Concentrations Of Major Cations Research Articles

New Diagram Useful for Classification of Groundwater Quality

Due to human and human activities the groundwater is polluted. This is the serious problem now a century. Thus the analysis of the water quality is very important to preserve and prefect the natural ecosystem.The primary objective of this paper is to study the groundwater quality parameters. The mechanism of chemical reactions leading to the change in the composition of groundwater and source of the dissolved ions in the groundwater can be understood by Banaga's diagram. The Banaga method is not only shows graphically the nature of a given water sample and dictates the relationship to other samples but there are a number of different methods and schemes used to classify natural water quality, source, origin and determine their suitability for different purposes depending on the concentrations of the basic components. The new diagram is useful for better understanding the evolution of hydrochemical parameters of groundwater that can be by plotting the concentration of major cations and anions in percentage of meq/l, and it is divides the water quality into five types. The results of this analysis were compared with the water quality standards of Piper diagram.

Monitoring the underground roadway water quantity and quality for irrigation use around the Barapukuria Coal Mining Industry, Dinajpur, Bangladesh

The influence of underground coal mining activities has become a leading issue in contaminating water resources as well as depleting the water layer around the mining area. The studied mining area is a plain land which is predominantly used for irrigation purposes where underground water is the main source of water for irrigation. In the case of Barapukuria Coal Mine (BCM), a huge volume of water is pumped regularly from the underground roadway to the surface. Thus, this study takes account of the estimated quantity and quality of water used for irrigation and other uses. Therefore, this study monitored and assessed the quantity and quality of inflow water in the roadway for 13 years. The observation shows that the inflow water volume was about 11,183.52m3/day in 2001, and it has increased up to 43,396.80m3/day in 2013. These results implied that the increment of inflow water intensities is very high with increasing the mining operation. As a result, it might be a considerable problem to deplete the natural water table, which could change the changing aquifer geometry and influence the safe extraction of coal in future. The qualitative assessment of water shows that the underground roadway water is suitable for irrigation purposes. The overall quality of water is largely controlled by rock weathering and evaporation natural processes in the area. In fact, the suitability of roadway water for irrigation was evaluated based on SSP, salinity hazard, sodium percent, sodium adsorption ratio, residual sodium carbonate, US salinity diagram, Wilcox's diagram, Kelly's ratio, permeability index, Magnesium Hardness, Total Hardness and so on. On the whole, the concentration of such parameters, major cations, anions, trace elements (e.g. As, Cd, Zn, Cr, Cl, Al, Mn), and other elements (e.g. TSS, DO, DOB, Oil and Grease, C. Count, T. Coliform, F. Coliform) did not exceed the permissible limit for irrigation purposes, and thus is suitable for irrigation uses. Conversely, the slight Mg hazard with moderately hard to hard tendencies of water bodies suggests the restricted utilization of this water for irrigation. Therefore, this study finally recommends that the ongoing monitoring program continues with necessary precautionary measures for maintaining the quality of roadway water in the underground tunnel of the mine.

Relating metals with major cations in oyster Crassostrea hongkongensis: A novel approach to calibrate metals against salinity

Despite salinity has been well documented for its significant effects on the bioaccumulation of many trace elements in biomonitors, no calibration method has been proposed to reduce such influences. For the first time, the present study established a novel method to calibrate biomonitoring data against salinity. Relationships between trace element concentration in oyster Crassostrea hongkongensis and the biological proxy for salinity were quantified based on laboratory exposure experiments. The method was then verified by the biomonitoring data of Pearl River Estuary (PRE). Tissue concentrations of trace elements (Cu, Zn, Ag, Cd, Pb, Cr, As, Se, and Ni) and major cations (Na, Mg, K, and Ca) in oysters exposed at 4 salinities (5, 12, 20, and 28psu) and low concentrations for 6weeks were measured to establish such quantitative relationships. Tissue Na, Mg, and K could be the proxy for salinity, while Na was the best one. Negative correlations between tissue concentrations of trace elements and Na after exposure were observed for metal cations such as Cu, Zn, Ag, Cd, and Pb, while tissue As, Se, and Ni were positively correlated with Na. In PRE, salinity significantly influenced the bioaccumulation of trace elements even under the multifactor-affected field conditions. The calibration method applied to the biomonitoring of PRE was verified to be feasible, and effectively reduced the influences of salinity. Therefore, calibration against salinity could facilitate the interpretation, comparability, and analysis of biomonitoring data.

Major anion and cation fluxes from the Central SiberianPlateau watersheds with underlying permafrost

The subarctic rivers of the Central Siberian Plateau have specific fed-characteristics due to the permafrost distribution and the active layer thawing dynamics. Two watersheds with different types of permafrost (from insular to continuous) are studied. Different data sources (Roshydromet and our own observations) are used for receiving anions’ (HCO3-, SO42-, Cl-) and cations’ (Ca2+, Mg2+) fluxes from the Nizhnyaya Tunguska river (1960-2011) and the Tembenchi river (1970-2011). The annual discharge of N. Tunguska for 1939-2011 is characterized by an increase of 0.3 km3/year/year, and for Tembenchi, 0.04 km3/year/year. The major part of the increase (about 60%) is due to spring flooding (May - June). The volume-weighted mean concentrations of major anions and cations in the N. Tunguska river water increased three times in the spring period (40.7 - 116.8 mg/l) and in the summer-fall period (74-212.9 mg/l). On the contrary, such concentrations decreased sharply during the winter mean water period. Due to these results, the total export of main anions and cations from the N. Tunguska river basin rose more than 4,5 times. Two possible reasons can be identified: 1) a water discharge increase of the Subarctic rivers (Peterson et al., 2002); 2) permafrost degradation induced by global climate warming (Frey and McClelland 2009).

Trace elements (Li, B, Mn and Ba) as sensitive indicators for salinization and freshening events in coastal aquifers

The current global intrusion of seawater into coastal aquifers causes salinization of groundwater and thus significant degradation of its quality. This study quantified the effect of seawater intrusion and freshening events in coastal aquifers on trace elements (Li, B, Mn and Ba) across the fresh-saline water interface (FSI) and their possible use as indicators for these events. This was done by combining field data and column experiments simulating these events. The experiments enabled quantification of the processes affecting the trace element composition and examination of whether salinization and freshening events are geochemically reversible, which has been seldom investigated.The dominant process affecting trace element composition during salinization and freshening is ion exchange. The results of the experiments show that the concentrations of major cations and Li+ were reversible during salinization and freshening, whereas B, Mn2+ and Ba2+ were not. During salinization, Li+ and B were depleted due to sorption by 10 and 100μmol·L−1, respectively, to about half of their expected conservative concentrations. The relative depletion of Li+ increased with distance from the shore, representing the propagation of salinization. Ba2+ and Mn2+ were desorbed from the sediment during salinization and enriched by tenfold in the aqueous phase compared to their concentration in seawater (~0.1 μeq·L−1). During freshening both were depleted by almost tenfold compared to their concentration in fresh groundwater (~0.7 μeq·L−1). The depletion of Mn2+ is a sensitive marker for freshening because Mn2+ has a strong affinity to the solid phase. Moreover, this study shows that both Mn2+ and Ba2+ can be used as sensitive hydrogeochemical tools to distinguish between salinization and freshening events in the FSI zone in coastal aquifers.

Spring water chemistry in a formerly glaciated area of western Poland: the contribution of natural and anthropogenic factors

To assess natural and anthropogenic impacts on spring water chemistry, seasonal and spatial hydrochemical changes in 20 springs were studied in the western part of Poland. Spring water was sampled every 3 months from November 2011 to October 2013. The analyses investigated major cation, anion, and trace element concentrations. Moreover, water temperature, electrical conductivity, and pH were measured in the field. For five springs, isotopic analyses of nitrates were conducted. The results revealed that the water composition was similar for most of the elements studied. However, in the case of Fe, Mn2+, Pb2+, and nitrates, spatial and seasonal variations were relatively significant. The concentrations of total iron and manganese were found to exceed the Polish legal limits for drinking water in 70 and 85 % of the springs, respectively. In addition, Pb2+ levels were found to be highly variable; in some periods, the concentration was 10 times higher than the limit for drinking water. In some springs, elevated nitrate concentrations were found with a maximum of 74-mg NO3 −/L, which is also in excess of the legal limit. The seasonally high levels of total Fe and Mn2+ are considered to be related to natural geo- and hydrochemical changes, but the high concentrations of Pb2+ and nitrates suggest anthropogenic pollution. The nitrates originate from agricultural practices, whereas Pb2+ may come from several sources. Hydrochemical monitoring must, therefore, consider seasonal variations, because the water properties may not permit its use during some periods, i.e., for drinking purposes.

Kinetic speciation of mercury–humate complexes in aqueous solutions by using competing ligand exchange method

Competing ligand exchange method (CLEM) in conjunction with direct mercury analyzer (DMA) was found to be a useful method for kinetic speciation study of (mercury–humic acid) Hg–HA complexes in aqueous systems. Ambersep GT74 (containing a thiol functional group) was used as a suitable competing ligand for this study. The CLEM/DMA was used to estimate lability and dissociation rate constant of Hg–HA complexes in aquatic systems. Influences of pH, metal loading and varying major cation (Ca2+) concentrations on Hg–HA complexes were investigated. Concentration of dynamic Hg–HA complexes gradually increased with increasing Hg loading in the system. The dissociation rate constant (kd1) of labile Hg–HA complexes were found to vary from 4.3×10−3s−1 to 9.2×10−3s−1 with increasing Hg loading from 1.0×10−8M to 1.42×10−7M. The concentrations of Hg–HA complexes with low thermodynamic stability were found to be similar at pH 4 and 5 (~59% and 58% of the total Hg with kd1 values of ~2×10−3 and 1.7×10−3s−1, respectively). The complexation of Hg with HA was found to increase with increasing pH from 4 to 7. The concentration of inert complexes (c2) with dissociation rate constant (kd2) gradually increased with increasing pH. Increasing concentration of Ca2+ in the model solutions increased the concentrations of Hg–HA dynamic complexes in the system. This finding suggests that the Hg–HA bond is predominantly ionic in nature. It suggests that Ca2+ ions screen out Hg2+ ions from undergoing complexation reaction with HA.

Survey of Uruguayan Freshwater Water Quality for Crop Irrigation

The increase in global demand for food and biofuels, has led to an high demand for agricultural products. That situation implies an intensification of production systems, and develop strategies to ensure stability against drought, and moreover a better levels of productivity. Objectives that could be achieved with the irrigation of crops; however, it can promote negative impacts due to cumulative effects on soil quality, which depend on the chemical composition of the water used. This paper show the results of a national study of freshwater quality, on 100 river watersheds (up to 100,000 ha), which correspond to a cumulative drainage area of 70% of country surface. In these freshwaters the following parameters was evaluated: electrical conductivity, concentration of major cations (Na, K, Ca, Mg), alkalinity, and pH. The results showed Ca, Mg, K, and Na concentrations in ranges of 0.0-45.1, 0.0-14.1, 0.019-16.8, and 0.78 -139 mg L-1, respectively. The alkalinity was in range of 32 to 420 CaCO3 mg L-1, and this variable was the most important contribution to get the different values of electrical conductivity of water, which had values between 71.6 and 1047 micro Siemens cm-1. These features allow propose at least 3 freshwater ecoregions (coastal and central-south; basalt; Northeast and southeast) at Uruguay, based on the chemical composition of studied freshwaters. Moreover, SAR values (([Na] / [(Ca + Mg) / 2] 1/2) of these waters shown a 99% of them has good quality characteristics for the development of irrigation, because they have a SAR below 10.

Hydrogeochemical Processes Influencing Groundwater Quality in the Black Volta Basin of Ghana

Hydrogeochemical processes influencing groundwater quality in the Black Volta Basin of Ghana have been studied. Groundwater samples were collected from 93 water points for physico-chemical analysis using standard methods. Major cation concentration was, generally, in the order of Ca²⁺> Na⁺>Mg²⁺>K⁺ while major anion concentration followed the order HCO₃->Cl->SO₄^2-. Mineral weathering (rock dissolution) and ion exchange were the controlling factors of groundwater composition. Stability diagrams show groundwater to be largely in equilibrium with Montmorillonite and Kaolinite and are quite reminiscent of climatic conditions pertaining to the geographical region of the basin. Ca-Mg-HCO₃ is the main groundwater type in the basin. Minor water types are Na-HCO₃ and Ca-Mg-SO₄. Principal Component Analysis (PCA), indicates that, HCO₃^- Ca²⁺, Mg²⁺, Na⁺ and F-contribute mainly to TDS and originate from the same-rock weathering.

Permafrost coverage, watershed area and season control of dissolved carbon and major elements in western Siberian rivers

Abstract. Analysis of organic and inorganic carbon (DOC and DIC, respectively), pH, Na, K, Ca, Mg, Cl, SO4 and Si in ~ 100 large and small rivers (< 10 to ≤ 150 000 km2) of western Siberia sampled in winter, spring, and summer over a more than 1500 km latitudinal gradient allowed establishing main environmental factors controlling the transport of river dissolved components in this environmentally important region, comprising continuous, discontinuous, sporadic and permafrost-free zones. There was a significant latitudinal trend consisting in a general decrease in DOC, DIC, SO4, and major cation (Ca, Mg, Na, K) concentration northward, reflecting the interplay between groundwater feeding (detectable mostly in the permafrost-free zone, south of 60° N) and surface flux (in the permafrost-bearing zone). The northward decrease in concentration of inorganic components was strongly pronounced both in winter and spring, whereas for DOC, the trend of concentration decrease with latitude was absent in winter, and less pronounced in spring flood than in summer baseflow. The most significant decrease in K concentration from the southern (< 59° N) to the northern (61–67° N) watersheds occurs in spring, during intense plant litter leaching. The latitudinal trends persisted for all river watershed size, from < 100 to > 10 000 km2. Environmental factors are ranked by their increasing effect on DOC, DIC, δ13CDIC, and major elements in western Siberian rivers as follows: watershed area < season < latitude. Because the degree of the groundwater feeding is different between large and small rivers, we hypothesize that, in addition to groundwater feeding of the river, there was a significant role of surface and shallow subsurface flow linked to plant litter degradation and peat leaching. We suggest that plant-litter- and topsoil-derived DOC adsorbs on clay mineral horizons in the southern, permafrost-free and discontinuous/sporadic permafrost zone but lacks the interaction with minerals in the continuous permafrost zone. It can be anticipated that, under climate warming in western Siberia, the maximal change will occur in small (< 1000 km2 watershed) rivers DOC, DIC and ionic composition and this change will be mostly pronounced in summer.

Suitability for human consumption and agriculture purposes of Sminja aquifer groundwater in Zaghouan (north-east of Tunisia) using GIS and geochemistry techniques.

In Tunisia, the water resources are limited, partially renewable and unequally distributed between the wet north and the dry south of the country. The Sminja aquifer in Zaghouan city is located in north-east of Tunisia, between latitudes 36°38' and 36°47' and longitudes 9°95' and 10°12'. This aquifer is used to satisfy the population needs for their domestic purposes and agricultural activities. Water analyses results are expressed by many methods, among which are geochemical methods combined with the geographic information system (GIS) (all schematic presentations of the diagram software (Piper, Riverside, Wilcox…), which can be used to assess the suitability of the Sminja aquifer groundwater for human consumption and irrigation purposes. A total of 23 wells were sampled in January 2013, and the concentrations of major cations (Na(+), Ca(2+), Mg(2+) and K(+)), major anions (Cl(-), SO4 (2-) and HCO3 (-)), electrical conductivity and total dissolved solids were analysed. In the Sminja groundwater, the order of the cations dominance was Na>Ca>Mg>K and that of the anions was Cl>HCO3>SO4. All of the analysed samples of the study area exceed chemical values recommended by the World Health Organisation guidelines and Tunisian Standards (NT.09.14) for potability but with different percentages. The aquifer spatial distribution of saturation indices reveals that all groundwater samples are under-saturated with gypsum, halite and anhydrite and are over-saturated with respect to calcite and dolomite based on water quality evaluation parameters for irrigation purposes; here, 87% of samples in Sminja aquifer groundwater are suitable, whereas 13% are unsuitable for irrigation uses.

Oxidation of organic contaminants by manganese oxide geomedia for passive urban stormwater treatment systems

To advance cost-effective strategies for removing trace organic contaminants from urban runoff, the feasibility of using manganese oxides as a geomedia amendment in engineered stormwater infiltration systems to oxidize organic contaminants was evaluated. Ten representative organic chemicals that have previously been detected in urban stormwater were evaluated for reactivity in batch experiments with birnessite. With respect to reactivity, contaminants could be classified as: highly reactive (e.g., bisphenol A), moderately reactive (e.g., diuron) and unreactive (e.g., tris(2-chloro-1-propyl)phosphate). Bisphenol A and diuron reacted with birnessite to produce a suite of products, including ring-cleavage products for bisphenol A and partially dechlorinated products for diuron. Columns packed with manganese oxide-coated sand were used evaluate design parameters for an engineered infiltration system, including necessary contact times for effective treatment, as well as the impacts of stormwater matrix variables, such as solution pH, concentration of natural organic matter and major anions and cations. The manganese oxide geomedia exhibited decreased reactivity when organic contaminants were oxidized, especially in the presence of divalent cations, bicarbonate, and natural organic matter. Under typical conditions, the manganese oxides are expected to retain their reactivity for 25 years.

River geochemistry, chemical weathering, and atmospheric CO2 consumption rates in the Virunga Volcanic Province (East Africa)

AbstractWe report a water chemistry data set from 13 rivers of the Virunga Volcanic Province (VVP) (Democratic Republic of Congo), sampled between December 2010 and February 2013. Most parameters showed no pronounced seasonal variation, whereas their spatial variation suggests a strong control by lithology, soil type, slope, and vegetation. High total suspended matter (289–1467 mg L−1) was recorded in rivers in the Lake Kivu catchment, indicating high soil erodibility, partly as a consequence of deforestation and farming activities. Dissolved and particulate organic carbon (DOC and POC) were lower in rivers from lava fields, and higher in nonvolcanic subcatchments. Stable carbon isotope signatures (δ13C) of POC and DOC mean δ13C of −22.5‰ and −23.5‰, respectively, are the first data to be reported for the highland of the Congo River basin and showed a much higher C4 contribution than in lowland areas. Rivers of the VVP were net sources of CH4 to the atmosphere (4–5052 nmol L−1). Most rivers show N2O concentrations close to equilibrium, but some rivers showed high N2O concentrations related to denitrification in groundwaters. δ13C signatures of dissolved inorganic carbon suggested magmatic CO2 inputs to aquifers/soil, which could have contributed to increase basalt weathering rates. This magmatic CO2‐mediated basalt weathering strongly contributed to the high major cation concentrations and total alkalinity. Thus, chemical weathering (39.0–2779.9 t km−2 yr−1) and atmospheric CO2 consumption (0.4–37.0 × 106 mol km−2 yr−1) rates were higher than previously reported in the literature for basaltic terrains.

Assessment of surface water quality of inland valleys for cropping in SW Nigeria

Inland valley agro-ecosystems which are a category of wetlands have potential for sustainable crop production relative to uplands. A major challenge to their utilisation in the study area is their heterogeneity in hydrology, morphology, soil types and agro-economy. The study assessed the surface water quality of three typologies of the agro-ecosystems—amphitheatre-like valley-heads (Am), valley-side (VS), and low depression (LD)—for cropping. Surface water of six sites were sampled during the wet and dry seasons. The physicochemical properties and metal concentrations of the samples were analysed. Descriptive statistics and water quality indices were used to assess the suitability of the waters of the agro-ecosystems for cropping. Results showed that the valleys have neutral to slightly alkaline waters. Values of physicochemical parameters are generally within the acceptable range for cropping. The concentration of major cations varied across the inland valley types, but exhibited similar characteristics within each valley. The dominance of the major cations is in the order of Na > Ca > K > Mg. ANOVA results indicated that there is no significant difference in the concentration of heavy metals across the valleys (F = 2.044, p = 0.138, α = 0.05). Generally, most of the physicochemical parameters and trace metals have low concentrations and are non-toxic to plants. Values of water quality indices (sodium adsorption ratio, soluble sodium percentage, total dissolved solids and permeability index) indicated that the concentrations of minerals in waters across the valley typologies are generally within permissible limits for cropping.

Linking trace element variations with macronutrients and major cations in marine mussels Mytilus edulis and Perna viridis.

Marine mussels have long been used as biomonitors of contamination of trace elements, but little is known about whether variation in tissue trace elements is significantly associated with those of macronutrients and major cations. The authors examined the variability of macronutrients and major cations and their potential relationships with bioaccumulation of trace elements. The authors analyzed the concentrations of macronutrients (C, N, P, S), major cations (Na, Mg, K, Ca), and trace elements (Al, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Ba, Pb) in the whole soft tissues of marine mussels Mytilus edulis and Perna viridis collected globally from 21 sites. The results showed that 12% to 84% of the variances in the trace elements was associated with major cations, and the tissue concentration of major cations such as Na and Mg in mussels was a good proxy for ambient seawater concentrations of the major cations. Specifically, bioaccumulation of most of the trace elements was significantly associated with major cations, and the relationships of major cations with trace cations and trace oxyanions were totally opposite. Furthermore, 14% to 69% of the variances in the trace elements were significantly associated with macronutrients. Notably, more than half of the variance in the tissue concentrations of As, Cd, V, Ba, and Pb was explained by the variance in macronutrients in one or both species. Because the tissue macronutrient concentrations were strongly associated with animal growth and reproduction, the observed coupling relationships indicated that these biological processes strongly influenced the bioaccumulation of some trace elements. The present study indicated that simultaneous quantification of macronutrients and major cations with trace elements can improve the interpretation of biomonitoring data.

Quantification of monomethylmercury in natural waters by direct ethylation: Interference characterization and method optimization

AbstractThe accurate analysis of monomethylmercury (MMHg) in natural waters is critical to understanding the biogeochemical cycling of mercury. Direct ethylation has emerged as an effective method for measuring MMHg in seawater without distillation. We evaluated the method's utility in other natural waters, characterized potential interferences, and optimized the method in an attempt to overcome these. The ethylation of MMHg by sodium tetraethylborate (NaBEt4) in pure water was unaffected by pH over the range 2.5–5.5. However, ethylation becomes sensitive to pH with increasing salinity, with the optimal pH narrowing to 4.0–4.1. An increase in NaBEt4 concentration eventually results in a decrease in MMHg ethylation, which occurs at lower NaBEt4 concentrations with increasing salinity. A NaBEt4 concentration of 6 mg L−1 was optimal. There was no interference by environmentally relevant concentrations of major cations, anions, nor many trace metals. However, micromolar concentrations of Cu2+, Zn2+, Pb2+, and Fe2+ decreased MMHg recoveries, but these interferences were eliminated with ethylenediaminetetraacetic acid. Sulfide and thiols at concentrations of only 2 µM depressed MMHg recoveries. Attempts to remove sulfide or overcome the interference it caused were unsuccessful, so the method is currently limited to oxic waters. Addition of 1.2 M chloride eliminated the interference by even 20 µM thiols. Dissolved organic matter (DOM) interferes with direct ethylation, but 1.2 M NaCl increased MMHg recoveries to > 90% even at DOM concentrations > 17 mg OC L−1. The optimized method was used to measure MMHg in hundreds of oxic filtered and unfiltered fresh and saline natural waters; MMHg recoveries averaged 92% ± 6%. The average percent relative standard deviation was < 10% for samples (n = 266) analyzed in triplicate. Daily detection limits for a 30 mL sample are < 25 fM.

Survey of Uruguayan Freshwater Water Quality for Crop Irrigation

The increase in global demand for food and biofuels, has led to an high demand for agricultural products. That situation implies an intensification of production systems, and develop strategies to ensure stability against drought, and moreover a better levels of productivity. Objectives that could be achieved with the irrigation of crops; however, it can promote negative impacts due to cumulative effects on soil quality, which depend on the chemical composition of the water used. This paper show the results of a national study of freshwater quality, on 100 river watersheds (up to 100,000 ha), which correspond to a cumulative drainage area of 70% of country surface. In these freshwaters the following parameters was evaluated: electrical conductivity, concentration of major cations (Na, K, Ca, Mg), alkalinity, and pH. The results showed Ca, Mg, K, and Na concentrations in ranges of 0.0- 45.1, 0.0-14.1, 0.019-16.8, and 0.78 -139 mg L-1, respectively. The alkalinity was in range of 32 to 420 CaCO3 mg L-1, and this variable was the most important contribution to get the different values of electrical conductivity of water, which had values between 71.6 and 1047 micro Siemens cm-1. These features allow propose at least 3 freshwater ecoregions (coastal and central-south; basalt; Northeast and southeast) at Uruguay, based on the chemical composition of studied freshwaters. Moreover, SAR values (([Na] / [(Ca + Mg) / 2] 1/2) of these waters shown a 99% of them has good quality characteristics for the development of irrigation, because they have a SAR below 10.

Processes controlling δ7Li in rivers illuminated by study of streams and groundwaters draining basalts

We evaluate the factors influencing the abundance, [Li], and isotopic composition of riverine Li delivered to the oceans through analyses and modeling of [Li] and δ7Li in streams and groundwaters draining a single continental lithology, the Columbia River Basalts (CRBs). The streams were sampled in different climate zones that lie east (dry), and west (wet) of the Cascades Mountains, and during two different seasons (summer and late winter) in order to evaluate climatic and seasonal influences on Li isotopes in rivers. Dissolved Li (δLidis7=+9.3 to +30.4) is systematically heavier than that of fresh or weathered CRBs (−4.7 to +6.0, Liu et al., 2013), suspended loads (−5.9 to −0.3), and shallow groundwaters (+6.7 to +9.4), consistent with previous studies showing that Li isotope fractionation is affected by equilibration between stream water and secondary minerals. However, the lack of correlation between δ7Lidis and climate zone, the uniform secondary minerals and bedrock, coupled with the highly variable (>20‰) δLidis7 indicate that other factors exert a strong control on δ7Lidis. In particular, the heavier Li in streams compared to the shallow groundwaters that feed them indicates that continued isotopic fractionation between stream water and suspended and/or bed loads has a major influence on riverine δ7Li. Seasonal δ7Li variation is observed only for streams west of the Cascades, where the difference in precipitation rate between the dry and wet seasons is greatest. Reactive transport model simulations reveal that riverine δ7Li is strongly controlled by subsurface residence times and the Li isotope fractionation occurring within rivers. The latter explains why there is no positive correlation between δ7Li and traditional weathering proxies such as Si or normalized Si in rivers, as riverine Li isotope fractionation drives δ7Li to higher values during transport, whereas the concentrations of major cations and anions are diluted. The varying residence time for groundwaters feeding the western streams in summer (long residence times, higher δ7Li, greater weathering) and winter (short residence times, lower δ7Li, less weathering) explains the observed seasonal variations. A global, negative correlation between δ7Li and Li/Na for streams and rivers draining basaltic catchments reflects the overall transport time, hence the amount of silicate weathering. Based on our results, the increase of δ7Li in seawater during the Cenozoic is unlikely related to changing climate, but may reflect mountain building giving rise to increased silicate weathering.

Hydrogeochemical characterization of a shallow groundwater system in the weathered basement aquifer of Ilesha area, southwestern Nigeria

Abstract. Hydrogeochemical characterization of a weathered basement aquifer in Ilesha area, southwest Nigeria, was carried out with respect to geogenic and anthropogenic influences on the shallow groundwater system. Physico-chemical parameters revealed a pH of 6.4–8.4 and EC of 22–825 μs/cm in the urban areas compared to a pH of 7.3–10.5 and relatively higher EC of 126–1027 μs/cm in the peri-urban area. The concentrations of major cations (Ca, Na, K, Mg) in the urban areas revealed relatively lower average concentrations of 28.4, 16.7, 8.4 and 5.0 mg/L, respectively, compared to 82.5, 33.4, 19.3 and 12.4 mg/L, respectively, for the peri-urban areas. The low concentrations of major cations in the urban areas can be attributed to low mineral dissolution of quartzite and muscovite quartz-schist bedrocks compared to the weathered granitic, amphibolite and biotite schist in the peri-urban areas. Hydrochemical characterization revealed two main water types; namely Ca-Mg-(Na)-HCO3 mostly in the urban areas suggesting CO2-charged infiltrating recharge rainwater, and Ca-Na-(K)-SO4-Cl type in the peri-urban areas as products of water–rock interactions.

Sources of major ions and processes affecting the geochemical and isotopic signatures of subsurface waters along a tropical river, Southwestern India

Systematic monitoring of subsurface hydrogeochemistry has been carried out for a period of one year in a humid tropical region along the Nethravati-Gurupur River. The major ion and stable isotope (delta O-18 and delta H-2) compositions are used to understand the hydrogeochemistry of groundwater and its interaction with surface water. In the study, it is observed that intense weathering of source rocks is the major source of chemical elements to the surface and subsurface waters. In addition, agricultural activities and atmospheric contributions also control the major ion chemistry of water in the study area. There is a clear seasonality in the groundwater chemistry, which is related to the recharge and discharge of the hydrological system. On a temporal scale, there is a decrease in major cation concentrations during the monsoon which is a result of dilution of sources from the weathering of rock minerals, and an increase in anion concentrations which is contributed by the atmosphere, accompanied by an increase in water level during the monsoon. The stable isotope composition indicates that groundwater in the basin is of meteoric origin and recharged directly from the local precipitation during the monsoonal season. Soon after the monsoon, groundwater and surface water mix in the subsurface region. The groundwater feeds the surface water during the lean river flow season.