Hydrochemical Water Research Articles

Rare earth element geochemistry of spring water, north western Bam, NE Iran

In this paper, based on the analysis of major ions and rare earth elements (REEs), spring water samples from the north western Bam area, central Iran were investigated for the hydrochemical processes, geochemical behavior of REEs and ion concentration background in the region . In the study area, the order of cation and anion abundance is Na+ > K+ > Mg2+ > Ca2+ and Cl− > SO 4 −2 > HCO3− > NO3−, and the dominated hydrochemical water are of Na–Cl type. The groundwater shows heavy REEs enrichment relative to light REEs. Depending on water types, REEs show different behaviors in study area. The increase in TDS and Fe contents in groundwater is accompanied by an increase in REE concentrations, while an increase in pH and Eh values is accompanied by a decrease in REE concentrations. Moreover, correlation analysis indicates that Eh–pH condition, TDS and Fe content, aquifer rock as well as their minerals play an important role in controlling the REE enrichment of groundwater.

Down-slope change in soil hydrogeochemistry due to seasonal water table rise: Implications for groundwater weathering

Abstract Landscape-scale chemical weathering has gone through a fundamental re-think due to: 1) the acknowledgement that a majority of solutes in most soils originate from wet fall and dry fall; and 2) that the zone of active weathering in many landscapes is much deeper than previously thought. With the goal of better understanding where weathering is occurring, a toposequence of five soil/regolith profiles from ridge crest to valley bottom in the Mt Lofty Range of South Australia was investigated using whole soil geochemistry, soil exchange pool and soil pore water hydrochemistry; stream water and groundwater hydrochemistry were analysed as well. This investigation aimed to: 1) trace water through soils, into the groundwater, and to the stream; and 2) investigate soil and regolith weathering hydrochemistry. The toposequence consists of podzolic Alfisols or texture-contrast Red-Brown Earths/Brown Chromosol soils which grade into saprolite which in turn grades into Precambrian meta-sedimentary bedrock. The groundwater table is shallow in the valley bottom, deepens upslope and has at least one metre seasonal rise and fall due to winter wet season recharge and summer dry season draw-down. Strontium isotope analysis of the groundwater, stream water, soil pore water, and soil exchange pool has established that the stream water is a mix of soil water and groundwater. This mix varies seasonally due to large changes in soil water input. Furthermore, in the down-slope soil sites, strontium isotope ratios of the soil exchange pool demonstrate a contribution to this pool from the bedrock groundwater. Up-slope soil sites that are well removed from the water table have exchange pool strontium isotope ratios that are much the same as the soil pore water. Thus, the dissolved solids in up-slope soils are dominated by wet fall–dry fall input whereas the dissolved solids in lower slope soils are dominated by weathering of high ratio Precambrian rock and saprolite transported by the groundwater system. This weathering is thought to be concentrated in the vadose zone at the transition between bedrock and saprolite.

Investigation of hydrogeochemical processes in groundwater resources located in the vicinity of a mine process water dam

The study aims to identify and describe the dominant hydrogeochemical processes and their contribution to the overall groundwater quality of an aquifer situated in the vicinity of a mine process water dam. The study site is located in a typical Karoo Basin of Southern Africa. Groundwater samples were collected from a network of boreholes designed to monitor the migration of contamination from the mine process water dam during a five year period from November 2007 to November 2011. The study utilises the expanded Durov diagram, bivariate plots and correlation coefficients statistics to analyse groundwater chemistry data. Based on analyses of the groundwater chemistry the study area was divided into two hydrogeochemical zones; the fresh background and contaminated groundwater. Fresh water in the background aquifer is characterised by a Na+–HCO3- hydrochemical groundwater type. Groundwater in the contaminated zone comprises of Mg2+–Cl− and Na+–Cl−, two main hydrochemical water types. High levels of EC and TDS that ranges from 63.10 to 1870mS/m and 690–11443mg/l respectively were measured in the contaminated groundwater indicating that the aquifer has been affected by saline water from the dam. Major ions of Mg2+, SO42- and Ca2+ measured in the contaminated portion of the aquifer are positively correlated to the conservative Cl− indicating that these ions were derived from the same saline source (dam). The study identified albite dissolution as the main hydrogeochemical process responsible for the evolution of fresh groundwater chemistry in the background aquifer. The aquifer on the down gradient of the process water dam is contaminated by saline water that evolved from the dam. There is evidence to show that the mine process water dam poses a serious threat of contaminating the groundwater with salts. A recommendation was therefore made to the responsible authorities to consider decommissioning of the facility given that the mine operations ceased some years back.

English

  This study was conducted on the hydrochemistry of shallow groundwater and surface water in the Ndop plain, North West Cameroon. The objectives were to determine the physico-chemical characteristics of water, controls on water chemistry and suitability for drinking and irrigation. Forty-six shallow groundwater and 26 surface water samples were investigated. Field measurements of physical parameters were preceded by chemical analyses of the samples for major ions and F-. About 69% of the water sources had pH values below 6.5, classifying the water as barely acidic. Electrical conductivity (<282 µS/cm) and total dissolved solids (<183 mg/l) were low suggesting low-mineralised and freshwater. The relative abundance of major ions (meq/l) was Na2+>Ca2+>Mg2+>K+ for cations and HCO3->>NO3-≥Cl->SO42- for anions. Major ion concentrations were low, and within the WHO guidelines for drinking water, but F-concentrations were much lower (<0.39 mg/l) and below guideline value. Main water types and proportions were Na-HCO3 (53 %), Ca-HCO3 (35 %) and a mixed Na-Ca-HCO3 (11%). Predominant processes influencing water chemistry were incongruent dissolution of silicate minerals and cation-exchange of Na+ in rocks for Ca2+ in water. The low major ion concentrations indicated low water-rock interactions and short residence time. The analysed water was suitable for irrigation.   Key words: Water chemistry, hydrochemical controls, drinking-irrigation quality, Ndop plain, Cameroon.

Hydrochemical water evolution in the Aral Sea Basin. Part I: Unconfined groundwater of the Amu Darya Delta – Interactions with surface waters

Summary The Aral Sea, which has been affected by lake level lowering of approximately 25 m and a salinity increase from 10 to >100 g/l since 1963, represents, along with the Amu Dary Delta a dynamic hydrological system under an arid climate regime. The system receives river water inflow at high seasonal and inter-annual variability from remote alpine source areas. In the Amu Darya Delta, there is a distinct salinity contrast between the low-salinity river water (∼1 g/l) and the salinity of the unconfined GW (GW unconf : 10–95 g/l). The GW unconf levels are predominantly controlled by the seepage of the river water inflow and GW discharge into the shrinking Aral Sea. In June 2009 and August 2009, we sampled water from various sources including surface waters, GW unconf , lake water and soil leachates for chemical analyses. Evaporative enrichment, precipitation/dissolution of gypsum and precipitation of calcite drive the GW unconf to an NaCl(SO 4 ) water type presenting a positive correlation between Na and SO 4 . We model the hydrochemical evolution of the GW unconf in a box model which considers the capillary rise of near-surface GW, the precipitation of minerals in the unsaturated horizon and the seasonal re-flushing of adhesive residual brines and soluble salts. The model documents a rapid increase in salinity over a few annual cycles. Furthermore, the model simulations demonstrate the importance of the aeolian redistribution of soluble salts on the hydrochemical GW evolution. In a lab experiment, halite, hexahydrite and starkeyite are precipitated during the late stages of evaporative enrichment from a representative local brine. Processes specific to different water compartments plausibly explain the variations of selected element ratios. For example, the precipitation of low-Sr calcite in irrigation canals and natural river branches of the delta lowers Ca/Sr. The dissolution of gypsum in soils (Ca/Sr mole ratio ∼ 150) and the possible precipitation of SrSO 4 associated with Sr-depletion in adhesive residual brines increases Ca/Sr in seepage and re-increases Ca/Sr in the unconfined GW. Aral Sea water, which receives high-Ca/Sr surface and groundwater inflow, developed due to continued precipitation of high-Ca/Sr calcite the almost lowest Ca/Sr ratio (∼25) over time. We observed spatial variations in the GW unconf composition: (i) ammonium levels increase strongly due to interaction with lake sediments rich in organic matter and (ii) distinct increases in levels of nitrate, U, Mo and Se locally reflect oxygenation when GW levels decrease. The Amu Darya Delta acts as a sink for boron (uptake via terrestrial vegetation) and a source for bromide (release by degradation of organically-bound Br). Our results concerning the hydrochemical evolution of the GW unconf and additional data from the Aral Sea constrain the parameter ‘GW discharge’ in water budget models of the lake and improve the basis for palaeoclimatic interpretations of sediment records from the Aral Sea.

Hydrochemical water evolution in the Aral Sea Basin. Part II: Confined groundwater of the Amu Darya Delta – Evolution from the headwaters to the delta and SiO2 geothermometry

Summary We studied 40 artesian wells (AWs) in the Amu Darya Delta. These wells include high-salinity (∼52 g/l) and saline (5–24 g/l) waters but are mostly low-salinity waters (1.3–2.9 g/l). The low-salinity AWs cluster into three types, reflecting the variable mixing of different end member solutes: (residual) brines and solutes deriving from silicate alteration, dissolution of limestone and dissolution of gypsum. The solutes are all undersaturated in calcite and gypsum, contain a substantial cation excess against dissolved inorganic carbon and are characterised by low Ca/SO4 ratios. On the basis of the hydrochemical mass budgets of model cases, we demonstrate that Na-rich Cl-brines (45–48%) and a Na2SO4-brine (30–47%) are the dominant solute components. The solutes derived from aluminium silicate alteration are minor components (7.3–19.4%). Even less important are solutes from limestone or gypsum dissolution (0.05–3.7%). These waters are unlikely to have originated from sediments hosting gypsum. The low-salinity AWs must have acquired their dominant hydrochemical signatures under non-equilibrium conditions between their remote (unknown) seepage areas and their discharge locations. This acquisition may have begun during the early hydrochemical groundwater evolution when meteoric or surface water passed the critical zone under an arid climate regime. Warmer saline AWs (∼40 °C) hosted in deeper Cretaceous formations contain a high portion of NaCl-rich brine (85%) and some are saturated in gypsum. These waters were derived from fluids rising along faults from pre-Cretaceous strata. The high-salinity and relatively cold AWs discharge close to the retreating Aral Sea south of its western basin. These AWs are suboxic, and Si concentrations are very low. The AW hydrochemical signatures reflect the dissolution of halite and gypsum. We observed positive correlations between temperature, Br, B and Si. The temperature correlation with bromide likely documents the transformation of organically bound Br. The silica concentrations in low-salinity AWs southeast of the Aral Sea (eastern basin) are close to quartz saturation and define a chemical Si-geothermometer.

Hydrochemical Characteristics and Water Quality Assessment of Groundwater in Daxing District of Beijing, China

Based on the groundwater samples collected in Daxing District of Beijing in June and October 2008, the groundwater quality is assessed and the groundwater hydrochemical characteristics are analyzed. The assessment of groundwater quality is conducted by using the F-value comprehensive assessment method, and GIS approach is used to obtain the zonation of groundwater quality. The results show that the groundwater quality is classified into II, III and IV class, and the groundwater quality gradually changes well from north to south. The groundwater of IV class is located in the northern part, which accounts for about 40% of the total area, and the major pollution factors are TDS and nitrate. The groundwater is mainly characterized by HCO3-Ca•Mg type. The concentrations of SO42-, NO3-, Ca2+ and TDS follow a decreasing trend generally from north to south, all of which have slight seasonal changes. Both natural factors and human activities have impacts on the chemical composition of the groundwater. The protection of groundwater environment in northern Daxing should be taken more seriously.

Hydro-Chemical Facies Water Sources. The Region Rabat-Sale-Zemmour-Zaer of Morocco

A sampling network of fifty-one (51) samples of water sources has been chosen as a geographic and habitat significant enough to afford to acquire representative data on the spatial variability of groundwater quality of the Rabat-Sale-Zemmour-Zaer. This network consists of three groups of water areas and covers almost the entire study site. With the help of the method of Piper diagram, the waters of different origins are easily differentiated

Hydrochemistry of groundwater with special reference to arsenic in Lakhimpur Kheri district, Uttar Pradesh, India

The present study aims to understand the severity of Arsenic contamination along with the hydrochemistry of ground water in Lakhimpur Kheri, one of the largest districts in Uttar Pradesh, India. Ground water samples collected from 102 handpumps from 15 blocks were analyzed for physicochemical parameters and Arsenic. The groundwater quality data were analysed statistically. The characteristic features of groundwater indicated the presence of As (0- 0.224 mg/L), Fe (0.011-8.634mg/L), Na + (2.84-62.12 mg/L), K + (1.21-51.20 mg/L), Ca 2+ (6-102mg/L), Mg 2+ (10-126), Cl - (2.19-133.96 mg/L), SO4 2- (1-269.92 mg/L), NO3 - (0.11-2.61 mg/L) and HCO3 - (122-549 mg/L). The pH of the groundwater was found to be neutral to slightly alkaline (6.88-8.45) with high EC (471-1569 µS/cm) and TDS (289-1042 mg/L). Of the total samples analysed, 41.18% contained As > 10µg/L, 13.73% contained As < 10µg/L, while in the rest of the samples As was found to be below detectable limit. Severe As contamination was reported mainly in six blocks of the study area- Pallia, Nighasan, Dhawahara, Ramia Beher, Isanagar and Nakaha. The highly contaminated block was Pallia where all the samples contained As above permissible limit. However, maximum As concentration (0.224 mg/L) was reported from a deep well handpump of village Dubha from Nighasan block. Both Shallow and deep bore handpumps were analysed to study the distribution pattern of As with depth. No systematic relationship was found. Arsenic showed insignificant correlation with EC, TDS, TH, Ca 2+ , Mg 2+ , Na + , K + , HCO3 - , NO3 - Cl - and SO4 2- but poor correlation with Fe (r 2 = 0.391) and pH (r 2 = 0.018). Factor analysis was applied to reveal the processes controlling the hydrochemistry of groundwater and to understand the factors responsible for the release of As in groundwater of the study area. Extensive study in the affected areas advocates that the leaching of Arsenic in underground water is controlled by the magnitude of oxidizing environmental conditions created in the affected zones where As (III) oxidized to As (V) is introduced in the aquifers and gets adsorbed on iron

Biogeochemical controls on daily cycling of hydrochemistry and δ13C of dissolved inorganic carbon in a karst spring-fed pool

Summary Variations in temperature, photosynthesis and respiration can force daily variations in pH, DO and DIC in surface water, potentially driving calcite precipitation or dissolution of calcium carbonate. Diel cycles of hydrochemistry and δ13CDIC were measured at high time-resolution (1 h) to assess the relative magnitudes of biological and geochemical controls on carbonate chemistry and carbon cycling in a spring-fed pool with flourishing submerged plants in Chongqing, SW China under sunny weather. Results show that there were no diurnal variations in the physical and chemical parameters of the Shuifang spring water. However, during the daytime periods, SC, Ca2+, alkalinity, NO 3 - and pCO2 in the pool water decreased to less than those in the spring water, while pH, DO and δ13CDIC in the pool water became greater than those in the spring water. Conversely, during nighttime periods, pool water SC, Ca2+, alkalinity, NO 3 - and pCO2 returned to or even became greater than the spring water, while pH, DO and δ13CDIC decreased to less than the spring water. This work shows that photosynthesis and respiration of subaquatic communities are the dominant processes influencing the observed diel variations of hydrochemistry in karst spring-fed pool water. During the daytime, a simultaneous increase of δ13CDIC and DO, and decrease in DIC indicates that photosynthesis was the primary control on hydrochemistry of the pool water. Conversely, the water remained saturated with respect to calcite (SIc ranging from 0.04 to 0.15) and δ13CDIC values decreased at nighttime, indicating that respiration of the subaquatic community had a dominant influence over calcite dissolution and outgassing in the pool water. The total amount of DIC loss was estimated to be about 110,785 mmol/day which represented about 1.33 kg C/day. More specifically, the amount of DIC loss through carbonate precipitation was about 38,775 mmol/day (0.47 kg C/day), whereas photosynthetic uptake was about 60,700 mmol/day (0.86 kg C/day) in the pool water. On one hand, the loss of C through consumption of CO2 during carbonate precipitation was balanced by carbonate dissolution. On the other hand, the loss of C by photosynthetic uptake was diverted into organic C and constitutes a relatively long-term natural carbon sink in the karst system. In addition, the diurnal variations of NO 3 - and pH in the pool water, caused by photosynthesis and respiration, indicated that biogeochemical processes impact water quality on a daily timescale.

Hydrochemical regime and water quality of rivers and reservoirs of basins of Shu, Esyl, Tobol, Sirdariya rivers for long-term cycle

Приведен анализ литературных данных и материалы собственных исследований по изучению режима основных и загрязняющих компонентов химического состава воды рек и водоемов бассейнов рек Шу, Есiл, Тобыл, Сырдарии в многолетнем цикле. Исследован фоновый гидрохимический режим рек и в современный период. Показано, что вода исследуемых рек загрязнена веществами минерального и органического происхождения (в основном соединениями марганца, фтора, фосфатов, нитратным и нитритным азотом), которые поступают в реки за счет естественных и антропогенных факторов. Общая минерализация воды рек по течению в большинстве случаев повышается.

Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation – Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

Abstract. This study demonstrates that alkaline earth elements in enamel of hippopotamids, in particular Ba and Sr, are tracers for water provenance and hydrochemistry in terrestrial settings. The studied specimens are permanent premolar and molar teeth found in modern and fossil lacustrine sediments of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by two orders of magnitude for Ba (120–9336 μg g−1) as well as for Sr (9–2150 μg g−1). The variations are partially induced during post-mortem alteration and during amelogenesis, but the major contribution originates ultimately from the variable water chemistry in the habitats of the hippopotamids which is controlled by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of MgO, Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel–dentin junction by a factor of 1.3–1.9. These elements are well correlated in single specimens, thus suggesting that their distribution is determined by a common, single process, which can be described by closed system Rayleigh crystallization of bioapatite in vivo. Enamel from most hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores. However, Ba/Sr ranges from 0.1 to 3 and varies on spatial and temporal scales. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic mantle rocks or Archean crustal rocks as the ultimate sources of Sr and Ba. This provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from 2 to 0.5. This trend can be correlated with changes in climate from humid to arid, in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that Ba mobility decreased with increasing aridification due to preferential deposition with clay and Fe-oxide-hydroxide or barite on the watershed of Lake Albert.

Shallow and deep aquifer hydrochemistry and chemical variability of water quality at Shariatpur district, Bangladesh

Water quality and hydrochemistry of Shariatpur district were evaluated in terms of hydrochemical composition and some important physico-chemical parameters. The groundwater of the study area is good for drinking, domestic as well as for irrigation purposes. Among the major ions, shallow tube well waters give higher concentration of Ca2+ which ranges from 24 to 260 mg/L. The deep tubewell waters show higher concentration of Na+ which varies from 74 to 582 mg/L during dry season. Among the trace elements most of the shallow aquifer samples show higher concentration of Fe2+, Mn2+ and As. Concentration of Fe2+ varies from 0.655 to 18.8 mg/L, and Mn2+ from trace to 0.868 mg/L during dry period. Hydrochemical analyses reveal significant seasonal variation in water quality of shallow aquifer. Both the shallow aquifer and the surface water of the study area are predominantly of Ca–Mg–HCO3 type, while the deep aquifer water is mainly of Na–K–Cl–SO4 type with slight inclination to Ca–Mg–HCO3 type. The study area is suitable for groundwater development if comprehensive and holistic approaches towards water resource management are taken into consideration.

Geochemistry of natural waters – The legacy of V.I. Vernadsky and his students

Abstract The geochemist, Vladimir Ivanovich Vernadsky has only recently become recognised internationally, despite being regarded as one of the greatest names in science of the 20th century in his homeland Russia. There are several reasons for his lack of renown in the west, but mainly because his most important work “ The Biosphere ” was only fully translated into English in 1997. This book and the ideas it contains are now becoming regarded as one of the pioneering works of the last century. It defines the biosphere as a unifying, holistic concept for the earth system at a time when reductionism was the driving motivation in scientific research. Above all, for earth scientists, Vernadsky regarded life as the driving geological force. However another, as yet unpublished work (in three volumes) entitled “ The History of Natural Waters ” also deserves similar attention. This book explores many concepts in hydrogeology, geochemistry, geofluid circulation and especially biology in which water is described as an integral part of the biosphere. Vernadsky’s teachers, including Mendeleev, Butlerov and Dokuchaev had a special influence on his early career path. He published prolifically in the 1920s and 1930s as well as founding several key institutions in Russia and Eastern Europe. The influence of the Russian school of landscape geochemistry, led by Dokuchaev also had a great influence on Vernadsky’s scientific work and productivity, as was a period of study in France in the 1920s. The History of Natural Waters covers the spectrum of hydrogeochemical phenomena, in rather a descriptive way, yet its influence as the foundation of later ideas on hydrochemical processes and water–rock interaction, as well as hydrogeology, can easily be recognised. As well as including the role of biology in hydrogeochemistry, this work clearly emphasises the role of mans’ influence on changing the chemistry of natural waters. Vernadsky adopted the concept of the ‘Noosphere’ (the evolution of human thought) to emphasis man’s role as a geological agent. His publications foreshadow Gaia theory some half a century later. Vernadsky’s works thus made a huge contribution to the development of many science areas and have changed the scientific world view; moreover they have defined the position of mankind in the evolution of the Earth and the biosphere and also put urgent questions for future generations with significance at the present time. His ideas have not always been understood and even more so recognised. He always remembered the words of Alexander von Humboldt: “A hundred years are necessary to reach the truth and another hundred in order to start following it”.

Hydrochemistry of geothermal water in Tianshui and adjacent area, Gansu province, China

A geochemical study on thermal water has been carried out in Tianshui and its adjacent area, Gansu province, China. Chemical and isotopic contents were employed in the investigation on the origin and evolution of thermal water and the evaluation of reservoir temperature in the geothermal systems. Thermal waters in Wushan and Tianshui are characterized by outlet temperatures from 15 to 38°C and low TDS (226–255 mg/L), defined as bicarbonate water. Its origin may be attributed to the interaction between meteoric rain, biotite plagioclase gneiss and carbonate reservoir rocks. In contrast, thermal waters in Tongwei and Qingshui have higher outlet temperatures of 25–54.2°C and a moderate TDS of 915–1,793 mg/L, regarded as sulfate waters. These sulfate waters may arise from the interaction between meteoric water, granite and amphogneiss. Isotopic data presented here suggest that thermal waters in the study area have a meteoric origin without being significantly effected by water–rock isotope exchange. Chemical geothermometry indicates the existence of a deep geothermal reservoir of low-to-medium enthalpy (70–111°C) in the Tianshui study area.

Hydrochemistry of groundwater in the Savelugu–Nanton District, Northern Ghana

Calcite (CaCO3), dolomite [CaMg(CO3)2], silicate dissolution, ion-exchange and reverse ion-exchange reactions are the predominant processes influencing groundwater quality in the Savelugu–Nanton District. The main objective of this study is to characterize groundwater and delineate water–rock interactions responsible for the chemical evolution of groundwater in the District. Eighty-one (81) boreholes were sampled for quality assessment. Results showed that, the pH of the boreholes are slightly acidic to basic ranging from 6.1–8.3 pH units. Conductivity values are low to high ranging from 147–23,200 μS/cm with, 23.5 % of groundwater within the study area being either brackish (1,500–5,000 μS/cm) or saline (>5,000 μS/cm) and therefore, unsuitable for potable purposes. TDS values in groundwater varied widely, ranging from 62–11,900 mg/L. 61.7 % of groundwater within the study area are fresh (TDS Na+ > Mg2+ > K+ and HCO3 − > Cl− > SO4 2− > NO3 − respectively. Multivariate statistical analysis showed expected process-based relationship derived mainly from the geochemical and biochemical processes within the aquifer. Hydrochemical facies using piper plot of major ions showed one major hydrochemical water type. The Ca–Mg–HCO3 water type. Due to the high cost of drilling of boreholes coupled with the high percentage (×1 %) of people without access to potable water in the Northern Region, it is recommended that the Government of Ghana and other stakeholders within the Water Sector take immediate measures to reduce (to recommended limits for potable uses) the levels of dissolved solids either by installing Reverse Osmosis equipments on such boreholes or employ other relatively known cheaper methods to reduce the dissolved solids to recommended limits. High yielding boreholes with hydrochemical parameters within WHO guideline limits in the Savelugu–Nanton District could also be mechanized to serve a wider area.

Isotopic and hydrochemical data to restrict the origin of the groundwater in the Badain Jaran Desert, Northern China

Despite its extreme aridity, the Badain Jaran Desert is rich in groundwater. In the southeastern part of the desert, it is characterized by coexistence of high megadunes and a great number of lakes. Deuterium and oxygen 18 isotope compositions as well as hydrochemistry of groundwater, lake water, soil water and river water were investigated in detail to gain an insight into their relationships and the origin of the ground-water. The results show that the groundwater and the lake water are genetically related, but unrelated to local precipitation and the leakage of Heine River at northern slope of Qilian mountain. δD and δ18O values of deep soil water (lower than 40 cm) and groundwater plot on the same evaporation line E11, which shows that they have the same recharge source. The point of intersection between E11 and LMWL suggests that the groundwater originates from the water resource which has a weighted mean value that is lighter by some 6‰ δ18O than the local precipitation in Badain Jaran Desert. 3H data of water samples shows that the groundwater in Badain Jaran Desert originates from the water recharged after the nuclear test. The deep fault zone underground maybe the water circulation channel based on Helium analysis of groundwater. The result has guiding significance to rational exploitation and utilization of the local groundwater.

Identifying key processes in the hydrochemistry of a basin through the combined use of factor and regression models

An innovative technique of measuring the intensities of major sources of variation in the hydrochemistry of (ground) water in a basin has been developed. This technique, which is based on the combination of R-mode factor and multiple regression analyses, can be used to measure the degrees of influence of the major sources of variation in the hydrochemistry without measuring the concentrations of the entire set of physico-chemical parameters which are often used to characterize water systems. R-mode factor analysis was applied to the data of 13 physico-chemical parameters and 50 samples in order to determine the major sources of variation in the hydrochemistry of some aquifers in the western region of Ghana. In this study, three sources of variation in the hydrochemistry were distinguished: the dissolution of chlorides and sulfates of the major cations, carbonate mineral dissolution, and silicate mineral weathering. Two key parameters were identified with each of the processes and multiple regression models were developed for each process. These models were tested and found to predict these processes quite accurately, and can be applied anywhere within the terrain. This technique can be reliably applied in areas where logistical constraints limit water sampling for whole basin hydrochemical characterization. Q-mode hierarchical cluster analysis (HCA) applied to the data revealed three major groundwater associations distinguished on the basis of the major causes of variation in the hydrochemistry. The three groundwater types represent Na–HCO3, Ca–HCO3, and Na–Cl groundwater types. Silicate stability diagrams suggest that all these groundwater types are mainly stable in the kaolinite and montmorillonite fields suggesting moderately restricted flow conditions.

Spatial and temporal variability of Atlantic salmon (Salmo salar L.) spawning activity in braided river channels: a preliminary assessment

The distribution of Atlantic salmon redds was recorded during two spawning seasons (2005 and 2006) along a 4 km braided reach of the river Feshie in the Cairngorm mountains, Scotland. Within this complex reach, four main channels types were differentiated on the basis of geographical water sources, channel morphology and hydrochemistry: (1) the main braided channels of the river Feshie; (2) groundwater channels fed by seepage at the edge of the floodplain; (3) hillslope tributary channels and (4) mixed channels downstream of confluences of two or more of types 1–3. The 2005 season was characterised by high and variable flows. In total, 223 redds were observed which were mainly (64%) located in groundwater channels, with relatively few (9%) in the more extensive sections of main channel. The second year had much lower and more stable flows. Here, a total of 337 redds were observed. The largest number were again located in the groundwater channels (44%), though spawning was more evenly distributed in the other channel types, including the main river (19%). It is hypothesised that the apparently more suitable characteristics of groundwater-fed channels relate to a more stable, richer environment for embryo development and juvenile growth, whilst hydraulic conditions and sediment stability in the main channel may create more adverse conditions for successful recruitment.

Three-dimensional geological modelling and multivariate statistical analysis of water chemistry data to analyse and visualise aquifer structure and groundwater composition in the Wairau Plain, Marlborough District, New Zealand

Concerns regarding groundwater contamination with nitrate and the long-term sustainability of groundwater resources have prompted the development of a multi-layered three-dimensional (3D) geological model to characterise the aquifer geometry of the Wairau Plain, Marlborough District, New Zealand. The 3D geological model which consists of eight litho-stratigraphic units has been subsequently used to synthesise hydrogeological and hydrogeochemical data for different aquifers in an approach that aims to demonstrate how integration of water chemistry data within the physical framework of a 3D geological model can help to better understand and conceptualise groundwater systems in complex geological settings. Multivariate statistical techniques (e.g. Principal Component Analysis and Hierarchical Cluster Analysis) were applied to groundwater chemistry data to identify hydrochemical facies which are characteristic of distinct evolutionary pathways and a common hydrologic history of groundwaters. Principal Component Analysis on hydrochemical data demonstrated that natural water–rock interactions, redox potential and human agricultural impact are the key controls of groundwater quality in the Wairau Plain. Hierarchical Cluster Analysis revealed distinct hydrochemical water quality groups in the Wairau Plain groundwater system. Visualisation of the results of the multivariate statistical analyses and distribution of groundwater nitrate concentrations in the context of aquifer lithology highlighted the link between groundwater chemistry and the lithology of host aquifers. The methodology followed in this study can be applied in a variety of hydrogeological settings to synthesise geological, hydrogeological and hydrochemical data and present them in a format readily understood by a wide range of stakeholders. This enables a more efficient communication of the results of scientific studies to the wider community.