Controlling Water Chemistry Research Articles

The Future of Nuclear Energy: Key Chemical Aspects of Systems for Developing Generation III+, Generation IV, and Small Modular Reactors

Nuclear power plants have the lowest life-cycle greenhouse gas emissions intensity and produce more electricity with less land use compared to any other low-carbon-emission-based energy source. There is growing global interest in Generation IV reactors and, at the same time, there is great interest in using small modular reactors. However, the development of new reactors introduces new engineering and chemical challenges critical to advancing nuclear energy safety, efficiency, and sustainability. For Generation III+ reactors, water chemistry control is essential to mitigate corrosion processes and manage radiolysis in the reactor’s primary circuit. Generation IV reactors, such as molten salt reactors (MSRs), face the challenge of handling and processing chemically aggressive coolants. Small modular reactor (SMR) technologies will have to address several drawbacks before the technology can reach technology readiness level 9 (TRL9). Issues related to the management of irradiated graphite from high-temperature reactors (HTR) must be addressed. Additionally, spent fuel processing, along with the disposal and storage of radioactive waste, should be integral to the development of new reactors. This paper presents the key chemical and engineering aspects related to the development of next-generation nuclear reactors and SMRs along with the challenges associated with them.

Nanoplastic in aqueous environments: The role of chemo-electric properties for nanoplastic-mineral interaction.

Due to increasing plastic production, the continuous release of primary and secondary nanoplastic particles (NPs, <1μm) has become an emerging contaminant in terrestrial environments. The fate and transport of NPs in subsurface environments remain poorly understood, largely due to the complex interplay of mineralogical, chemical, biological, and morphological heterogeneity. This study examines interactions between abundant subsurface minerals and NPs under controlled water chemistry (1mM KCl, pH5.5). These conditions minimize potential chemical effects from ions in solution, isolating the impact of mineral complexity. Surface-modified polystyrene nanoparticles (-COOH and -NH2 functional groups) are proxies for degradation products and organic associations found in environmental plastics. Experimental results are compared with theoretical predictions using DLVO (Derjaguin-Landau-Verwey-Overbeek) double-layer force models. Despite all studied minerals maintaining negative surface charges across varying pH, electrostatic double-layer (EDL) interactions played a minor role in NP attachment. Instead, mechanisms such as specific ion-binding interactions (mediated by trace metal ions), bridging via divalent ions, and hydrogen bonding were more significant. Evidence suggests that kinetic effects for most mineral-NP combinations persist beyond 24h. This study highlights the critical role of biogeochemical and mineralogical composition in controlling NP attachment and release in subsurface environments, with implications for their transport and fate in aquifers.

Identification of hydrochemical processes of groundwater in Nekor-Ghiss plain (Morocco): using the application of multivariate statistics and Geographic Information Systems (GIS) to map groundwater

In arid and semiarid zones, groundwater is a vital and indispensable natural resource. Indeed, these water resources have become extremely limited due to several factors, including climate change, salinization, and overexploitation. This study covers the hydrochemical characterization of groundwater in the Nekor-Ghiss plain which is located in northern Morocco. To achieve this objective, a set of 79 water samples was analyzed, for various physical and chemical parameters of the samples, including E.C, pH, TDS, HCO3−, SO42−, Ca2+, Mg2+, Na+, K+, PO43−, NO3−, NO2− and NH4+. Several methods were used to interpret the hydrochemical data, namely graphical methods, principal component analysis (PCA), hierarchical ascending classification, and ion exchange indices. A detailed geochemical study of groundwater is described to identify the origin of the chemical composition of groundwater. The results show that the samples studied are characterized by very high mineralization (> 1500 mg/l), with the predominance of Na+, Cl− and SO42− ions. The interpretation of geochemical signatures of groundwater in the Nekor-Ghiss plain shows sulfate-sodium (Na–SO4) and chloride-sodium (Na–Cl) facies. Natural geochemical processes are responsible for water regulation, while human activities exert a limited influence on this control. Marine intrusion, evaporation, and the ion exchange process largely control the chemistry of the aquifer. Using PCA to confirm controlled water chemistry processes revealed three homogeneous groups. The study contributes to a better understanding of the quality and mineralization of groundwater in the Nekor-Ghiss plain, and it will serve as a reference for other plains with similar characteristics.

Acid mine drainage from coal mines in the eastern Himalayan sub-region: Hydrogeochemical processes, seasonal variations and insights from hydrogen and oxygen stable isotopes

Uncontrolled coal mining using non-scientific methods has presented a major threat to the quality of environment, particularly the water resources in eastern himalayan sub-region of India. Water bodies in the vicinity of mining areas are contaminated by acid mine drainage (AMD) that is released into streams and rivers. This study attempted to assess the impact of AMD, deciphering hydrogeochemical processes, seasonal fluctuations, and stable isotope features of water bodies flowing through and around coal mining areas. Self-organizing maps (SOMs) used to separate and categorize AMD, AMD-impacted and non-AMD impacted water from the different study locations for two sampling seasons revealed four clusters (C), with C1 and C2 impacted by AMD, C3 and C4 showing negligible to no impact of AMD. AMD impacted water was SO42− - Mg2+- Ca2+ hydrochemical type with sulphide oxidation and evaporation dominating water chemistry, followed by silicate weathering during both the sampling seasons. Water with negligible-to-no AMD-impact was Mg2+- Ca2+- SO42− to Ca2+ - HCO3− to mixed hydrochemical type with rock weathering and dissolution, followed by ion exchange as major factors controlling water chemistry during both the sampling seasons. Most of physicochemical parameters of C1 and C2 exceeded the prescribed limits, whereas in C3 and C4 water samples, parameters were found within the prescribed limits. Stable isotopes of hydrogen (δ2H) and oxygen (δ18O) during post-monsoon (PoM) varied between -41.04 ‰ and -29.98 ‰, and −6.60 ‰ to −3.94 ‰; and during pre-monsoon (PrM) varied between −58.18 ‰ and - 33.76 ‰ and −8.60 ‰ to −5.46 ‰. Deuterium excess (d-excess) ranged between 1.57 ‰ and 12.47 ‰ during PoM and 5.70 ‰ to 15.17 ‰ during PrM season. The stable isotopes analysis revealed that evaporation, mineral dissolution and mixing with rainwater are the key factors in study area.

High-resolution mapping and multivariate technique (factor analysis) to support hydrogeochemical analysis and identification of surface water contamination

The study presented a high-resolution regional mapping of a significant Brazilian watershed, which is heavily influenced by mining, agriculture, and domestic/industrial effluents. Upper São Francisco Basin encompasses the largest karst area in the country and includes three important Brazilian biomes: Cerrado, Atlantic Forest, and Caatinga. Surface water (1418 samples) was collected during the dry season and was analyzed for physical-chemical parameters, cations, anions, and some metals. The spatial distribution and abundance of variables were assessed, and the processes controlling the sources of dissolved loads in surface waters were discussed. The results indicate that rock weathering is the primary factor controlling water chemistry, with a strong influence of carbonate and silicate minerals. Anthropogenic activities, particularly agriculture, play a key role in the chemical composition of the microbasins. Soil erosion and leaching processes also contribute significantly to the region, driven by land use practices and mineral extraction, which intensify erosion processes. The northern sector of the Upper São Francisco Basin, characterized by an arid climate and Caatinga vegetation, experiences low precipitation and high evapotranspiration rates. The VG stands out due to the presence of the karst zone and for the mixture of natural to anthropogenic sources.

Influence of clay minerals on pH and major cation concentrations in acid-leached sands: Column experiments and reactive-transport modeling

A series of laboratory experiments are conducted to simulate the acidification and subsequent recovery of a sand aquifer exploited by in situ recovery (ISR) mining. A sulfuric acid solution (pH 2) is first injected into a column packed with sand from the Zoovch Ovoo uranium roll front deposit (Mongolia). Solutions representative of local groundwater or enriched in cations (Na+, Mg2+) are then circulated through the column to simulate the inflow of aquifer water. pH and major ion concentrations (Na+, Cl−, SO42−, Ca2+, Mg2+, K+) measured at the column outlet reproduce the overall evolution of porewater chemistry observed in the field. The presence of minor quantities of swelling clay minerals (≈6 wt% smectite) is shown to exert an important influence on the behavior of inorganic cations, particularly H+, via ion-exchange reactions. Numerical models that consider ion-exchange on smectite as the sole solid-solution interaction are able to reproduce variations in pH and cation concentrations in the column experiments. This highlights the importance of clay minerals in controlling H+ mobility and demonstrates that sand from the studied aquifer can be described to a first order as an ion-exchanger. The present study confirms the key role of clay minerals in controlling water chemistry in acidic environments through ion-exchange processes. In a context of managing the long-term environmental footprint of industrial and mining activities (ISR, acid mine drainage…), this work will bring insights for modeling choices and identification of key parameters to help operators to define their production and/or remediation strategies.

Ведение ВХР с применением реагентов ВТИАМИН на ТЭЦ с сезонным режимом работы

The main equipment of the thermal power plant (TPP) includes a E-120-7.0-500GM steam boiler produced by LLC “Belenergomash – BZEM” with a single-stage evaporation circuit. The operating mode of the thermal power plant has seasonal characteristics. During the period of February to the end of August the equipment is stopped as a reserve. Dosing of AMINAT PK-3 does not provide the required pH level in steam and feed water, so the reagent for water-chemical regime and preservation has been substituted with VTIAMIN KR-33. The complex reagent VTIAMIN KR-33 ensures both the maintenance of the required quality indicators of the coolant along the path and promotes the formation of a protective barrier film on the internal heating surfaces. To check water-chemical regime, the existing automatic chemical control system has been updated. Panels have been installed for automatic chemical control of pH value, electrical conductivity of direct and H-cationized samples. The filter material has been replaced and the mechanical filters have been connected. The first stage of the filter has been replaced, the second stage of the filter and final purification filters Н-OH have been installed. The authors have demonstrated the possibility to use boilers with seasonal operating modes and measuring the electrical conductivity of cooled water and steam samples as a chemical control of water chemistry. It is found out that dosing the VTIAMIN KR-33 reagent with periodic dosing of the VTIAMIN D-8 reagent into the boiler water prevent the precipitation of hardness salts and other impurities coming with the return condensate. Analysis of the indicators of the water chemistry regime at the thermal power plant when dosing the VTIAMIN KR-33 reagent at two points has shown that the pH value of the feed water is in the range of 8,8–9,0 and the indicators of the water chemistry regime in terms of the content of iron, silicic acid and sodium are also within the norm limits. The composition of the reagents is selected. Flexibility of water chemistry management is ensured. It has been shown that the dosage of the amine-containing reagent VTIAMIN neutralizes the negative effects of aggressive gases (carbon dioxide and oxygen) due to their binding and the formation of a protective film of the magnetite-amine type on heating surfaces. Introduction of the water chemical regime when the equipment is stopped as a reserve does not require additional preservation measures.

Hydrogeochemical characterization of groundwater in mountainous catchment and its suitability for drinking purposes in Irob, Tigray, Northern Ethiopia

Abstract The primary source of drinking water in Ethiopia's semi-arid mountainous regions is groundwater. The present study aims to assess the hydrogeochemical characteristics of low-grade basement rocks dominated by mountainous catchments. Moreover, it examines the suitability of the groundwater quality for drinking purposes in Irob, Tigray, northern Ethiopia. However, relatively little is known about the water chemistry and groundwater quality of the resources in the area. Fifteen samples of groundwater were collected and examined for ions according to standard procedures. The outcomes were assessed against the World Health Organization (WHO) drinking water quality criteria. To identify the source of dissolved ions and the process involved, graphic interpretations were applied. The results show that Ca–Mg–SO4–HCO3 and Ca–SO4–HCO3 were the dominant water types. Gibbs plots and ionic ratios reveal that silicate weathering, carbonate dissolution and ion exchange control water chemistry. Furthermore, the findings reveal that 60, 80, 46.67, 46.67, 60, 6.67, 60 and 53.33% of samples are above the safe limits of the WHO for hardness, alkalinity, total dissolved solids, electrical conductivity, calcium (Ca2+), potassium (K+), bicarbonate (HCO3-) and sulfate (SO42-), respectively. Consequently, the groundwater quality assessment demonstrates that the water sources in lower parts of the catchment are unsuitable for drinking.

Characterization of Dominant Hydrogeochemical Processes in Groundwater in Onitsha Area, Southeastern Nigeria

The characterization of the dominant hydrogeochemical processes in groundwater in Onitsha area, southeastern Nigeria was carried out. This is to identify the dominant mechanisms responsible for the evolution and the chemical composition of the water sources. A total of fifteen (15) groundwater samples were collected from different locations in the study area in August 2022 and these samples were subjected to chemical analysis using standard methods. The results indicated that the water quality parameters were within the World Health Organization acceptable limits for drinking quality although turbidity in six of the samples exceeded the guideline values. The hydrochemical facies were determined using various plots. Piper diagrams indicated that Ca2+ - Mg2+ - Cl- – SO42- was the dominant facies with Ca2+ and Cl- as the dominant ions. The Durov diagram indicate recharge water in limestone and sandstone aquifers and influenced by important ion exchange reactions. However, the Gibbs plots mainly plotted in the rock dominance zone indicating that the major processes controlling water chemistry in the study area were water-rock interaction and dissolution of rock minerals. The ionic ratio plots were employed to determine the mechanisms and reactions prevalent in the study area that influenced the water chemistry. Na/Cl plot indicated that the excess of Cl- over Na+ was balanced by Ca2+ and Mg2+ while the depletion of Na+ with respect to Clindicated ion exchange reaction which could be attributed to silicate weathering confirming the Na/Cl plot conclusions. The relative abundance of anionic facies shows that Cl- + SO42- were more abundant than HCO3- and the plot of Ca2+ + Mg2+ ions against HCO3- ions depict samples with excess Ca2+ + Mg2+. However, Ca2+ +Mg/HCO3 ratio was less than one (&lt;1) and indicated fresh recharge water.

The implication of the hydrogeochemical processes for groundwater chemistry in a semi-arid region: A case study of the Bokoya massif (Central Rif, Morocco)

Natural and anthropogenic factors control groundwater chemistry in the semi-arid area in northern Morocco called Bokoya massif. The main goal of this study was to evaluate the geochemical processes that affected groundwater mineralization in the Bokoya massif. As a result, In April 2016, sixty-one (61) water samples were collected from various locations, including wells and springs throughout the Bokoya massif, and analyzed for physicochemical parameters using standard methods. The descriptive study of the physicochemical parameters revealed that the waters were neutral to slightly basic (pH values range between 7,16 and 8,5) and moderately to strongly mineralized (TDS values range between 555,20 and 7980,10 mg/l). Sodium chloride was the dominant hydrochemical facies in the groundwater of the study area, with a percentage reaching (80%) noting the minority of magnesium bicarbonate facies and the absence of sodium bicarbonate and chlorinated calcium type. The tests of the ionic ratio (Cl- /Na+, Cl-/HCO3- versus Cl-, Ca2+/Mg2+, Ca2+/SO4-, Ca2+/Mg2+ versus Cl-, (Ca2+ Mg2+)/ HCO3-), indicate that the order of the dominant cations is Na+ &gt;Ca2+&gt;Mg2+&gt;K+ and of the dominant anions is Cl- &gt;HCO3-&gt;SO42-. It suggests that the dominant factors controlling water chemistry are rock dissolution and evaporation, silicate weathering, and ion exchange. Gibbs diagram defines the relationship between water chemistry and the lithology of the aquifer. It showed that most of the groundwater composition in this area is linked to the geochemical processes of evaporation and crystallization, and carbonates and silicate alteration control the minority.

Evaluation of drinking and irrigation water quality, and potential risks indices in the Dera Ismail Khan district, Pakistan

This study sought to asses drinking and irrigation water quality in the Dera Ismail (DI) Khan District, Pakistan with the aid of using drinking water quality index (WQI) and irrigation water quality indices (IWQI). Seventy two water samples were collected from various water sources such as tube wells, dug wells, hand pumps, streams, and springs throughout the DI Khan district. The investigated physicochemical parameters include pH, TDS, EC, turbidity, total hardness, major cations (Na, K, Ca, Mg), anions (Cl, HCO3, SO4), and heavy metals (Fe, Mo, Cr, Ni, Cu, and Zn). IWQI used in the study includes Kelly's ratio (KR), permeability index (PI), sodium percent (Na%), Magnesium Hazard (MH), potential salinity (PS), residual sodium carbonate (RSC), and sodium adsorption ratio (SAR). With the mean value of 63, WQI revealed that most samples are placed in the good category, with a smaller fraction in the excellent and poor classes. On the other hand, a health risk assessment of the data pointed out that the molybdenum (Mo) and chromium (Cr) concentrations in drinking water could pose health risks to children of the concerned population. Rock weathering appears to be the dominant hydro-geochemical pathway controlling water chemistry, Ca–Mg–HCO3 being the dominant facies, followed by Na–HCO3. Kelly's ratio (KR), sodium percent (Na%), sodium adsorption ratio (SAR), and residual sodium carbonate (RSC) had values higher than the recommended threshold. The use of water for irrigation of agricultural fields may raise relevant ecological concerns in the studied district.

Applying Multivariate Analysis and Machine Learning Approaches to Evaluating Groundwater Quality on the Kairouan Plain, Tunisia

In the Zeroud basin, a diverse array of methodologies were employed to assess, simulate, and predict the quality of groundwater intended for irrigation. These methodologies included the irrigation water quality indices (IWQIs); intricate statistical analysis involving multiple variables, supported with GIS techniques; an artificial neural network (ANN) model; and an XGBoost regression model. Extensive physicochemical examinations were performed on groundwater samples to elucidate their compositional attributes. The results showed that the abundance order of ions was Na+ &gt; Ca2+ &gt; Mg2+ &gt; K+ and SO42− &gt; HCO3− &gt; Cl−. The groundwater facies reflected Ca-Mg-SO4, Na-Cl, and mixed Ca-Mg-Cl/SO4 water types. A cluster analysis (CA) and principal component analysis (PCA), along with ionic ratios, detected three different water characteristics. The mechanisms controlling water chemistry revealed water–rock interaction, dolomite dissolution, evaporation, and ion exchange. The assessment of groundwater quality for agriculture with respect IWQIs, such as the irrigation water quality index (IWQI), sodium adsorption ratio (SAR), sodium percentage (Na%), soluble sodium percentage (SSP), potential salinity (PS), and residual sodium carbonate (RSC), revealed that the domination of the water samples was valuable for agriculture. However, the IWQI and PS fell between high-to-severe restrictions and injurious-to-unsatisfactory. The ANN and XGBoost regression models showed robust results for predicting IWQIs. For example, ANN-HyC-9 emerged as the most precise forecasting framework according to its outcomes, as it showcased the most robust link between prime attributes and IWQI. The nine attributes of this model hold immense significance in IWQI prediction. The R2 values for its training and testing data stood at 0.999 (RMSE = 0.375) and 0.823 (RMSE = 3.168), respectively. These findings indicate that XGB-HyC-3 emerged as the most accurate forecasting model, displaying a stronger connection between IWQI and its exceptional characteristics. When predicting IWQI, approximately three of the model’s attributes played a pivotal role. Notably, the model yielded R2 values of 0.999 (RMSE = 0.001) and 0.913 (RMSE = 2.217) for the training and testing datasets, respectively. Overall, these results offer significant details for decision-makers in managing water quality and can support the long-term use of water resources.

Linking multivariate statistical methods and water quality indices to evaluate the natural and anthropogenic geochemical processes controlling the water quality of a tropical watershed.

The improvement of water management requires monitoring techniques that accurately evaluate water quality status and detect the effects of land use changes on water chemistry. This study aimed to evaluate how multivariate statistical methods and water quality indices can be applied together to evaluate the processes controlling water chemical composition and the overall water quality status of a tropical watershed. Thirty-four water samples were collected in the Formoso River basin, located on the border of the Amazon Forest. Water parameters were measured in situ using a multiparameter and in the lab using spectroscopic and volumetric techniques. The water quality dataset was interpreted through principal component analysis, multivariate linear regression, and water quality indices. Statistical methods allowed us to identify the sources and geochemical processes controlling water quality chemistry, which were carbonate dissolution, runoff/erosion, nutrient input due to anthropogenic activities, and redox reactions in flooded zones. They were also used to create linear functions to evaluate the effects of land use changes on the geochemical processes controlling water chemistry. Conversely, the water quality indices provide information about the overall condition of the water. The Weight-Arithmetic Quality Index correctly evaluates water suitability for its multiple uses, according to the Brazilian guidelines. Conversely, the Ontario Water Quality Index is not suitable to evaluate the water quality of tropical rivers, since the usual higher water temperature and the low oxygen contents associated with tropical environments result in biased water quality evaluations by this index.

Hydrogeochemistry, ionic speciation, controlling processes and agricultural suitability of groundwaters in sections of the semi-arid basement complex of north–central Nigeria

In order to ascertain the governing mechanisms, sources, and speciation of ionic species, identify hydrochemical facies, and assess their appropriateness for agricultural use, groundwaters from several portions of the semi-arid basement complex of north–central Nigeria were analyzed based on chemistry. Basement aquifers made of gneiss-migmatites, metasediments, and granitoids store groundwater. Standard analytical techniques were used to analyze the fluids for main cations, anions, and physical characteristics. The results showed that the waters were slightly acidic (with a mean pH of 5.38, below the permissible range of 6.5–8.5), and that the predominant cations and anions were Na+ >Ca2+ >K+ >Mg2+ and Cl− > NO3- > HCO3- > SO42−, respectively. Analysis of the ions' stoichiometric ratios reveals that alkali elements predominate, making up about 55.3% of the ions and being connected to silicate weathering. Based on ionic ratio calculations, it was determined that ion exchange was a key factor controlling water chemistry. Ionic species cross plots show that silicate weathering (sodic and calcic plagioclase) predominates. Hydrochemical facies, Gibbs plots, and principal component (correlation, cluster and factor) studies all show that ionic elements are geogenic, essentially coming from the weathering of silicates with ion exchanges. Based on predicted saturation indices, hydrochemical modeling by the computer program VISUAL-MINTEQ reveals that the majority of main ions occur in free mobile states with associated mineral species, all at undersaturated levels. Based on measurements of the sodium adsorption ratio (SAR), sodium percentage (% Na), and chloro-alkaline indices (CAI), the waters have been evaluated for their suitability for agricultural use.

Large seasonal and spatial variability in δ44/40Ca values in the Godavari River, India: Implications for basalt weathering, groundwater interaction, and carbonate precipitation

We present stable calcium isotopic compositions (δ44/40Ca) of the Godavari River, the largest river in peninsular India, from the upper 750 km of its course, where it primarily drains the Deccan basalts. In addition to river water samples collected during the pre-monsoon and monsoon seasons, we also present δ44/40Ca values of groundwater, bedrock Deccan basalts, suspended and bedload sediments, and carbonate nodules from the Godavari Basin as well as zeolites and hydrothermal calcite from several locations within the Deccan Traps. The δ44/40Ca values (reported relative to NIST SRM 915a) of the dissolved load of the Godavari River main channel display large variability during both the pre-monsoon (0.73–1.64 ‰) and the monsoon (0.56–1.28 ‰) seasons. In the upper reaches (within 160 km of the source), the river water samples during both seasons show δ44/40Ca values (0.56–0.89 ‰) and Sr/Ca (mmol/mol) ratios (1.47–2.86), which are in the same range as that of the bedrock Deccan basalts (0.53–0.78 ‰ and 1.1–5.19 mmol/mol, respectively), suggesting control of water chemistry by basalt weathering. In contrast, in the middle reaches of the river (beyond 160 km from the source), the riverine δ44/40Ca values (0.99–1.64 ‰) are much higher than δ44/40Ca of bedrock basalt, but similar to that of groundwater in the middle reaches. We conclude that groundwater discharge to the river during the low-flow period has a significant control on the observed high δ44/40Ca values of the Godavari River. Additionally, the positive correlation between δ44/40Ca values versus Sr/Ca ratios and weak positive correlation of δ44/40Ca values versus saturation index of calcite suggests that carbonate precipitation from the river water impacts the δ44/40Ca values of the Godavari River in the middle reaches; this conclusion is consistent with the low δ44/40Ca of acetic-acid leached carbonate nodules (0.52–0.56‰) collected from the Godavari riverbed.The δ44/40Ca values of zeolites exhibit a large range from −0.72‰ (heulandite) to 1.67‰ (apophyllite) while the δ44/40Ca values of leached hydrothermal calcite samples range from 0.75‰ to 0.92‰. These values indicate that weathering of these Ca-bearing minerals has limited contribution to the calcium isotopic composition of the Godavari River, which contrasts with observations from relatively smaller rivers draining basalt in Iceland. The δ44/40Ca values of the dissolved load of the basalt-draining Godavari River is significantly higher than the estimated global riverine input to the oceans (0.88‰); given the high weatherability of basalts, the high δ44/40Ca values of basalt-draining rivers suggests that the estimate of the δ44/40Ca value of the average continental flux to the oceans may have been underestimated. The results of this study also demonstrate distinct differences in geochemical and Ca isotopic compositions of basalt-draining rivers from Iceland and India, which reflects fundamental differences in the weathering process in very different climatic regions.

Application of AI Identification Method and Technology to Boron Isotope Geochemical Process and Provenance Tracing of Water Pollution in River Basins

River water is the most important water source that people can use. Since the 20th century, human influence on river courses has become increasingly serious. The quantitative analysis of water quality is even more difficult. According to the characteristics of Fenhe water chemistry, pollution time and pollution control factors, the contribution rate of people in the polluted water body is not clear. Therefore, this paper aims to use AI identification methods and technologies to study water pollution and provenance tracing. The combination of major elements, trace elements and stable isotopes was used to study the chemical characteristics, water quality status, and sources of pollution of the Fenhe water in the Fenhe area. Because the water contains a large number of pollution sources, it is difficult to find the source using traditional methods. Using correlation analysis, principal component analysis, multi-factor regression analysis, trend analysis and other methods, the macroelements and trace elements in the water body of the Fenhe River were analyzed. The boron sources in the Fenhe river were qualitatively and quantitatively analyzed using mass spectrometry equilibrium equation. Using the boron isotope value of the river, it showed a spatial variation of upstream (+5.1‰) &lt; middlestream (+8.6‰) &lt; downstream (+9.5‰) in dry season, and showed a spatial variation of upstream (+6.1‰) &lt; downstream (+7.2‰) &lt; middlestream (+9.0‰) in the wet season. The contribution of silicate to B is calculated by subtracting the contribution of other resources from the comprehensive contribution rate. It is found that the contribution of silicate is about 38.8%, 22% in dry season and 49.2%, 17% in wet season. The research results have provided a reliable scientific basis for the protection of water resources and pollution control in the Fenhe River Basin. Therefore, the above research confirms the role of AI identification method in the process of boron isotope geochemistry and provenance tracing of water pollution in river basins.

Cambios temporales y espaciales en la química del agua superficial en un río mediterráneo de Chile central: el caso del río Mataquito (~35°S)

Spatial and temporal changes in water chemistry were evaluated using surface water extracted from a Mediterranean river basin, i.e., The Mataquito River, central Chile. The processes that control water chemistry dynamics in the basin were determined by assessing the relationship between hydrologic events (rainfall, river flow, runoff rates), physical-chemistry properties, and major ion concentrations/distributions along the river. During the rainy period, major ion levels were controlled predominantly by weathering (rainfall). During the dry period, seawater intrusion was the main factor controlling water chemistry. Unusually high chlorine and sulfate concentrations suggested anthropogenic sources of the ions entering the basin. Thus, pollution from industrial and agricultural activities in the basin might be quantitatively important and should be considered in future studies of this area.

Performance influence of polyacrylic acid dispersant on nuclear grade anion exchange resin

Secondary circuit water chemistry control is vital for the safe operation of nuclear power plants. Polyacrylic acid (PAA) is used in the secondary circuit water system to reduce the fouling of the steam generator (SG) because of its good dispersion effect. However, PAA as a macromolecular organic matter possibly causes organic fouling for anion exchange resin of the water purification system and affects its performance. Some research reported that the performance of resin changes after PAA application. But it is not clear whether this change is related to PAA. In this research, the anion resins were performed for five cycles, and each cycle included batch PAA adsorption, dynamic PAA desorption and resin rinse. Results showed that NaOH solution could realize the desorption of PAA on anion resin, but desorption solution and rinse water consumption slightly increased with the cycle number. Meanwhile, residual PAA linearly increased with the cycle number, but the rate was relatively slow. Furthermore, the performance influence of PAA on anion resin was investigated. The exchange capacity and kinetic performance for anion resin slightly decreased after PAA cycle. The effluent conductivity of anion resin bed increased after PAA cycle, but it could not cause the adverse influence of sodium leakage. The contrast experiment of H2SO4 cycle showed that resin aging was the primary reason for the change of resin performance, rather than residual PAA. Within the fewer cycles, PAA and anion resin had better compatibility.

Effect of a Small Amount of Cr and Mo on Aqueous CO2 Corrosion of Low-Alloyed Steel and Formation of Protective FeCO3 in Near-Saturation Conditions

The effect of a small amount (1 wt%) of Cr or Mo on aqueous CO2 corrosion of low-alloyed steel and the formation of protective FeCO3 corrosion product layers was investigated under controlled water chemistry conditions, where the bulk saturation value of FeCO3 was maintained at near-saturated condition. Changes in CO2 corrosion rate with exposure time were monitored by linear polarization resisitance measurements. The surface morphology and the composition of the corrosion product layers were analyzed by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction, and transmission electron microscopy. Results showed that the emergence of a continuous Fe3C layer created favorable conditions at the surface of nonalloyed steel (containing no Cr and Mo) for semiprotective FeCO3 to form even though the bulk saturation value of FeCO3 was maintained at near-saturated condition. However, semiprotective FeCO3 was not observed on the surface of 1% Cr steel and 1% Mo steel, but rather discontinuous and porous corrosion product layer was formed. Due to the hydrolysis reactions of Cr3+ and Mo3+, and the discontinuous structure of the corrosion product layers, the surface conditions for 1% Cr steel and 1% Mo steel were not favorable for the formation of FeCO3 under the experimental conditions of this study.

Hydrogeochemical characterization of the groundwater of Lahore region using supervised machine learning technique.

The cationic and anionic composition in groundwater can be better understood by identifying the type of hydrogeochemical processes influencing groundwater chemistry. This research deals with the characterization of groundwater samples by considering the likely role of hydrogeochemical processes and the factors responsible for the weathering process. The study applies statistical methods and supervised machine learning algorithm (i.e., logistic regression model) on the large data set of 1300 water samples from the Lahore district of Punjab, Pakistan. All the water samples were collected by the local authorities from a deep unconfined aquifer (> 350 ft in depth) for the years of 2005 to 2016. The characterization of groundwater quality parameters includes pH, total dissolved solids (TDS), electrical conductivity (EC), total hardness (TH), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl-), bicarbonate (HCO3-), nitrate (NO3-), and sulfate (SO42-). The results show the sequence of the major ion in the following order: Na+ > Ca2+ > Mg+ > K+ and HCO32- > SO42- > Cl- > NO3-. The ionic ratios and Gibb's plot revealed that the prominent hydrogeochemical facies of aquifer water is Ca-HCO3, Ca-Na-HCO3, and mixed Ca-Mg-Cl type rock-weathering process, especially carbonate and silicate weathering, as significant process controlling water chemistry. The statistical evaluation of the prepared regression model determined its prediction accuracy as 92.2%, which means the model is highly efficient and satisfies the analysis. The outcomes of this study favor the utilization of such methods for other areas with large data sets.