Water Environment Improvement Research Articles

Simulation and Analysis of Water Quality Improvement Measures for Plain River Networks Based on Infoworks ICM Model: Case Study of Baoying County, China

The water environment of plain river networks can be self-cleaning to a certain extent, but if the wastewater load exceeds a certain threshold, it can disturb the natural balance and cause water pollution. This underlines the importance of water pollution control measures. However, the development of water pollution control measures requires a large number of hydrological and hydrodynamic parameters and the establishment of corresponding relationships through modelling. Therefore, this study mainly used the Infoworks ICM model to construct a detailed hydrological–hydrodynamic water environment analysis model for the Yundong area of Baoying County, Yangzhou City, China, screened the main pollution source areas and pollution time periods of the typical rivers in the study area, and proposed effective improvement measures according to the actual situation of the study area. The results show that after the synergistic effect of multiple measures, the water quality can reach the Class III standard (GB3838-2002). This study can provide a reference for the water environment management and improvement of the plain river network and has good application prospects.

Water environment collaborative governance policy in the Yangtze River Delta

ABSTRACT Water environment collaborative governance is an important policy agenda during the Yangtze River Delta integration. Based on collaborative theory and policy value theory, this essay finds 144 water environment collaborative governance policies in the region from 2007 to 2022. It utilizes a policy collaborative model to discuss the water environment collaborative governance state at the regional and provincial levels in this region. Results show that 87.5% of water environment collaborative governance policies are enacted by local government in the region in this period, the main policy aims of which are water resource protection and wastewater pollution control. More policy attention will need to be paid to water environment restoration and off-office auditing of cadres. While administration policies and legal interventions are the main policy levers, economic policies and personal policies are relatively underused. Policy elements are significantly diversified at the provincial level in the region. In response to the findings above, this essay offers advice to improve water environment collaborative governance in the Yangtze River Delta region on four aspects: giving local governments full discretion in wastewater pollution treatment; giving full play of the water pollution control policies' value; adopting differentiated water pollution control policies; and strategies among the local government in the region, exerting policy stability.

Areal artificial recharge has changed the interactions between surface water and groundwater

Artificial groundwater recharge is increasingly utilized globally for addressing regional groundwater issues due to its effectiveness and ease of application. However, due to the complexity of the interaction of groundwater systems with the external environment and its inherent latency, governance effects are difficult to quantify and are not fully understood yet. In this study, the efficiency of areal artificial groundwater recharge was determined and the interactions with surface water were analyzed by field surveys, sample analysis, water balance reconstruction, and model simulation. A typical groundwater recharge region in the Beijing-Tianjin-Hebei region, China, was focused. Additionally, the response of groundwater flow and water quality to areal artificial groundwater recharge was quantified. Results showed that areal artificial groundwater recharge changes the relationship between surface water and groundwater, with an efficiency of 70 % under high recharge and fluctuation, and decreasing to 20–30 % after the groundwater level was stabilized. The impact on the hydrodynamic field were primarily manifested as the formation of water mounds near river channels, which expand laterally up to 9.2 km from the recharging river channel one year after implementation.Then the impact increases to 14.9 km and continues to expend a year after cessation. The areal artificial groundwater recharge has simultaneously improved the water quality by 23 % in monitoring wells within a 10 km distance from the river channel. The results of this study quantify the impacts of area artificial recharge on groundwater and provide references for the improvement of water resources and water environment in those similar regions.

Investigating the impact of artificial intelligence development on water pollution in China

Analysing the impacts of AI development on water pollution is of great significance for improving water environment management measures and promoting global sustainable development. In this study, macro and micro panel data of China from 2008 to 2019 were used to measure the development level of AI at the industry and provincial levels in China, and a panel data regression model was constructed to analyse the effects of AI development on water pollution and regional heterogeneity. The measurement results show that the development level of AI is increasing. Among the six industries, the intelligence level of the manufacturing industry has developed the fastest, by approximately 48.74 times compared with the baseline. At the provincial level, Guangdong Province made the greatest progress in intelligence level, increasing by approximately 23.6 times. The regression results show that AI technology is helpful in reducing the level of water pollution, and this conclusion remains valid after the regression of instrumental variables and robustness testing. In terms of regional heterogeneity, AI technology can significantly reduce the degree of water pollution in eastern and western China. However, the development of AI technology in the central region has no significant impact on water pollution, and a risk of increasing the degree of water pollution exists. The reasons may be that the eastern region has high levels of economic vitality and technological innovation and a strong ability to transform AI achievements, which can significantly improve the water environment. Industrial support policies in the western region are strong, and the application of AI can quickly improve production methods and significantly reduce water pollution levels. In comparison, the levels of economic development, technological innovation, and policy support in the central region need to be strengthened, so the environmental effect of AI is not significant.

Progress and future of China's aquatic ecological environment protection

AbstractSafeguarding water resources, aquatic habitats, and ecosystems is paramount for the well‐being of the populace, the future of the nation, and the sustainable development of China. With the relentless progression of ecological and environmental protection and the establishment of an ecological civilization, China's aquatic ecological environment protection has undergone five decades of exploration. The water environment protection paradigm has gradually transitioned from emphasizing pollutant emission concentration control and total pollutant emission control to prioritizing water environment quality improvement. Particularly in the past decade, regions nationwide have conducted proactive explorations and practices in source control, emission abatement, and quality enhancement. This paper systematically reviews the achievements in China's water environmental quality improvement and the characteristics of water environment management at various stages over the past half‐century. Considering the deployment of “three waters” coordination (water resources, water environment, and water ecology), green development, pollution, carbon reduction, and so forth, this paper analyzes the challenges confronted by China's aquatic ecological environment protection. Finally, future directions are prospected from six aspects: green development, climate change response, water resource allocation optimization, collaborative governance of multiple pollutants, aquatic ecological protection strengthening, and intelligent management improvement.

Spatiotemporal pattern of coastal water pollution and its driving factors: implications for improving water environment along Hainan Island, China.

In the context of human activities and climate change, the gradual degradation of coastal water quality seriously threatens the balance of coastal and marine ecosystems. However, the spatiotemporal patterns of coastal water quality and its driving factors were still not well understood. Based on 31 water quality parameters from 2015 to 2020, a new approach of optimizing water quality index (WQI) model was proposed to quantitatively assess the spatial and temporal water quality along tropical Hainan Island, China. In addition, pollution sources were further identified by factor analysis and the effects of pollution source on water quality was finally quantitatively in our study. The results showed that the average water quality was moderate. Water quality at 86.36% of the monitoring stations was good while 13.53% of the monitoring stations has bad or very bad water quality. Besides, the coastal water quality had spatial and seasonal variation, along Hainan Island, China. The water quality at "bad" level was mainly appeared in the coastal waters along large cities (Haikou and Sanya) and some aquaculture regions. Seasonally, the average water quality in March, October and November was worse than in other months. Factor analysis revealed that water quality in this region was mostly affected by urbanization, planting and breeding factor, industrial factor, and they played the different role in different coastal zones. Waters at 10.23% of monitoring stations were at the greatest risk of deterioration due to severe pressure from environmental factors. Our study has significant important references for improving water quality and managing coastal water environment.

Evolutionary Trend Analysis of Agricultural Non-Point Source Pollution Load in Chongqing Based on Land Use Simulation

Analysis of the relationship between future land use change and agricultural non-point source pollution (ANPSP) evolution is vital to promoting sustainable regional development. By simulating future land use types, we can identify and analyze the evolution trend of ANPSP. This study takes Chongqing as a case study to establish an integrated solution based on the PLUS model, output coefficient model, and GIS technology. The solution can simulate data, identify trends, and identify key control areas under future development scenarios. The results show that the PLUS model can simulate land use types at the provincial scale with high accuracy, with a Kappa coefficient of around 0.9. The land use type changes show that urban expansion has occupied a large amount of cultivated land. From 2000 to 2020, the proportion of high-load areas with TN pollution load levels was 4.93%, 5.02%, and 4.73%, respectively. Under the two scenarios in 2030–2050, the number of high-load areas decreased, and the average load level decreased from west to east. Sensitivity analysis found that risk changes are more sensitive to the increase in fertilizer application. When the TN and TP output coefficients are increased, the number of towns with increased levels is greater than those with decreased levels when the output coefficients are decreased. Sensitivity analysis can better identify key pollution control areas. The areas sensitive to changes in farmers’ behavior are mainly the Hechuan District, Nanchuan District, Qijiang District, Jiangjin District, and Bishan District. This study provides data and decision-making support for rural green development and water environment improvement.

Hydrodynamic effects and water environment improvement of topographic reconstruction in shallow lakes

This paper focuses on a typical shallow lake, Lake Changdanghu, which is subject to frequent hydrodynamic disturbances and suspended sediment deposition, resulting in reduced water clarity and the degradation of the grass-type ecosystem. Using a combination of long-term systematic observations and numerical simulations, the impact of terrain modification on the hydrodynamic characteristics of Lake Changdanghu and its resulting environmental improvements are systematically analyzed. The results indicate that there is a significant correlation between the wind wave intensity, suspended solids concentration of the water, and water clarity. The artificial shoal project effectively reduces the local wind wave intensity, increases the water area of the weak waves, and alters the flow structure and transport path of the lake. The wave reduction effect of the artificial shoal significantly improves the transparency of the local water, especially under high wind wave conditions, with a 60% increase in the sheltered area, significantly improving the physical habitat environment. Additionally, the flow resistance and guidance roles of the artificial shoal concentrate the impact of the poor water quality of the inflow in a local area, reducing its adverse effects on the main body of the lake. Our research demonstrates that for shallow lakes, the water transparency can be improved, the physical habitat conditions for aquatic vegetation can be enhanced, and grass-type ecosystems can be gradually restored through artificial intervention and vegetation recovery projects by reducing the wave energy, flow resistance, and guidance through the construction of artificial shoals. This approach achieves long-term maintenance of eutrophication control and water quality improvement in shallow lakes.

Spatial and Temporal Distribution and Risk Assessment of Heavy Metals in Surface Water of Changshou Lake Reservoir, Chongqing

To understand the water pollution status and environmental risks of Changshou Lake, the concentrations of heavy metals (Cr, Cu, Zn, As, Cd, and Pb) in the water were collected and analyzed during different seasons. The study investigated temporal and spatial variations, distribution characteristics, pollution levels, and health risks associated with heavy metals in Changshou Lake. The results showed that all six heavy metals were below than the Class Ⅰ standard of the Surface Water Environmental Quality Standard (GB 3838-2002), but recent years have witnessed an increasing trend, with Cu, As, and Pb showing a significant increase (P<0.05). The temporal and spatial distributions of these heavy metals were different. Temporally, Cr and Cd concentrations in surface water were higher in summer, As and Zn were higher in spring, and Pb and Cu were higher in autumn and winter. Spatially, the concentrations of Cr, As, Cu, Zn, and Pb showed higher concentrations in the southern outlet of the reservoir, the northwestern Longxi River inlet, and the central part of the reservoir, whereas Cd was higher in the northern stagnant area. The overall levels of heavy metals in the water body of Changshou Lake were low, with Cr and Cu slightly polluted, while other heavy metals were identified as having an insignificant pollution level. Drinking water was the primary exposure pathway to carcinogenic and non-carcinogenic heavy metals in surface water bodies. The health risk values of Cr and As in water bodies were high, ranging from 6.2×10-10 to 3.0×10-4 and 5.1×10-8 to 3.9×10-5, respectively. The corresponding contribution rates for children and adults to the total health risk were high, with Cr accounting for 87.18% and 87.20%, respectively, while As accounted for 12.73% and 12.71%, respectively. Therefore, it is crucial to prioritize environmental risks associated with Cr and Cu, as well as the health risks associated with Cr and As in Changshou Lake These findings provide a scientific foundation for water pollution control and environmental quality improvement in Changshou Lake, and rational development and utilization of water resources.

Research Progress on the Degradation of Organic Pollutants in Water by Activated Persulfate Using Biochar-Loaded Nano Zero-Valent Iron.

Biochar (BC) is a new type of carbon material with a high specific surface area, porous structure, and good adsorption capacity, which can effectively adsorb and enrich organic pollutants. Meanwhile, nano zero-valent iron (nZVI) has excellent catalytic activity and can rapidly degrade organic pollutants through reduction and oxidation reactions. The combined utilization of BC and nZVI can not only give full play to their advantages in the adsorption and catalytic degradation of organic pollutants, but also help to reduce the agglomeration of nZVI, thus improving its efficiency in water treatment and providing strong technical support for water resources protection and environmental quality improvement. This article provides a detailed introduction to the preparation method and characterization technology, reaction mechanism, influencing factors, and specific applications of BC and nZVI, and elaborates on the research progress of BC-nZVI in activating persulfate (PS) to degrade organic pollutants in water. It has been proven experimentally that BC-nZVI can effectively remove phenols, dyes, pesticides, and other organic pollutants. Meanwhile, in response to the existing problems in current research, this article proposes future research directions and challenges, and summarizes the application prospects and development trends of BC-nZVI in water treatment. In summary, BC-nZVI-activated PS is an efficient technology for degrading organic pollutants in water, providing an effective solution for protecting water resources and improving environmental quality, and has significant application value.

Ubiquitous occurrence of 1,4-dioxane in drinking water of China and its ecological and human health risk

The occurrence and distribution of 1,4-dioxane was investigated in 280 source and finished drinking water samples from 31 Chinese cities, based on which its ecological and health risks were systematically evaluated. The findings demonstrated that 1,4-dioxane was detected in about 80.0 % samples with values ranging from n.d. to 7757 ng/L in source water and n.d. to 2918 ng/L in drinking water. 1,4-Dioxane showed limited removal efficiency using conventional coagulation–sedimentation–filtration processes (14 % ± 48 %), and a removal efficiency of 35 % ± 44 % using ozonation-biological activated carbon advanced treatment processes. Relatively higher concentrations, detection frequency and environmental risk were observed in Taihu Lake, Yellow River, Yangtze River, Zhujiang River, and Huaihe River mainly in the eastern and southern regions, where there are considerable industrial activities and comparatively high population densities. The widespread presence as by-products during manufacturing consumer products e.g., ethoxylated surfactants, suggested municipal wastewater discharges were the dominant source for the ubiquitous occurrence of 1,4-dioxane, while industrial activities, e.g. resin manufacturing, also contribute considerably to the elevated concentrations of 1,4-dioxane. The estimated risk quotients were in the range of <1.5 × 10−4 for ecological risk, <5.0 × 10−3 by oral exposure and < 5.0 × 10−2 by inhalation exposure for health risk, illustrating limited ecological harm to water environment or chronic toxicity to human health. For carcinogenic risk, 1,4-Dioxane presented a mean risk of 1.8 × 10−6 by oral exposure, which slightly surpassed the recommended acceptable levels of U.S. EPA (<10−6), and risk from inhalation exposure could be negligible. The pervasiveness in drinking water, low removal efficiencies during water treatment processes, and suspected health impacts, highlighted the necessity to set related water quality standards of 1,4-dioxane in order to improve water environment in China.

Characterizing the water resource-environment-ecology system harmony in Chinese cities using integrated datasets: A Beautiful China perspective assessment

Integrated management and synergistic improvement of the water system is a topic of widespread concern. This study innovatively integrates three functions of quality assessment, synergy evaluation, and driving influence determination to establish a systematic framework assessing water system harmony. A case study of 336 Chinese cities is further performed by combining multi-scale and multi-source datasets. The results show China's water system quality has improved from 2015 to 2022. Development in the water resource, environment, and ecology subsystems have been differentiated, with 0.05 %, 4.33 %, and −1.64 % changes, respectively. The degradation of water ecology and the weak synergy with the other two subsystems have limited China's water system harmony. Water environment improvement played a contributive role in improving the water system quality. The contribution structure of water resources, environment, and ecology has shifted towards equilibrium in recent years. We found and highlighted the north-south differentiation of water system harmony in Chinese cities. The Beijing-Tianjin-Hebei and its surroundings, the Yangtze River Delta, and the middle reaches of the Yangtze River are identified as priority regions for water system harmony improvement. The primary contribution of this study is to propose an assessing concept of water resource-environment-ecology system harmony, establish well-structured assessment methods, and integrate the multiple data sources. The novel methods and findings, including the indicator system, application of data mining and decomposing methods, and the city-level water system harmony map, deconstruct and quantify the complex and diverse water system, supporting clearer and more efficient water management policymaking.

Further study on particle size, stability, and complexation of silver nanoparticles under the composite effect of bovine serum protein and humic acid.

Silver nanoparticles (AgNPs) are widely used due to their unique antibacterial properties and excellent photoelectric properties. Wastewater treatment plants form a pool of AgNPs due to the social cycle of wastewater. During biological treatment processes, the particle size and stability of AgNPs change. We studied the particle size changes and stability of silver nanoparticles in the presence of bovine serum albumin (BSA) and humic acid (HA). The experimental results indicated that silver nanoparticles can complex with the functional groups in BSA. For AgNP-BSA composites, as the BSA concentration increases, the size of the silver nanoparticles first decreases and then increases. AgNPs can combine with the amide, amino, and carboxyl groups in HA. As the concentration of HA increases, the particle size and large particle size distribution of AgNPs increase. This increasing trend is more obvious when the HA concentration is lower than 20 mg L-1. When HA and BSA exist at the same time, HA will occupy the adsorption sites of BSA on the surface of AgNPs, and the AgNP-HA complex will dominate the system. This study aims to provide key operational control strategies for the process operation of wastewater treatment plants containing AgNPs and theoretical support for promoting water environment improvement and economic development such as tourism.

Organizational-Economic Measures and Tools for the Multifunctional Use of Aquaculture Facilities in Ukraine

Introduction. The world is aware of the importance of preserving natural resources and is shifting its focus to a social perspective, reflecting the acceptance of sustainable development principles. Aquaculture management must consider the impacts on the ecosystem and community, ensuring a balance in the use of water resources. Aquaculture can become a sustainable way to generate economic resources, and has recreational and cultural applications. This study examines the possibilities of using aquaculture in educational and cultural activities, public leisure, aesthetic education, and the development of park areas, as well as for other multifunctional purposes that contribute to improving water environment management and creating new ecological jobs.&#x0D; Aim and tasks. The study aims to develop a conceptual vision of multifunctional aquaculture facilities as innovative and recreational centres for new jobs and the development of the local economy, considering socio-ecological and economic motivational mechanisms and effects that have not been previously investigated.&#x0D; Results. The variability of directions for the development of aquaculture activities in the context of implementing marine strategies, Sustainable Development Goals, and reduction of the negative consequences of water pollution due to military actions. Socio-ecological and economic motivational mechanisms have been developed to form aquaculture facilities as centres of a green corridor or a concentration of ecologically safe zones to integrate them into urban and rural spaces. Measures for integrating aquaculture into tourism activities and the scientific concept of the concentration of ecologically safe territories with an aquaculture core in terms of organizational measures and possible effects are proposed.&#x0D; Conclusions. A conceptual vision of multifunctional aquaculture facilities with the functions of reproduction, education and cultural-recreational enlightenment in terms of scientific and educational, decorative and circular facilities was proposed. The scientific concept of the concentration of ecologically safe territories with an aquaculture core in terms of organizational measures and possible effects was proposed.

Assessing the impact of water-sediment factors on water quality to guide river-connected lake water environment improvement

The substantial impacts of exogenous pollutants on lake water quality have been extensively reported. Water-sediment factors, which are essential for regulating water quality in river-connected lakes, have not been studied in depth under different hydrological conditions. This study has combined a 31-year water environmental dataset (1991–2021) regarding Dongting Lake and a vector autoregression model (VAR) in order to investigate the impulse response characteristics and contributions of water quality caused by water-sediment factors across different periods. Our analysis suggests that total nitrogen (TN) exhibited a significant increasing trend, whereas total phosphorus (TP) increased to 0.17 mg/L, and then decreased to 0.07 mg/L from 1991 to 2021. The inflow of suspended sediment discharge (SSD) decreased significantly during the study period, mainly because of the decrease in SSD in the three channels (TC). In the pre-Three Gorges Dam (TGD) period, water discharge (WD) and SSD were the Granger causes of TN and TP. In the post-TGD periods this relationship disappeared because of the construction of the TGD, which reduced the inflow of SSD and WD into the lake. Water quality indicators showed an instant response to the shock from themselves with high values, whereas the impulse response of the water quality to water-sediment factors exhibited lagged variations. This meant that the water quality indicators displayed a high impact by themselves across the different periods, with values varying from 67 % to 95 %. Water level (WL) and SSD were the predominant water-sediment factors for TP in the pre-TGD period, with the impact on TP changes accounting for 11 % and 9 %, respectively, whereas the contribution of SSD decreased to 2 % in the post-TGD period. WL was the most crucial water-sediment factor for CODMn during the different periods, with contributions varying from 17 % to 20 %. To improve the water quality of Dongting Lake, in addition to the implementation of strict controls on excessive external nutrient loading, regulating water-sediment factors according to the hydrological features of Dongting Lake during different periods is vital.

Temporal and spatial changes of water quality in intensively developed urban rivers and water environment improvement: a case study of the Longgang River in Shenzhen, China.

The water quality status, spatial and temporal change processes, and water environment improvement process of urban rivers are valuable lessons to be learned under the sustainable development strategy. This study aims to reveal the water environment improvement process of intensively developed urban rivers, elucidate the spatial and temporal distribution characteristics of major pollutants, and provide recommendations for their water environment management. Water quality data from eight monitoring sites (2007-2020) in the Longgang River basin in Shenzhen, China, and comprehensive pollution index method (CPI), modified comprehensive pollution index method (M-CPI), and Pearson correlation analysis method were used for comprehensive analysis. The study shows that TN, TP, NH3-N, and COD have the greatest influence on the water quality of Longgang River, with the average pollution contribution of 53.39%, 14.49%, 11.66%, and 4.92%, in order. In 2015-2020, the water quality of the main stream of the Longgang River in the wet season was worse than that in the dry season, while the water quality of the tributaries Dingshan River and the Huangsha River in the dry season was worse than the wet season. The spatial distribution characteristics based on M-CPI indicate that the water quality of the lower reaches of Longgang River, the tributaries Dingshan River and Huangsha River, is relatively poor. In addition, the water environment improvement process of Longgang River can be divided into 3 stages: engineering stage (2007-2013, rating changed from heavily polluted to basically qualified), bottleneck stage (2013-2017, rating fluctuated slightly above and below basically qualified), and ecological restoration stage (2017-2020, rating reached qualified in 2019).

Analysis of Ningxia Hui Autonomous District’s Gray Water Footprint from the Perspective of Water Sustainability

Gray water footprint (GWF) is an effective method to evaluate the degree of water pollution and water quality. It is the amount of freshwater needed to dilute water pollutants to meet ambient water quality standards. Accounting and analyzing the GWF will be significant for promoting an improved water environment and sustainable water ecology in Ningxia Autonomous District. We accounted for the GWF of all cities in Ningxia from 2012 to 2020 and evaluated its spatial-temporal variations by the GWF accounting method proposed by Hoekstra. Then, the Logarithmic Mean Divisia Index (LMDI) method was applied to investigate the contributions of four driving factors: the population scale effect, economic development effect, technological effect, and industrial structure effect. And then, the changes in the GWF in the Ningxia region were analyzed. The results showed that the GWF in the Ningxia region changed from 79.21 × 108 to 29.09 × 108 m3/yr during 2012–2020, making a significant decreasing trend. Among all cities, Wuzhong City contributes the most in terms of the GWF. More specifically, economic development and technology structure are the positive and negative drivers of the GWF, respectively. The water pollution levels in Ningxia (0.49–1.3) indicated that the waste assimilation capacity has fallen short of taking up the pollutant load, which had an unfavorable impact on the groundwater according to actual water quality data. NO3-N and NH3-N are detected in the groundwater throughout the Ningxia region, with the highest NH3-N content in the groundwater in Yinchuan, which almost exceeded the groundwater quality standard of category III. Above all, this study reflected the current water pollution situation better by combining the GWF with actual water quality data in Ningxia. The finding of this study is valuable for addressing water quality threats and developing sustainable development.

Spatiotemporal Patterns of Ammonia Nitrogen and Chemical Oxygen Demand in the Huaihe River–Hongze Lake System (Eastern China)

Understanding variations in contaminant concentrations and exploring their driving factors are essential for pollution control and water environment improvement. The Huaihe River Basin, as an important region in the eastern region of China, has attracted much attention to its water environment issues in recent years. Therefore, an in-depth analysis of spatiotemporal patterns of water quality parameters was carried out on the Huaihe River–Hongze Lake system, for the period 1998–2018, using the Mann–Kendall test (MKT) and wavelet transforms (WTs). Significant decrease trends of ammonia nitrogen (AN) and chemical oxygen demand (COD) concentrations were detected in the Huaihe River (HR) before 2008 using the MKT. High concentration in the contaminant load was a result of the effect of increased construction and decreased forest on increasing input of pollutants during this period. The results of the WT showed how factors (e.g., streamflow and water temperature), except land use, affect the variations in AN and COD concentrations. The comparison of spatiotemporal patterns of AN and COD between the HR and Hongze Lake (HL) showed their differences in contaminant transport regimes. The contaminants were rapidly transported downstream along the HR with high streamflow during the wet season, while these in the HL were less responsive due to the long residence time of the water body. In addition, rebounds of contaminant concentrations occurred many times at the confluence between the HR and the HL due to strong river–lake interactions, especially in the flood season. These results have implications for future water environment management in the Huaihe River Basin and in similar settings worldwide.

Characterization of dissolved organic matter content, composition, and source during spring algal bloom in tributaries of the Three Gorges Reservoir

Dissolved organic matter (DOM) is a key component of aquatic ecosystem function and biogeochemical processes. The characteristics of DOM in tributaries of the Three Gorges Reservoir (TGR) during the severe spring algal bloom period and their relationship with algal growth are unclear. In this study, the content, composition, and source of DOM in the Pengxi River (PXR) and Ruxi River (RXR) exhibiting typical TGR bloom problems were analyzed using various physicochemical indexes, carbon isotopes, fatty acids, and metagenomics. The results showed that chlorophyll a content increased with rising DOM concentration in the PXR and RXR. The dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) contents in the two rivers were 4.656–16.560 mg/L and 14.373–50.848 μg/L, respectively, and increased during the bloom period. Four fluorescent components were identified, namely, two humic-like substances, and two protein-like substances. Proteobacteria, bacteroidetes, and actinobacteria were the greatest contributors to DOM content. The carbon fixation pathway of microorganisms increased the DOC concentration in both rivers during the bloom period. Physicochemical parameters (WT, pH, DO, and PAR) affected the DOM concentration by influencing microbial activity and DOM degradation. DOM in both rivers was derived from allochthonous and autogenous sources. Meanwhile, the DOC content was more strongly correlated with allochthonous sources. These findings might provide essential information for improving water environment management and algal bloom control in the TGR.

Variation and internal-external driving forces of grey water footprint efficiency in China's Yellow River Basin.

Grey water footprint (GWF) efficiency is a reflection of both water pollution and the economy. The assessment of GWF and its efficiency is conducive to improving water environment quality and achieving sustainable development. This study introduces a comprehensive approach to assessing and analyzing the GWF efficiency. Based on the measurement of the GWF efficiency, the kernel density estimation and the Dagum Gini coefficient method are introduced to investigate the spatial and temporal variation of the GWF efficiency. The Geodetector method is also innovatively used to investigate the internal and external driving forces of GWF efficiency, not only revealing the effects of individual factors, but also probing the interaction between different drivers. For demonstrating this assessment approach, nine provinces in China's Yellow River Basin from 2005 to 2020 are chosen for the study. The results show that: (1) the GWF efficiency of the basin increases from 23.92 yuan/m3 in 2005 to 164.87 yuan/m3 in 2020, showing a distribution pattern of "low in the western and high in the eastern". Agricultural GWF is the main contributor to the GWF. (2) The temporal variation of the GWF efficiency shows a rising trend, and the kernel density curve has noticeable left trailing and polarization characteristics. The spatial variation of the GWF efficiency fluctuates upwards, accompanied by a rise in the overall Gini coefficient from 0.25 to 0.28. Inter-regional variation of the GWF efficiency is the primary source of spatial variation, with an average contribution of 73.39%. (3) For internal driving forces, economic development is the main driver of the GWF efficiency, and the interaction of any two internal factors enhances the explanatory power. For external driving forces, capital stock reflects the greatest impact. The interaction combinations with the highest q statistics for upstream, midstream and downstream are capital stock and population density, technological innovation and population density, and industrial structure and population density, respectively.