The removals of arsenic and selenium pollutants are always urgent desires for the water security. In this study, both sorption and catalysis strategies were combined for the effective removals of As(V) and Se(VI) over magnetic graphene oxide sheets (GOs)-oxidized carbon nanotubes (OCNTs) hydrogels. The sorption behavior facilitated the operation of catalysis reactions, meanwhile, the catalytic reduction promoted the release of occupied sorption sites and then restarted a new sorption-catalysis cycle. The synergic effect of sorption and catalysis realized 258.2 mg g⁻¹ for As(V) enrichment capacity on MPG2T1, and ultra-fast sorption and catalysis equilibriums were identified within 9 min. In the case of Se(VI), a moderate enrichment performance was observed to be 46.2 mg g⁻¹. Similarly, the ultra-fast sorption and reduction of Se(VI) were realized within 2 min. In the competition experiments, only SO₄²⁻, SO₃²⁻, and HPO₄²⁻ showed interference for As(V) and Se(VI) removals. These results testified the superiority of the synergy effect of sorption and catalysis, and the feasibility of 3D magnetic GOs-OCNTs hydrogel in practical implementations.

The frequent occurrence of microcystins (MCs) has caused a series of water security issues worldwide. Although MC pollution in natural waters of China has been reported, a systematic analysis of the risk of MCs in Chinese lakes and reservoirs is still lacking. In this study, the distribution, trend, and risk of MCs in Chinese lakes and reservoirs were comprehensively revealed through meta-analysis for the first time. The results showed that MC pollution occurrence in numerous lakes and reservoirs have been reported, with MC pollution being distributed in the waters of 15 provinces in China. For lakes, the maximum mean total MC (TMC) and dissolved MC (DMC) concentrations occurred in Lake Dianchi (23.06 μg/L) and Lake Taihu (1.00 μg/L), respectively. For reservoirs, the maximum mean TMC and DMC concentrations were detected in Guanting (4.31 μg/L) and Yanghe reservoirs (0.98 μg/L), respectively. The TMC concentrations in lakes were significantly higher than those in the reservoirs (p < 0.05), but no difference was observed in the DMC between the two water bodies (p > 0.05). Correlation analysis showed that the total phosphorus concentrations, pH, transparency, chlorophyll a, and dissolved oxygen were significantly related to the DMC in lakes and reservoirs. The ecological risks of DMC in Chinese lakes and reservoirs were generally at low levels, but high or moderate ecological risks of TMC had occurred in several waters, which were not negligible. Direct drinking water and consumption of aquatic products in several MC-polluted lakes and reservoirs may pose human health risks. This study systematically analyzed the pollution and risk of MCs in lakes and reservoirs nationwide in China and pointed out the need for further MC research and management in waters.

Groundwater is essential for regional ecological-economic system and is an important resource of drinking water, especially in the Chinese Loess Plateau (CLP), where is a typical water-limited ecosystem. Groundwater quality deterioration will affect water security and exacerbate the water shortages. Groundwater hydrochemistry, pollution source apportionment, quality and health risks were evaluated based on analysis of major ions and selected trace elements in seasonal samples of the Fen River Basin (FRB) in the eastern CLP. Groundwaters in the FRB were mainly HCO₃⁻-Ca²⁺-Na⁺ water type with low dissolved solutes in upstream samples, high values in midstream samples and medium values in downstream samples. Solutes in upstream samples were mainly derived from carbonate weathering, while those in midstream and downstream samples came from silicate weathering, evaporites dissolution and anthropogenic sources. Self-organizing map (SOM) showed the hydrochemistry remained unchanged from dry to wet season for most sampling points. The seasonal variations of Ag, Cd, Ni, Pb, and Tl were significant due to anthropogenic input. High NO₃⁻ in upstream and downstream samples resulted primarily from sewage discharge, and high SO₄²⁻ in midstream and downstream samples was from gypsum- and coal-related industries. In addition, anthropogenic input related to coal industries significantly aggravates pollution of As, Ni, Ag, Fe, and Mn. Influenced by evaporites and anthropogenic input, midstream samples had high salinity, total hardness and water quality indices (WQIs) and were unsuitable for irrigation or drinking purposes. Seasonal variation of WQI in the FRB was unsignificant except Jiaokou River sub-basin, where groundwater quality was worse in the wet season than the dry season due to coal mining. Great attention should be paid to the high non-carcinogenic risks of exposure to F, V, Mn, and Cr via dermal absorption, particularly for children. Overall, groundwater quality in the FRB was best in upstream, medium in midstream and worst in midstream based on different index. Groundwater quality is deteriorated by anthropogenic input and the sewage discharge in the FRB should be strictly controlled. Our report provides a reference for groundwater pollution evaluation and source identification in similar areas.

Water diversion has been increasingly applied to improve water quality in many water bodies. However, little is known regarding pollution by organic micropollutants (OMPs) in water diversion projects, especially at the supplier, and this pollution may threaten the quality of transferred water. In the present study, a total of 110 OMPs belonging to seven classes were investigated in water and sediment collected from a supplier of the Yangtze River within four water diversion projects. A total of 69 and 58 target OMPs were detected in water and sediment, respectively, at total concentrations reaching 1041.78 ng/L and 5942.24 ng/g dry weight (dw). Polycyclic aromatic hydrocarbons (PAHs) and pharmaceuticals were the predominant pollutants identified. When preliminarily compared with the pollution in the receiving water, the Yangtze River generally exhibited mild OMPs pollution and good water quality parameters, implying a clean water source in the water diversion project. However, in Zongyang and Fenghuangjing, PAHs pollution was more abundant than that in the corresponding receiving water in Chaohu Lake. Ammonia nitrogen pollution in the Wangyu River was comparable to that in Taihu Lake. These findings imply that water diversion may threaten receiving waters in some cases. In addition, the risks of all detected pollutants in both water and sediment were assessed. PAHs in water, especially phenanthrene and high-molecular-weight PAHs, posed high risks to invertebrates, followed by the risks to fish and algae. Pharmaceuticals, such as antibiotics and antidepressants, may also pose risks to algae and fish at a number of locations. To the best of our knowledge, this report is the first to describe OMPs pollution in water diversion projects, and the results provide a new perspective regarding the security of water diversion projects.

Outlet infrastructure and hypersaline discharge from large-scale desalination operations have the potential to impact marine environments. Here, we present the results of a six-year M-BACI assessment of the impacts of desalination discharge outlet construction and hypersaline effluent on the cover of habitat-forming species on temperate reefs. The construction of the desalination outlet caused a decrease in the cover of Ecklonia radiata (kelp) and an increase in the cover of algal turfs up to 55 m from the outlet. Following the commencement of discharging of hypersaline brine, the impact to E. radiata and algal turfs persisted, but decreased in spatial extent to be less than 25 m from the outlet. Hypersaline discharge was also associated with a significant decline in the cover of sponges in outlet compared to reference sites. Overall, our results demonstrate that the water security benefits from large-scale desalination may sometimes be appropriately balanced against the associated ecological consequences.

The over-exploitation of water resources causes water resource depletion, which threatens water security, human life, and social and economic development. Only by clarifying the spatial pattern, changing trends, and influencing factors of water storage can we promote the rational development of water resources and relieve the pressure on water resources. However, there is still a lack of research on these aspects. In this study, the water-scarce area in Shandong Province, China, was selected to quantify the spatial and temporal changes in the terrestrial water storage (TWS) and groundwater storage (GWS) over the past 30 years. Nighttime light data were used to characterize the urbanization level (UL) and explore the effects of human activities (i.e., UL) and climate change (temperature and precipitation) on the TWS and GWS. The results show that 1) from 1990 to 2018, the overall TWS exhibited a significant decreasing trend (− 0.084 cm yr⁻¹). The change trend of the GWS was consistent with that of the TWS (− 0.516 m³ yr⁻¹). Spatially, there was significant spatial heterogeneity in the trend of the TWS and GWS. At the grid and prefectural scales, the TWS mainly exhibited a downward trend in the central and western regions, and an upward trend in the eastern region of Shandong Province. For the GWS, all cities exhibited a decreasing trend at the prefectural scale, whereas 92% of the regions exhibited a decreasing trend with less spatial heterogeneity at the grid scale. 2) Precipitation was the mean factor controlling the total amount of TWS and GWS in Shandong Province. Precipitation and temperature positively affected water storage, and the UL negatively affected it. At the prefectural scale, except for a few cities which were greatly influenced by the UL, the dominant factor of the TWS and GWS was precipitation in the other cities. At the grid scale, for the TWS, precipitation was the predominant factor in 51.82% of the entire region, followed by the UL (44.14%) and temperature (4.04%). For the GWS, precipitation was the predominant factor in 55.73% of the area, and the other 44.27% of the area was mainly influenced by the UL. Overall, precipitation and the UL were the key factors affecting the TWS and GWS. The results of this study provide a theoretical and decision-making basis for the optimal allocation and sustainable use of regional water resources.

Water is an essential component of agriculture-food production. As the biomass and biofuel are known excellent sources of renewable and sustainable energy, cultivating process consumes significant quantities of water. Without sufficient, good-quality and easily accessible water, the European agriculture-food production could thus be under threat. This research analyses the impact of the water supply on the bioenergy production in the 28 European Union countries, for the 1990–2018 period within the pathway of the European Union 2030 agenda for sustainable development. The findings using the generalised least squares (GLS) technique show that bioenergy production and population density appear to decrease water supply. Precisely, the magnitude of the effects is − 0.224 and − 0.136 for developing countries and developed countries in the EU, respectively. This indicates that a serious reduction of water security is more likely to happen in developed countries than in developing countries as a result of the increase in bioenergy consumption. In the meantime, fossil fuel, income generation activities and institutional quality have already positively affected water supply. Thus, these findings implied that water scarcity is becoming one of the main obstacles for bioenergy expansion and growth. The results were also further verified by the random effect and pooled oriented least squares method. This study recommends that the Member of the European Union States should continue to increase bioenergy production in the energy mix efforts without any strenuous water security issues. Notwithstanding, there are several situations where a developing bioenergy industry is unlikely to be constrained by water shortage, and with the drive of bioenergy demand, the efforts might unlock new opportunities to adapt to water-related challenges and to improve water usage efficiencies. The authorities should illustrate organised water security and sustainable bioenergy policy by way of developing alternative strategies in reducing fossil fuel power and related CO₂ emissions, accordingly to the unique characteristics of both developed and developing countries in the EU.

Several studies were carried out and drought coexistence technologies were developed to deal with the problem of drought in semiarid regions, such as the construction of underground dams, which became a tool for rural development, mainly for family agriculture. However, there are still scarce informations regarding technical studies on the water security level of underground dams, especially about trace metal contamination due to the use and agricultural occupation of the soils downstream of the dams. In this work, the level of contamination of trace metals in waters of underground dams, during two hydrological years, was evaluated around of the sub-basin of the Cobras river, in the Rio Grande do Norte state, Brazil. The analysis of the results indicated that the water samples stored in the Alexandre and Ginaldo underground dams are within the permitted drinking patterns and did not suffer, on the other hand, any alteration in their quality that requires treatment for human consumption, fitting into Class 1. Most of the samples from the waters of the Boa Vista and Ademar dams are above the maximum allowable value for iron (Fe), lead (Pb), chromium (Cr), and nickel (Ni), requiring a differentiated treatment for human consumption, and can be classified as Class 2. The probable contamination of the waters stored in the underground dams may be of geological origin, since the largest accumulation of trace metals occurred in the lower area of the river course greater drained area, leading to believe that the metals come from the rock weathering that make up the geological framework of the region.

The purpose of this study is to explore the empirical relationship between foreign direct investment (FDI), population, energy production, and water resources in South Asia. The newly developed approach dynamic common correlated effects (DCCE) by Chudik and Pesaran (Journal of Econometrics 188:393–420, 2015a) for measuring co-integration has been applied in the present study. This procedure provides significant robust outcomes in the presence of cross-sectional dependence among the cross-sectional units. The findings confirmed that earlier models, such as mean group (MG), pooled mean group (PMG), and augmented mean group (AMG), which have been used in the literature for long data, provide misleading results in the presence of cross-sectional dependence among the cross-sectional units. A statistically significant and negative result has been observed between FDI, population, energy production, and water resources in South Asia. The governments of South Asian economies must encourage green FDI initiatives for water management, ensuring water security, securing natural resources for enhancing the sustainable development of regional economies.

Water security is a compound concept coupling multi-dimensional perspectives, such as resource utilization, environmental protection, and disaster prevention. With this concern, this study focuses on the spatial–temporal dynamics of water security with considering water disaster risk index (WDRI), water environment risk index (WERI), and water supply–demand. WERI centers on risk source’s hazard, control effectiveness, and risk receptor’s vulnerability. Indices related to hazard, exposure, and vulnerability are used for evaluating WDRI. A multi-objective fuzzy membership function is presented for determining the indices’ weight, and the distribution pattern of water security is illustrated based on cluster analysis. A real-world case study of Beijing-Tianjin-Hebei urban agglomeration (BTHUA) is given for verifying availability of the evaluation framework. Results indicate the general water security in BTHUA with a critical safe state yet a downward trend. Opposite change characteristics of water security exist between its southern and northern cities. WDRI and WERI show the trends of increasing (with a growth rate of 0.48%) and decline (with an average decrement rate of 0.56%), respectively. Beijing has high-value WDRI and WERI, and the order of WDRI and WERI is presented as follows: Beijing (0.67) > Tianjin (0.54) > Hebei (0.33) and Beijing (0.69) > Tianjin (0.58) > Hebei (0.16), respectively. Cluster analysis reveals a poor match relation between water security and regional socio-economic development. Areas with high-level economic development (e.g., Beijing and Tianjin) have poor environmental performances, with WDRI and WERI of 0.54 ~ 0.68 and 0.57 ~ 0.70, respectively. Additionally, water resources overload index of BTHUA is 8.513, which is higher than Chengdu-Chongqing urban agglomeration (1.431), Triangle of Central China (0.228), and Yangtze River Delta urban agglomeration (0.742). Findings can provide a theoretical reference for promoting sustainable utilization of water resources in BTHUA and the other areas with prominent water problems.