Search Results (8,356)

The transport–diffusion problem of point-source solutes in water environmental flows is an important issue in environmental fluid mechanics, with significant theoretical and practical implications for sustainable development and the ecological management and environmental protection of water. This study presents a model for instantaneously released multi-point-source solutes, utilizing the separation of variables method and Duhamel’s principle to solve classical mathematical physics equations. The zeroth-order and first-order concentration moment equations, which are crucial for predicting the cross-sectional average concentration of instantaneously released point-source solutes, are systematically addressed. The accuracy of the analytical results is confirmed by comparing them with the relevant literature. Furthermore, a general discussion is provided based on the study’s findings (including an ideal physical model of Couette flow), and an analytical solution (a recursive relationship) for higher-order concentration moments is deduced. Finally, this study quantitatively discusses downstream environmental ecological effects by examining the movement of released point-source solute centroids in the river, illustrating that the time needed for the released point-source solute to have an environmental–ecological impact downstream of the river is dependent on the initial release location. Under the specified engineering parameters, for the release location at the bottom boundary point of the channel (z₀ = 0 m), the midpoint (z₀ = 5 m), and the water-surface point (z₀ = 10 m), the time for additional displacement of released solute centroid to reach the asymptotic value in three cases is 4.0 h, 1.0 h, and 4.5 h; the asymptotic values are approximately −0.087 km, 0.012 km, and 0.055 km, respectively. These results not only correspond with the conclusions of previous research but also provide a more extensive range of numerical results. This study establishes the groundwork for theoretical research on more complex water environmental flow models and provides a theoretical basis for engineering computations aimed at contributing to the environmental management of rivers and lakes. Full article

Reverberation is the main background interference in active sonar and seriously interferes with the extraction of the target echo. Active sonar systems can use short-pulse continuous wave (CW) signals to reduce the reverberation intensity. However, as the pulse width of the CW signals decreases, the reverberation envelope exhibits a high-frequency oscillating phenomenon. Active sonar often uses the cell average constant false alarm ratio (CA-CFAR) method to process the reverberation, which steadily decays with transmission distance. However, the high-frequency oscillation of the reverberation envelope deteriorates the performance of CA-CFAR, which causes a higher false alarm rate. To tackle this problem, the formation mechanism of the high-frequency oscillation characteristics of the reverberation envelope of the short-pulse-width CW signals is modeled and analyzed, and on this basis, an α filter is designed to suppress the high-frequency oscillation of the reverberation envelope before applying CA-CFAR. The simulation and lake trial results indicate that this method can effectively suppress high-frequency oscillations of the reverberation envelope, as well as exhibit robustness and resistance to reverberation interference. Full article

Assessing bacterial communities across water resources is crucial for understanding ecological dynamics and improving water quality management. This study examines the functional profiles of bacterial communities in drinking water resources in Mega Manila, Philippines, including Laguna Lake tributaries, pre-treatment plant sites, groundwater sources, and post-treatment plant sites. Using eDNA sequencing, flux balance analysis, and taxonomy-to-phenotype mapping, we identified metabolic pathways involved in nutrient metabolism, pollutant degradation, antibio- tic synthesis, and nutrient cycling. Despite site variations, there are shared metabolic pathways, suggesting the influence of common ecological factors. Site-specific differences in pathways like ascorbate, aldarate, and phenylalanine metabolism indicate localized environmental adaptations. Antibiotic synthesis pathways, such as streptomycin and polyketide sugar unit biosynthesis, were detected across sites. Bacterial communities in raw and pre-treatment water showed potential for pollutant degradation such as for endocrine-disrupting chemicals. High levels of ammonia-oxidizing and sulfate-reducing bacteria in pre- and post-treatment water suggest active nitrogen removal and pH neutralization, indicating a need to reassess existing water treatment approaches. This study underscores the adaptability of bacterial communities to environmental factors, as well as the importance of considering their functional profiles in assessing drinking water quality resources in urban areas. Full article

High-mountain water bodies represent critical components of their ecosystems, serving as vital freshwater reservoirs, environmental regulators, and sentinels of climate change. To understand the environmental dynamics of these regions, comprehensive analyses of lakes across spatial and temporal scales are necessary. While remote sensing offers a powerful tool for lake monitoring, applications in high-mountain terrain present unique challenges. The Ancash and Cuzco regions of the Peruvian Andes exemplify these challenges. These regions harbor numerous high-mountain lakes, which are crucial for fresh water supply and environmental regulation. This paper presents an exploratory examination of remote sensing techniques for lake monitoring in the Ancash and Cuzco regions of the Peruvian Andes. The study compares three deep learning models for lake segmentation: the well-established DeepWaterMapV2 and WatNet models and the adapted WaterSegDiff model, which is based on a combination of diffusion and transformation mechanisms specifically conditioned for lake segmentation. In addition, the Normalized Difference Water Index (NDWI) with Otsu thresholding is used for comparison purposes. To capture lakes across these regions, a new dataset was created with Landsat-8 multispectral imagery (bands 2–7) from 2013 to 2023. Quantitative and qualitative analyses were performed using metrics such as Mean Intersection over Union (MIoU), Pixel Accuracy (PA), and F1 Score. The results achieved indicate equivalent performance of DeepWaterMapV2 and WatNet encoder–decoder architectures, achieving adequate lake segmentation despite the challenging geographical and atmospheric conditions inherent in high-mountain environments. In the qualitative analysis, the behavior of the WaterSegDiff model was considered promising for the proposed application. Considering that WatNet is less computationally complex, with 3.4 million parameters, this architecture becomes the most pertinent to implement. Additionally, a detailed temporal analysis of Lake Singrenacocha in the Vilcanota Mountains was conducted, pointing out the more significant behavior of the WatNet model. Full article

This study investigates the genesis of analcite in black shale from continental lakes and its implications for hydrocarbon enrichment, with a case study of the Permian Pingdiquan Formation in the Junggar Basin, Xinjiang, China. As an alkaline mineral, analcite is extensively developed in China’s lacustrine black shale hydrocarbon source rocks and is linked to hydrocarbon distribution. However, the mechanisms of its formation and its impact on hydrocarbon generation and accumulation remain insufficiently understood. This paper employs a multi-analytical approach, including petrological observations, geochemical analysis, and X-ray diffraction, to characterize analcite and its association with hydrocarbon source rocks. The study identifies a hydrothermal sedimentary origin for analcite, suggesting that it forms under conditions of alkaline lake water and volcanic activity, which are conducive to organic matter enrichment. The analcite content in the studied samples exhibits a significant variation, with higher contents associated with hydrocarbon accumulation zones, suggesting its role in hydrocarbon generation and accumulation. This paper reports that analcite-bearing rocks display characteristics of high-quality reservoirs, enhancing the permeability and porosity of the rock, which is essential for hydrocarbon storage and migration. In conclusion, this paper underscores the importance of analcite as a key mineral indicator for hydrocarbon potential in black shale formations and provides valuable insights for further geological and hydrocarbon exploration in similar settings. Full article

Exploring eco-environmental quality dynamics in the Daihai Lake Basin has significant implications for the conservation of ecological environments in the semi-arid and arid regions of northern China. Based on the Google Earth Engine (GEE) platform, the remote sensing ecological index (RSEI) was constructed by coupling Landsat SR remote sensing data from 1985 to 2022. The spatial significance of the RSEI was analyzed using linear regression equations and an F-test. The spatial correlation, distribution characteristics, and driving factors behind the RSEI were explored using Moran’s index and a geodetector. The results indicated that (1) the RSEI was appropriate for evaluating eco-environmental quality in the Daihai Lake Basin. (2) From 1985 to 2022, the eco-environmental quality of the Daihai Lake Basin exhibited a positive trend but remained subpar. (3) A positive spatial autocorrelation was demonstrated for eco-environmental quality with increasing spatial aggregation. (4) Significant eco-environmental quality degradation (slope < 0) occurred primarily in Sanyiquan Town in the northeastern region of the basin and in Tiancheng Township in the southeastern region. Conversely, a notable improvement (slope > 0) was predominantly observed in Yongxing and Liusumu in southwestern Daihai. (5) The improvement in the ecological environment of the Daihai Lake Basin was primarily attributed to an increase in NDVI and WET and a decrease in NDBSI and LST. The interaction between NDVI and LST had the greatest explanatory power for the ecological environment. Among the external driving factors, DEM (elevation) was the dominant factor in the RSEI and had the strongest explanatory power. The interaction between DEM and LST was the most significant, and the driving factors were enhanced. This study provided a theoretical basis for the sustainable development of the Daihai Lake Basin, which is crucial for the local ecological environment and economic development. Full article

In recent years, the role of the atmosphere in the formation of the chemical composition of water in Lake Baikal and its tributaries has been increasing. In this regard, the study of equivalent black carbon (eBC) in the air above the lake and its coast has an important practical application. This paper presents the results of the mass concentration of eBC and submicron aerosol in the air above the water area of Lake Baikal, which were obtained during expeditions onboard research vessels in the summer of 2019 and 2023. We analyzed the data from the coastal monitoring station Listvyanka. To measure eBC, an MDA-02 aethalometer was used in the water area of the lake, and a BAC-10 aethalometer at the Listvyanka station. The background level of the eBC concentration in the air at different areas of the lake ranged between 0.15 and 0.3 µg m⁻³. The results of the two expeditions revealed the influence of the coastal settlements and the air mass transport along the valleys of the lake’s large tributaries on the five- to twentyfold growth of the eBC concentration in the near-water atmosphere. In the diurnal dynamics of eBC near settlements, we recorded high values in the evening and at night. In background areas, the diurnal dynamics were poorly manifested. In the summer of 2019, there were smoke plumes in the water area of Lake Baikal from distant wildfires and a local fire site on the east coast of the lake. The eBC concentration increased to 5–6 µg m⁻³, which was 10 to 40 times higher than the background. The long-range transport of plumes from coal-fired thermal power plants in large cities of the region made the major contribution to the eBC concentration at «Listvyanka» in winter, which data on aerosol, gas impurities, and meteorological parameters confirmed. Full article

The surrounding environment of architectural heritage sites is integral to cultural heritage protection; plant landscapes play crucial roles in them. Controlling plant spaces and appearances is essential for preserving plant landscapes. A World Cultural Heritage Site, the Summer Palace has undergone multiple changes since the 1860s; restoring and protecting plant landscapes has been an ongoing research focus. However, data accuracy limitations have hindered analyses of the overall spatial characteristics of historical gardens. Here, the historical dynamics and unique landscape features of plants on the front hill of Longevity Hill (FLH) are explored, and conservation and renewal strategies are proposed. Geographic information system (GIS) and WSL Monoplotting Tool are used to identify historical plant spaces. Plant space types are classified, and their landscape characteristics are analyzed. On the basis of historical events, the historical plant spaces on the FLH can be divided into two major categories and six subcategories. The vegetation retention area (south side) was less affected, and the plant landscape along Kunming Lake was the most well-preserved. However, the vegetation-damaged area (north side) was impacted more in the western part than in the eastern part, with notable changes in spatial landscape characteristics, particularly regarding forest function, morphology, and structure. Strategies are proposed for reducing human intervention and adjusting retention areas; furthermore, historical images and spatial grading in damaged areas can be used to suggest landscape adjustment and restoration strategies. This study introduces a method for analyzing the historical characteristics of plant landscapes over time that can be used to protect cultural heritage sites worldwide. Full article

Hypophthalmichthys nobilis are widely distributed in the Yangtze River basin and its related lakes. They are an important economic fish species and are a famous cultured species known as the “Four Famous Domestic Fishes” in China. Currently, with the fishing ban in the Yangtze River basin, fishing for H. nobilis in the natural water bodies of the Yangtze River basin has been completely prohibited. In order to identify the sources of H. nobilis appearing in the market, further control and accountability is necessary to trace the sources of H. nobilis in the Yangtze River basin and its related water bodies. Therefore, this study identified and traced different sources of H. nobilis through muscle element fingerprint analysis (EFA). The results show that H. nobilis from different stations have characteristic element compositions. The characteristic element of H. nobilis from Wuhan (WH) is Pb, which is significantly higher than that in other stations; the characteristic element from Anqing (AQ) is Hg, which is significantly higher than that in other stations; and the characteristic element from Taihu (TH) is Al, which is significantly higher than that in other water areas. Multivariate analysis selected different spatial distribution patterns in four discriminative element ratios (Pb/Ca, Cr/Ca, Na/Ca, and Al/Ca) in the muscle of H. nobilis in the Yangtze River basin and its related lakes. This study suggests that the screened discriminative elements can be used to visually distinguish different sources of H. nobilis and to quickly trace and verify the origin of newly emerging samples. Therefore, the use of selected discriminative element fingerprint features to trace the origin of new samples has been proven to be feasible. By further discriminating and verifying the muscle element fingerprints of new samples, the discrimination rate is high. Therefore, a multivariate analysis of muscle element fingerprints can be used for tracing the origins of samples of unknown origin in market supervision. Full article

Under the background of global change, the lake water environment is facing a huge threat from eutrophication. The rapid increase in curly-leaf pondweed (Potamogeton crispus L.) in recent years has seriously threatened the ecological balance and the water diversion safety of the eastern route of China’s South-to-North Water Diversion Project. The monitoring and control of curly-leaf pondweed is imperative in shallow lakes of northern China. Unmanned Aerial Vehicles (UAVs) have great potential for monitoring aquatic vegetation. However, merely using satellite remote sensing to detect submerged vegetation is not sufficient, and the monitoring of UAVs on aquatic vegetation is rarely systematically evaluated. In this study, taking Nansi Lake as a case, we employed Red–Green–Blue (RGB) UAV and satellite datasets to evaluate the monitoring of RGB Vegetation Indices (VIs) in pondweed and mapped the dynamic patterns of the pondweed Fractional Vegetation Coverage (FVC) in Nansi Lake. The pondweed FVC values were extracted using the RGB VIs and the machine learning method. The extraction of the UAV RGB images was evaluated by correlations, accuracy assessments and separability. The correlation between VIs and FVC was used to invert the pondweed FVC in Nansi Lake. The RGB VIs were also calculated using Gaofen-2 (GF-2) and were compared with UAV and Sentinel-2 data. Our results showed the following: (1) The RGB UAV could effectively monitor the FVC of pondweed, especially when using Support Vector Machine that (SVM) has a high ability to recognize pondweed in UAV RGB images. Two RGB VIs, RCC and RGRI, appeared best suited for monitoring aquatic plants. The correlations between four RGB VIs based on GF-2, i.e., GCC, BRI, VDVI, and RGBVI and FVC_SVM calculated by the UAV (p < 0.01) were better than those obtained with other RGB VIs. Thus, the RGB VIs of GF-2 were not as effective as those of the UAV in pondweed monitoring. (2) The binomial estimation model constructed by the Normalized Difference Water Index (NDWI) of Sentinel-2 showed a high accuracy (R² = 0.7505, RMSE = 0.169) for pondweed FVC and can be used for mapping the FVC of pondweed in Nansi Lake. (3) Combined with the Sentinel-2 time-series data, we mapped the dynamic patterns of pondweed FVC in Nansi Lake. It was determined that the flooding of pondweed in Nansi Lake has been alleviated in recent years, but the rapid increase in pondweed in part of Nansi Lake remains a challenging management issue. This study provides practical tools and methodology for the innovative remote sensing monitoring of submerged vegetation. Full article

Sustainable potable groundwater supply is crucial for human development and the preservation of natural habitats. The largest endorheic inland lake in Kazakhstan, Balkhash Lake, is the main water resource for the arid southeastern part of the country. Several ore enrichment plants that are located along its shore have heavy metal pollution potential. The study area is located around a plant that has an evident anthropogenic impact on the Balkhash Lake aquatic ecological system, with ten known heavy metal toxic hotspots endangering fragile habitats, including some indigenous human communities. This study assessed the risk of heavy metal contamination from tailing dump operations, storage ponds, and related facilities and suggested management practices for preventing this risk. The coastal zone risk assessment analysis used an innovative integrated groundwater numerical flow and transport model that predicted the spread of groundwater contamination from tailing dump operations under several mitigation strategies. Heavy metal pollution prevention models included a no-action scenario, a filtration barrier construction scenario, and two scenarios involving the drilling of drainage wells between the pollution sources and the lake. The scenario assessment indicates that drilling ten drainage wells down to the bedrock between the existing drainage channel and the lake is the optimal engineering solution for confining pollution. Under these conditions, pollution from tailings will not reach Lake Balkhash during the forecast period. The methods and tools used in this study to enable mining activity without environmental implications for the region can be applied to sites with similar anthropogenic influences worldwide. Full article

The protection and restoration projects of the mountain-river-forest-field-lake-grass (MRFFLG) system are the mainstream focus of China’s current ecological environment protection. A reasonable method for calculating ecosystem service values (ESVs) is a prerequisite for determining the ecological service functions of a watershed. However, how to effectively implement and evaluate the systematic nature of the ecological protection and restoration of the MRFFLG system remains one of the pressing issues. This paper takes the protection and restoration project of the MRFFLG system in the Hunjiang River Basin (HRB) of Jilin Province, China, as an empirical case. Firstly, it constructs an ESVs system to quantify the comprehensive ecological protection and restoration effects of the MRFFLG system. The results show that the forest ecosystem in the HRB has the highest ecological value. Furthermore, by introducing the interval planning method, an uncertain optimization model is constructed with the objective function of maximizing the ecosystem service value of the HRB, and constraints such as restoration costs, unit restoration price, and restoration area. The results show that the total ESVs has increased, with a maximum increase of 348,413.79 × 10⁴ CNY. Finally, the introduction of the fuzzy method reduced the total interval of ESVs by 49.89%, effectively shortening the assessment interval. This study applies the interval-fuzzy method to the protection and restoration projects of the MRFFLG system, effectively measuring the comprehensive management effects of the MRFFLG system in the HRB. This paper provides a theoretical basis for the development of subsequent MRFFLG projects and offers theoretical references for promoting the ecological environment assessment of the comprehensive MRFFLG system. Full article

The global proliferation of synthetic microfiber waste has emerged as a pressing environmental concern due to its widespread distribution in both aquatic and terrestrial ecosystems. Primary sources of synthetic microfibers include laundering of synthetic textiles, manufacturing, and plastic breakdown, with transport via wastewater, runoff, atmospheric deposition, and animal ingestion. This review highlights the sources of microfiber formation and accumulation, ranging from freshwater lakes and rivers to deep-sea sediments. The presence of microfibers in agricultural soils, urban dust, and even remote locations indicates atmospheric transportation and diverse accumulation patterns. Additionally, this review discusses the transportation of microfibers through various pathways and elaborates on various treatment technologies for microfiber removal and reduction. The potential human health impacts and mitigation solutions are also highlighted. Overall, this review aims to provide comprehensive knowledge of the sources, transport mechanisms, and accumulation patterns of synthetic microfibers, emphasizing their multifaceted environmental impact and the need for further research to develop effective solutions. Full article

East African lakes support the food and water security of millions of people. Yet, a lack of continuous long-term water quality data for these waterbodies impedes their sustainable management. While satellite-based water quality retrieval methods have been developed for lakes globally, African lakes are typically underrepresented in training data, limiting the applicability of existing methods to the region. Hence, this study aimed to (1) assess the accuracy of existing and newly developed water quality band algorithms for East African lakes and (2) make satellite-derived water quality information easily accessible through a Google Earth Engine application (app), named LAndsat water QUality retrieval tool for east African lakes (LAQUA). We collated a dataset of existing and newly collected in situ surface water quality samples from seven lakes to develop and test Landsat water quality retrieval models. Twenty-one published algorithms were evaluated and compared with newly developed linear and quadratic regression models, to determine the most suitable Landsat band algorithms for chlorophyll-a, total suspended solids (TSS), and Secchi disk depth (SDD) for East African lakes. The three-band algorithm, parameterised using data for East African lakes, proved the most suitable for chlorophyll-a retrieval (R² = 0.717, p < 0.001, RMSE = 22.917 μg/L), a novel index developed in this study, the Modified Suspended Matter Index (MSMI), was the most accurate for TSS retrieval (R² = 0.822, p < 0.001, RMSE = 9.006 mg/L), and an existing global model was the most accurate for SDD estimation (R² = 0.933, p < 0.001, RMSE = 0.073 m). The LAQUA app we developed provides easy access to the best performing retrieval models, facilitating the use of water quality information for management and evidence-informed policy making for East African lakes. Full article

Many saline lakes are temporary, with large variations in salinity, and their biota is adapted to withstand unfavorable periods. Utracan Lake, in a protected area in central Argentina, was studied on three occasions under different environmental conditions. In 2007, depth and salinity were 2 m and 33 g/L, and six species were recorded in the zooplankton. In 2009–2010, its maximum depth was 0.3 m, its salinity exceeded 230 g/L, and only Artemia persimilis was recorded. Field studies to compare the active zooplankton of a third period were combined with laboratory tests to ascertain the composition of the egg bank (flotation with sucrose) and zooplankton succession (hatching from sediments). In 2017–2018 (third period), the depth and salinity were 1.75 ± 0.17 m and 47.19 ± 11.40 g/L, respectively. Five species were recorded, and A. persimilis was found coexisting with cladocerans, copepods, and rotifers. Brachionus plicatilis, Hexarthra fennica, Boeckella poopoensis, A. persimilis, and a single specimen of Moina eugeniae were recorded in hatching experiments; however, the latter species was not recorded again. No cladoceran ephippia were recorded in the flotation tests. Salt accumulation on the sediments during the Utracan drought (2010–2016) would have deteriorated the ephippia. The register of M. eugeniae in 2017–2018 could be largely because of recolonization by waterfowl. The conservation of Utracan Lake is therefore advisable, and the same goes for other nearby saline lakes, which can act as sources of propagules that cross terrestrial areas through transport by wind or zoochory. Full article