Yangtze River Water Research Articles

Multi-scale deterioration of physical and mechanical properties of argillaceous siltstone under cyclic wetting-drying of Yangtze River water

Cyclic interactions between rocks and water have general significance and are particularly relevant to engineering failures and geohazards. A comprehensive investigation of the multi-scale deterioration effects and mechanisms of cyclic wetting-drying on rocks can contribute to better engineering applications, but the probabilistic characterization of rock mass properties under cyclic wetting-drying remains a problem due to the difficult-to-test parameters and limited data. Numerous experiments on rock samples of argillaceous siltstone subjected to cyclic wetting-drying of Yangtze River water demonstrate progressive alteration of rock properties on multiple scales, including changes in mineralogy, grain structure, computed tomography, microporosity, and complexity of micropores, with calcite and albite being the most active minerals. The uniaxial compression strength and indirect tensile strength decrease exponentially with the cyclic number, while the Young's modulus increases. Considering the probabilistic characteristics of the geological strength index, the probabilistic mechanical properties of rock mass of studied argillaceous siltstone are then estimated through the generalized Hoek-Brown criterion. The results indicate that the uniaxial compression strength and indirect tensile strength of rock mass both follow lognormal distributions, while the Young's modulus follows a skewed distribution. Long-term strength parameters of rock and rock mass can also be determined as they exhibit exponential trends with the cyclic number. During the cyclic wetting-drying process, the water-rock interactions produce progressive changes in mineral compositions, microstructures, and micropores; with the accumulation of variations of physical properties, defects grow and develop into weak zones, thus the mechanical properties of argillaceous siltstone are significantly weakened. Investigations of the wetting-drying effects on the geological strength index and probabilistic characteristics of rock sample properties are recommended to accurately evaluate rock mass properties affected by cyclic wetting-drying.

One-pot hydrothermal synthesis of MoS2 modified sludge biochar for efficient removal of tetracycline from water

Efficient removal of tetracycline (TC) has become a global challenge because the unsatisfactory removal rate of traditional sewage treatment technology. A carbon-based material (MoS2@SBC) was synthesized by one-pot hydrothermal method using municipal sludge as the feedstock to remove TC from water. Characterization analysis showed that MoS2@SBC had abundant functional groups (e.g., -OH, CO, SH) and large surface area. The maximum adsorption capacity of MoS2@SBC for TC could reach 229.2 mg/g at 298 K. Elovich model and Langmuir model better fitted the kinetics and isotherms data, respectively, which illustrated that chemisorption dominated the process of TC adsorption onto MoS2@SBC. Liquid film diffusion and intraparticle diffusion simultaneously controlled the adsorption process. The thermodynamics study described that adsorption was a spontaneous, endothermic and randomness increasing process. The ionic species/strength and solution pH were the critical factors affecting the adsorption process. The kinetics, isotherms and thermodynamics analysis, together with characterization results demonstrated that π-π conjugation, H-bonding, electrostatic interaction and pore filling were the main adsorption mechanisms. Additionally, the adsorption capacity of MoS2@SBC for TC in the actual waters (Yangtze River water and Nanhu Lake water) was inhibited. Furthermore, NaOH regeneration could maintain the sustainable adsorption performance of MoS2@SBC. This study developed a promising adsorbent for TC removal and provided a resource utilization approach for sludge.

Occurrence, spatial variation, seasonal difference, and ecological risk assessment of organophosphate esters in the Yangtze River, China: From the upper to lower reaches

A comprehensive contamination profile of organophosphate esters (OPEs) in the Yangtze River in China has not yet been characterized. In this study, we investigated the occurrence, spatial variation, and seasonal difference of 18 selected OPEs in surface water samples of the Yangtze River mainstream. To characterize the contamination profile of the OPEs, we collected 144 Yangtze River water samples from 72 sampling sites in December 2020 and June 2021. Four alkyl-OPEs [trimethyl phosphate, triethyl phosphate (TEP), tributyl phosphate, and tris(2-butoxyethyl) phosphate (TBOEP)] and three halogenated OPEs [tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate] were the most frequently detected target compounds (>95%). TCIPP (median: 34.6 ng/L), TEP (median: 26.2 ng/L), and TCEP (median: 17.9 ng/L) were the most abundant compounds, while the median values of the others were below 10 ng/L. Additionally, the concentrations of most OPEs gradually/dramatically increased from upstream to downstream Yangtze River. Notably, the median concentration of summed OPEs in Shanghai (415 ng/L; downstream) was approximately ten times higher than that in Qinghai (45.7 ng/L; upstream). Urban sampling sites had significantly or slightly higher concentrations of most OPEs than rural sampling sites. Moreover, the OPE concentrations in the river water differed between the winter and summer. The concentrations of summed OPEs (median: 117 vs. 106 ng/L), summed alkyl-OPEs (67.0 vs. 45.8 ng/L; p < 0.05), and summed aryl-OPEs (0.48 vs. 0.17 ng/L; p < 0.05) were slightly or significantly higher in December than those in June; nevertheless, summed halogenated OPEs were slightly higher in June (62.2 vs. 50.2 ng/L) than that in December. Compared with previously reported data for OPEs in other major rivers worldwide, the Yangtze River water had relatively lower concentrations of the OPEs than those in the rivers of developed countries and regions. Ecological risk assessment suggested that tris(2-ethylhexyl) phosphate and TCEP posed relatively high risks (RQ: 1.01 and 0.98, respectively) at the maximum concentration, and TBOEP posed a moderate risk (RQ: 0.25). This is the first study to comprehensively characterize the contamination profile of the Yangtze River by the OPEs.

Adsorption mechanisms of metal ions (Pb, Cd, Cu) onto polyamide 6 microplastics: New insight into environmental risks in comparison with natural media in different water matrices

Microplastics (MPs) are ubiquitous in the environment and have a great potential to coexist with metal ions. This work investigated the adsorption–desorption behaviors of three divalent metal ions (Cu, Cd, Pb) on polyamide 6 (PA6) MPs and natural media (riverside soil and marine sediment) and compare their environmental risks. The result showed that the adsorption amounts of metal ions onto PA6 MPs followed the order of Cd(II) (1.210 μmol/g) < Cu(II) (2.299 μmol/g) < Pb(II) (3.756 μmol/g). The adsorption of metal ions on PA6 was significantly affected by water chemistry, including solution pH, salinity, and the concentration of citric acid (CA) and humic acid (HA). Natural water matrices (Yangtze River water and Seawater) enhanced the uptake of three metal ions by PA6 MPs. The analysis of Fourier transform-infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) highlighted the importance of amide groups in controlling the adsorption of metal ions onto PA6 MPs. Site energy distribution indicated that the adsorption of metal ions mainly involved chemisorption. The retention factor (Rf) calculated by the adsorption–desorption behavior of three heavy metal ions indicated that the risk of metal ions posed by PA6 MPs was higher than that of natural media. Among all water matrices, the metal ion/PA6 MPs combinations posed the highest environmental risk in the simulated gastric fluid. This work highlights the behavior of PA6 MPs as metal ions vectors and provides strong evidence the assessment of environmental risk posed by MPs/metal ions combinations, opening new insight into understanding the environmental impacts of MPs.

Cost-effective and eco-friendly superadsorbent derived from natural calcium-rich clay for ultra-efficient phosphate removal in diverse waters

High-performance phosphate adsorbents integrated with the advantages of excellent adsorption performance, low cost, strong adaptability, and environmental friendliness have always been desirable, because the existing rare earth-free adsorbents were confined to poor adsorption ability and the rare earth-based adsorbents were confined to high cost and waste of rare earth resources. Here, in line with the concept of “from nature, for purifying nature”, a novel cost-effective and robust phosphate adsorbent was synthesized from natural calcium-rich clay (a very abundant and inexpensive raw material) by coupling the hydrothermal reaction with a simple pyrolysis process. The natural calcium-rich clay was firstly reacted with sodium silicate to form silicate precursor, which was then calcined to obtain superadsorbent with a number of available sites for capturing phosphates. The experimental adsorption capacity of the superadsorbent for phosphate is as high as 372.57 mg/g, which is 24.27 times that of raw clay, and is obviously superior to most other adsorbents. A satisfactory adsorption capacity was still attained in a broad pH range of 4 ∼ 12. After adsorption with 3 g/L of the superadsorbent, 99.99% of the phosphate in the initial phosphate solution (200 mg/L) was removed. After adsorption with 4 g/L of the adsorbent, the phosphate in natural water (e.g., Yellow river water, seawater, Yangtze river water, and Tap water) can be almost completely removed, and the total P concentration in the actual phosphate solution can be reduced to below 0.01 mg/L, which is significantly better than the commercially available phosphorus adsorbents. The in-depth structural analysis of the adsorbent after adsorption revealed that the adsorption of phosphate on the superadsorbent was mainly driven by chemical complexation interactions.

Study of the Lateral Bearing Capacity and Optimization Reinforcement Scheme of an Open Caisson with Consideration of Soil Disturbance

The bearing capacity of an open caisson under lateral loads is a key factor affecting the normal operation of an open caisson. It will inevitably have a disturbing effect on the surrounding soil layers during the sinking process of the caisson; that is, a disturbance ring will develop around the caisson. Based on the Jurong Yangtze River water supply project, the lateral bearing characteristics of the open caisson are analyzed by the numerical method with due consideration to soil disturbance, and the reinforcement scheme is optimized. The numerical results show that when the thickness of the disturbance ring is less than 0.5 m the disturbance ring has little effect on the lateral bearing capacity of the open caisson. An arc-shaped cement–soil reinforcement at the loading area can effectively improve the lateral bearing performance of the caisson. The optimized reinforcement thickness is 2 times that of the disturbance ring, and the reinforcement angle is approximately 60°.

Surface water isoscapes (δ18O and δ2H) reveal dual effects of damming and drought on the Yangtze River water cycles

The water regimes and biogeochemical cycles are remarkably affected by river damming and drought around the world. However, the dual effects on river water cycles have not yet attracted sufficient attention along the Yangtze River because of the relative consistency of annual water regimes. This study first explored the altered water cycle associated with damming and drought using surface water isoscapes (δ18O and δ2H) of river and lake water along the Yangtze River during the flooding seasons of 2016 and 2018, combined with other historical isotopic data from 2003 to 2013. The results show that river water isotopes are markedly varied on both spatial and temporal scales. The relatively more enriched river water representing δ18O values were observed from 2003 to 2007 compared with those in 2018, which were possibly caused by increased evaporative fractionation under abnormal drought conditions in the Yangtze River. Spatially, river water δ18O values exhibited a positive trend from upstream to the lower reaches because of the contrasting recharged sources, complex mixing, and evaporation from upstream to the lower reaches of the Yangtze River. This trend was related to variations in surface water temperature and water evaporation during the flooding seasons evidenced by a significant correlation between river isotopes and river water temperature. Moreover, the large variability in deuterium-excess (d-excess) and δ18O in the downstream could be inherited from the upstream because of short residence time and incomplete mixing in the Three Gorges Reservoir (TGR) during the initial stage of the Three Gorges Dam (TGD) operation (2003–2007). In contrast, the relatively lower variability of d-excess and δ18O was found in the downstream area due to the complete mixing in the TGR, causing the homogenization of reservoir water during the normal operation stage after 2010 (e.g., 2013 and 2018). Drought stimulates evaporative fractionation on river water and result in more negative d-excess values especially in 2006. The dual effects of river damming and drought remarkably changed the longitudinal hydrological connectivity and water cycle dynamics by prolonging the residence time and enhancing the water mixing, which should be thoroughly considered for water resource management, especially for regions with heavily-regulated rivers.

Multifunctional natural sepiolite nanofibre composite demulsifiers for efficient purification of oils and dyes in simulated and actual wastewater

Purifying stubborn wastewater containing stable oil droplets, high levels of oils, and other contaminants such as dyes to obtain fresh water is highly desirable but challenging. Here, a magnetically recyclable multifunctional β-cyclodextrin (β-CD)-modified sepiolite@Fe3O4 (SP@Fe3O4/APTES-CD) composite demulsifier with excellent demulsification capability and dye removal efficiency was developed, and the high-efficiency purification of the complex and stable emulsified wastewater with or without dyes was achieved after treatment with the demulsifier. The composition, structure and physicochemical properties of the multifunctional demulsifiers were discussed in detail, and the effects of the components in the emulsion (e.g., salts, oils, and surfactants) on the demulsification efficiency of the demulsifier were evaluated. It was revealed that the usage condition of the SP@Fe3O4/APTES-CD demulsifier is not limited by the types of water and oils. The demulsifier can purify not only the oil/deionized water emulsions, but also the oil/natural water (seawater, Yellow River water and Yangtze River water) emulsion with a very high oil-water separation efficiency of 99.6%. The oil-water separation efficiency of n-hexane/water, kerosene/water, gasoline/water, carbon tetrachloride/water, and soybean oil/water emulsions by the demulsifier are 98.5%, 99.8%, 99.1%, 98.7% and 99.2%, respectively. The anionic dye Congo red (CR) and cationic dye Methylene blue (MB) in the surfactants-stabilized O/W emulsion can be simultaneously removed after demulsification process with a removal efficiency larger than 99%. The demulsification process of surfactant-stabilized emulsion with the demulsifier can be accelerated by applying an external magnetic field to realize magnetically controlled demulsification. In addition, the SP@Fe3O4/APTES-CD demulsifier is very effective in separating and purifying the practical emulsified wastewater produced from steel mills within 20 s to obtain clean water. The demulsifier can still keep better demulsification efficiency after being recycled and reused for more than ten cycles.

Elemental Analysis of Environmental Waters by Solution Cathode Glow Discharge—Atomic Emission Spectrometry (SCGD-AES) with a Multifunctional Injection System

A multifunction sample injection system combined with solution cathode glow discharge—atomic emission spectrometry (SCGD-AES) was developed based on several simple devices (six-way valve, peristaltic pump and medical injector). The equipment enables two analytical modes (continuous flow and flow injection), selected according to the sample. Moreover, the equipment can be operated at atmospheric pressure without any inert gas. Under the optimal experimental conditions (1150 V discharge voltage, 2.5 mm discharge gap, 2.32 mL min−1 flow rate and solution pH 1.0), ten elements (Na, K, Mg, Cu, Rb, Ag, Tl, Cd, Zn, and Mn) were determined using SCGD-AES in the continuous flow and flow injection modes. The detection limits for metals were from 0.1 to 264 µg L−1 (continuous flow mode) and 0.9 to 282 µg L−1 (flow injection mode). The relative standard deviations of the spectral intensities were below 2%. The instrumentation was successfully applied to the Yangtze River and reservoir water samples. The accuracy and viability were confirmed by comparison with inductively coupled plasma—atomic emission spectrometry (ICP-AES) measurements.

Impacts of the Yangtze River Water Transfer Project on water quality of Lake Chaohu in different typical years

“引江济巢”作为引江济淮的起始段工程，承担着改善巢湖水质的重要任务，调水路线的选取对水质改善效果有关键影响.本文基于MIKE21模型构建了巢湖水动力水质模型，分别模拟了丰水年、平水年和枯水年情景下巢湖流场和总氮、总磷浓度时空分布特征，以及不同调水路线在各典型年对巢湖水质的影响.结果显示巢湖流场和水质分布有明显的空间差异性，受入湖负荷和流量影响，巢湖在丰水年水质较差，整体来说东湖区水质优于西湖区.相比其他年份，丰水年调水对湖区水质的改善作用最明显；不同调水路线中，自白石天河入流相较兆河入流对巢湖，尤其是西湖区水质改善明显.;As the starting part of the Yangtze River Water Transfer Project, it plays an important role in improving the water quality of Lake Chaohu. The selection of the water diversion route has a key impact on the water quality improvements. Based on the two-dimensional model MIKE21, we simulated the hydrodynamic and water quality distribution of Lake Chaohu in wet, normal and dry years, as well as the influence of different water diversion routes on the water quality of Lake Chaohu in different years. The results showed that there were obvious spatial heterogeneity in the flow field and water quality of Lake Chaohu. The water quality of Lake Chaohu was poor in wet year and was better in the eastern area than that in the western area. Compared with other years, the water diversion in wet years has the most obvious effect on improving the water quality in the lake area. In different water diversion routes, the inflow from Baishitian River has significantly improved the water quality of Lake Chaohu, especially the west lake area, compared with the inflow of Zhaohe River.

Improved Transformer Model for Enhanced Monthly Streamflow Predictions of the Yangtze River

Over the past few decades, floods have severely damaged production and daily life, causing enormous economic losses. Streamflow forecasts prepare us to fight floods ahead of time and mitigate the disasters arising from them. Streamflow forecasting demands a high-capacity model that can make precise long-term predictions. Traditional physics-based hydrological models can only make short-term predictions for streamflow, while current machine learning methods can only obtain acceptable results in normal years without floods. Previous studies have demonstrated a close relation between El Ni&#x00F1;o-Southern Oscillation (ENSO) and the streamflow of the Yangtze River. However, traditional models, holding the encoder&#x2013;decoder architecture, only have one encoder block that can not support bivariate time series forecasting. In this study, a transformer-based double-encoder-enabled model was proposed, called the double-encoder Transformer, with a distinctive characteristic: "cross-attention" mechanism that can capture the relation between two time series sequences. Using river flow observation collected by the Yangtze River Water Resources Commission and El Ni&#x00F1;o-Southern Oscillation (ENSO) observation collected by the National Oceanic and Atmospheric Administration, the model can achieve better performance. By using variational mode decomposition (VMD) technique for preprocessing, the model can make precise long-term predictions for the river flow of the Yangtze River. A monthly prediction of 21 years (from January 1998 to December 2018) was made, and the results indicate that the double-encoder Transformer outperforms mainstream time series models.

Imine-linked covalent organic frameworks coated stir bar sorptive extraction of non-steroidal anti-inflammatory drugs from environmental water followed by high performance liquid chromatography-ultraviolet detection

In this study, spherical imine-linked covalent organic frameworks (COFs) were fabricated from 2,5-dimethoxybenzene-1,4-dialdehyde (DMTP) and 1,3,5-tris (4-aminophenyl) benzene (TAPB) and named as TAPB-DMTP-COFs. The resulting powders were coated onto bare glass bars via physical-adhesion to obtain TAPB-DMTP-COFs coated stir bars. The self-made stir bars exhibited higher extraction efficiency (74–85%) and faster dynamics (50 min) towards non-steroidal anti-inflammatory drugs (NSAIDs) over ethylene glycol-Silicone (42–68%, 180 min) and polydimethylsiloxane (3–61%, 180 min) coated stir bars. Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS), zeta potential and water contact angle were employed to provide a comprehensive understanding of the adsorption mechanism between the coating and analytes. The results displayed that methoxy group worked as an adsorption site helping the adsorption of interest NSAIDs onto the TAPB-DMTP-COFs coating and hydrogen bonds formed between the O atoms and the analytes. Additionally, the adsorption mechanisms possibly also involved π-π interaction and hydrophobic interaction. Moreover, TAPB-DMTP-COFs coated stir bars exhibited good stability and could be reused more than 60 times. Subsequently, a method by combining TAPB-DMTP-COFs coated stir bar sorptive extraction (SBSE) with liquid chromatography (HPLC)-ultraviolet detector (UV) was established for the determination of four NSAIDs in environmental waters. Under the optimized conditions, the established method showed a wide linear range of 0.2/1–500 μg/L for interest NSAIDs, the limits of detection varied from 0.039 to 0.312 μg/L. Yangtze River water, East Lake water and Spring water were subjected to the proposed method, the recoveries in spiked samples were 84.7–104%, 81.2–101% and 82.6–97.6%, respectively.

Improved solution cathode glow discharge micro-plasma source with a geometrically optimized stainless steel auxiliary cathode for optical emission spectrometry of metal elements

An improved micro-plasma source for the quantitative analysis of heavy metal elements by solution cathode glow discharge-optical emission spectrometry (SCGD-OES) was developed. The glow-discharge plasma source was fabricated using a geometrically optimized stainless steel auxiliary cathode solution and a tungsten anode. Optimum discharge could be attained at reduced solution flow rates under the following operating conditions: pH 1.0 (HNO3); a discharge current of 80 mA; a solution flow rate of 1.65 mL/min; and a discharge gap of 2.5 mm. The detection limits (DLs) of the improved micro-plasma source for K, Na, Ni, Cd, Co and Hg were 0.17, 0.06, 18, 10, 25 and 66 μg/L, respectively. The recoveries of metal elements from spiked samples of spring river, Yangtze River and reservoir water measured by SCGD-OES showed good agreement with those obtained using ICP-OES. The results from this study may provide a new direction for the design of glow discharge sources for the in situ determination of metal elements in complex water samples.

Water Chemical Characteristics and Influence of Exogenous Acids in the Yangtze River Basin

To explore the influence of human activities on the Yangtze River water chemistry, water samples were obtained from a representative section the main river stem/branch in wet and normal seasons in 2016. Ion ratio analysis, principal component analysis(PCA), and chemical ion balance calculations were performed, and carbonate rock dissolution rates were determined based on carbonate and exogenous acids. The result show that HCO3-Ca is the dominant hydrochemistry type, indicating that the dissolution of carbonate rocks in the basin is the main process affecting hydrochemistry, and carbonate acid is significant in the weathering of carbonate rocks. In addition, the proportion of carbonate acid dissolution in the wet and normal seasons accounted for 60.33% and 59.14% of the total dissolution, respectively. The dissolution ratio among the different sampling points was notable, which indicates that the carbon sink effect of exogenous acid cannot be ignored. In addition, cation exchange some influence on hydrochemistry but was not the main reaction process. Compared with hydrological monitoring data for the last few years, the weathering of rocks by sulfuric and nitrate acids has strengthened, and the negative effects of anthropogenic pollution in the Yangtze River have increased.

Occurrence and transport of perfluoroalkyl acids (PFAAs) in a Yangtze River water diversion project during water diversion and flooding

Water diversion is increasingly utilized for water supply, flood control, irrigation, and water quality improvement in many water bodies globally. Our findings indicate that micropollutants such as perfluoroalkyl acids (PFAAs) can be transported via dual-source water diversion projects during water diversion and flood discharge, which may negatively impact both receiving water bodies. However, the sources, spatiotemporal variations, and fluxes of PFAAs under water diversion projects remain unclear. Here we report patterns of 18 PFAA compounds in the surface water at 14 sites of a dual-source water diversion project (Wangyu River) connecting the Yangtze River and Taihu Lake in China. We found multiple contamination hotspots with PFHxA and PFOA dominantly originating from industrial and domestic sources during water diversion from the Yangtze River to Taihu Lake. During the severe flooding in summer 2020, PFAA concentrations ranged from 82.0 to 114.0 ng L−1, while the concentrations and relative contributions of individual perfluoroalkane sulfonic acids (PFSAs) increased along the mainstream due to the tributaries’ contribution and high contamination level in the lake. Based on the spatiotemporal patterns of PFAA pollution, the flux of total PFAAs including both dissolved-phase and SS-phase into Taihu Lake was estimated as 26.6 kg in January 2020 as a reference value for water diversion. To our knowledge, this is the first report to describe the sources, occurrences, and transport of PFAAs in a dual-source water diversion project during water diversion and flooding. The results provide a novel perspective regarding the ecological safety of dual-source water diversion projects.

Study on the proportion and flow path of Yangtze River water diversion into Taihu Lake

Abstract The purpose of this study is to quantify the proportion and flow path of the water diversion from Yangtze River (YRD) into Taihu Lake. Based on the analysis of rainfall and data of Taihu basin in the recent 30 years, a 1-D hydrodynamic model of the main inflow river network area of Taihu basin was constructed, coupled the convection-diffusion model with conservative material, the characteristics of YRD and the water inflow into Taihu Lake (WITL) in three typical years were calculated. The results show that the YRD has shown a significant upward trend in the past 30 years, accounting for 26.4, 35.6 and 42% of the total WITL in three typical years of wet, normal and dry conditions respectively. From the perspective of space, Taige River is the largest river in the western part of the lake that is affected by the river diversion (35%–72%), and Wuxi River is the smallest (1–3%). In addition, the primary flow path of YRD to Taihu Lake was through the Wuyi River and Lake Gehu from the water diversion station west of the Zao River.

Ratiometric fluorescent sensing of mercury (II) ion based on the Pt nanozyme-triggered fluorescence resonance energy transfer between Si quantum dots and 2,3-diaminophenazine

The demand for efficient methods to determine mercury ion (Hg2+) is increasing. Herein, we developed a ratiometric fluorescence assay by the coupling of nanozyme and fluorescence resonance energy transfer (FRET) to determine Hg2+. Platinum nanoparticles (PtNPs) was synthesized as effective nanozyme to catalyze the oxidation of o-phenylenediamine (OPD) at the presence of hydrogen peroxide (H2O2) to produce 2,3-diaminophenazine (DAP). The fluorescence emission of Si quantum dots (QDs) at 414 nm (I414) was observed to be quenched by DAP (emission at 576 nm (I576)) via FRET mechanism, whereas Hg2+ can depress the catalytic activity of PtNPs to generate DAP. Based on this principle, SiQDs/PtNPs/OPD/H2O2-based ratiometric fluorescence assay was developed that the emission ratio of DAP and SiQDs (I576/I414) decreased with a higher concentration of Hg2+. Noteworthy, the sensitivity of such system was found to be related with the value of I576/I414. The developed assay offered a detection range of 20–3000 nM and a detection limit of 10.5 nM. This assay was applied to analyze Yangtze river water, and its reliability has been validated by the standard ICP-MS method. Our work provided an effective and convenient method for Hg2+ detection.

Short-term forecast of Yangtze River water level based on Long Short-Term Memory neural network

The water level fluctuation forecast of Yangtze River plays an important role in the navigation planning and other areas. This study used LSTM neural network to make short term forecast of the water level of Nanjing navigable river, focusing on the 2 days, 3 days and 5 days-forecast from the past 14 days. The error of mean square reached 0.064, 0.121 and 0.195, showing a rather accurate prediction. The model was also suitable for longer time series prediction. This study optimized the model by adjusting the hyper-parameters using qualitative and quantitative analysis and further decided that the batch size equals to 90 and the epoch equals to 250 in the case of 5 days-forecast from the past 14 days. The prediction accuracy increased by 21% with a good prediction performance, and the error of mean square was reduced to 0.153. It provided a reference for the selection of hyper-parameters for the prediction of water level in Nanjing station by LSTM neural network.

Retrieval and Spatio-Temporal Variations Analysis of Yangtze River Water Clarity from 2017 to 2020 Based on Sentinel-2 Images

The Yangtze River is the third longest river in the world. Monitoring and protecting its water quality are important for economic and social development. Water clarity (Secchi disk depth, SDD) is an important reference index for evaluating water quality. In this study, Sentinel-2 multispectral instrument (MSI) remote sensing images were utilized together with the Forel-Ule index (FUI) and hue angle α to construct an SDD retrieval model, which was applied to the Yangtze River from 2017 to 2020, which was used to describe color in the International Commission on Illumination (CIE) color space to construct an SDD retrieval model that was applied to the Yangtze River for the period 2017–2020. Further, the spatial distribution, seasonal variation, inter-annual variation, and driving factors of the observed SDD variations were analyzed. The spatial distribution pattern of the Yangtze River was high in the west and low in the east. The main driving factors affecting the Yangtze River SDD was sediment runoff, water level, and precipitation. The upstream and downstream Yangtze River SDD were negatively correlated with the change in water level and sediment runoff, whereas the midstream Yangtze River SDD was positively correlated with the change in water level and sediment runoff. The upper and lower reaches of the Yangtze River and overall SDD showed a weak downward trend, and the middle reaches of the Yangtze River remained almost unchanged.

Determination of 2, 4-Dichlorophenol, 2, 4-Dinitrophenol, and Bisphenol a in River Water by Magnetic Solid-Phase Extraction (MSPE) Using β-Cyclodextrin Modified Magnetic Ferrite Microspheres and High-Performance Liquid Chromatography – Diode Array Detection (HPLC-DAD)

β-Cyclodextrin modified magnetic microspheres were synthesized and used as an effective adsorbent for the solid-phase extraction of three phenols from water samples. Scanning electron microscopy and Fourier transform infrared spectrometry were used to characterize the adsorbents. The major parameters affecting the extraction and desorption efficiencies, such as adsorbent dosage, extraction time, pH, ionic strength, and eluent type were systematically optimized. Under these conditions, three phenols in water samples were extracted and determined by high performance liquid chromatography (HPLC) with diode array detection (DAD). Limits of detection (LODs) of 0.04–0.34 ng mL−1 and limits of quantification (LOQs) from 0.13 to 1.14 ng mL−1 were achieved with good repeatability (relative standard deviation <7.5%). The developed method was applied for the determination of 2,4-dichlorophenol, 2,4-dinitrophenol and bisphenol A in spiked Yangtze River water, and the recoveries were from 81.0% to 94.9%. The results demonstrated that the combination of magnetic solid-phase extraction (MSPE) with HPLC-DAD is suitable for the determination of trace phenolics in environmental water.