non-radical pathway, and 1O2 was the reactive oxygen species in the Cu(II)/PMS system. Finally, a possible degradation pathway of AO7 was elucidated. The feasibility of in situ utilizing high salinity and trace cupric species to accelerate the degradation of organic pollutants by the Cu(II)/PMS process in water and wastewater was demonstrated. However, the identification of undesired chlorinated by-products reminds us of cautiousness in assessing the application of Cu(II)/PMS system under chloride-rich environment. The findings of this work provide a simple and efficient approach to apply PMS in the remediation of refractory organic contaminants in the presence of trace cupric species under a high salinity environment with a wide range of pH.

随着"陆海统筹"海洋保护战略的提出,近海水质修复越来越依靠对污染源数据的准确掌握,而活性磷酸盐和总无机氮等常规水质指标不能对海洋中陆源污染物进行有效指示.因此,本研究利用三维荧光光谱结合平行因子分析（EEM-PARAFAC）等技术分析了象山港和东海不同深度有色溶解性有机质（CDOM）的组成和分布特征,探讨基于CDOM快速分析技术的近海水质评价方法.结果表明,象山港水质受沿岸排放影响显著,其氮磷营养盐、陆源腐殖质（EEM-PARAFAC组分C1和C4）和生活源类蛋白质（C3和C5）物质显著高于东海表层水体.在东海水体中,5个荧光组分的高值区主要分布在北部近岸表层海域,与盐度分布相反,清晰表明长江冲淡水等陆源输入对CDOM的显著影响.相关性分析表明,陆源物质输入是东海表层水体中污染物的重要来源,而底层污染物的来源则更为复杂.总体上,污水类物质较大程度地改变了东海北部表层CDOM的组成.本研究表明,利用EEM-PARAFAC等技术可快速有效地识别海洋中CDOM的来源,深刻揭示了陆源排放对海洋水质的影响程度,可为"陆海统筹"海洋保护策略提供技术支撑.

Microplastics are being widely discussed as an emerging global environmental contaminant. Microplastic pollution usually originates from land-based sources, which are then mainly transported through hydrological and atmospheric pathways and accumulated in terrestrial, freshwater and marine ecosystems. Urban environments represent a condensed area of human activities (including the production and use of plastic materials), and urban rivers may therefore be a key transporter of microplastic pollution. Understanding microplastic abundances in urban rivers is potentially important in finding effective means of reducing fluvial microplastic discharge. This study quantified microplastic abundances in surface waters along the Fenghua River, Ningbo, a coastal megacity in East China. Microplastic pollution was distributed unevenly along the river, with concentrations ranging from 300 n/m(3) to 4000 n/m(3) (0.3 - 4.0 n/L). Average concenterations were 1620.16 +/- 878.22 n/m(3) (1.62 +/- 0.88 n/L) in summer (43 sampling points) and 1696.08 +/- 983.52 n/m(3) (1.70 +/- 0.98 n/L) in winter (17 sampling points). The most common microplastic shapes, sizes, colors and types of polymers were fiber, <0.5mm, transparent and polypropylene, respectively. Using multidimensional scaling analysis, microplastic distribution patterns were related to seasonal factors and levels of urbanization. No clear relationships were found, with implications for site selection when studying microplastics and the challenges of attributing sources to microplastic pollution in urban rivers.

Freshwater systems are vitally important, supporting diversity and providing a range of ecosystem services. In China, rapid urbanization (over 800 million urban population) has led to multiple anthropogenic pressures that threaten urban freshwater environments. Microplastics (<5 mm) result from intensive production and use of plastic materials, but their effects in urban freshwater environments remain poorly understood. Rising concerns over the ecological effects of microplastics have resulted in increased attention being given to this contaminant in Chinese freshwater systems. Some studies provide quantitative data on contamination loads, but in general relevant knowledge in freshwater environment remains narrow in China, and lacking adequate understanding of threshold levels for detrimental effects. Notably, non-standardized sample collection and processing techniques for point and non-point sources have hindered comparisons of contamination loads and associated risk. Meanwhile, legislative frameworks for managing microplastics in China remain in their infancy. This manuscript critically reviews what is known of the nature and magnitude of microplastic pollution in Chinese freshwater environments, and summarizes relevant Chinese legislation. It provides recommendations for improving the legislative framework in China and identifies research gaps that need to be addressed to improve management and regulatory strategies for dealing with microplastic pollution in Chinese urban freshwater environments.

Microplastic pollution is an emerging threat to global freshwater ecological security. The emission and discharge of microplastic pollutants is highly associated with human activities and, therefore, cities are particularly at risk of microplastic pollution because they are a concentrated zone of plastic industry and use. Urban rivers may also be significant in transporting microplastic pollution from cities to other areas. Because of rapid urbanization, Chinese coastal cities are potentially at increasing risks of microplastic pollution from freshwater, atmospheric and terrestrial environments. Previous studies discovered that urban factors, including local population density, economic structures, and land-use patterns play decisive roles in microplastic pollution in China’s urban catchments. This study builds on past work by analysing the relationship between urban factors and freshwater microplastic pollution along an urban river channel in Ningbo, a megalopolis on the East Coast of China. The microplastic abundance in the Fenghua River, Ningbo, was compared to equivalent measures in other research. This study also considers local urban developments, revealing some of the core factors affecting urban microplastic pollution levels. This manuscript ultimately aims to find countermeasures for controlling China’s urban microplastic pollution. These measures will also provide some new perspectives for Chinese cities to deal with the spread and emission of other artificial contaminants in the future, so as to maintain the sustainable development in China, and extensively to other cities in the region.