With a mean precipitation rate, much lower than that of the world, Iran is among the countries that face severe water challenges. The present study has dealt with the evaluation of hydrochemistry of Faryab spring water in Hormozgan Province, Iran. Four different composite water samples have been analyzed to detect major anions, cations, total dissolved solids, electrical conductivity, pH, and sodium absorption ratio. The dominant water type was detected as sodium-chloride, with remarkable high concentration of sodium and chloride ions that makes it unfit for drinking purposes. Regarding irrigation use, high values of electrical conductivity (29989 to 31983 µS/cm) and sodium absorption ratio (SAR) (58.1 to 61) indicate a very high risk level for salinity and sodium alkali hazards, respectively. Abundance of secondary minerals such as halite and gypsum is considered to be the main reason for remarkably-high TDS values. Intensity of salt domes within the area would also facilitate solution/dissolution process of Na+ and Cl- into water column.

Evaluation of the geochemistry and hydrochemical quality of Bam salt dome located in southern Iran, was conducted in this study. Two composite samples from salt units were collected and analysed by XRD and XRF to determine their mineral and elemental compositions. Water samples were also collected from the only spring in the area and analysed for major anions, cations and some toxic elements. The results indicated halite as the major mineral present, while quartz, anhydrite and dolomite were present at minor levels. The presence of anhydrite and dolomite together with quartz had negative effects on edible salt quality. The dominant water type in the area was sodium-chloride. Negligible sulphate and calcium contents may be attributed to anhydrites detected in the geological texture of the study area. According to a Schoeller diagram, the water is not suitable for drinking. Concentrations of toxic metals in the salt sample were significantly higher than those in water samples. Such a result can be viewed as an opportunity to produce edible salts from the evaporation of spring water.

Water quality has recently emerged as one of the utmost severe ecological problems being faced by the developing countries all over the world, and Bangladesh is no exception. Both surface and groundwater sources contain different contaminants, which lead to numerous deaths due to water-borne diseases, particularly among children. This study presents one of the most comprehensive reviews on the current status of water quality in Bangladesh with a special emphasis on both conventional pollutants and emerging contaminants. Data show that urban rivers in Bangladesh are in a critical condition, especially Korotoa, Teesta, Rupsha, Pashur, and Padma. The Buriganga River and few locations in the Turag, Balu, Sitalakhya, and Karnaphuli rivers have dissolvable oxygen (DO) levels of almost zero. Many waterways contain traces of NO3, NO2, and PO4-3 pollutants. The majority of the rivers in Bangladesh also have Zn, Cu, Fe, Pb, Cd, Ni, Mn, As, and Cr concentrations that exceed the WHO permissible limits for safe drinking water, while their metal concentrations exceed the safety threshold for irrigation. Mercury poses the greatest hazard with 90.91% of the samples falling into the highest risk category. Mercury is followed by zinc 57.53% and copper 29.16% in terms of the dangers they pose to public health and the ecosystem. Results show that a considerable percentage of the population is at risk, being exposed to contaminated water. Despite hundreds of cryptosporidiosis cases reported, fecal contamination, i.e., Cryptosporidium, is totally ignored and need serious considerations to be regularly monitored in source water.

The largest and most variable step of selenium (Se) assimilation into aquatic ecosystems is the rapid uptake of aqueous Se by primary producers. These organisms can transfer more harmful forms of Se to higher trophic levels via dietary pathways, although much uncertainty remains around this step of Se assimilation due to site-specific differences in water chemistry, hydrological and biogeochemical characteristics, and community composition. Thus, predictions of Se accumulation are difficult, and boreal lake systems are relatively understudied. To address these knowledge gaps, five static-renewal field experiments were performed to examine the bioaccumulation of low, environmentally relevant concentrations of Se, as selenite, by naturally grown periphyton from multiple boreal lakes. Periphyton rapidly accumulated Se at low aqueous Se concentrations, with tissue Se concentrations ranging from 8.0 to 24.9 μg/g dry mass (dm) in the 1–2 μg Se/L treatments. Enrichment functions ranged from 2870 to 12 536 L/kg dm in the 4 μg Se/L treatment, to 11 867–22 653 L/kg dm in the 0.5 μg Se/L treatment among lakes. Periphyton Se uptake differed among the five study lakes, with periphyton from mesotrophic lakes generally accumulating more Se than periphyton from oligotrophic lakes. Higher proportions of charophytes and greater dissolved inorganic carbon in more oligotrophic lakes corresponded to less periphyton Se uptake. Conversely, increased proportions of bacillariophytes and total dissolved phosphorus in more mesotrophic lakes corresponded to greater periphyton Se uptake. Periphyton community composition and water chemistry variables were correlated, limiting interpretation of differences in periphyton Se accumulation among lakes. The results of this research provide insight on the biodynamics of Se assimilation at the base of boreal lake food webs at environmentally relevant concentrations, which can potentially inform ecological risk assessments in boreal lake ecosystems in North America.

Nanoplastics (NPs) are becoming emerging pollutants of global concern. Understanding the environmental behavior of NPs is crucial for their environmental and human risk assessment. In this study, the aggregation and stability of polystyrene (PS) NPs were investigated under different hydrochemical conditions such as pH, salt type (NaCl, CaCl₂, Na₂SO₄), ionic strength (IS), and natural organic matter (NOM). The critical coagulation concentrations of PS NPs were determined to be 158.7 mM NaCl, 12.2 mM CaCl₂, and 80.0 mM Na₂SO₄. Ca²⁺ was more effective in destabilizing PS NPs, compared to Na⁺, owing to its stronger charge screening effect. In the presence of monovalent ions, NOM reduced aggregation through steric repulsion, whereas in the case of divalent ions, NOM induced aggregation through cation bridging. Initial and long-term stability studies demonstrated that, in waters with high IS and NOM content, NOM was the most significant factor affecting NPs aggregation. PS NPs would be highly suspended in all freshwaters, and even in wastewater, whereas they would aggregate rapidly and deposit in seawater. Finally, a statistical model was established to evaluate the hydrodynamic diameter of NPs in different waters. The results indicated the stability of PS NPs in natural aquatic environments and their potential for long-term transport.

The vadose zone is the first natural layer preventing groundwater pollution. Understanding virus transport and retention in the vadose zone is necessary. The effects of different interfaces and mechanisms on virus transport and retention were investigated by studying Escherichia coli phage migration in laboratory-scale columns under unsaturated conditions. The E. coli phage was used as a model virus. Colloid filtration theory, extended Derjagin–Landau–Verwey–Overbeek theory and two−site kinetic deposition model were used to calculate fitted parameters and interaction energies to assess virus retention at different interfaces. The collector diameters and the size of E. coli phages in the influent and effluent were compared to assess the effect of straining. The results indicated that the roles of solid–water interfaces (SWIs) and air–water interfaces (AWIs) in retaining E. coli phages are strongly controlled by the moisture content and hydrochemical conditions. Decreasing the moisture content and increasing the ionic strength (IS) of the suspension increased E. coli phage retention. At suspension ISs of 0.01 or 0.03 M and various moisture contents, E. coli phages were mainly retained at the SWIs rather than AWIs. When the IS was increased to 0.06 M, the viruses were strongly retained by becoming attached to both SWIs and AWIs. The role of straining in virus retention could not be ignored. Viruses were retained more at the SWIs and less straining occurred under acidic conditions than under neutral or alkaline conditions. This was mainly because of the effects of the pH and IS on surface charges and the model virus particle size. This study has important implications for modeling and predicting virus transport in soil affected by rainfall, snowmelt, and human activities (e.g., irrigation and artificial groundwater recharging).

This study aimed to evaluate the hydrochemistry of the water resources of the Weibei Plain, Northern China, as well as the risks posed by high groundwater nitrate concentrations to human health. Groundwater and surface water samples numbering 168 and 14, respectively, were collected during the dry and wet seasons. Water in the study area was weakly alkaline, falling into a hard-fresh or hard-brackish category. The groundwater chemical types were mainly SO₄·Cl–Ca·Mg (59.5%) and HCO₃–Ca·Mg (28.6%), whereas the dominant chemistry type of surface water was SO₄·Cl–Na (78.6%). Groundwater showed relatively high concentrations of NO₃⁻, with average dry and wet season concentrations of 212 mg·L⁻¹ and 223 mg·L⁻¹, respectively, whereas surface water had a low NO₃⁻ content. The major processes affecting water chemistry were determined to be rock weathering, such as silicate weathering and evaporative dissolution, as well as cation exchange. NO₃⁻ in groundwater was found to mainly originate from anthropogenic inputs such as agricultural production and domestic sewage. The entropy-weight water quality index (EWQI) assessment showed that although the quality of surface water was generally good, more than half of the groundwater samples failed drinking water standards, with NO₃⁻ identified as being the most problematic parameter affecting the water quality evaluation. Risk assessment of high groundwater nitrate concentrations indicated that long-term domestic use of groundwater in the study area can put the health of residents at great risk. Totals of 81% and 75% of the groundwater samples exceeded the acceptable limit for non-carcinogenic risk (HI = 1) to infants during the dry and wet seasons, respectively, whereas 75% and 71.3% of samples exceeded the acceptable limit for children, respectively. Future management of water in the Weibei Plain should prioritize the control groundwater nitrate pollution.

The sulfate pollution in water environment gains more and more concerns in recent years. The discharge of domestic, municipal, and industrial wastewaters increases the riverine sulfate concentrations, which may cause local health and ecological problems. To better understand the sources of sulfate, this study collected water samples in a typical agricultural watershed in East Thailand. The source apportionment of sulfide was conducted by using stable isotopes and receptor models. The δ³⁴SSO₄ value of river water varied from 1.2‰ to 16.4‰, with a median value of 8.9‰. The hydrochemical data indicated that the chemical compositions of Mun river water were affected by the anthropogenic inputs and natural processes such as halite dissolution, carbonate, and silicate weathering. The positive matrix factorization (PMF) model was not suitable to trace source of riverine sulfate, because the meaning of the extracted factors seems to be vague. Based on the elemental ratio and isotopic composition, the inverse model yielded the relative contribution of sulfide oxidation (approximately 46.5%), anthropogenic input (approximately 41.5%), and gypsum dissolution (approximately 12%) to sulfate in Mun river water. This study indicates that the selection of models for source apportionment should be careful. The large contribution of anthropogenic inputs calls an urgent concern of the Thai government to establish effective management strategies in the Mun River basin.

Uranyl carbonate (UC(VI)) is a stable form of uranyl (U(VI)) that widely coexists with amorphous colloidal silica (ACSi) and humic acid (HA) in carbonate-rich U-contaminated areas. In this context, the cotransport behavior and mechanism of UC(VI) with ACSi (100 mg L⁻¹) and HA colloids in saturated porous media were systematically investigated. It was found that the ACSi and strip-shaped HA have a strong adsorption capacity for UC(VI), and their adsorption distribution coefficient (Kd) is 4–5 orders of magnitude higher than that of quartz sand (QS). In the ternary system, UC(VI) was mainly existing in the colloid-associated form at low UC(VI) concentration (4.2 × 10⁻⁶ M). Compared with the individual transport of UC(VI), the presence of ACSi and strip-shaped HA in the binary system promotes the transport of low-concentration UC(VI) (4.2 × 10⁻⁶ M) but shows a hindering effect when UC(VI) = 2.1 × 10⁻⁵ M. When ionic strength (IS) increased from 0 to 100 mM, the individual transport of UC(VI) and ACSi was weakened owing to the masking effect and the compression of the electrical double layer, respectively; this weakening effect is more pronounced in the binary (UC(VI)–ACSi) system. Notably, the transport of UC(VI) and ACSi in the ternary system is independent of the changes in IS due to the surface charge homogeneity strengthening the electrostatic repulsion between HA and QS. The Derjaguin–Landau–Verwey–Overbeek theory and retention profiles reveal the co-deposition mechanism of ACSi and UC(VI) in the column under different hydrochemical conditions. The nonequilibrium two-site model and the mathematical colloidal model successfully described the breakthrough data of UC(VI) and ACSi, respectively. These results are helpful for evaluating the pollution caused by UC(VI) migration in an environment rich in HA and formulating corresponding effective control strategies.

In recent years, with the expansion of the Weining county in the northeast of Caohai wetland, the construction of a new port in the north, and the large-scale development of cultivated land in the east, land use patterns in lakeshore areas have changed. These changes have affected the state of lake shores water bodies in complex ways, resulting in varying degrees of local water pollution. To explore the distribution and transformation characteristics of water chemistry and heavy metals in different areas of a water body under the influence of different land uses, especially the interactions between water chemical factors and heavy metals in different areas of a water body, this study used Circos diagrams, originally used in biological genetic analysis, to visualize these interactions. This is the first time that the Circos diagram has been applied to the analysis of environmental interactions. The results showed that there are significant differences in the distribution of water chemical factors and heavy metals in different areas of the Caohai wetland. In particular, Cd is affected by anthropogenic sources. The Cd content is higher in the NCL and UL areas, which are at greater risk from pollution. The factors controlling heavy metal levels in water bodies were different in the different regions. The NCL region was mainly affected by construction excavation ore, UL was mainly affected by man-made industrial inputs, CL was mainly affected by pesticide and fertilizer inputs, and ML and FL were mainly affected by Eh and DO. The PCA results showed that the sources of heavy metals in different types of water bodies in the lakeshore zone were both natural and anthropogenic. Therefore, controlling pollutants, reducing environmental pollution inputs to the lakeshore zone, and strengthening supervision and management near wetlands may be of great significance for handling heavy metal pollution.