Hydrochemical Characteristics Research Articles

Gas and water performance from the full-cycle of coalbed methane enrichment-drainage-output: A case study of Daning-jixian area in the eastern margin of Ordos Basin

Coalbed water (CBW), as a stratigraphic fluid, is stored and transported together with coalbed methane (CBM), and has an important influence on the generation, transport, enrichment and production patterns of CBM. In order to study the interaction mechanism between CBM and CBW in the full cycle of CBM enrichment-drainage-output, we collected CBW samples from typical wells at different production times and development data of CBM wells in Daning-jixian area in the eastern margin of Ordos Basin. According to the geochemical test results of CBW samples and the main parameters of 5# coal seam, the basic characteristics of CBW in the study area were analyzed. Then, the control of hydrochemical field on CBM enrichment, the influence of hydrodynamic field on CBM drainage, and the connection between CBW evolution and gas production were discussed, respectively. The results show that in the low burial depth area of the 5# coal seam in the monoclinic structure, the ion concentration of CBW is higher, and the Cl–Na coefficient, desulfurization coefficient and carbonate equilibrium coefficient are relatively small, making it a relatively enriched area for CBM. CBM production in high hydrodynamic areas has a greater need for drainage and depressurization, and the average daily gas production is relatively small. The evolution in daily gas production and the hydrochemical characteristics of CBW during CBM drainage show a good correlation. Every increase in gas production is accompanied by an increase in TDS and a decrease in Cl–Na​ coefficient, desulfurization coefficient and carbonate equilibrium coefficient in the extracted water.

Hydrochemical characteristics and driving factors of travertine deposition in Huanglong, Sichuan, SW, China.

The hydrochemical characteristics were analyzed by mathematical statistics, the hydrochemical types were analyzed by Piper three line diagram, and the sources and influencing factors of main ions in surface water were discussed by Gibbs diagram and ion correlation analysis. The results show that the TDS of surface water in the study area is 109-559 mg·L-1, and the average value is 318.67 mg·L-1; The pH value is 6.81-8.62, and the average value is 7.85. Most of them belong to weakly alkaline water. The surface water cation is mainly Ca2+ and Mg2+, the anion is mainly HCO3- and the hydrochemical type is HCO3-Ca. Through the correlation analysis of the main ions, it can be seen that TDS has a significant positive correlation with Na+, K+, Mg2+, Ca2+ and HCO3-, and these ions contribute to TDS. HCO3- has a significant correlation with Na+, K+ and Mg2+ and comes from carbonate rocks. According to the analysis of water-rock model, the hydrochemical genesis of surface water in the study area is mainly controlled by rock weathering, most ions are weathered and dissolved by carbonate rock and evaporated salt rock and a few cations are affected by water ion exchange.

Response of OC, TN, and TP deposition mediated by aquatic photosynthetic community structures in shallow karst surface waters under different land uses

Land use change alters the hydrochemical features, nutrient outputs, and community structure of aquatic photosynthetic organisms in watersheds and has an important impact on C, N, and P biogeochemical processes. In shallow water environments, sediments are the most important burial sites for C, N, and P; however, the factors underlying the control of their deposition by land use changes remain unclear. In this study, the relationship among hydrochemical features, aquatic photosynthetic organism community structure, and C, N, and P deposition in surface waters associated with different land uses was studied at the Shawan Karst Water-Carbon Cycle Test Site, Puding, SW China, by combining field monitoring and laboratory experiments performed over a complete hydrological year from September 2018 to August 2019. The results indicate that (1) OC and TN deposition showed small differences among ponds associated with five land uses, while TP was significantly higher in ponds associated with shrubland and grassland than in ponds of cultivated land, bare soil, and bare rock. (2) Cultivated land increased OC and TN deposition by increasing N and P output and planktonic algae biomass in surface waters, while grassland and shrubland ponds mainly by increasing DIC output and macrophyte biomass. (3) Compared with cultivated land, grassland and shrubland significantly enhanced TP deposition by promoting the deposition of calcium-bound P and biogenic P from macrophytes and their epiphytic algae in surface waters. In conclusion, the shift of cultivated land and bare soil to grassland and shrubland may be conducive to the formation of benign aquatic ecosystems and stabilization of C, N, and P sinks in karst shallow surface waters.

Evaluation of Efficiency of Groundwater Desalination Plants in Different Hydrogeological Conditions in Salahaddin Governorate/ Iraq

Five groundwater desalination plants elected in the province of Salahuddin, these plants are Rimth, AlRaml, Albo Hamed, Albo Rahil, and Mcelila which supplied from Al-Naamah, Zgiton, Baiji-Tikrit, West Samarra, and West Makhoul hydrogeological basins respectively.
 Hydrogeological, hydraulic and hydrochemical characteristics of the five sub- basins were reviewed, it is found that the selection of the locations of these stations did not depend on certain criteria, especially the hydrochemical parameters which are the principal in the desalination. So, there are a lot of wells in these sub-basins, have best quality than the supply wells of the stations under study.
 17samples were collected for selected desalination stations, three or four samples for each station included raw water (well water), desalinated water, mixed desalinated water, and rejected water, the field and laboratory tests were conducted on the different types of sampled water, the concentrations of more than seventy element were measured, included major anions and cations, minor and trace elements, the results were compared with local and international standards for drinking water. it is found that the raw water unsuitable for human use, the desalinated and mixed desalinated water are within the allowable limits of these standard, but these standards ignored most of the trace elements which were not discussed in the documents that annexed with these standard, and did not specify the permitted upper limits, despite the that some of these elements increases in the desalinated water in comparison with the raw water, light has been focused to the negative effects of these elements on public health.
 The efficiency of desalination evaluated for these stations depending on the qualitative standards, then, the qualitative criteria were adopted for quantitative evaluation, and show that the stations with high efficiency, its efficiency in removing dissolved solids (TDS) ranged between (81.31% - 98.18%), regarding to quantitative desalination efficiency, the percentage of desalinated water to the raw ranged between (29% -70.37%).

Hydrochemical and Isotopic Evidence for Groundwater Conversion of Surface Water in Alpine Arid Areas: A Case Study of the Datong River Basin

Global warming and regional extreme climates will lead to unbalanced rainfall, melting glaciers, and permafrost degradation in alpine and arid mountain plains, thereby changing the regional hydrological cycle. The relationship between surface water and groundwater conversion is one of the important scientific issues of hydrological cycle climate response in alpine arid areas. Taking the Datong River Basin at the southern foot of the Qilian Mountains as the study area, based on 119 sets of basic hydrochemical parameters and deuterium-oxygen isotope data, using multivariate statistical analysis and isotopic techniques, the hydrochemical characteristics of surface water and groundwater in the basin and their mutual transformation process were studied. The results showed that the surface water was HCO3-Mg·Ca type, which was mainly controlled by rock weathering, whereas the groundwater was HCO3-Mg·Ca type and Cl·SO4-Na type, which was controlled by rock weathering and evaporation concentration. There was a small amount of calcium and magnesium feldspar dissolved in the upstream groundwater, and the chemical components of the midstream groundwater were mainly the weathering and dissolution of carbonate rocks. The contribution rates of weathering filtration, anthropogenic activities, native sedimentary environment, alternating adsorption of cations, and other factors to the chemical components of surface water and groundwater in the study area were 39.1%, 15.0%, 12.6%, 13.8%, and 19.5%, respectively. The deuterium and oxygen isotope contents of Datong River water showed a trend of enrichment to depletion along the groundwater flow direction. The δD and δ18O isotope test results showed that the deuterium and oxygen isotope content in the Datong River along the groundwater flow showed a trend of enrichment to depletion. The upper and middle reaches of the Datong River were mainly recharged by atmospheric precipitation, whereas the lower reaches were affected by geological structure and influenced by hydrogeological conditions, which was mainly due to diving and spring water overflow to supply river water, as the discharge area of groundwater.

Magmatic fluid input controlling the geochemical and isotopic characteristics of geothermal waters along the Yadong-Gulu rift, southern Tibetan Plateau

Geothermal resources, regarded as sustainable green energy, are attracting increasing attention. The southern Tibetan Plateau possesses the most abundant intermediate-high geothermal resources in China and has enormous potential for geothermal exploration. Geothermal waters from the Yadong-Gulu Rift (YGR), which is considered as the most active geothermal belt of the plateau, are studied based on hydrochemical and isotopic characteristics to understand the spatial variations of fluid origin, evolution, and circulation mechanism as well as heat sources. The hydrochemical characteristics of cold springs and surface waters are consistently characterized by Ca-HCO3 dominated (Ca-HCO3 and Ca-HCO3·SO4) waters while those of geothermal springs present extensive variability with Na-Cl dominated (Na-Cl·HCO3, Na-HCO3·Cl, Na·Ca-Cl·HCO3) and Na-HCO3 waters. The main geochemical processes controlling the geothermal springs are combinations of silicate weathering, carbonate dissolution, and cation exchange. The characteristics of trace alkali metals and B indicate they undergone common/similar deep process and the potential input of magmatic degassing. The δD and δ18O values suggest that cold springs and surface waters are recharged by meteoric water, and geothermal springs are replenished by meteoric water, snow-melt, and magmatic fluid. The mass balance model reveal that dominant carbon sources for geothermal waters can be deeply derived CO2 (i.e., magmatic source and metamorphic source), contributing from 77% to 99%. Based on empirical chemical geothermometers, Si-Enthalpy mixing model, and geothermometrical modelling, the calculated reservoir temperatures are highly variable (137-312 °C). The circulation depths of geothermal waters are 2.45-6.85 km. A conceptual model is proposed to reveal the deep groundwater circulation.

The Influence of Shallow Peatland Water Quality on Characteristics of the Occurrence of Selected Herb Species in the Peatlands of Eastern Poland

The aim of the analysis was to compare the physicochemical variables of the quality of shallow groundwater in the peatlands of Eastern Poland in the context of the occurrence of selected herb species with similar habitat requirements: bogbean (Menyanthes trifoliata), small cranberry (Oxycoccus palustris), and purple marshlocks (Comarum palustre). The analysis of the quality variables of the shallow groundwater included the following physicochemical variables: reaction (pH), electrolytic conductivity (EC), dissolved organic carbon (DOC), total nitrogen (Ntot.), ammonium nitrogen (N-NH4), nitrite nitrogen (N-NO2), nitrate nitrogen (N-NO3), total phosphorus (Ptot.), phosphates (P-PO4), sulphates (SO2), sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg). Internal metabolism was shown to influence the hydro-chemical status of peatland water, free of substantial human impact. The variables tested were within the range of the habitat preferences of the herb species and indicated that they have a wide ecological tolerance. However, their identical habitat preferences were not reflected in identical values for the physicochemical variables of the water essential for building populations of these species. The occurrence of these plant species was also shown to be determined by the hydro-chemical characteristics of the habitat, but the characteristics of their occurrence did not indicate the hydro-chemical aspect of the habitat.

Hydrochemical characteristics and quality assessment of groundwater in Guangxi coastal areas, China

Groundwater is a main source of water supply in Guangxi Province, China. The urbanization expansion and ocean dynamic may change the groundwater quality, which is an important issue due to its effects on human health. In this paper, the influence of seawater intrusion and anthropogenic activity on the Guangxi coastal aquatic environment was assessed by geochemical and multivariate statistical methods. The result indicated that the chemical composition of groundwater in the study area is obviously associated with seawater and the main groundwater types were Ca·Na–Cl, Ca·Na–HCO3, and Ca–HCO3·Cl. The groundwater evolution path from land to sea in Guangxi is Ca–HCO3 → Na·Mg–Cl. The origin of salts in the study area is mainly controlled by mineral weathering, the hydrogen and oxygen isotopes contents point to the aqueous source of atmospheric precipitation. According to the results of PCA, seawater intrusion and pollution caused by human activities play an increasingly important role in the evolution of groundwater characteristics. Seawater intrusion is the main factor for the increase of groundwater salinity in Guangxi, while domestic sewage, industrial waste, fertilizers, and pesticides may contribute to the nitrate pollution of groundwater, especially in Beihai. The degree of groundwater nitrate pollution is as follows: Fangchenggang < Qinzhou < Beihai, which is associated with the degree of urbanization in the coastal area. Finally, the results of the water quality index (WQI) assessment show that 82.8 % of the samples were classified as excellent, while there is still a need to be vigilant about groundwater pollution caused by seawater intrusion and groundwater pollution. The results will be valuable for sustainable groundwater resource management in Guangxi coastal zone.

Geochemical characteristics and water quality assessment in the Mt. Changbai volcanic field, Northeastern China

The chemistry of groundwater is an important determinant of water quality, which is vital to human health and the ecosystem. It is estimated that 10% of the worldwide population lives in the vicinity of an active volcano; in these regions, the quality of the water could greatly affect crop yield and soil fertility. The Mt. Changbai volcanic field (CVF), located on the border between China and North Korea, is the most well-preserved typical forest ecosystem in eastern Asia, providing various ecological services to human beings. Many types of water bodies, including hot springs, cold springs, and surface water bodies (e.g. rivers and pools) are distributed in the volcanic field. In this study, the geochemical characteristics of these water types, the quality of the water for irrigation purposes, as well as the water quality-related natural mechanism of the water chemistry in the CVF were systematically studied. The results indicate that the hydrochemical characteristics of the water samples in the CVF show the obvious difference between the volcanic cone and the peripheral areas. Significant spatial variation in the water quality was found in the CVF, where water in the peripheral areas was found to be of better water quality than that in the volcanic cone. The hot spring water in the CVF is not only unsuitable for drinking, but also unsuitable for irrigation. Water-rock interactions, ion exchange, and the addition of magmatic volatiles as well as atmospheric and anthropogenic sources are the main source and controlling factors of ions in the water in the CVF. The results of this study can be used as a reference for the sustainable management of groundwater resources in dormant volcanoes.

Hydrochemistry, Sources and Management of Fracturing Flowback Fluid in Tight Sandstone Gasfield in Sulige Gasfield (China)

Hydraulic fracturing technologies have been frequently utilized in the oil and gas industry as exploration and development efforts have progressed, resulting in a significant increase in the extraction of natural gas and petroleum from low-permeability reservoirs. However, hydraulic fracturing requires a large amount of freshwater, and the process results in the production of large volumes of flowback water along with natural gas. In this study, three tight sandstone gas wells were fractured in the Sulige gasfield (China), and a total of 103 flowback fluid samples were collected. The hydrochemical characteristics, water quality and sources of hydrochemical components in the flowback fluid were discussed. The results show that the flowback fluid is characterized by high salinity (Total dissolved solids (TDS) up to 38,268mg/L, Cl- up to 24,000mg/L), high concentrations of metal ions (e.g., Fe, Sr2+, Ba2+) and high chemical oxygen demand (COD). The flowback fluid is a complex mixture of fracturing fluid and formation water, and its composition is impacted by water-rock interactions that occur during hydraulic fracturing. The major contaminants include COD, Fe, Ba2+, Cl-, Mn and pH, which constitute a high risk of environmental pollution. Meanwhile, chemical elements such as K, Ba and Sr are unusually enriched in the flowback fluid, which has an excellent potential for recycle of chemical elements. The Sulige gasfield's flowback fluid recovery methods and treatment scenarios were discussed, taking into consideration the pollution and resource characteristics of the flowback fluid. Options for dealing with the flowback fluid include deep well reinjection, reuse for making up fracturing fluid, recycling of chemical elements and diverse reuse of flowback water. This research offers guidance for managing the fracturing flowback fluid in unconventional oil and gas fields.

Hydrochemical Characteristics and Quality Assessment of Surface Water in Sidakan-Balakyan River, Kurdistan Region, NE, Iraq

The hydrochemical characteristics of surface water are studied to understand their source, type of water, and evolution. This study aims to determine the hydrochemical characteristics and controlling factors, by evaluating the water quality of the Sidakan-Balakyan River. The samples were collected along the Sidakan-Balakyan River to the junction point of the Sidakan-Rwanduz Rivers, for each sample, physical (pH, EC, Temperature, Turbidity, TDS and T.H) and chemical parameters (Mg2+, Ca2+, K+, Na+, HCO3-, Cl-, SO42- and NO3-) were analyzed. The results showed that all water samples were within the acceptable range. The results obtained from the Piper and Chadha diagram indicate that the studied water samples during High Flow Period is Mg- Bicarbonate type as well as Ca+2 and SO4-2, whereas during Low Flow Period in Sidakan river is Mg2+- Bicarbonate, But in Balakyan and Rwanduz rivers are Ca2+- Bicarbonate. Moreover, based on Gibbs Diagram, water samples were distributed in the rock weathering dominance section. Based on TDS and T.H of water samples were found to be moderately hard fresh water. Additionally, the river water can not be used for drinking directly. Most samples have a good to excellent water quality index except for some samples which are unsuitable during High Flow Period.

Assessment of shallow groundwater aquifer in an arid environment, Western Saudi Arabia

In arid and semi-arid regions like the Kingdom of Saudi Arabia (KSA), groundwater is considered the main source for drinking and agricultural uses due to low precipitation and limited surface water resources. The aim of this research is to evaluate the hydrogeological and hydrochemical characteristics of groundwater in Wadi Marawani basin for sustainable development. To achieve this goal, standard analytical methods have been used to determine the physicochemical parameters in sixty-four samples. Groundwater quality and controlling factors were evaluated using diagrams (Piper, Gibbs, Chadha, and HEF) and irrigation indices such as Sodium percentage (Na%), Soluble Sodium Percentage (SSP), Permeability Index (PI), Residual Sodium Bicarbonate (RSBC) and Kelly Index (KI). Also, the Support Vector Machine for Regression (SVMR) and the Multiple Linear Regression (MLR) models have been applied to predict the irrigation parameters. The results revealed that the Quaternary aquifer of unconfined condition is the main source of groundwater in Wadi Marawani basin. Depth to water measurements in sixty-two wells indicated that the groundwater flows from east to west towards the Red Sea coast. The ionic composition of the analyzed water samples showed that, Ca–HCO3, Na–Cl, mixed Ca–Mg–Cl–SO4, and Na–Ca–HCO3 are the main water types. Assessment of groundwater quality indicates that, 33%, 86%, 100%, 100% and 69% of groundwater samples are suitable for irrigation based on the calculated irrigation indices Na%, SSP, PI, RSBC and KI respectively. The SVMR model is outperformed the MLR in prediction of the irrigation indices. There was no overfitting or underfitting in the datasets used to measure, calibrate, and validate the SVMR model of four irrigation indices. Finally, this study can provide a holistic view of groundwater management for agricultural uses in the Wadi Marawani basin.

Isotopic and Hydrochemical Characteristics of the Changqing-Xiaolipu Water Resource, Jinan, Eastern China: Implications for Water Resources in the Yellow River Basin

The Yellow River has played an indispensable role in supporting Chinese civilization because it provides water resources and rich soil for agriculture. This study analyzes the major ions and the isotopic ratios of the hydrogen (δD), oxygen (δ18O), and carbon (14C) of groundwater samples to identify the sources of recharge and the impact of the Yellow River on the Changqing-Xiaolipu karst aquifer. The major ion/Cl− ratios generally follow the mixing line between the Yellow River and the karst groundwater recharge in the southern mountain areas, indicating the importance of mixing under natural influences in the Yellow River Basin. The dominant hydrochemical type of karst groundwater is Ca·Mg-HCO3·SO4, whereas that of Yellow River water is Ca·Na·Mg-SO4·Cl. Most karst groundwater consists of 10–30% Yellow River water, indicating that the water resources of the Yellow River Basin are generally supplemented by the Yellow River. Therefore, the Yellow River must be considered during the characterization of the chemistry and budget of water resources in the Yellow River Basin.

Hydrochemical Characteristics and Ion Source Analysis of the Yarlung Tsangpo River Basin

In order to investigate the hydrochemical characteristics and their controlling factors, 212 water samples from the Yarlung Tsangpo River and its tributaries were collected over three precipitation periods in 2018 and analyzed using mathematical statistics, the Gibbs and ion ratio methods, and principal component analysis. The results showed the following: (1) The cations in the water were mainly Ca2+, Na+ and Mg2+, and the anions HCO3− and SO42− were predominant, accounting for more than 97% of the total anion concentrations. The concentration of total dissolved solids (TDS) was 204.51 mg/L. The water chemistry type was SO4·(HCO3)−Ca·(Mg) water. (2) The concentrations of major ions in the Yarlung Tsangpo River fluctuate, but in general, the vast majority of the major ions in the water follow the trend of both first increasing and then decreasing in the three precipitation periods. The hydrochemical features of the Yarlung Tsangpo Basin have seasonal differences. (3) The Gibbs model and the PCA analyses showed that the Yarlung Tsangpo River water chemical components are mainly affected by rock weathering. In addition, the influence of the mining industry also plays an important role. The heavy metal concentrations in the three precipitation periods of the Yarlung Tsangpo River could reach the standard of first-class surface water quality.

Hydrogeochemical Characteristics and Isotopic Tools Used to Identify the Mineralization Processes of Bottled Mineral Water in Morocco

Bottled waters are among the most important products in the human diet. In Morocco, eleven bottled mineral waters were analyzed (physicochemical composition and water stable isotopes) to identify their geologic origins and hydrochemical characteristics. The study of the ionic ratios shows that the mechanisms of water–rock interaction, such as the dissolution of carbonate and silicate minerals, influence the chemistry of these mineral waters, which are controlled by lithology and tectonics, sometimes with the influence of deep flux through fractures. The water from the Oulmes plateau shows a Na-HCO3 chemical facies in relationship with alkaline granite. Moreover, the carbonated waters (EMG and EMGL) are characterized by high concentrations of Si, Li, Rb, Sr, and Cs due to deep CO2 flux origin. The waters of Saiss, Middle Atlas, and Rif are of the Ca-HCO3 type linked mainly to carbonate formation. The stable isotope contents of water range from −7.74 to −5.35‰ for δ18O and −45.4 to −30.4‰ for δD. The recharge altitude of the aquifer was estimated to be between 250 and 1200 m, following a δ18O altitudinal gradient between 0.25 and 0.27‰ per 100 m. The industrial production process and the natural presence or artificial addition of CO2 can also influence the isotopic composition of water. These results can be a relevant guide to decision makers for better exploitation and assessment of the water quality.

Hydrogeochemical processes in rural coastal aquifer (Haha region, Morocco).

In arid and semi-arid regions, groundwater is the principal source of urban and rural water supply. Given that groundwater is the only source of water supply in the Haha region (Moroccan Atlantic coast), the evaluation of this vital resource, using the hydrogeochemical approach, is the main objective of this study. The interpretation of these analytical data showed that the chemical composition of the groundwater is of Ca-Mg-Cl, Na-HCO3, and Na-Cl, with the dominance of the first type. Hydrochemical characteristics using the bivariate diagrams of major (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, NO3-, and SO42-) and some trace elements (Br- and F-), mineral saturation indices, and statistical analysis show that the water-rock interaction, cation exchange processes, and marine effect are the main processes that control groundwater mineralization. Also, the majority of analyzed samples have concentrations above the thresholds for human consumption fixed by WHO, especially F-, NO3-, K+, Cl-, and HCO3- concentrations. This requires treatment of this groundwater before any consumption and domestic uses. For agricultural uses, the groundwater of the Haha region remains adequate, especially for plants, which can withstand water with electrical conductivity greater than 1000 µS/cm. However, the results obtained can be used as a basis for decision-makers for better water management in the Haha region.

Understanding regional groundwater flow using water-rock interaction processes and anthropic signatures in a fractured volcanic aquifer

This research evaluated the hydrochemistry of a fractured volcanic aquifer at Paraná 3 Basin, in the western region of the state of Paraná, southern Brazil. Geochemical rock data from the literature were used to describe the distinctive characteristics of the principal geological units in the area, Pitanga and Paranapanema Formations, both belonging to the Serra Geral Group. Data from x-ray diffraction were obtained to deepen the study of hydrogeochemical processes. Previous studies did not consider the differences in the lithogeochemistry of the group, in the terms contemplated in this research. In addition, the research also approaches the evaluation of the flow depth contribution in the groundwater chemistry and the analysis of hydrogeochemistry processes. For this analysis, a set of chemical data was utilized on 35 groundwater samples from water supply boreholes at Paraná 3 Basin. From shallow to deep flow, there was an increase in pH, electrical conductivity, total dissolved solids, total alkalinity and a decrease in CO2. These parameters exert the main physical-chemical groundwater controls, which are identified by changes in the major ions along the flow lines, as well as by variations in trace elements. The water-rock interaction becomes increasingly evident in the intermediate and deep flows, standing the higher alkalinity, pH, electrical conductivity, total dissolved solids (TDS) and most of the trace elements at Pitanga Formation. Pitanga Formation presents higher medians of alkalinity (95.5 mg.L-1), electrical conductivity (225 μS.cm-1) and TDS (140.0 mg.L-1) than Paranapanema Formation (57.0 mg.L-1; 130 μS.cm-1 and 90.0 mg.L-1, respectively). Furthermore, the pH distribution shows greater values starting at the 60% percentile in Pitanga Formation (8.24), compared to Paranapanema (8.10). Despite such differences, it was not possible to distinguish the geological units with the hydrochemical characterization, probably because both units are mainly represented by rocks of basic composition, with a similar mineralogical basis. The shallow hydrogeochemical processes are characterized by the weathering of Fe–Mg silicates and plagioclase, changing to a predominance of ion exchange in deeper flows. Calcite precipitation is a secondary process, associated with calcium consumption towards deeper flows. Anthropic influences are mainly observed with more elevated concentrations of NO3-, PO43-, Cl- and K+, occurring in the entire basin, and they are strongly evidenced by the correlation between Cl- and NO3- in most samples.

Hydrogeophysical and Hydrochemical Assessment of the Northeastern Coastal Aquifer of Egypt for Desalination Suitability

Recently the limited freshwater resources have become one of the most significant challenges facing Egypt. Thus, new resources of drinkable water are required to meet the growing population demands and the national projects, to support the country’s economy. Saline groundwater desalination is an option that can support limited freshwater resources. This research represents a detailed analysis of hydrogeological and hydrochemical characteristics of a coastal aquifer in the West Port Said area, northeastern Egypt, to assess the desalination suitability of the aquifer, especially when the nearby seawater is contaminated. The hydrogeological characterization included various integrated approaches: geophysical survey, field investigations, wells drilling, well logging, pumping tests, and water sampling. The results show that: (1) The subsurface lithology consists of sandstone and clay, and three water bearing layers: A, B and C. (2) The average porosity values are 22%, 27.5%, and 25% for layers A, B, and C, respectively. The hydraulic conductivity values fall in the ranges of 5.8–12.7 m/day for layer A, 7.6–11.7 m/day for layer B, and 11.1–19.5 m/day for layer C, while the highest transmissivity values are in ranges of 5.8 × 102–12.7 × 102 m2/day for layer A, 7.6 × 102–11.7 × 102 m2/day for layer B and 11.1 × 102–19.5 × 102 m2/day for layer C. (3) The average storage values are 2.1 × 10−3, 1.8 × 10−3 and 5.3 × 10−3 in layers A, B and C, respectively. (4) Layers A and B showed Na-Cl-type, similar to seawater, but free from oil pollution. These results show layer B’s higher productivity and better quality. Despite the salinity, desalination technology can improve.

Hydrochemical characteristics and water quality assessment of snow cover in the northeastern tibet plateau

Snow cover as an important water resource is essential for regional water environment system. The Three-Rivers Headwater Region (THR) in the Tibetan Plateau is the source of the Yellow River, the Yangtze River and the Lantsang River with fragile ecological environment and large snow cover. The analysis of hydrochemistry in snow cover can provide reliable data for the research of environmental changes. Snow cover samples in 57 sites across the THR region were collected, and arsenic (As) and major ions were analyzed to investigate the distribution characteristics. The snow cover samples were weakly alkaline with water type of SO4–Cl–Ca–Mg. The As concentration varied from 0.24 to 6.12 μg/L with average value of 1.25 μg/L. Major ions and As have similar distribution characteristics, with higher levels in the northern part of the study area due to anthropogenic influence and special geography. Qualitative and semi-quantitative analysis of snow cover samples based on principal component analysis and absolute principal component score-multiple linear regression indicated that As was substantially controlled by burning of fossil fuels and local mining activities, while major ions mainly derived from terrestrial dust, human activities and marine sources. Although there were different trajectories at the sampling points, the air mass in THR was mainly controlled by the westerly circulation. The water quality of THR was excellent with water quality index <50. This work will shed lights for the migration and transformation of pollutants in the Tibet Plateau and for assessing the impact of human activities on geochemical cycling of pollutants.

Community Structure and Abiotic Characteristics of Pelagic Microalgal in Adjacent Areas of the Barents Sea and Kara Sea

This study aimed to confirm the hypothesis of a floristic identity between the southeastern Barents Sea and the southwestern Kara Sea. We conducted integrated studies of pelagic microalgae communities including microscope cell counting and taxonomical identification as well as photosynthetic pigments determination and defining of hydrological and hydrochemical characteristics during a cruise in late August and the first half of September 2020. As far as we are concerned, no such observations had been carried out in this region at this time of the year before. During our observations, 35 species were identified, 14 (40%) of which were present in both water bodies. The communities of both regions were in a state corresponding to the autumn stage of the annual succession cycle. In the southeastern Barents Sea, the mean abundance of organisms in the water column varied from 10.650 to 41.840 cells per liter with a biomass of 71.04 to 300.55 µg/L. In the southwestern Kara Sea, these values were 3.510–28.420 cell/L and 16.31–66.96 µg/L, respectively. In general, the results of a comparative analysis suggest that the pelagic algal communities in the regions under comparison, despite the difference in hydrological parameters, demonstrate similar qualitative and quantitative characteristics and thus may belong to the same phytogeographic region.