Chemical Composition Of River Water Research Articles

Hydrochemical characterization and pCO2 dynamics in the surface waters of Himalayan River: A case study of river Alaknanda.

Chemical weathering processes are becoming increasingly important in studies on carbon cycling because they are responsible for increased solute fluxes in the proglacial zone, can effectively sequester atmospheric CO2 and raise carbon budgets for lateral transport via rivers. Here, we examined the hydrochemical and hydrogeochemical processes, solute sources and factors controlling riverine pCO2 of the Alaknanda River and its tributaries for three sampling seasons, viz. pre-monsoon (May 2021), post-monsoon (October 2021) and winter (January 2022). The surface water is enriched with Ca2+ and Mg2+ as the dominant cations, while HCO3- and SO42- were the major anions. Gibbs's plot confirmed rock weathering as the leading mechanism in controlling the hydrochemistry of the basin. The chemical composition of river water was mainly regulated by the weathering of carbonate end members: dolomite, limestone and feldspar along with small inputs from silicate weathering. The mean pCO2 values in the mainstream (1702.7 µatm), Pindar (2267.9 µatm) and Mandakini (1136.1 µatm) revealed the streams were oversaturated with CO2 having a higher rate of exporting excess CO2 gas to the atmosphere. The study showed the persistence of high pCO2 closed system characteristics associated with increased suspended sediment concentration resulting from carbonate weathering, dominance of HCO3- over SO42- and thereby results in high values of C ratio. Principal component analysis of the water chemistry suggests that weathering contributes about 41%, while humans contribute about 13% of the ionic load to the river. This study is one of its kind to understand the system characteristics of Alaknanda River water.

Type of probability distribution reflects how close mixing dynamics in river chemistry are to thermodynamic equilibrium

The distribution of geochemical species are typically either (log)normally distributed or follow power laws. Here we link these types of distributions to the dynamics of the system that generates these distributions, showing that power laws can emerge in dissipative systems far from equilibrium while (log)normal distributions are found for species for which the concentrations are close to equilibrium. We use observations of the chemical composition of river water from the sampling space in central Italy as well as discharge data to test this interpretation. We estimate the dissipation rate that results when groundwater drains into the river and the dissolved chemical species mix with the river water. We show that calcium (Ca2+) and bicarbonate (HCO3−) concentrations are close to saturation along most of the downstream length of the Arno river, with decreasing dissipation rates and a lognormal distribution, while sodium (Na+) and chloride (Cl−) concentrations increase substantially downstream, show increased dissipation rates, and are power-law distributed. This supports our hypothesis that power law distributions appear to be indicative of dissipative systems far from thermodynamic equilibrium, while (log)normal distributions indicate weakly dissipative systems close to equilibrium. What this implies is that probability distributions are likely to be indicative of the thermodynamics of the system and the magnitude of disequilibrium constrains the range over which power-law scaling may be observed. This should help us to better identify the generalities and mechanisms that result in these common types of distributions and to better classify variability in systems according to how dissipative these are.

Identification of Hydrochemical Characteristics, Spatial Evolution, and Driving Forces of River Water in Jinjiang Watershed, China

Rivers are an important source of water in humid regions, but their availability is greatly limited by water chemistry. In order to accurately identify the changes in river water chemical composition, the compositional analysis method (CoDA) is proposed from the perspective of compositional data analysis theory, which considers the geochemical riverine system as a whole and detects the compositional changes of the entire watershed. The basic data analysis is carried out by traditional analysis methods, and the results show that the hydrochemical characteristics of different sections of the basin have significant features. The water chemistry of Dongxi River is of the HCO3− Ca type. The water of the Xixi River shows a gradual evolution from the HCO3-Ca type and high SO42− content in the upper reaches to the Cl-Ca type in the lower reaches. The hydrochemistry of river water in the watershed is mainly affected by rock weathering leaching (PC1) and agricultural and domestic pollutant discharge (PC2), with a contribution rate of 48.4% and 19.7%, respectively. Rock weathering, mining, and agricultural pollution are the main factors affecting the chemical composition of river water in different regions. The spatial composition of a single sample at different scales is monitored by the Mahalanobis distance approach in an iterative manner to minimize the influence of a single anomaly on the composition center. The results show that the main reasons for the change in river water chemical composition along the Xixi River are attributed to mine pollution, domestic pollution, and tea plantation and that along the Dongxi River is caused by domestic pollution. The hydrochemical composition changes after the confluence of the Xixi River and Dongxi River are mainly affected by human activities and seawater in urban areas. This research could provide new perspectives and methods for detecting the influences of human and natural factors on the hydrochemistry of river water in humid regions worldwide.

Resilience and high compositional variability reflect the complex response of river waters to global drivers: The Eastern Siberian River Chemistry database

The chemical composition of river waters represents an important matter of investigation to understand environment modifications in response to climate changes and global warming. Prolonged dry periods, heavy flood events, degradation of the lands and ice thawing, modify the chemical composition of river waters influencing the drivers governing the complex dynamics of river catchments where everything comes together. In this framework, Compositional Data Analysis (CoDA) offers methods in which the complex structure of the river water composition and the interrelationships among the various components are put into the proper context for their statistical analysis. In this research, we propose a new CoDA approach combining the robust Mahalanobis distance (D) calculus of ilr-transformed chemical variables and the perturbation difference, both with respect to a pristine compositional benchmark. The aim was to trace the change in the chemical composition of the Eastern Siberian River Chemistry Database where degradation of the permafrost for global warming produces important effects on natural waters. The findings indicate complex multiplicative laws and feedback mechanisms governing solutes in Eastern Siberian rivers, with high values of D found where permafrost is more discontinuous. Perturbations clearly discriminate chemical components more resilient to stresses induced by global changes (Ca2+, Mg2+ and HCO3−) from those whose variability is not maintained under control (Cl−, Na+, SO42−). These outcomes open up a new scenario in searching for spatiotemporal resilience metrics to reveal rivers response to environmental changes.

USE OF THE DYNAMIC LIGHT SCATTERING TO ASSESS THE EFFICIENCY OF SEPARATION OF SUSPENDED AND COLLOIDAL PARTICLES IN RIVER WATERS BY FILTRATION AND CENTRIFUGATION

Link for citation: Shulkin V.M. Use of the dynamic light scattering to assess the efficiency of separation of suspended and colloidal particles in river waters by filtration and centrifugation. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 88-97. In Rus. The relevance of the study is stipulated by the need to control the completeness and accuracy of the separation of suspended and colloidal particles using filtration and centrifugation methods during the analysis of the chemical composition of river waters. The main goal: to test and evaluate the possibility of using the method of dynamic light scattering to monitor the effectiveness of separation of suspended and colloidal particles of river waters by filtration and centrifugation. Objects: waters of typical rivers of the south of the Russian Far East with different levels of anthropogenic load and landscape structure of watersheds, which leads to obvious variations in the concentration levels of dissolved, colloidal and suspended forms of chemical elements in rivers, as well as to different content and grain size composition of suspended matter. Methods: measurement of the dynamic light scattering intensity, including its size distribution, using the Photocor COMPACT Z device in unfiltered samples of river waters, as well as in the filtrates through capsule and membrane filters with varying degrees of clogging, and in the supernatants obtained under various conditions. At the same time, the sum content of suspended and coarse-colloidal particles in the initial samples of river waters was determined gravimetrically after filtration through membrane filters with a pore size of 0,45 μm. Results. The dynamic light scattering intensity in unfiltered river waters demonstrates a significant linear dependence on the suspension content in the range of 5–150 mg/l, determined gravimetrically. In filtrates via a membrane or capsule filter of 0,45 μm, the dynamic light scattering intensity does not depend on the suspension content in the unfiltered samples. Analysis of the size distribution of dynamic light scattering intensity in the unfiltered samples, and in the filtrates confirms the removal efficiency of particles larger than 0,45 μm both at the filtration through membrane or capsule filters, and at the centrifugation for 30' at 4500 rpm. Dynamic light scattering allows characterizing the efficiency of separation of suspended and coarse-colloidal particles in river waters from thin colloids and dissolved forms using membrane and capsule filters, as well as centrifugation. Thus, it becomes possible to control the processes of filters clogging and choose the optimal method for separation of suspended and colloidal particles at the chemical analysis of river waters.

Hydrochemical characteristics of the Upper reaches of the Tisza River


 
 
 The purpose of this study is to analyse the hydrochemical regime and surface water quality of the upper reaches of the Tisza River from its source to Tiachiv, which also includes the transboundary section of the river. The data of the Borys Sreznevskyi Central Geophysical Observatory of the State Emergency Service of Ukraine for the period 1984-2018, as well as the results of route surveys during 2015-2018 served as materials for the study. The hydrological parameters of the river, in particular the level and flow of water, the distribution of the flow and the change of power sources throughout the year were analysed. Based on of the collected materials, a detailed analysis of the hydrochemical indicators of the water quality of the Tisza, Black Tisza, and White Tisza rivers was carried out. During the research, the natural conditions of the territory and economic activity were studied and their influence on the values of physic-chemical indicators, main ions and mineralization of water, biogenic substances, heavy metals and specific pollutants was analysed. The ratio of seasonal, average annual, average multi-year and maximum permissible concentra-tions (MPC) of hydro-chemical indicators was considered to determine their seasonal variability and multi-year dynamics. The role of natural factors in the formation of the chemical composition of river waters is determined, and the main sources of anthropogenic influence are also indicated. Seasonal variability of the indicated groups of indicators was also analysed considering different phases of river water content. It was determined that the waters of the headwaters of the Tisza River are calcium carbonate, moderately fresh with average mineralization (192-245 mg∙dm-3) and clear seasonal variability. Cases of increased concentrations of nitrogen-containing compounds in the waters of the upper reaches of the Tisza River due to the intensive decomposition of organic substances from house- hold wastewater were revealed. High concentrations of iron in river waters were recorded, which is related to the peculiarities of the geological structure of the territory. The seasonal variability of the content of synthetic surfactants was established. A decrease in the content of specific pollutants during the study period was observed.
 
 

CO2 Release Driven by the Combination of Sulfide Oxidation and Carbonate Dissolution in the Upper Changjiang River: Effect of Erosion and Lithology on Chemical Weathering

AbstractThe positive link between weathering and orogeny suggests that the drawdown of atmospheric carbon dioxide (CO2) over the Cenozoic should be closely related to the enhanced silicate weathering caused by Cenozoic orogeny, especially the uplift of the Tibetan plateau. However, the uplift of orogens could also exhume carbonate and sulfide minerals, the coupling weathering of which can act as a source for atmospheric CO2 at the long‐term timescale and counteract the CO2 consumption by silicate weathering. In this study, the solute concentrations and isotopic ratios in the upper Changjiang River are determined to investigate the co‐weathering of silicate, carbonate, and sulfide minerals and its impact on the long‐term carbon cycle. An inverse mixing model incorporating elemental and isotopic ratios is established to quantitatively identify the sources of cations and weathering acids. The inversion of our samples reveals that carbonate weathering dominates the chemical composition of river water, even with the presence of secondary calcite precipitation. The sulfide oxidation widely occurs in the study area and the bulk of generated sulfuric acid is buffered by carbonate minerals. The erosion is decoupled from sulfide oxidation and chemical weathering, likely due to lithology and secondary calcite precipitation. Overall, we find that the CO2 release from sulfide oxidation coupled with carbonate dissolution exceeds the CO2 drawdown from silicate weathering in the Changjiang River basin, indicating the weathering will act as a source for atmospheric CO2 at the timescale between marine carbonate compensation (105 years) and sulfate reduction (<10 Ma).

Characteristics and Driving Factors of Hydrochemical Evolution in Tuochangjiang River Basin, Western Guizhou Province

Tuochangjiang River is a typical mining-type watershed in the karst mountainous area of western Guizhou province. The study of its hydrochemical evolution characteristics and driving factors is of great significance to the local economic development and the scientific management of water resources. The samples of river water, spring water, and mine water in the Tuochangjiang River Basin were collected, and the sources of solutes and their contribution to the chemical components of river water were discussed by means of hydrochemical diagrams, mathematical statistics, and the absolute principal component scores-multivariate linear regression model (APCS-MLR). The results showed that the pH of the river water ranged between 7.30 to 8.31, and the TDS value ranged between 40 to 520 mg·L-1, which was mainly contributed by Ca2+, Na+, HCO3-, and SO42-. The dominant cations in river water were Ca2+ and Na+, the dominant anions were HCO3- and SO42-, and the main water chemistry transitioned from HCO3-Ca to HCO3-Ca·Na and HCO3·SO4-Ca·Na type, whereas that of the mine water was mainly the HCO3-Na and HCO3·SO4-Na types. The chemical composition of river water was affected by rock weathering, exchange adsorption of anions, mineral dissolution and precipitation, and human activities, in which Ca2+, Mg2+, and HCO3- were mainly derived from the weathering and dissolution of carbonate and silicate rocks, Na+and SO42- were mainly from the discharge of mining wastewater, and Cl- and NO3- were affected by domestic sewage and agricultural activities, respectively. APCS-MLR analysis further showed that the river water solutes mainly included five sources:discharge of mining wastewater, dissolution of soil minerals, geological background, agricultural activities, and unknown sources, and their contribution rates to river water were 23.49%, 35.04%, 13.87%, 7.96%, and 20.63%, respectively. Mining factors and soil factors were the most important sources of solutes in the river water, and they were the main driving factors for the hydrochemical evolution of the Tuochangjiang River Basin.

The Role of Subaquatic Springs in the Formation of Flow, Temperature and Chemical Composition of River Water in the Reserve

The Role of Subaquatic Springs in the Formation of Flow, Temperature and Chemical Composition of River Water in the Reserve

Assessment of non-point source of pollution using chemical mass balance approach: a case study of River Alaknanda, a tributary of River Ganga, India.

The low ionic concentration meltwaters of the rivers originating from the Himalayan glaciers play a significant role in diluting the high solute load emanating from Ganga plain catchments. Hence, any change in the qualitative and quantitative characteristics of the Himalayan tributaries of River Ganga under the changing climatic scenario will impact the hydrochemical parameters of River Ganga as well. Hydrochemical investigations have been carried out in the River Alaknanda, a tributary of River Ganga during the period September 2016-May 2018 and revealed that TSS and COD values were observed above the prescribed criteria limit of 10mg/L for drinking purpose for river as prescribed by CPCB. The anions for all sampling sites and seasons were observed to be in decreasing order of HCO3- > SO42- > Cl- > NO3- and cations Ca2+ > Mg2+ > Na+ > K+. The weathering of rock forming minerals of drainage basin is responsible for the chemical composition of river water. HCO3- being the dominant anion in the study area accounts for its presence due to carbonate and silicate weathering. Ion exchange process controls the major ion chemistry of the river water. The assessment and management of non-point sources (NPS) pollution are difficult by any deterministic method and require a vast amount of data to compensate for their extent of contamination, in the account of their prevailing nature in response to hydrological processes and land use patterns. In the present investigation, the application of a simple chemical mass balance approach based on law of conservation of mass/matter has been applied on River Alaknanda, a tributary of River Ganga for measuring the chemical mass loadings of some selected water quality constituents, viz., major cations (sodium, potassium, calcium, magnesium, and ammonium) and major anions (chloride, sulfate, nitrate, and phosphate) at upstream and downstream of different point source locations for examining the contribution made by non-point sources of pollution to the river. Time series analysis of various ion concentrations at point source sites and upstream/downstream sites inferred that the fluvial variations pertaining to ion concentration and flux are strongly dependent on the seasonal changes. More contribution (> 30-50%) for almost all constituents from uncharacterized sources was observed in the months of November to February, which may be attributed to intensified agricultural activities during the winter months particularly cereals and vegetables.

ТЕНДЕНЦИИ ИЗМЕНЧИВОСТИ ХИМИЧЕСКОГО СОСТАВА И СТЕПЕНИ ЗАГРЯЗНЕННОСТИ ВОДЫ РЕКИ КУБАНЬ

Introduction. The paper explores the long-term spatial and temporal variability of the chemical composition and water quality in the Kuban River. Methods. To study the variability of the chemical composition of river water, we analyzed data from systematic observations over the concentrations of major ions, biogenic and organic substances, petroleum products and heavy metals from 2010 to 2017. To describe the variability of water quality, we used such indicators as water quality class, water pollution level, and characteristic pollutants. Results. It is shown that the spatial change in the chemical composition is uneven — a number of components in the water have low concentrations in the upper reaches, increasing in the lower part of the river. Others are characterized by high concentrations in the middle reaches, followed by a decrease towards the mouth. Over time, the change in the concentrations of chlorides, sulfates, organic substances and petroleum products increases. As for the content of nitrates, a slight decrease was detected in its variability. For the remaining chemicals, there were no clear trends. We established that in most cases the water in the Kuban River can be classified as polluted and very polluted (water quality class 3). We also found that the nature of river water pollution regarding a number of components is stable. Conclusion. In modern conditions of sharp climate changes and anthropogenic impact, the identified features of the chemical composition and trends in water quality variability of the Kuban River are of great practical importance and can be used in the development of environmentally sound recommendations for improving water quality and the state of water ecosystems in the river basin.

ПІДРУЧНИК «АГРОГІДРОХІМІЯ» (2021 р.) - ВНЕСОК У РЕАЛІЗАЦІЮ ПОЛОЖЕНЬ «НІТРАТНОЇ ДИРЕКТИВИ» 91/676/ЄEC В УКРАЇНІ

The article presents and analyzes the textbook “Agrohydrochemistry” (author V.K. Khilchevsky – professor of the Taras Shevchenko National University of Kyiv), published in 2021. The textbook examines the main problems associated with the growth of the chemicalization of agriculture and the protection of water resources. Due to agriculture, there is a noticeable impact on the quality of natural waters in the world, especially in regions of intensive agriculture, to which Ukraine belongs. Increased concentrations of nutrients and various types of pesticides are found in the waters of small and large rivers, groundwater. Therefore, the issues of studying the main sources of agricultural pollution of natural waters and the processes that contribute to this are relevant. Among the main sources of pollution of natural waters with wastewater, namely industrial, household and agricultural – the latter have a specific character of formation and flow into water bodies. If industrial and domestic wastewater is localized behind the formation and place of discharge into the sewer network, then the formation and supply of chemicals from agricultural land is dispersed throughout the catchment area and natural ways of entering (hydrographic network) into water bodies. The attention of the world community to the impact of agrochemicals on the quality of natural waters is evidenced by the Directive 91/676/EU adopted in the European Union of December 12, 1991 “On the protection of waters from pollution caused by nitrates from agricultural sources” (abbreviated as “Nitrogen Directive”), which in turn is a local manifestation of the integrating directive 2000/60/EC of October 23, 2000 “On the establishment of a framework for Community activities in the field of water policy” (abbreviated WFD – “EU Water Framework Directive”), aimed at achieving a good ecological state of natural waters in the regions river basins. Agrohydrochemistry is a direction in hydrochemistry that studies the effect of agrochemical agents on the chemical composition of natural waters using theoretical methods and the results of experimental studies in watersheds. The textbook, which consists of 9 chapters, gives an idea of the formation of the balance of chemicals in the soil, the use of various types of fertilizers and pesticides, and the possible ways of their entry into water bodies. Methods for calculating the flow of chemicals into water bodies are presented. The theoretical provisions are illustrated by the materials of our own research on the effect of agrochemicals on the chemical composition of river waters in the Dnieper basin. The textbook is designed for students of the specialty “Earth Sciences” of educational programs of the hydrological profile of higher educational institutions..

River bank filtration for sustainable water supply on Gorganroud River, Iran

River bank filtration (RBF) is one among the managed aquifer recharge methods which is inexpensive and sustainable means to improve the quality of surface waters undergoes natural treatment by subsurface flow through the aquifer medium. This study was carried out to investigate the feasibility of a RBF to improve water quality of Gorganroud River, Iran. For this purpose, 48 water samples were simultaneously collected from three water sources (river, production well, and groundwater) to analyze twenty-six water quality parameters. Hydrogeochemical results revealed that the production well together with river water had a similar origin whereas the groundwater was different. Furthermore, the water quality of production well is mainly controlled by the chemical quality of the Gorganroud River water together with microbial, chemical, and physical processes that occur during the RBF. Results showed that 12 out of 26 the water quality parameters (e.g., total coliforms, turbidity, color, salinity, ammonia, nitrite, nitrate, BOD, COD, iron, manganese, and pH) decreased in the production well. The average removal efficiency of total coliforms bacteria, turbidity, and color parameters was found to be about 98, 97.7, and 72%, respectively. Results of Tukey and Games-Howell tests indicated that there was no statistical difference between chemical composition of river water and the production well water (except ammonia, calcium, and magnesium). Results revealed that the natural attenuation of surface water using the RBF can effectively enhance the water quality index values of the extraction well. Therefore, the RBF system is an effective approach to treat Gorganroud River water that will expand the natural treatment options available to Iranian water utilities in Golestan Province.

Application of water quality indices to the assessment of the effect of geothermal water discharge on river water quality – case study from the Podhale region (Southern Poland)

In the European Union the basic requirements in the subject of the appropriate quality of water, constituting a habitat for fish, was established in Directive 2006/44/EC (EU, 2006) on the quality of fresh waters needing protection or improvement in order to support fish life (currently implicitly repealed by Directive 2000/60/EC). This legislation presents the list of parameters that should be controlled together with their guide and mandatory levels, methods of analysis as well as minimum sampling and measuring frequency. Based on the case study from the Podhale region in southern Poland, the impact of used geothermal water discharge on river water quality was assessed, in particular in the context of the quality of the life of salmonid fish species. The variability of the chemical composition of river water as a result of used geothermal water discharge was assessed both in statistical terms and in correlation to river flows. To quantify the water quality in terms of protection of the fish life, a new Fish-Water Pollution Index was developed. In the presented case, similarly to the Water Quality Indices and Heavy Metal Pollution Indices, also the Fish Water Pollution Indices values calculated upstream and downstream of the used geothermal water discharge, do not display significant differences.

A new Alpine geo-lithological map (Alpine-Geo-LiM) and global carbon cycle implications

Abstract The chemical composition of river waters gives a measure of the atmospheric CO2 fixed by chemical weathering processes. Since the dominating factors controlling these processes are lithology and runoff, as well as uplift and erosion, we introduce a new simplified geo-lithological map of the Alps (Alpine-Geo-LiM) that adopted a lithological classification compliant with the methods most used in literature for estimating the consumption of atmospheric CO2 by chemical weathering. The map was used together with published alkalinity data of the 33 main Alpine rivers (1) to investigate the relationship between bicarbonate concentration in the sampled waters and the lithologies of the corresponding drained basins, and (2) to quantify the atmospheric CO2 consumed by chemical weathering. The analyses confirm (as known by the literature) that carbonates are lithologies highly prone to consuming atmospheric CO2. Moreover, the analyses show that sandstone (which could have a nonnegligible carbonate component) plays an important role in consuming atmospheric CO2. Another result is that in multilithological basins containing lithologies more prone to consuming atmospheric CO2, the contribution of igneous rocks to the atmospheric CO2 consumption is negligible. Alpine-Geo-LiM has several novel features when compared with published global lithological maps. One novel feature is due to the attention paid in discriminating metamorphic rocks, which were classified according to the chemistry of protoliths. The second novel feature is that the procedure used for the definition of the map was made available on the Web to allow the replicability and reproducibility of the product.

ГЕОХІМІЧНА ХАРАКТЕРИСТИКА РІЧКОВИХ ТА ҐРУНТОВИХ ВОД (Зовнішня зона Передкарпатського прогину)

Geochemical peculiarities of river and groundwaters of the Outer zone of the Precarpathian deep have been established. It is revealed that the main feature of the distribution of salt composition indicators in the Dniester River and its influxes is hydrochemical zonality, which does not depend on the flow direction of the rivers, but is consistent with the physics-geographical and geological features of the area to which the man-made factor is imposed. There is an increase in concentrations of sulfate, calcium in the left bank confluent of the river Shchyrka. The waters from the Tysmenytsya, Kolodnitsa and Dniester rivers in the village Kolodrubi are characterized by the highest amounts of sodium and chlorides and are sodium chloride-hydrocarbonate composition. The water composition of the Dniester River (Rozvadiv village), its confluents Bystrytsia and Letnyanka are hydrocarbonate calcium (sodium-magnesium-calcium), Shchyrka, Vereshchitsa – sulfate-hydrocarbonate calcium (magnesium-calcium). The index of biochemical oxygen consumption for 5 days in the waters of Tysmenytsya River reached 4.5 mg O2/dm3, while in other rivers it was 0.70‒3.20 mg O2/dm3. The content of O2 soluble in the waters of the river Vereshchytsya was 0.29 mg/dm3, the value of biochemical oxygen consumption was 11.4 mg O2/dm3. In the chemical composition of river waters, there is an increase in the concentrations of sodium, potassium and chloride ions from the left bank to the right bank confluents of the Dniester. In the left-bank confluents, in the chemical composition of water dominate the contents of calcium and hydrocarbons ions. The heterogeneity of the lithological composition, the instability of the thickness of the aquifer both in the horizontal and vertical directions, and the different technogenic influence form the irregularity of pollution and its local distribution in groundwater.

Пространственно-временные изменения вещественного состава донных отложений и речных вод Туганского россыпного узла (Томская область)

The changes in the chemical and mineral composition of bottom sediments and waters of the Omutnaya River (the element of the Omutnaya–Kirghizka–Tom–Ob river system) during the main phases of the water regime in 2018–2019 within the planned Tugan placer deposit (ore minerals—ilmenite and zircon) have been studied. Geochemical parameters were estimated using an inductively coupled plasma mass spectrometry method. It was obtained that the spatiotemporal changes in the gross contents of chemical elements are generally interrelated with their migration forms. General increase in the concentrations of substances in suspended form is predominant and noted in spring floods, with dissolved—in the winter low-water period. Changes in the chemical composition of bottom sediments (fraction up to 1 mm) during the year and from the source to the mouth of the river due to the influence of local geological and hydrological factors are weaker than the corresponding changes in the chemical composition of river waters. Based on the studies, it was shown that the maximum concentrations of ore elements within the halos of placer deposits are most likely under conditions of a relatively stable (geologically) decrease in the intensity of water exchange.

Hydrochemistry and Its Controlling Factors of Rivers in the Source Region of the Nujiang River on the Tibetan Plateau

The chemical composition of river water collected from the main stream of the Naqu and its tributaries was analyzed to reveal its hydrochemical characteristics and to evaluate the water quality for irrigation purposes. Based on 39 samples, the results revealed mildly alkaline pH values and total dissolved solids (TDS) values ranging from 115 to 676 mg/L, averaging 271 mg/L. Major ion concentrations based on mean values (mg/L) were in the order of Ca 2 + > Na + > Mg 2 + > K + for cations and HCO 3 − > SO 4 2 − > Cl − > CO 3 2 − for anions. Most hydrochemical types were of the Ca–HCO3 (~74.36%) type. Cluster analysis (CA) suggested that the hydrochemical characteristics upstream of the main stream of the Naqu were obviously different from those from the middle and downstream of the main stream and its tributaries. The analysis shows that the Sangqu, Basuoqu, Mumuqu, Zongqingqu, Mugequ basin tributary, and the Gongqu basin tributary were mainly affected by carbonate weathering. Carbonate and silicate weathering commonly controlled the hydrochemistry upstream and downstream of the main Naqu, Chengqu, and Mugequ streams. The middle of the main stream of the Naqu was mainly affected by silicate weathering, and anhydrite/gypsum dissolution mainly affected the hydrochemistry of the main Gongqu stream. The quality of water samples was suitable for irrigation purposes, except for one sample from the main stream of the Mugequ.

Controlling Factors of Surface Water Ionic Composition Characteristics in the Lake Genggahai Catchment, NE Qinghai–Tibetan Plateau, China

This study has determined the major ion compositions of surface waters within the basin of Lake Genggahai, northeastern Qinghai–Tibetan Plateau, China. The results showed that the anions in the groundwater and river water of Genggahai Lake are mainly HCO3−, and the cations are mainly Ca2+ + Na+. Evaporite, carbonate, and silicate in the basin all have an impact on the chemical composition of river water and groundwater. Among them, carbonate weathering has a relatively larger contribution. The grazing activities of herdsmen in the basin have had a certain degree of impact on the water quality of river basins and groundwater. The anion of lake water is dominated by Cl−, and the cation is mainly Na+. The content change is mainly affected by the change of corresponding ion content in groundwater coming into the lake and the evaporation of lake water. Among them, Cl− in lake water is more affected by the change of Cl− content in the groundwater coming into the lake, while Na+ in lake water is more affected by evaporation. More specifically, the low concentrations of Ca2+ and HCO3− in lake water were determined to be related to the photosynthesis of aquatic plants in the lake.

Major ion chemistry of a representative river in South-central China: Runoff effects and controlling mechanisms.

The Gan River is a large tributary of the Yangtze River in Jiangxi Province, South-central China. Hydrochemical data for this river were analyzed for the period 1958-2016. Ca2+, Na+ + K+, HCO3-, and SO42- were dominant in river water, and pH and total dissolved solids (TDS) varied from 6.0 to 8.8 and 15.7 to 141 mg/L, respectively. The chemical composition of river water was different between the two periods 1958-1979 and 1980-2016. Monthly yields of all ions were positively correlated with river runoff. Monthly yields of SO42-, NO3-, and Cl- were more positively correlated with river runoff before 1980, indicating non-point sources, while multiple sources were indicated after 1980. Sea salt-sourced Cl- comprised less than 19% of the total Cl- in river water. Weathering of basin rocks with sulfuric acid reflected strengthening of anthropogenic activities after 1980. This was reflected by increases in Cl-/(Na+ + Cl-) and SO42-/(Na+ + Cl-) with gross domestic production, population, coal consumption, fertilizer use, and wastewater discharge. Although water quality in the Gan River makes the water acceptable for drinking according to the World Health Organization standards, increases in Cl- and NO3- concentrations after 1980 are of some concern.