Although freshwater and estuary systems are recognized as origins and transport pathways of plastics to the oceans, there is a lack of comparison of microplastics in different water bodies or river ...networks. In the present study, the spatial distribution of microplastics was compared across different water bodies, including city creeks (Shanghai), rivers (Suzhou River and Huangpu River), an estuary (Yangtze Estuary) and coastal waters (East China Sea) in the Yangtze Delta area. Significant spatial differences of microplastic abundances were revealed across the sampling areas. The results showed that the abundance of microplastics was higher (1.8–2.4 items/L) in freshwater bodies than that in estuarine and coastal water (0.9 items/L). In the Suzhou River and the Huangpu River, microplastics showed trends of increasing abundance downstream, where the peak of microplastic pollution is closer to the city center and the estuary. In respect of abundance, microplastics are likely to be transported from pollution sources to sink areas via river networks. The proportion of fibers was the highest in city creeks (88%), followed by the Suzhou River (85%), the Huangpu River (81%), the Yangtze Estuary (66%) and the East China Sea (37%). Similarly, polyesters dominated in city creeks and rivers. The results suggest that both the abundance and properties of microplastic pollution varies across different water bodies. Microplastic pollution in small freshwater bodies is more serious than in estuarine and coastal waters. Therefore, we support prioritization of water monitoring for microplastics within entire river networks, instead of single water body surveys.
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•Abundance and properties of microplastics showed variations in different water bodies.•Urban rivers contained highest level of microplastics.•Microplastic pollution in small water bodies is more serious than in estuary and coastal waters.•Microplastics are likely to be transported from pollution sources to sink via river networks.
The abundance and properties of microplastic pollution varies between different water bodies from urban creeks to coastal waters.
Water quality is a big concern for the humankind as it is the most important natural resource. However, the non-controlled growth of rural and urban areas in rapidly developed countries such as India ...is affecting water quality. In this research, we pretend to assess and demonstrate the heavy-metal status of three different water bodies of Indus, Beas and Sutlej Rivers and Harike Wetland. Data on water quality from 2013 to 2017 were analyzed through multivariate statistic techniques (cluster analysis - CA - and principal component analysis - PCA) and compared among them using public water pollution indexes. The results of CA and PCA showed that Sutlej River and Harike Wetland are included in the same group, whereas Beas River formed a separate one. This may be due to the high content of Pb, Cu, and Zn in these water bodies as compared with Beas River. The Pb content of all the water bodies exceeded the limit for EPR, BIS and WHO guidelines for drinking water. The heavy-metal pollution index was also applied to the contents of different heavy metals to find which water body is more polluted, and from their results, it was found that Harike Wetland and Sutlej River are critically polluted with heavy metals.
Abstract Employing deep learning techniques for the semantic segmentation of remote sensing images has emerged as a prevalent approach for acquiring information about water bodies. Yet, current ...models frequently fall short in accurately extracting water bodies from high-resolution remote sensing images, as these images often present intricate details of terrestrial objects and complex backgrounds. Vegetation, shadows, and other objects close to water boundaries have increased similarity to water bodies. Moreover, water bodies in high-resolution images have different boundary complexities, shapes, and sizes. This situation makes it somewhat challenging to accurately distinguish water bodies in high-resolution images. To overcome these difficulties, this paper presents a novel network model named EU-Net, specifically designed to extract water bodies from high-resolution remote sensing images. The proposed EU-Net model, with U-net as the backbone network, incorporates improved residual connections and attention mechanisms, and designs multi-scale dilated convolution and multi-scale feature fusion modules to enhance water body extraction performance in complex scenarios. Specifically, in the proposed model, improved residual connections are introduced to enable the learning of more complex features; the attention mechanism is employed to improve the model's discriminative ability by focusing on important channels and spatial areas. The implemented multi-scale dilated convolution technique enhances the model's receptive field while maintaining the same number of parameters. The designed multi-scale feature fusion module is capable of processing both small-scale details and large-scale structures in images, while simultaneously modeling the spatial context relationships of features at different scales. Experimental results validate the superior performance of EU-Net in accurately identifying water bodies from high-resolution remote sensing images, outperforming current models in terms of water extraction accuracy.
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•Protonated porous g-C3N4/BiVO4 Z-scheme heterojunction was prepared.•HCN/BV-5 displayed the potential of simultaneous photocatalytic degradation antibiotic wastewater and hydrogen ...production.•HCN/BV-5 exhibited the excellent H2 evolution performance in different real-world water bodies.•HCN/BV-5 displayed the universal applicability to the degradation of antibiotics wastewater.•A possible photocatalytic mechanism based on Z-scheme heterojunction was proposed.
Inspired by organic contaminants acting as sacrificial agents to accelerate the photocatalytic H2 evolution, protonated porous g-C3N4/BiVO4 Z-scheme photocatalysts was prepared through simple one-step hydrothermal method for the degradation of ofloxacin (OFL) wastewater with simultaneously hydrogen production. The optimal g-C3N4/BiVO4 (HCN/BV-5) sample could degrade the OFL wastewater with a hydrogen yield of 80.7 μmol·g−1∙h−1, demonstrating the potential in protonated porous g-C3N4/BiVO4 Z-scheme photocatalyst synchronous photocatalytic degradation antibiotic wastewater and hydrogen production. By carrying out the free radical quenching experiments and electron spin resonance experiments, it proved that the ·OH and h+ radicals played the most positive roles in the simultaneous OFL antibiotic wastewater degradation and hydrogen production process. Meanwhile, the HCN/BV-5 also exhibited a significantly H2 evolution performance in different real-world water bodies and universal applicability to the degradation of antibiotics wastewater. This work presents a new idea for alleviating current energy crisis and addressing environmental problems.
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•ZnO/g-C3N4 Z-scheme heterojunction photocatalyst is constructed.•ZnO/g-C3N4 exhibits superior efficiency in H2O2 production under simulated sunlight.•A photocatalytic sterilization ...process for natural water bodies using H2O2 generated in situ is established.•This process has a good inactivation effect on the microorganisms in natural water bodies.•·OH and ·O2– act as the main active species in sterilization process.
In this work, a novel ZnO/g-C3N4 heterojunction catalyst was prepared by a thermal polycondensation process and has been applied for H2O2 production and in situ sterilization in natural waters irradiated by simulated sunlight. The H2O2 production efficiency of this process was measured, and its in situ sterilization ability in natural waters was evaluated. In addition, the remaining sterilization ability of the process was also assessed. The ZnO/g-C3N4 heterojunction catalyst with 10 wt% ZnO exhibited the best performance in H2O2 production of 5312.45 μmol·L−1 after 8 h, which was nearly 2.65 times greater than that of pure g-C3N4. Moreover, the bactericidal rate reached 97.4% on 10% ZnO/g-C3N4 after 60 min, while 47.3% on pure g-C3N4. H2O2 and sunlight alone had limited bactericidal effects, only 10.3% and 27.6%. It was proven that the H2O2 generated in situ achieved high-efficiency bacterial inactivation through the effect of sunlight excitation. ·OH and ·O2– were verified to play main roles in the inactivation of bacteria, which contributed to about 44.2% and 40.4% respectively. In addition, the mold was completely inactivated after 20 min and had similar mechanism of bacterial inactivation, showing good applicability of this process. This work may provide new ideas for realizing the in situ disinfection using sunlight as driving force and cleaning treatment of natural water bodies.
Microplastics (MP) are recognized as a growing environmental hazard and have been identified as far as the remote Polar Regions, with particularly high concentrations of microplastics in sea ice. ...Little is known regarding the horizontal variability of MP within sea ice and how the underlying water body affects MP composition during sea ice growth. Here we show that sea ice MP has no uniform polymer composition and that, depending on the growth region and drift paths of the sea ice, unique MP patterns can be observed in different sea ice horizons. Thus even in remote regions such as the Arctic Ocean, certain MP indicate the presence of localized sources. Increasing exploitation of Arctic resources will likely lead to a higher MP load in the Arctic sea ice and will enhance the release of MP in the areas of strong seasonal sea ice melt and the outflow gateways.
Intermittent surface water frequently transitioning between water and land over months and years, plays a crucial and increasingly significant role in both social and ecological systems. However, ...their vital and dramatic dynamics have mainly remained invisible due to monitoring limitations. We present a new remote sensing framework to capture the long-term monthly dynamics of surface water bodies, applying it to Poyang Lake, the largest freshwater lake in China. This framework employed a random forest classifier on all available Landsat data to identify monthly surface water bodies. Additionally, we developed a Spatial and Temporal Neighborhood Similarity-based Gap Filling method to restore water bodies obscured by clouds and ensure spatial integrity. Furthermore, we introduced an index to quantify the intermittency of surface water bodies on a scale from 0 to 1, allowing for the classification of water bodies into three categories: perennial, wet intermittent, and dry intermittent. Employing this framework, we reconstructed the most complete monthly 30-m surface water dataset for cloudy regions to date, covering April 1986 to September 2023, demonstrating a strong correlation (Spearman's rank correlation coefficient of 0.909) with observed water levels. The results reveal a landscape dominantly composed of intermittent water bodies (91.2%), with a rapidly shrinking trend of perennial water bodies at 1303.58 ha per year. Notably, 162,685 ha (21.9%) of water bodies transitioned toward drier and more intermittent statuses. Dry intermittent water bodies exhibited the most pronounced land-water transitions, with the highest water-to-land (82.5%) and land-to-water (89.9%) proportions among the three categories. By uncovering the hidden dynamics of intermittent surface water, and highlighting its prevalence, expansion, and vulnerability, this framework paves the way for a better understanding of these critical water dynamics across the globe.
•Presented a novel framework for detailed monitoring of surface water dynamics•Created an innovative index to quantify the intermittency of water bodies•Reconstructed a spatiotemporally-complete 450-month time series of surface water•Poyang Lake comprises 91.2% intermittent water and the remainder perennial•Revealed 21.9% of water bodies transitioned to drier and more intermittent state
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•279 cities have water bodies with stable area and location; however, only 33.69 % of them have stable rural areas with low land cover transformation.•SUHIW exhibits a similar ...interannual variation to SUHIR in cities with stable rural areas, indicating that water bodies can serve as a stable reference for SUHI measurements.•Water bodies are more accurate for measuring the interannual variation in SUHI intensity compared to rural areas in cities experiencing rapid land cover changes.
Accurate measurement of urban heat islands (UHI) intensity is a necessary prerequisite for understanding UHI formation mechanisms and subsequently implementing effective prevention and control measures. The selection of a stable reference is a significant challenge in this process. In particular, rapid urbanization can lead to changes in land cover types. This process hinders the selection of a typical non-urban area as a stable reference for accurately measuring surface urban heat islands (SUHI) intensity. Among various land cover types, water bodies are widely distributed and stable during urban development. Nevertheless, the use of water bodies as a stable reference for SUHIs remains controversial. For 185 global cities, we first clustered the land cover transformation rates and then compared the interannual variations in SUHIW and SUHIR in these cities by using remote sensing data from MODIS. The trends of interannual intensities of the SUHIW and SUHIR in the stable group are similar, indicating that water bodies have the same effect on SUHI measurements as stable rural areas. However, the magnitude of the difference between the SUHIW and the SUHIR (SD) becomes more significant in cities with rapid changes in rural areas. As a stable reference, water bodies can be used to accurately measure the variation in the SUHI affected only by urbanization under the background climate, while the land cover transformation of rural areas changes the land surface temperature (LST) and thus affects the SUHI intensity. The findings of this study quantitatively demonstrate the feasibility of using water bodies as SUHI references from an urban dynamics perspective and provide direction for studying SUHIs under climate change.
The size, shape, and connectivity of water bodies (lakes, ponds, and wetlands) can have important effects on ecological communities and ecosystem processes, but how these characteristics are ...influenced by land use and land cover change over broad spatial scales is not known. Intensive alteration of water bodies during urban development, including construction, burial, drainage, and reshaping, may select for certain morphometric characteristics and influence the types of water bodies present in cities. We used a database of over one million water bodies in 100 cities across the conterminous United States to compare the size distributions, connectivity (as intersection with surface flow lines), and shape (as measured by shoreline development factor) of water bodies in different land cover classes. Water bodies in all urban land covers were dominated by lakes and ponds, while reservoirs and wetlands comprised only a small fraction of the sample. In urban land covers, as compared to surrounding undeveloped land, water body size distributions converged on moderate sizes, shapes toward less tortuous shorelines, and the number and area of water bodies that intersected surface flow lines (i.e., streams and rivers) decreased. Potential mechanisms responsible for changing the characteristics of urban water bodies include: preferential removal, physical reshaping or addition of water bodies, and selection of locations for development. The relative contributions of each mechanism likely change as cities grow. The larger size and reduced surface connectivity of urban water bodies may affect the role of internal dynamics and sensitivity to catchment processes. More broadly, these results illustrate the complex nature of urban watersheds and highlight the need to develop a conceptual framework for urban water bodies.
•A calculation method for the combustion override degree is proposed.•The SWB induces unstable combustion front propagation or even extinguishment.•The SWB facilitates the propagation speed ...enhancement of combustion front.•The location and scale of SWB seriously influence the combustion performance during the ISC.
In-situ combustion (ISC) is an effective alternative method for the development of heavy oil reservoirs, especially in the later stage of steam injection and a large majority of high water-saturated channels have been formed during this phase. The water-saturated channels, also known as secondary water body (SWB), is regarded as a sensitive factor to the ISC performance. The effect of the SWB with different scales and locations was investigated by using combustion tube experiments. Results show that the existence of SWB is conducive to improving the propagation speed of combustion front combined with the reduction of combustion stability during the ISC process. As combustion front propagates to the SWB, the temperature is quickly decreased accompanied by an unstable propagation process, which inevitably induces the significant reduction of the O2 availability and COx emission concentration. Additionally, oversized SWB would lead to a worse combustion process with much lower COx concentration and O2 availability or even fall into an extinguishment process. Better combustion performance and oil recovery factor are obtained when SWB has large spacing to the gas injection well or exists in the lower layer. Whereas the premature O2 breakthrough and unstable fire front propagation are generated if the SWB is close to the gas injection well or forms in the upper layer. The findings of this study are significant for better understanding the ISC performance with the consideration of SWB in heavy oil reservoirs.
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