Hydrogeochemistry of Hot Springs and the 2018 Mojiang M 5.9 Earthquake-Related Chemical Changes in the Simao Basin, China

The Simao Basin is characterized by strong tectonic activity and frequent seismicity. This study investigated the hydrochemical characteristics of 21 thermal springs in the Simao Basin from 2018 to 2020. In this study period, the 2018 Mojiang M5.9 earthquake caused several hydrochemical changes. The results indicate that the Simao Basin contained saline spring waters, HCO3−-rich spring waters, and SO42−-rich spring waters. In the study area, the water chemistry types were controlled by stratum lithology. Saline springs flowed through red beds and dissolved large amounts of halite, which is a rich source of Cl−and Na+ ions. In the hot spring waters, Ca2+ (Mg2+) and HCO3− were mainly derived from the dissolution of carbonate minerals, gypsum, and anhydrite of Triassic rocks. The higher SO42- content in the hot spring waters was caused by the pyrite present in Ailaoshan metamorphic rocks. The reservoir temperatures (121–289 °C) in the Simao Basin were estimated by the silica-enthalpy mixing model equation and the silica-enthalpy diagram. The hot springs had higher reservoir temperatures (>250 °C) and were mainly located at the edges of the basin. Metamorphic rocks exposed in the region had low permeabilities and these springs was close to nearby deep faults that provided deep heat. In most springs, the concentrations of Ca2+ and HCO3− ions increased obviously before the 2018 Mojiang M5.9 earthquake; however, the concentrations of these ions decreased after the earthquake. The hydrogeochemical variations might be attributed to the vigorous water-rock interactions and the mixing of secondary fluids. The entry of cold shallow groundwater caused changes in the reservoir temperatures of some spring samples.

Hydrochemical characteristics, hydraulic connectivity and water quality assessment of multilayer aquifers in Western Suzhou City, Northern Anhui Province, China

The present study focuses on the shallow phreatic aquifer (SA) and the upper confined aquifer (CA) developed in Cenozoic loose strata, which are the major regional groundwater resources for drinking, irrigation, industry and other water-related activities. Seven samples from SA and seventeen samples from CA were analyzed to depict the hydrochemical characteristics, categorize the hydrochemical facies, evaluate the hydraulic connectivity, and appraise the drinking water and irrigation water quality. The abundance of cations is Na+ > Ca2+ > Mg2+ > K+ and the anions is HCO3− > SO42− > Cl− in both aquifers, respectively. Groundwater chemistry is controlled by water-rock interactions such as halite dissolution, ion exchange, reverse ion exchange, silicate weathering, and followed by the dissolution of Glauber's salt. The low connectivity and moderate connectivity between these two aquifers has engendered. The majority of the ion concentrations are within the limit for drinking, only one sample from the shallow aquifer are greater than the limit of 250 mg/L, a total of 29% from the shallow unconfined aquifer and 14% from the confined aquifer were not within the limit of 250 mg/L. The sodium absorption ratio (SAR), residual sodium carbonate (RSC) and soluble sodium percentage (%Na) values reveal that all the samples are appropriate for irrigation uses. The the US salinity laboratory (USSL) diagram shows that sixteen CA samples and all the SA samples fall in the C3S1 zone, implying high salinity hazard and low alkalinity hazard.

Spatial hydrochemical structure in surface waters of the Southern ocean between Africa and Antarctica

Some hydrochemical characteristics and, first of all, the main nutrients (phosphorus, nitrogen, silicon) can be used as markers for distinguishing different types of water masses and positions of the main fronts of the Southern Ocean. The seasonal and interannual variability of these characteristics also reflects the character of biological processes in the surface layer of the ocean, which is important for assessing biological productivity. The aim of this study was to analyze the main features of the spatial distribution of hydrochemical characteristics in the surface layer in the Atlantic and Indian Ocean sectors of the Southern Ocean between the Subantarctic Front and the shores of Antarctica and assess their seasonal (spring–autumn) and interannual variability for the observation period from 2008 to 2020. We describe the surface nutrient concentrations between Africa and Antarctica along the transects that cross the Subantarctic Front (SAF) in the north, the Polar Frontal Zone (PFS), Polar Front (PF) and Antarctic Zone water in the south. The findings revealed an increase in dissolved oxygen and nutrients towards the south. Nitrates changed values within the SAF from 15 μM to 24 μM, whereas values from 1.2 μM to 1.7 μM were observed for phosphates. Silicate increased considerably within the Polar Front, from 6.6 μM to 20.8 μM. An analysis was carried out of the seasonal and interannual variability of the hydrochemical conditions in the surface layer of the Southern Ocean. The interannual variability of the nutrients was determined by the spatial variability of the main fronts of the Antarctic Circumpolar Current (ACC) and the intensity of the largescale Weddell Gyre (WG). Since 2017, there has been an increase in the meridional transfer of waters: in the Antarctic Summer 2017–2018, there was a spreading of high-nutrient WG waters toward the north, and in the Summer 2019–2020, the low-nutrient waters anomaly was transferred far to the south (up to 60°S).According to the data obtained, the seasonal dynamics of the nutrients in the surface layer of the Southern Ocean was rather weakly expressed. An exception is the high-latitude waters of the Cooperation and Davis Seas, where maximum seasonal variability of the hydrochemical characteristics was observed. The highest rate of nutrient consumption was observed in the coastal area of the Cooperation Sea near the fast ice edge from mid–December to early January and reached 3.2 μM per day for silicate, 1.8 μM per day for nitrates, and 0.12 μM per day for mineral phosphorus. The results of the long-term monitoring of the hydrochemical conditions in the Cooperation Sea made it possible to distinguish conditionally “warm” years with early vegetation (at the end of December) and intensive consumption of nutrients by phytoplankton, and “cold” years, when the formation of high-latitude “oases” in December–January was not observed.

Prospects for the whiteleg shrimp Penaeus vannamei (Boone, 1931) cultivation in different regions of Russia, taking into account the hydrochemical characteristics of watebodies and the seasonal dynamics of temperature indicators

Whiteleg shrimp Penaeus vannamei (Boone, 1931) is one of the most popular and promising objects of world aquaculture. In this article possibilities and prospects of cultivating this species in Russia, the results of studies of temperature and salinity effects on the survival rate, growth, activity and food intake of white-footed shrimp were discussed. The critical values of temperature and salinity for this species have been determined. The most progressive for whiteleg shrimp cultivation are the southern regions of Russia, which have an extended sea coastline or a lot of hyperhaline or brackish waterbodies. Technologies combining commercial pond rearing with preliminary rearing of juveniles in RAS are recommended to use to increase the efficiency of cultivation.

Hydrochemical Characteristics, Quality Assessment and Solute Source Identification of Coal Bearing Fractured Aquifer in Dingji Coal Mine, Huainan Coalfield, China

Coal-bearing fractured aquifer is regarded as one of the most dynamic mine water inrush sources, and after pumping and treating, it can be used as a water supply for coal mine production, coal preparation plant, rural irrigation, and even reserved drinking water source. Hence, this study focuses on the hydrochemical characteristics, ion source, and water quality evaluation with respect to drinking and irrigation of the coal-bearing fractured aquifer in Dingji coal mine, Huainan coalfield, China. Descriptive statistics and hydrochemical classification diagrams including the Piper diagram and Chadha rectangular diagram were carried out to depict the hydrochemical characteristics and facies. The water quality of the aquifer was assessed for irrigation and drinking purposes using the WHO threshold value, water quality index (WQI), SAR, % Na and RSC. Hydrochemical formation mechanism and solute origin of major ions were explained by Gibbs diagram, bivariate diagrams, and multivariate statistical analysis. The results show that the dominant hydrochemical facies are the Cl-Na type and the HCO3-Na type. The sequence of ions is Na+ > Ca2+ > Mg2+ for cations, and HCO3? > Cl- > SO42- > CO32- for anions. The main solute sources are controlled by various factors including the dissolution of halite, sulfate, and carbonate rocks, the weathering of silicate, and cation exchange. Water quality assessment based on WQI suggests that none of the samples fall under the excellent category, even 32.5% is not suitable for direct drinking. Meanwhile, the samples of the aquifer are generally unsuitable for irrigation. Before utilization for irrigation and even drinking, appropriate water treatment should be applied to guarantee its security during usage.

Hydrochemical Characteristics and Cause Analysis of Natural Water in the Southeast of Qinghai-Tibet Plateau

This study investigated the hydrochemical characteristics and formation mechanism of natural water in the southeastern Qinghai-Tibet Plateau. To this end, 19 groundwater samples were collected, tested, and analyzed using various methods, such as mathematical statistics, a Piper diagram, correlation analysis, Gibbs plots, and an ion ratio analysis. The results show that the dominant anions are HCO3− and SO42−, and the dominant cations are Ca2+ and Mg2+, which accounted for 98.50% and 85.94% of the total amount of anions and cations, respectively. The samples were weakly alkaline water, where the TDS (total dissolved solids) ranged from 28.00 mg/L to 242.00 mg/L, with an average value of 129.10 mg/L. The hydrochemical types were mainly Ca·Mg-HCO3·SO4—accounting for 42.10%. The hydrochemical evolution process was found to be mainly controlled by the weathering and dissolution of carbonate and silicate rocks. The main sources of Na+ and K+ are rock salt and silicate rocks, and those of Ca2+, Mg2+, HCO3−, and SO42− are from the dissolution of dolomite, calcite, gypsum, and other calcium and magnesium bearing minerals. In addition, atmospheric precipitation serves as a replenishment source of natural water in the region, and the recharge is affected by evaporation.

Hydrochemical Characteristics of Surface Waters and Their Relationships to the Kashin–Beck Disease in Longzi County, Tibet

Although previous studies have been reported between the Kashin–Beck Disease (KBD) epidemic and the hydrochemical characteristics of surface waters, the etiology of the disease remains unclear. In the present study, we investigated the relationship between the KBD and the environment by comprehensively examining the hydrochemical characteristics of surface waters in Longzi County, Tibet, and the spatial incidence of the disease. Results show that, the pH (mean = 7.27±0.30), TH (mean = 57.08±45.74 mg L–1), and TDS (mean = 67.56±44.00 mg L–1) of surface waters in KBD endemic areas are lower than for those in the non-KBD endemic areas (means of pH = 7.49±0.30; TH = 262.06±123.29 mg L–1; TDS = 253.25±100.39 mg L–1). These results suggest that long-term consumption of low TDS, essential trace elements (e.g., nickel, cobalt, iron, selenium, zinc, molybdenum, and iodine) deficient, and potential toxic elements (such as arsenic) enriched waters by humans likely causes the KBD. Environmental factors such as the geology and geomorphology may produce biogeochemical imbalance, geomorphic, vegetation types and local climatic conditions may have significant impact on food fungi toxin poisoning and water organic compound poisoning, and these are also important in the KBD occurrence.