Composition Of Surface Waters Research Articles

GEOCHEMISTRY OF GROUNDWATERS AND SURFACE WATERS, AND GROUND ICE OF THE OKA PLATEAU, EASTERN SAYAN (RUSSIA)

The study area is located in the Eastern Sayan hydrogeological folded area. The objects of the study were groundwaters, surface waters and ground ice in the Sentsa River basin on the Oka Plateau. Cold and thermal groundwaters are associated with Proterozoic and Paleozoic metamorphic and igneous rocks. Their discharge as springs occurs in the river valleys along fault zones. Ground ice was studied in mineral frost mounds (lithalsas) composed of clays, clayey silts and silts of lacustrine-alluvial and fluvioglacial genesis. It has been established that thermal and cold groundwaters have HCO3 Ca-Na compositions, river and lake waters, as a rule, have HCO3 Ca-Na compositions, and ground ice melts – HCO3, SO4-HCO3 and NH4-HCO3 Ca. Thermal waters are largely enriched in Li, Be, B, Si, Mn, Ga, Ge, Se, As, Br, Rb, Sr, Cs, Ba and all REE relative to river and rain waters, and have the highest values of trace elements enrichment factor (EFREE). The latter shows that atmospheric precipitation participates in the formation of the composition of groundwaters (cold and thermal) and surface waters. The specificity of the geochemistry of ground ice is determined by the composition of precipitation, the injection of ice-forming groundwater from taliks, the interaction in the water-rock system, and the presence of organic matter in unconsolidated sediments. The participation of river water and groundwater in the formation of the frost mound ice core is also evidenced by similar values of stable isotopes (δ18O, δD) in surface water, groundwater and ground ice. The 3He/4He ratio points to a possible influx of mantle helium into thermal waters, and δ13С points to the magmatic and thermometamorphic mechanisms of carbon dioxide accumulation in thermal waters. The 87Sr/86Sr ratio in travertines indicates a significant contribution of intrusive rocks to the formation of fluid composition.

Risk assessment and quantification of elemental concentrations in river and stream in Nigeria

The rising prevalence of elements in surface water is becoming a major global environmental problem due to their resistance to change and capacity to accumulate in organisms. Humans are causing significant heavy metal contamination in the aquatic environment, which is killing aquatic creatures. The purpose of this study is to determine the elemental composition of surface water in Ogun State. Water samples were collected from a river that flows alongside Liberty Estate in Ewupe, Ado-Odo Ota Local Government Area, and a stream that runs alongside Pacific Estate in Iganmode. The element composition of water samples was determined using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Several components were found to exceed the limitations imposed by the World Health Organisation (WHO) and the Environmental Protection Agency (EPA). In River I, sodium (Na) had the highest apparent concentration, whereas titanium (Ti) had the lowest average concentration. In River II, silicon (Si) had the highest apparent concentration, whereas chromium (Cr) had the lowest average concentration. Titanium (Ti) had the lowest mean concentration value, whereas sodium (Na) appeared to have the highest concentration in stream I. Stream II has the highest concentration of sodium (Na), while Uranium (U) has the lowest average concentration value. Nonetheless, the incremental lifetime cancer risk (ILCR) values for adults and children who drink river and stream water are similar, ranging from 10–9 to 10–8. This implies a high carcinogenic risk (CR) linked with drinking water from both sources. Children who had access to both stream and river water demonstrated higher risk levels than adults. Routine studies of the state's streams and rivers should be conducted to avoid the subtle impact that may emanate from the water bodies.

Динамика анионно-катионного состава поверхностных вод реки Усмань в пределах Воронежского государственного природного биосферного заповедника

Hydrochemical analysis determined the ionic composition of surface waters of the Usman river within the Voronezhsky Nature Reserve. The influence of natural factors in the formation of anionic-cationic water composition is determined. Revealed changes in the hydrochemical composition of the river with high forest cover. Results of the analysis will serve as the natural values of ion concentrations in the analysis of the ecological state of rivers located near the Voronezhsky Nature Reserve. Keywords: RIVER, HYDROCHEMICAL ANALYSIS, ANIONS, CATIONS, NATURE RESERVE, ECOLOGICAL STATE

Mesoporous architectural magnetic halloysite-polymer beads for removing toxic streptomycin from water: A sustainable remediation approach

Streptomycin (STR) is a widely used antibiotic to treat various infectious diseases in humans and animals. Increased STR production and distribution result in harmful residue in soil and water. Consequently, STR exists in biotic- and abiotic-counterpart of the environment and poses potential toxicity and risk due to its bioaccumulation and biomagnification properties. Sustainable remediation of STR from wastewater requires selective, minimal, low-cost, regenerable, and reusable materials as adsorbents. In this study, magnetic-halloysite incorporated polymer composite beads (SPHM) were synthesized and used for the efficient clean-up of toxic STR from wastewater. SPHM has a mesoporous structure with an abundance of oxygen-containing functional groups and exhibits a synergistic STR clean up performance (qm = 235.71 ± 13.98 mg/g). Sorption and interfacial studies revealed that diffusion, hydrophobic and ionic interactions, including electrostatic interaction, are involved in STR remediation. Electrostatic interaction plays a vital role alongside the physical sorption mechanism due to the presence of hydroxyl and carboxyl groups induced from poly (vinyl alcohol) and sodium alginate. Moreover, X-ray photoelectron spectroscopy (XPS) and Time-of-flight secondary ion mass spectrometry (ToF-SIMS) analyses confirm the involvement of opposing charged groups of SPHM and STR in adsorption. SPHM can be magnetically separated in just 20 s and is regenerable and reusable up to 10 times, with outstanding performance and stability. The sorption process requires only a minimal amount of SPHM, i.e., 0.5 g/L for STR clean-up. Even the natural surface water composition did not affect its performance. Hence, natural nanoclay-based, biocompatible and low-cost SPHM has a great potential for the sustainable remediation of streptomycin and other similar antibiotics from wastewater.

Transition from a mixotrophic/heterotrophic protist community during the dark winter to a photoautotrophic spring community in surface waters of Disko Bay, Greenland.

Unicellular eukaryotic plankton communities (protists) are the major basis of the marine food web. The spring bloom is especially important, because of its high biomass. However, it is poorly described how the protist community composition in Arctic surface waters develops from winter to spring. We show that mixotrophic and parasitic organisms are prominent in the dark winter period. The transition period toward the spring bloom event was characterized by a high relative abundance of mixotrophic dinoflagellates, while centric diatoms and the haptophyte Phaeocystis pouchetii dominated the successive phototrophic spring bloom event during the study. The data shows a continuous community shift from winter to spring, and not just a dormant spring community waiting for the right environmental conditions. The spring bloom initiation commenced while sea ice was still scattering and absorbing the sunlight, inhibiting its penetration into the water column. The initial increase in fluorescence was detected relatively deep in the water column at ~55 m depth at the halocline, at which the photosynthetic cells accumulated, while a thick layer of snow and sea ice was still obstructing sunlight penetration of the surface water. This suggests that water column stratification and a complex interplay of abiotic factors eventually promote the spring bloom initiation.

Groundwater‐surface water interaction, dissolved organic carbon oxidation and dissolution in carbonate aquifers

AbstractThe high primary porosity and permeability of eogenetic karst aquifers permit water recharged through secondary dissolution features to be temporarily stored in aquifer matrix porosity. The recharged water contains elevated dissolved organic carbon (DOC) concentrations that, when oxidized, enhance limestone dissolution and impact carbon cycling. We evaluate the relationship between DOC oxidation and limestone dissolution using observations at a stream sink‐rise system and reversing spring in the Floridan aquifer, north‐central Florida, USA, where subsurface residence times of recharged water are days and months, respectively. We estimate water chemical compositions during surface water‐groundwater interactions at these two systems with mixing models of surface water and groundwater compositions and compare them with measured DOC, dissolved inorganic carbon (DIC), Ca2+ and dissolved organic nitrogen (DON) concentrations. Differences between measured and modelled concentrations represent net changes that can be attributed to calcite dissolution and redox reactions, including DOC oxidation. DOC losses and Ca2+ gains exhibit significant (p < 0.01) inverse linear correlations at both the reversing spring (slope = −0.9, r2 = 0.99) and the sink‐rise system (slope = −0.4, r2 = 0.72). DOC oxidation in both systems was associated with decreases in the molar C:N ratio (DOC:DON). Significant (p < 0.01) positive linear correlations between increases in Ca2+ and DIC concentrations after correcting for DIC derived from calcite dissolution occurred at both the reversing spring (slope = 1.3, r2 = 0.99) and the sink‐rise system (slope = 1.61, r2 = 0.75). Greater deviations from the expected slope of −1 or +1 at the sink‐rise system than at the reversing spring indicate DOC oxidation contributes less dissolution at the sink‐rise system than at the reversing spring, likely from shorter storage in the subsurface. A portion of the deviation from expected slope values can be explained by the dissolution of Mg‐rich carbonate or dolomite rather than pure calcite dissolution. Despite this, slope values reflect kinetic effects controlling incomplete consumption of carbonic acid during dissolution reactions.

Impact of soil compaction and irrigation practices on salt dynamics in the presence of a saline shallow groundwater: An experimental and modelling study

AbstractSoil salt accumulation is a widespread problem leading to diminished crop yield and threatening food security in many regions of the world. The soil salinization problem is particularly acute in areas that lack adequate soil water drainage and where a saline shallow water table (WT) is present. In this study, we present laboratory‐scale column experiments, extending over a period of more than 400 days that focus on the processes contributing to soil salinization. We specifically examine the combined impact of soil compaction, surface water application model and water quality on salt dynamics in the presence of a saline shallow WT. The soil columns (60 cm height and 16 cm diameter) were packed with an agricultural soil with bulk densities of 1.15 and 1.34 g/cm−3 for uncompacted and compacted layers, respectively, and automatically monitored for water content, salinity and pressure. Two surface water compositions are considered: fresh (deionized, DI) and saline water (~3.4 mS/cm). To assess the sensitivity of compaction on salt dynamics, the experiments were numerically modelled with the HYDRUS‐1D computer program. The results show that the saline WT led to rapid salinization of the soil column due to capillarity, with the salinity reaching levels much higher than that at the WT. However, compaction layer provided a barrier that limited the downwards moisture percolation and solute transport. Furthermore, the numerical simulations showed that the application of freshwater can temporarily reverse the accumulation of salts in agricultural soils. This irrigation strategy can help, in the short‐term, alleviate soil salinization problem. The soil hydraulic properties, WT depth, water quality, evaporation demand and the availability of freshwater all play a role in the practicability of such short‐term solutions. The presence of a saline shallow WT would, however, rapidly reverse these temporary measures, leading to the recurrence of topsoil salinization.

Toxic Element Contamination Sources in the Surface and Groundwater of the Elbrus Region: Geochemistry and Health Risks

The region surrounding the Elbrus volcano in the Great Caucasus is a popular tourist destination, home to native people and an area of the richest ore mineral resources. Based on the chemical composition of surface water, mineral, and groundwater in the Elbrus area, as well as statistical and thermodynamic calculations, waters with high concentrations of Mn, Cu, Zn, Mo, Ba, W, Pb, and As were identified, possible mineral phases that may lead to these metal concentrations in water were estimated, and risks to human health were assessed. Two main sources of surface water pollution have been identified: (1) water from tailings that are enriched due to oxidation of sulfide minerals is considered a source of As (181 µg/L) and Mo (2070 µg/L) pollution in the area of the Tyrnyauz W-Mo deposit; and (2) CO2-rich waters of deep horizons discharge on the earth surface with high concentrations of As (828 µg/L) and W (504 µg/L). It has been shown that compared to all toxic elements studied, only Mo and As have adverse non-carcinogenic effects on adult health. The estimated carcinogenic risk of As in the mine area was 1.7 × 10−3 and exceeded the generally accepted range of 10−4 to 10−6. In order to minimize the health risks, regular monitoring of water quality is required when mining activities on the Tyrnyauz W-Mo deposit are renewed.

Microplastics abundance, distribution and composition in surface waters, sediments and fish species from Amir-Kalayeh Wetland, Northern Iran.

Microplastics (MPs) pollution is considered as a globally pervasive threat to aquatic ecosystems and many studies reported this pollution in different aquatic ecosystems. However, studies on MPs pollution in wetlands are still scarce. Therefore, the aim of present study was to investigate the presence of MPs in the surface water, sediment and different fish species of Amir-Kalayeh wetland, Northern Ian. Surface water and sediment samples were collected from six stations during June to July 2022. Moreover, the gills and gastrointestinal tract (GIT) of 54 fish specimens belonging to four species including Cyprinus carpio, Tinca tinca, Esox lucius and Silurus glanis were analysed. MPs were detected in all samples with an average of 2.15 ± 1.98 items/m3 for surface water, 51.66 ± 32.20 items/kg dry weight for sediments, 0.17 ± 0.17 items/individual for fish GIT and 0.12 ± 0.12 items/individual for fish gills. There was no significant relationship between MPs abundance in surface waters and sediments as well as between MPs abundance in environmental matrices and fish (P > 0.0.5). In terms of feeding habit, no significant differences were observed between the number of MPs found in omnivorous and carnivorous fish species (P > 0.05). Moreover, no significant relationship was detected between the MPs abundance in fish tissues and body size (P > 0.05). MPs were mainly fibers, mostly transparent, and in a range size of 70-5000 µm. The dominant MPs type was nylon in all samples. This study will help increase our knowledge about MPs pollution in inland freshwater systems and suggests that management policies take essential steps to reduce this insidious problem in freshwater ecosystems.

Origin and stability of pit lake water in Baiyinhua, Inner Mongolia, based on hydrochemistry and stable isotopes

ABSTRACT Isotope technology is widely used in geochemical mechanisms analysis; however, studies on the origin of pit lake water by isotopes in coal concentration areas in grassland are rare. In this study, 20 groups of water samples were collected, which were subjected to chemical analysis to determine the hydrogeochemical characteristics of pit lake water. The mechanisms of pit lake water formation and recharge–evaporation were ascertained through principal component analysis and the Rayleigh fractionation model. The results indicate that the phreatic water is least affected by evaporation, followed by confined water, surface water and pit lake water. The ionic composition of surface water, phreatic water and most of the confined water is mainly affected by leaching, some confined water can be recharged by surface or phreatic water; while the ionic composition of pit lake water is dominantly affected by evaporation (69.4 %) and is less affected by groundwater recharge (17.1 %) and human activities (11.5 %). The pit lake water is recharged by precipitation, phreatic water and the lateral runoff of confined water; however, the proportion of phreatic and confined water recharge is small. The evaporative loss of the pit lake water is 40–61 % of the initial water body.

Role of stable isotopes in revealing moisture sources and rainfall variability in India

Precipitation is a crucial component of the water cycle and is essential for the livelihood of people and ecosystems; therefore, understanding precipitation parameters is vital. Stable isotopes in precipitation can provide important information on precipitation sources, atmospheric circulation patterns, and hydrological processes. In this study, stable isotopes in precipitation for four cities in India were analyzed, namely New Delhi, Hyderabad, Shillong, and Calicut, using data from the International Atomic Energy Agency (IAEA) Global Network for Isotopes in Precipitation (GNIP). The GNIP data were supplemented with in-situ measurements. Results showed the correlations between climate-related factors such as surface air temperature and precipitation levels with the stable isotope composition of precipitation. The relationships critically explore interannual variations in the isotope data over the last three decades. The Local Meteoric Water Line (LMWL) for New Delhi and Hyderabad had intercepts less than 10‰, implying a higher evaporation effect over precipitation, consistent with arid and semi-arid regions with increased altitude. The weighted average value of d-excess for southern and Himalayan points were 10.7 and 12.7, respectively, and the average value of δ¹⁸O were − 3.65 and − 5.84, and δ²H were − 16.8 and − 35.8. The d-excess value was significantly lower in the Northern part (New Delhi), with an average weighted value of 6.6. The key values include the isotopic composition of rainfall in different regions of India, the LMWL for different stations, the d-excess value, and the consistency of meteoric water lines with regional and global values. The results of this study provide valuable information on the variability of stable isotopes in precipitation in India. The study's outcomes can be compared with the isotopic composition of surface water and groundwater. This discovery offers more understanding of the isotopic differences that occur on a smaller scale during organized convection and the factors that affect them. As a result, it enhances our ability to decipher the paleoclimate data in arid, semi-arid, and subtropical monsoon regions.

Temporal variation in vitamin B12 concentration and their impact on phytoplankton composition of surface waters of a coastal ocean off Japan (Ariake Sea)

Temporal variation in vitamin B12 concentration and their impact on phytoplankton composition of surface waters of a coastal ocean off Japan (Ariake Sea)

Tungsten stable isotope composition of the upper continental crust

Tungsten (W) stable isotope data for twenty-four composites made from the fine-grained matrix of glacial diamictites, deposited between the Mesoarchean and the Paleozoic, as well as two Archean tonalite-trondhjemite-granodiorites (TTG) are used to refine the W isotope compositions (expressed as δ186W deviations from the NIST 3163 W standard) of the upper continental crust (UCC). To do this we evaluate W isotope fractionation in the diamictites as the result of both magmatic and low-temperature processes. The δ186W values of the diamictites are heterogeneous (0.017 ± 0.011 ‰, 2SE to 0.182 ± 0.007 ‰, 2SE), encompassing the range of previously published values for igneous rocks. We find that δ186W correlates positively with the diamictite’s chemical index of alteration (CIA), a measure of the degree of chemical weathering in the provenance, suggesting that the continental regolith (i.e., surface material composed of weathered residues) is isotopically heavy for W. Since W in rivers and ocean water is also isotopically heavy, this suggests that equilibration with Fe-Mn-oxides controls the W isotope composition of surface waters and that such oxides are not important constituents of the regolith, whose W is likely accommodated in clays. Using diamictites with low CIA (<60, n = 9), we calculate an average δ186W of 0.046 ± 0.036 ‰ (2SD) for the UCC, from 2.3 to 0.3 Ga. This average is combined with the TTG data of this study, as well as data from the literature for upper crustal rocks to obtain a representative δ186W value of the UCC of 0.046 ± 0.046 ‰ (2SD). The W stable isotope composition of the UCC is lighter than that of mantle-derived melts (MORB and OIB, with an average δ186W = 0.082 ± 0.026 ‰, 2SD), and much lighter than the weighted average δ186W of intra-oceanic arcs (δ186W = 0.104 ± 0.052 ‰, 2SD), though the spread in the arc rocks is large. The significant difference in δ186W between average intra-oceanic island arc lavas and UCC is intriguing given that continental crust is thought to form primarily via arc magmatism. This difference suggests that not all modern intra-oceanic arcs are representative of those that formed the continental crust. Rather, only arcs that are enriched in incompatible trace elements, which also tend to have lighter W isotope compositions, may have been involved in making new continental crust. Alternatively, there may have been a secular change in the W isotope composition of arc magmas.

An improved prediction model for COD measurements using UV-Vis spectroscopy.

In the 21st century, although water quality has been improved in the last two decades, water pollution by organic contaminants has remained a non-negligible issue in China, so Chemical-Oxygen Demand (abbreviated as COD, unit: mg L-1) is often used as the main index to measure the degree of surface water pollution. UV-Vis spectroscopy, as a sensitive and rapid analytical technique, is a green detection technology suitable for automatic online COD detection equipment. However, due to the complex composition of surface water, the interference degree of the UV-Vis spectrum caused by turbidity is strongly correlated with the size, type and color of particulate matter in the solution, which results in noise sensitivity and poor generalization of the current detection model. Therefore, the main purpose of this research is to improve the traditional detection model performance by using deep learning and a spectrum preprocessing algorithm. Firstly, we used an improved noise filter based on discrete wavelet transforms to solve the noise sensitivity. Secondly, we proposed a novel COD detection network to address poor generalization. Thirdly, we collected a total of 2259 water samples' UV-Vis absorption spectra and corresponding COD as a dataset. Then, we pipelined the improved noise removal algorithm and proposed COD detection network, as a complete COD prediction model. Finally, the experiment on the dataset shows that the COD prediction model has a good performance in terms of both noise tolerance and accuracy.

Chemodiversity of riverine dissolved organic matter: Effects of local environments and watershed characteristics

Riverine dissolved organic matter (DOM) is crucial to global carbon cycling and aquatic ecosystems. However, the geographical patterns and environmental drivers of DOM chemodiversity remain elusive especially in the waters and sediments of continental rivers. Here, we systematically analyzed DOM molecular diversity and composition in surface waters and sediments across 97 broadly distributed rivers using data from the Worldwide Hydrobiogeochemistry Observation Network for Dynamic River Systems (WHONDRS) consortium. We further examined the associations of molecular richness and composition with geographical, climatic, physicochemical variables, as well as the watershed characteristics. We found that molecular richness significantly decreased toward higher latitudes, but only in sediments (r = -0.24, p < 0.001). The environmental variables like precipitation and non-purgeable organic carbon showed strong associations with DOM molecular richness and composition. Interestingly, we identified that less-documented factors like watershed characteristics were also related to DOM molecular richness and composition. For instance, DOM molecular richness was positively correlated with the soil sand fraction for waters, while with the percentage of forest for sediments. Importantly, the effects of watershed characteristics on DOM molecular richness and composition were generally stronger in waters than sediments. This phenomenon was further supported by the fact that 11 out of 13 watershed characteristics (e.g., the percentages of impervious area and cropland) showed more positive than negative correlations with molecular abundance especially in waters. As the percentage of forest increased, there was a continuous accumulation of the compounds with higher molecular weight, aromaticity, and degree of unsaturation. In contrast, human activities accumulated the compounds with lower molecular weight and oxygenation, and higher bioavailability. Our findings imply that it may be possible to use a small set of broadly available data types to predict DOM molecular richness and composition across diverse river systems. Elucidation of mechanisms underlying these relationships will provide further enhancements to such predictions, especially when extrapolating to unsampled systems.

Feasibility study of multisensor systems for the assessment of water pollution index induced by heavy metal contamination

The development of the analytical instruments for rapid in-field evaluation of integral surface water quality parameters is an urgent analytical task. Using three different sensor devices (optical sensor for cadmium, voltammetric sensor for lead and potentiometric multisensor system), we have explored the possibility of direct quantification of water pollution index (WPI) for contaminations induced by heavy metals. We have applied linear (partial least squares, PLS) and non-linear (kernel regularized least squares, KRLS) multivariate regression tools to construct predictive models evaluating the content of individual metals and WPI in complex aqueous media simulating surface water composition. We have also explored the potential of data fusion at different levels combining the signals from all three sensor devices. The results indicate that all the instruments retain the sensitivity towards target analytes in complex aqueous samples containing humic substances and that the direct quantification of WPI in the range from 1 to 4 is possible using the employed instruments with RMSE values around 0.14.

INFLUENCE ON GROUNDWATER EXCHANGE BETWEEN CONFLUENTS ON THE ECOLOGICAL QUALITY OF SURFACEWATER BODIES

The article raises the question of the influence on surface water bodies downstream of the Dnipro River, taking into account the geological influence on one river on another. Such studies are necessary to establish the factors influencing the composition of surface waters of rivers and to determine the stability of the ecological quality of surface water bodies such as the left tributaries of the Dnipro – Desna, Sula, Psel, Vorskla and Samara. Detection of the influence on upstream tributaries on downstream, taking into account the presence of groundwater, was carried out using the example of chloride dynamics. Correlational dependences were constructed between chloride concentrations in observation posts located the closest to Dnipro. The obtained results confirm the influence of tributaries on each other. In order to confirm the conclusions obtained regarding the influence on rivers due to groundwater, studies with other impurities present in tributaries are needed. The obtained results can be used for the development and implementation of a mathematical model for forecasting the ecological state of surface water bodies within the sub-basin.

Hydrochemical Characteristics and Control Factors of Surface Water and Groundwater in Huainan Coal Mine Area

To clarify the hydrochemical characteristics and control factors of surface and underground water in Huainan mining area, 115 groups of groundwater and 30 groups of surface water samples were collected, and the hydrogeochemical characteristics of surface water and groundwater in Huainan mining area were analyzed. Additionally, the hydrochemistry evolution law was discussed by comprehensively using mathematical statistics, the Piper triangular diagram, Gibbs diagram, mineral stability field diagram, and ion ratio relationship, etc. The results showed that the groundwater and surface water in the study area were weakly alkaline, the dominant anion was HCO3-, and the dominant cations were Ca+ and Na+. The hydrochemical types of groundwater and surface water were dominated by HCO3-Ca type and HCO3-Ca·Na·Mg type, respectively. The hydrochemical composition of groundwater and surface water was mainly controlled by rock weathering, as well as by alternating adsorption of cations and evaporation concentration. Silicate and carbonate minerals were mainly dissolved in the water-rock interaction. The main ions such as Ca2+, Mg2+, and HCO3- came from the dissolution of carbonate rocks. The Cl-, SO42-, NO3-, and Ca2+ were affected by exogenous inputs caused by human activities. The chemical components of groundwater and surface water in Huainan coal mining area were affected by water-rock interactions and human activities, and groundwater was greatly affected by human activities.

Hydrochemical Characteristics and Control Factors of Surface Water in Kuaize River Basin at the Upper Pearl River

The Kuaize River is a small typical karst watershed in the source area of the Pearl River as well as an important coal mining area in Eastern Yunnan with a fragile ecological environment. Strengthening the research on the water environment in the region plays an important role in supporting the comprehensive management of the ecological environment and water resources in the source region of the Pearl River. Through the systematic collection of surface water, karst groundwater, and mine water samples, mathematical statistics analysis, correlation analysis, ion ratio analysis, absolute principal component scores multiple linear regression(APCS-MLR), and other methods were used to study the characteristics of hydrochemical evolution and control factors in Kuaize River Basin. The results showed that the average pH value of surface water in Kuaize River Basin was 7.8, which was weakly alkaline. The main cations were Ca2+ and Na+, showing the characteristics of Ca2+>Na+>Mg2+>K+. The main anions were HCO3- and SO42-, showing the characteristics of HCO3->SO42->NO3->Cl-. The variation coefficients of Na+, SO42-, and NO3- in surface water were high, showing strong spatial variability. The water chemical type of the trunk stream was mainly HCO3-Ca, whereas the water chemical type of the tributary was relatively complex, mainly HCO3-Ca, HCO3-Ca·Na, and HCO3·SO4-Ca·Na. The chemical composition of surface water was mainly affected by rock weathering, cation exchange, and human activities. Ca2+, Mg2+, Na+, and HCO3- in surface water mainly came from the weathering of carbonate rock and silicate rock; SO42- mainly came from the oxidation of sulfide, such as pyrite in coal seams; K+, Cl-, and NO3- mainly came from domestic sewage and agricultural activities. The APCS-MLR receptor model analysis results showed that the surface water in the Kuaize River Basin was mainly affected by sulfide oxidation, carbonate weathering, weathering of silicate rock in mine water, domestic sewage, agricultural activities, and unknown sources. In general, the contribution rate of human activities such as mining, domestic sewage, and agricultural activities to the surface water reached 47.17%, indicating that human activities were the key driving factor of surface water chemistry in the Kuaize River Basin.

Assessment of groundwater recharge and connectivity with surface water in a mountainous watershed using natural tracers in Daejeon, Korea

The water supply from headwater streams in mountainous regions is considered an important source for sustaining both water quality and quantity in lowland areas. The Korean terrain is characterized by mountainous regions, the hydrological environment is significantly impacted by seasonal weather conditions. This study focused on investigating the hydrochemistry and isotopic composition of groundwater and surface water to identify hydrological connectivity within a mountainous watershed area in Daejeon, Korea. The estimated recharge rate using water budget methods suggests that approximately 20% of the total precipitation contributes to groundwater recharge in this site. The δ18O–δ2H values of the water samples indicate a meteoric water source for groundwater recharge, while the isotope composition of surface water reveals altitude effects, implying that groundwater recharges at a higher altitude region. Additionally, water revealed altitude effects suggesting that the groundwater was inferred to recharge at a higher altitude region. The hydrochemical conservative components (87Sr/86Sr ratio and Cl−) indicate that this watershed undergoes temporary similar water–rock interactions along its flow path, but it is also impacted by anthropogenic contaminants from the surrounding public area. The results of the three-component endmember mixing analysis demonstrate that groundwater is predominantly influenced by surface water, indicating a close interrelationship among various water bodies in mountain hydrology. These findings provide a comprehensive approach to water resource management by combining recharge rate estimation and the assessment of water body connectivity using natural tracers.