Groundwater mineralisation processes in Mediterranean semi‐arid systems (Cap‐Bon,North east of Tunisia): hydrogeological and geochemical approaches

The groundwater of the Korba plain represents major water resources in Tunisia. The Plio‐Quaternary unconfined aquifer of the Cap‐Bon (north‐east Tunisia) is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction. The degradation of the groundwater quality is characterized by the salinization phenomena. Groundwater were sampled and analysed for physic‐chemical parameters: Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^‐, SO₄^2‐, HCO₃^‐, NO₃^‐, pH, electrical conductivity (EC), and the temperature (T°). The hydrochemical analysis is coupled with the calculation of the saturation indexes (SI gypsum, SI halite, SI calcite and SI dolomite), ionic derivation and with the ion correlations compared to chloride concentrations: Na⁺/ Cl^‐, Ca²⁺/ Cl^‐ and Mg²⁺/ Cl^‐ ratios. Seawater fractions in the groundwater were calculated using the chloride concentration. Those processes can be used as indicators of seawater intrusion progression. EC methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water–seawater interface of coastal groundwater exchange. The mixing zone between freshwater and saltwater was clearly observed from the EC profile in the investigated area where a strong increase in EC with depth was observed, corresponding to the freshwater and saltwater interface. Results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange. These results, together with EC investigation, indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in Korba coastal plain. Further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.     

Lithological and hydrological controls on water composition: evaporite dissolution and glacial weathering in the south central Andes of Argentina (33°–34°S)

Lithological and hydrological influence on fluvial physical and chemical erosion was studied in a glacierized sedimentary basin with high evaporite presence. Suspended particulate matter (SPM), total dissolved solids (TDS) and major ion concentrations were analysed for 2 years of different hydrologic condition: (i) 2009–2010, Q = 100% average; and (ii) 2010–2011, Q = 60% average. Annual hydrograph was simple regime‐type with one peak in summer related to snow melting. The intra‐annual SPM and TDS variations were directly and inversely associated to Q, respectively. Snow chemistry showed continental influence (Na⁺/Ca²⁺ = 0.17), and atmospheric input of TDS was <1% of the total exported flux. River water was highly concentrated in Ca²⁺ and SO₄²⁻ (~4 mmol l⁻¹) and in Na⁺ and Cl⁻ (~3 mmol l⁻¹). Ca²⁺/SO₄²⁻ and Na⁺/Cl⁻ molar ratios were ~1 and related to Q, directly and inversely, respectively. Major ion relationships suggest that river chemistry is controlled by evaporite (gypsum and halite) dissolution having a summer input from sulfide oxidation and carbonate dissolution, and a winter input from subsurface flow loaded with silicate weathering products. This variation pattern resulted in nearly chemostatic behaviour for Ca⁺, Mg²⁺ and SO₄²⁻, whereas Na⁺, Cl⁻ and SiO₂ concentrations showed to be controlled by dilution/concentration processes. During the 2009–2010 hydrological year, the fluxes of water, SPM and TDS registered in the snow melting–high Q season were, respectively, 71%, 92% and 67% of the annual total, whereas for equal period in 2010–2011, 56% of water, 86% of SPM and 54% of TDS annual fluxes were registered. The SPM fluxes for 2009–2010 and 2010–2011 were 1.19 × 10⁶ and 0.79 × 10⁶ t year⁻¹, whereas TDS fluxes were 0.68 × 10⁶ and 0.55 × 10⁶ t year⁻¹, respectively. Export rates for 2009–2010 were 484 t km² year⁻¹ for SPM and 275 t km² year⁻¹ for TDS. These rates are higher than those observed in glacierized granite basins and in non‐glacierized evaporite basins, suggesting a synergistic effect of lithology and glaciers on physical and chemical erosion. Copyright © 2014 John Wiley & Sons, Ltd.     

Hydrochemical characteristics and salinization processes of groundwater in the shallow aquifer of Eastern Laizhou Bay,China

Groundwater salinization has become a crucial environmental problem worldwide and is considered the most widespread form of groundwater contamination in the coastal zone. In this study, a hydrochemical investigation was conducted in the eastern coastal shallow aquifer of Laizhou Bay to identify the hydrochemical characteristics and the salinity of groundwater using ionic ratios, deficit or excess of each ions, saturation indices and factor analysis. The results indicate that groundwater in the study area showed wide ranges and high standard deviations for most of hydrochemical parameters and can be classified into two hydrochemical facies, Ca²⁺‐Mg²⁺‐Cl^‐ facies and Na⁺‐Cl^‐ facies. The ionic ratio, deficit or excess of each ions and SI were applied to evaluate hydrochemical processes. The results obtained indicate that the salinization processes in the coastal zones were inverse cation exchange, dissolution of calcite and dolomite, and intensive agricultural practices. Factor analysis shows that three factors were determined (Factor 1: TDS, EC, Cl^‐, Mg²⁺, Na⁺, K⁺, Ca²⁺ and SO₄^2‐; Factor 2: HCO₃^‐ and pH; Factor 3: NO₃^‐ and pH), representing the signature of seawater intrusion in the coastal zone, weathering of water–soil/rock interaction, and nitrate contamination, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Hydrogeochemical characteristics of surface water and groundwater in the karst basin,southwest China

Groundwater is a very significant water source used for irrigation and drinking purposes in the karst region, and therefore understanding the hydrogeochemistry of karst water is extremely important. Surface water and groundwater were collected, and major chemical compositions and environmental isotopes in the water were measured in order to reveal the geochemical processes affecting water quality in the Gaoping karst basin, southwest China. Dominated by Ca²⁺, Mg²⁺, HCO₃^? and SO₄^2?, the groundwater is typically characterized by Ca? Mg? HCO₃ type in a shallow aquifer, and Ca? Mg? SO₄ type in a deeper aquifer. Dissolution of dolomite aquifer with gypsiferous rocks and dedolomitization in karst aquifers are important processes for chemical compositions of water in the study basin, and produce water with increased Mg²⁺, Ca²⁺ and SO₄^2? concentrations, and also increased TDS in surface water and groundwater. Mg²⁺/Ca²⁺ molar ratios in groundwater decrease slightly due to dedolomitization, while the mixing of discharge of groundwater with high Mg²⁺/Ca²⁺ ratios may be responsible for Mg²⁺/Ca²⁺ ratios obviously increasing in surface water, and Mg²⁺/Ca²⁺ ratios in both surface water and groundwater finally tending to a constant. In combination with environmental isotopic analyses, the major mechanism responsible for the water chemistry and its geochemical evolution in the study basin can be revealed as being mainly from the water–rock interaction in karst aquifers, the agricultural irrigation and its infiltration, the mixing of surface water and groundwater and the water movement along faults and joints in the karst basin. Copyright © 2009 John Wiley & Sons, Ltd.     

不同上覆水氟浓度对湖泊沉积物氟释放与微生物群落的影响

通过模拟沙湖沉积物-水系统,以沙湖原水氟离子（F^-）浓度为1倍浓度（0.69 mg/L）,设置0.5倍浓度、1倍浓度、1倍浓度灭菌、2倍浓度和4倍浓度共5个实验组,探究不同上覆水F^-浓度背景下沙湖沉积物中F^-的迁移.结果表明,沉积物F^-的释放量随上覆水F^-浓度的增加而呈下降的趋势,其中2倍和4倍浓度组的沉积物由释放F^-转变为吸附F^-.碱性水体有利于沉积物F^-的释放,即随着pH增大,F^-释放量也会增加.微生物的Beta多样性层次聚类分析表明,F^-会抑制Paenisporosarcina与Thiobacillus的相对丰度,但对Fusibacter的生命活动具有促进作用.根据各浓度组间优势菌属相对丰度与环境因子的冗余分析可得,Acinetobacter、Thiobacillus相对丰度与pH呈负相关;Fusibacter相对丰度与F^-浓度呈显著正相关,而Thiobacillus的相对丰度则与F^-表现出弱负相关.通过对各浓度组中重要离子的分析发现,0.5倍组和4倍组中F^-的迁移受Ca²⁺、HCO₃^-和SO₄^2-浓度影响较大;相关性分析表明0.5倍浓度组的Ca²⁺、HCO₃^-浓度与F^-浓度呈极显著正相关,而4倍组中F^-浓度和Ca²⁺、HCO₃^-浓度呈负相关,SO₄^2-浓度和F^-浓度的相关性则是0.5倍组呈负相关,4倍组呈极显著正相关.本文在不同上覆水F^-浓度背景下全面探究了沙湖沉积物中F^-释放和迁移机理,为沙湖及其他含氟地表水的氟污染防治提供理论支持.     

Hydrogeochemical Evolution of Interaction Between Surface Water and Groundwater Affected by Exploitation

Hydrogeochemical evolution of interactions between surface water and groundwater is crucial for guaranteeing water supply quality in a riverside water source area. This study focuses on the seasonal and spatial characteristics of hydrogeochemical evolution affected by groundwater exploitation in the Hulan water source area using hydrochemical analyses and stable isotope tracers. Results show that the concentrations of major ions and total dissolved solids (TDS) increase considerably during the dry season. A bicarbonate water type is primarily produced by the dissolution of calcite, dolomite and gypsum, as well as the cation exchange and human activities. Along the typical infiltration path, the proportions of surface water increase with proximity to the river from 8%-63% during the wet season to 11%-84% during the dry season, which are attributed to an increased hydraulic gradient by exploitation. The typical path is classified into two zones. The first is the intensive mixing zone (within 1 km) with increasing concentrations of major ions and TDS due to mixing effect. The second is the exploitation influence zone (1-3.3 km) with increased concentrations of Ca²⁺, Mg²⁺, SO₄²⁻, and HCO₃⁻ during the dry season due to two reasons of seasonal variations in evaporation, stronger water-rock interactions and mixing effects with increased surface water by exploitation.     

Hydrogeochemical evolution of Ordovician limestone groundwater in Yanzhou,North China

Major‐ion compositions of groundwater are employed in this study of the water–rock interactions and hydrogeochemical evolution within a carbonate aquifer system. The groundwater samples were collected from boreholes or underground tunnels in the Ordovician limestone of Yanzhou Coalfield where catastrophic groundwater inflows can be hazardous to mining and impact use of the groundwater as a water supply. The concentration of total dissolved solid (TDS) ranged from 961 to 3555 mg/l and indicates moderately to highly mineralized water. The main water‐type of the middle Ordovician limestone groundwater is Ca‐Mg‐SO₄, with SO₄^2‐ ranging from 537 to 2297 mg/l, and average values of Ca²⁺ and Mg²⁺ of 455.7 and 116.6 mg/l, respectively. The water samples were supersaturated with respect to calcite and dolomite and undersaturated or saturated with respect to gypsum. Along the general flow direction, deduced from increases of TDS and Cl^‐, the main water–rock interactions that caused hydrogeochemical evolution of the groundwater within the aquifer were the dissolution of gypsum, the precipitation of calcite, the dissolution or precipitation of dolomite, and ion exchange. Ion exchange is the major cause for the lower mole concentration of Ca²⁺ than that of SO₄^2‐. The groundwater level of Ordovician aquifer is much higher than that of C‐P coal‐bearing aquifers, so the potential flow direction is upward, and the pyrite in coal is not a possible source of sulfate; additional data on the stable sulfur and oxygen isotopic composition of the sulfate may be helpful to identify its origin. Although ion exchange probably accounts for the higher mole concentration of Na⁺ than that of Cl^‐, the dissolution of aluminosilicate cannot be ruled out. The data evaluation methods and results of this study could be useful in other areas to understand flow paths in aquifers and to provide information needed to identify the origin of groundwater. Copyright © 2012 John Wiley & Sons, Ltd.     

淮北临涣矿采煤沉陷区不同水体水化学特征及其影响因素

为研究淮北临涣矿采煤沉陷区不同水体的补给水源及溶质来源,在现场调查的基础上,系统采集丰水期、平水期、枯水期沉陷区积水、地表河水和浅层地下水样进行测试分析,采用Piper三线图、Gibbs图和因子分析方法,对不同水体水化学特征及其影响因素进行讨论.结果表明:地表水水体总溶解性固体(TDS)质量浓度表现为枯水期丰水期平水期,浅层地下水表现为枯水期平水期丰水期,地表水TDS质量浓度明显高于浅层地下水.地表水中主要阴阳离子为Na~+、Cl~-和SO_4~(2-),水化学类型主要为SO_4~(2-)-Cl~--Na~+型;浅层地下水离子以HCO_3~-、Ca~(2+)和Mg~(2+)为主,表现为HCO_3~--Ca~(2+)-Mg~(2+)型.结合Gibbs图和因子分析可知,地表水受蒸发作用、地表径流以及采煤活动等因素影响,浅层地下水在一定程度上体现出大气降水和地表水补给的特点,受岩石风化作用影响较为明显.     

Impact of Ca2+ and Mg2+ on the Removal of F− by Magnesium Potassium Phosphate

This study investigates the influence of Ca²⁺ and Mg²⁺ on the removal of F^? by magnesium potassium phosphate (MPP) from water. The kinetic experiments reveal that the F^? concentration decreased from 3.5 to 3.31 mg L^?1 in a single (F^?) system and to 1.45 mg L^?1 in a ternary system (F^?, Ca²⁺, and Mg²⁺) after 1 min, respectively. Thus, the F^? removal efficiencies are found to increase by about 53% with the co‐active effect of Ca²⁺ and Mg²⁺ in the solution. Moreover, Ca²⁺ and Mg²⁺ are almost completely removed in the F^?, Ca²⁺, and Mg²⁺ system. According to the pseudo‐first‐order modeling, the rate constants k for F^?, Ca²⁺, and Mg²⁺ are 0.00348, 0.0106, and 0.0159 min^?1 respectively; thus, Mg²⁺ > Ca²⁺ > F^?. In the ternary system, the removal efficiencies are 53.29–66.03% for F^?, 99.99–100% for Ca²⁺, and 87.21–95.19% for Mg²⁺ with initial pH 5–10. The removal efficiencies of F^? increases with increases in initial concentrations of F^?, Ca²⁺, and Mg²⁺. The removal of F^? is governed by two routes: 1) adsorption by electrostatic interactions and outer sphere surface complexation; 2) co‐precipitation with Ca₃(PO₄)₂, CaHPO₄, Mg₃(PO₄)₂, and Mg(OH)₂.     

Effects of ultrafiltration on salt migration and isotopic composition of pore water in groundwater depression area in Hengshui,NCP

Clay aquitards are semipermeable membranes that allow groundwater flow while retarding solute migration has been researched extensively but also subjected to much debate. At present, there is no evidence of whether the physical and chemical properties of clay soil and the isotopic composition of pore water affect the semipermeable membrane effect. In this study, we collected clay samples from drilling cores (30–90 m) in the Hengshui area located in the North China Plain (NCP), then extracted pore water using a high-pressure squeezing device. Vertical hydrochemical and isotopic profile variation trends for the pore water were revealed using hydrochemical (Cl⁻, Na⁺, Ca²⁺, K⁺, Mg²⁺, and SO₄²⁻) and stable isotopic measurements of H, O and Cl. The results showed that the hydrochemical clay interlayer pore water of the saline aquifer is Cl/SO₄-Na/Mg type and the average total dissolved solids (TDS) are 10.17 g/L. However, the hydrochemical clay aquitard pore water is of the Cl/SO₄-Na/Ca type with an average TDS of 1.90 g/L. The hydrochemical clay interlayer pore water of aquifer II is of Cl-Na/Ca type with an average TDS of 1.10 g/L. Our results showed that the water quality of the aquifer II is not affected by the upper part of the saline aquifer, thus the clay aquitard acts as a significant barrier to salt movement. A polarization layer concentrated in ions was formed between the upper part of the saline aquifer and the clay aquitard. The concentration polarization layer increases the salt-inhibition effect. H, O and Cl isotopic composition results showed significant fractionation. The pore water of aquifer II lacked heavy isotopes (²H, ¹⁸O, ³⁷Cl), but had significant heavy isotope enrichment in the concentrated polarized layer (the δ²H value was −76‰, the δ¹⁸O value was −8.4‰, and the δ³⁷Cl value was 1.59‰). Hyperfiltration thus played a significant role in isotope fractionation.     

Origin and evolution of two contrasting thermal groundwaters (CO2-rich and alkaline) in the Jungwon area,South Korea: Hydrochemical and isotopic evidence

In the Jungwon area, South Korea, two contrasting types of deep thermal groundwater (around 20–33 °C) occur together in granite. Compared to shallow groundwater and surface water, thermal groundwaters have significantly lower δ¹⁸O and δD values (> 1‰ lower in δ¹⁸O) and negligible tritium content (mostly < 2 TU), suggesting a relatively high age of these waters (at least pre-thermonuclear period) and relatively long subsurface circulation. However, the hydrochemical evolution yielded two distinct water types. CO₂-rich water (P_CO2 = 0.1 to 2 atm) is characterized by lower pH (5.7–6.4) and higher TDS content (up to 3300 mg/L), whereas alkaline water (P_CO2 = 10^− 4.1–10^− 4.6 atm) has higher pH (9.1–9.5) and lower TDS (< 254 mg/L). Carbon isotope data indicate that the CO₂-rich water is influenced by a local supply of deep CO₂ (potentially, magmatic), which enhanced dissolution of silicate minerals in surrounding rocks and resulted in elevated concentrations of Ca²⁺, Na⁺, Mg²⁺, K⁺, HCO₃⁻ and silica under lower pH conditions. In contrast, the evolution of the alkaline water was characterized by a lesser degree of water–rock (granite) interaction under the negligible inflow of CO₂. The application of chemical thermometers indicates that the alkaline water represents partially equilibrated waters coming from a geothermal reservoir with a temperature of about 40 °C, while the immature characteristics of the CO₂-rich water resulted from the input of CO₂ in Na–HCO₃ waters and subsequent rock leaching.     

Hydrochemical Analyses and Evaluation of Groundwater Resources of North Jordan

The hydrochemical analyses of twenty-three springs were used to determine the properties and types of groundwater of the Tertiary-Quaternary Aquifer of northern Jordan. The result shows that the geological formation influences the quality of the investigated groundwater more than the anthropogenic factors. The water of the Quaternary-Tertiary aquifer is enriched in Ca⁺⁺ due to the dissolution of the nearby carbonate rocks. The investigated water has a low EC values with Ca(Na)-HCO₃ water type. Most springs belong to this hydrochemical facies except Malka. Groundwater in the Malka wells has high salinity with NaCl waters and a strong Ca(Mg)-HCO₃ facies (900 to 1000 mg/l TDS). The area long-term hydrochemical data have been also evaluated; general trend of increase of the analyzed ion was observed. Bicarbonate represents the most abundant anion in the studied water, which exceeds the permissible limits. Nitrates (NO ₃ ^? ) also exceed the permissible limit and are the most common contaminant in the investigated water. Data on dissolved major and trace elements (K⁺, Na⁺, Mg²⁺, Ca²⁺, Cl^?, SO ₄ ^2? , Fe, Zn, Cu and Pb) in the investigated water revealed that the concentrations lie within the natural background range. The positive correlation values between various ions indicate that most of ions come from same lithological sources. According to the residual sodium carbonate, and EC values, the studied springs are suitable for agricultural purposes.     

Strontium Migration in Groundwater of Fluvioglacial Sediments in the Khibiny Massif

The regularities of Sr absorption by different Quaternary fluvioglacial sediments, containing groundwater within the Khibiny massif, have been studied. The studied sediments have been shown to adsorb Sr as a result of the cation exchange and complexing on the solid phase surface, which is responsible for the absorbing capacity of the sediments in the wide range of natural water pH. The base exchange capacity of Sr has been established to largely depend on the concentration of the macrocomponents (Ca²⁺ and Mg²⁺) in the groundwater. It has been noted that the migration mobility of Sr is low under the conditions of almost neutral water typical of the soil horizon in the studied area.     

Controls of Geochemical and Hydrogeochemical Factors on Arsenic Mobility in the Hetao Basin,China

High arsenic (As) groundwater is frequently found in inland basins, but little is known about As pools in sediments and their influences on aqueous As distributions. The Hetao Basin is a typical inland basin, where groundwater As concentrations generally increase from alluvial fans to flat plain. Two sites are only 1700 m apart, but groundwater As concentrations at the depth range of 15 to 80 m are quite different, ranging from 7.0 to 31.7 μg/L at site B1 and from 5.2 to 99.8 μg/L at site B2. Sediment geochemistry and groundwater hydrochemistry at two sites were characterized. No distinct differences were observed in the bulk geochemistry of sediments. Sequential extractions of 39 sediments were conducted to determine why As was easily released to groundwater at one site and not the other. Results showed that at site B1 most of solid As was associated with amorphous Fe-(oxyhydr)oxides, whereas at site B2 the strong adsorption pool dominated. Furthermore, higher dissolved Fe²⁺ and lower ORP in groundwater at site B2 suggested more strongly reducing conditions compared to site B1. High concentrations of NH₄⁺ and HCO₃⁻ at site B2 were consistent with As release coupled to microbially induced reductive dissolution of Fe-(oxyhydr)oxides. Other processes, such as the competitive adsorption of HCO₃⁻, As desorption under weakly alkaline pH conditions, may also influence the partitioning of As between groundwater and sediments. This study highlights the differences in how As is associated with sediments between high and low As aquifers and the contribution of chemical characteristics to As release.     

Hydrogeochemistry and quality of groundwater in a part of Damodar Valley,Eastern India: an integrated geochemical and statistical approach

The influence of geochemical processes and quality of groundwater in a rural tract of Damodar Valley region were investigated. The study has distinguished the groundwater as fresh, soft to moderately hard and mainly CaHCO₃ type. The paired samples student’s t test shows the significant seasonal variations of pH, HCO₃^?, and Fe. Amphoteric exchange has lessened HCO₃^? concentration in post-monsoon which subsequently has caused to drop pH. Quite the reverse, the monsoon precipitation has triggered the additional release of Fe from iron-bearing sediments. The contaminant Cl^? is from the domestic wastewater as is evidenced by field observations. The inter-variable relations, cation and anion mechanisms, and mineral saturation indices reveal that the dissolutions of silicate and carbonate minerals are the primary sources of major ions in groundwater. The chloro-alkaline indices showed the role of ion exchange too in water chemistry. The R-mode factor analysis also successfully identified two dominant processes regulating water chemistry—geogenic sources (Ca²⁺, Mg²⁺, Na⁺, and HCO₃^?) and anthropogenic inputs (mainly Cl^?). The groundwater is found unsuitable for drinking at 82 and 93% of wells in pre- and post-monsoon seasons, respectively mainly due to elevated Fe content. The water from more than 90% of wells is appropriate for irrigation uses. The study recommends the proper treatment of contaminated water for consumption and measures to protect the groundwater from the waste water infiltration.     

Geochemical and Spatial Appraisal of Fluoride in the Soils of Indo‐Gangetic Plains of India Using Multivariate Analysis

The geochemical characteristics and the spatial distribution of the fluoride were studied in the soils of Indo‐Gangetic plains using multivariate analysis. The fluoride (F) distribution in soil profiles and surface soil (0–15 cm) samples were studied. It was found that total fluoride (TF) in the profiles ranged from 248 to 786 mg kg^?1 with a mean of 515.1 mg kg^?1 whereas CaCl₂ extractable soluble fluoride (F_Ca) was found to be in the range of 1.68 to 99.1 mg F kg^?1 soil. On the other hand, in surface soils, the TF and F_Ca ranged from 118 to 436 mg kg^?1 with a mean of 251.2 mg kg^?1 and 1.01 to 5.05 mg kg^?1 with a mean of 2.12 mg kg^?1, respectively, in the study area. The principal component analysis revealed that the natural weathering of fluoride bearing rock and minerals, various ion‐exchange and dissolution processes in the soil, alkalinity, sodium adsorption ratio, calcium (Ca), magnesium (Mg), and clay contents of the soil are responsible for high fluoride occurrence in the area. The fluoride contamination index developed by using these factors could explain more than 76% variance of F contamination due to F_Ca in soils. The interpolated kriged map of F_Ca in surface soil indicated a distinct loop of 1.0–2.0, 2.0–3.0, 3.0–4.0, and >4.0 mg kg^?1.     

Chloride source delineation in an urban-agricultural watershed: Deicing agents versus agricultural contributions

Analyses (n = 525) of chloride (Cl⁻), bromide (Br⁻), nitrate as nitrogen (NO₃-N), sodium (Na⁺), calcium (Ca²⁺) and potassium (K⁺) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl⁻ originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl⁻ concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl⁻ concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl⁻ to Br⁻ (p = .045), to NO₃-N (p < .0001), to Ca²⁺ (p < .0001), and to Na⁺ (p < .0001) to be significantly different between urban and agricultural waters. While Cl⁻ ratios indicate that road salt was the dominant source of Cl⁻ in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl⁻ dynamics; however, agricultural practices contributed Cl⁻ year-round, elevating stream base flow Cl⁻ concentrations above the background level.     

Hydrogeochemistry and environmental impact of geothermal waters from Yangyi of Tibet,China

The Yangyi geothermal field, located 72 km northwest to Lhasa City, capital of Tibet, has a high reservoir temperature up to at least 207.2 °C. The geothermal waters from both geothermal wells and hot springs belong to the HCO₃ (+CO₃)–Na type. Factor analysis of all the chemical constituents shows that they can be divided into two factors: F₁ factor receives the contributions of SO₄²⁻, Cl⁻, SiO₂, As, B, Na⁺, K⁺, and Li⁺; whereas F₂ factor is explained by HCO₃⁻, F⁻, CO₃²⁻, Ca²⁺, and Sr²⁺. The F₁ factor can be regarded as an indicator of the reservoir temperature distribution at Yangyi, but its variable correlation with the results of different geothermometers (Na–K, quartz and K–Mg) does not allow one to draw further inferences. Different from F₁, the F₂ factor is an indicator of a group of hydrogeochemical processes resulting from the CO₂ pressure decrease in geothermal water during its ascent from the deep underground, including transformation of HCO₃⁻ to CO₃²⁻, precipitation of Ca²⁺ and Sr²⁺, and release of F⁻ from some fluoride-bearing minerals of reservoir rocks. The plot of enthalpy vs. chloride, prepared on the basis of Na–K equilibrium temperatures, suggests that a parent geothermal liquid (PGL) with Cl⁻ concentration of 185 mg/L (that of sample YYT-8) and enthalpy of 1020 J/g (corresponding to a temperature of 236–237 °C, i.e., somewhat higher than that of sample YYT-6) is present in the geothermal reservoir of the Yangyi area, below both the Qialagai valley and the Bujiemu valley, although the samples less affected by mixing and cooling (YYT-6 and YYT-7) come from the second site. The discharge of geothermal waters with high contents of toxic elements such as B, As and F into the Luolang River, the only drinking water source for local residents, has caused slight pollution of the river water. Great care should therefore be taken in the geothermal water resource management at Yangyi.     

Water quality and hydrogeochemical characteristics of the River Buyukmelen,Duzce, Turkey

The River Buyukmelen is located in the province of Duzce in northwest Turkey and its water basin is approximately 470 km². The Aksu, Kucukmelen and Ugursuyu streams flow into the River Buyukmelen. It flows into the Black Sea with an output of 44 m³ s⁻¹. The geological succession in the basin comprises limestone and dolomitic limestone of the Yılanlı formation, sandstone, clayey limestone and marls of the Akveren formation, clastics and volcano‐clastics of the Caycuma formation, and cover units comprised of river alluvium, lacutrine sediments and beach sands. The River Buyukmelen is expected to be a water source that can supply the drinking water needs of Istanbul until 2040; therefore, it is imperative that its water quality be preserved. The samples of rock, soil, stream water, suspended, bed and stream sediments and beach sand were collected from the Buyukmelen river basin. They were examined using mineralogical and geochemical methods. The chemical constituents most commonly found in the stream waters are Na⁺, Mg²⁺, SO²⁻₄, Cl⁻ and HCO₃⁻ in the Guz stream water, Ca²⁺ in the Abaza stream water, and K⁺ in the Kuplu stream water. The concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺, SO²⁻₄, HCO⁻₃, Cl⁻, As, Pb, Ni, Mn, Cr, Zn, Fe and U in the Kuplu and Guz stream waters were much higher than the world average values. The Dilaver, Gubi, Tepekoy, Maden, Celik and Abaza streams interact with sedimentary rocks, and the Kuplu and Guz streams interact with volcanic rocks. The amount of suspended sediment in the River Buyukmelen in December 2002 was 120 mg l⁻¹. The suspended and bed sediments in the muddy stream waters are formed of quartz, calcite, plagioclase, clay (kaolinite, illite and smectite), muscovite and amphibole minerals. As, Co, Cd, Cr, Pb, Ni, Zn and U have all accumulated in the Buyukmelen river‐bed sediments. The muddy feature of the waters is related to the petrographic features of the rocks in the basin and their mineralogical compositions, as most of the sandstones and volcanic rocks (basalt, tuffite and agglomerate) are decomposed to a clay‐rich composition at the surface. Thus, the suspended sediment in stream waters increases by physical weathering of the rocks and water–rock interaction. Owing to the growing population and industrialization, water demand is increasing. The plan is to bring water from the River Buyukmelen to Istanbul's drinking‐water reservoirs. According to the Water Pollution Regulations, the River Buyukmelen belongs to quality class 1 based on Hg, Cd, Pb, As, Cu, Cr, Zn, Mn, Se, Ba, Na⁺, Cl⁻, and SO²⁻₄; and to quality class 3 based on Fe concentration. The concentration of Fe in the River Buyukmelen exceeds the limit values permitted by the World Health Organization and the Turkish Standard. Because water from the River Buyukmelen will be used as drinking water, it will have an adverse effect on water quality and humans if not treated in advance. In addition, the inclusion of Mn and Zn in the Elmali drinking‐water reservoir of Istanbul and Fe in the River Buyukmelen water indicates natural inorganic contamination. Mn, Zn and Fe contents in the waters are related to geological origin. Moreover, the River Buyukmelen flow is very muddy in the rainy seasons and it is inevitable that this will pose problems during the purification process. Copyright © 2005 John Wiley & Sons, Ltd.     

巴丹吉林沙漠湖泊水化学空间分布特征

通过对巴丹吉林沙漠腹地拐子湖-地质公园一线51个湖泊水,8个泉水,12个井水及1个雨水水样的水化学成分分析,初步探讨了沙漠湖泊水化学分布特征及其影响因素.结果表明由东南边缘至腹地湖泊总体上依次呈硫酸盐型-碳酸盐型-氯化物型分布.东南边缘以Na+、Cl-、SO24-为主的湖泊因矿化度分异,形成Ca2+、Mg2+含量不同的三种亚型,其中高矿化度的Na-Cl-(SO4)型湖泊在腹地湖泊群中也有出现,表现出地理上的不连续分布;边缘若干湖泊受局部地理环境的影响水离子多含Na+、Cl-、CO32-+HCO3-.综合分析表明湖泊水化学型的空间分异与区域气候差异和气候变化有关,湖水直接或间接地接受当地降水补给,但不排除外源地下水补给对其有一定贡献.通过对比不同时段部分沙漠湖泊水化学特征发现近十年以来腹地湖泊补给源或受气候干暖化影响使其水化学特性较边缘湖泊的变化大.