Effects of alteration on element distributions in archean tholeiites from the Barberton greenstone belt,South Africa

Major and trace element and modal analyses are presented for unaltered, epidotized, and carbonated tholeiite flows from the Barberton greenstone belt. Au, As, Sb, Sr, Fe⁺³, Ca, Br, Ga, and U are enriched and H₂O, Na, Mg, Fe⁺², K, Rb, Ba, Si, Ti, P, Ni, Cs, Zn, Nb, Cu, Zr, and Co are depleted during epidotization. CO₂, H₂O, Fe⁺², Ti, Zn, Y, Nb, Ga, Ta, and light REE are enriched and Na, Sr, Cr, Ba, Fe⁺³, Ca, Cs, Sb, Au, Mn, and U are depleted during carbonization-chloritization. The elements least affected by epidotization are Hf, Ta, Sc, Cr, Th, and REE; those least affected by carbonization-chloritization are Hf, Ni, Co, Zr, Th, and heavy REE. Both alteration processes can significantly change major element concentrations (and ratios) and hence caution should be used in distinguishing tholeiites from komatiites based on major elements alone. The amount of variation of many of the least mobile trace elements in the altered flows is approximately the same as allowed by magma model calculations. Hence, up to about 10% carbonization and 60% epidotization of tholeiite do not appreciably affect the interpretation of trace-element models for magma generation.     

Investigation of time-dependent reactions of H+ ions with variable and constant charge soils: a comparative study

A sampling-separation method and a dynamic monitoring method were used to investigate the time-dependent reactions of H⁺ ions with two contrasting types of soil, variable charge soils (VCS) and constant charge soils (CCS), by directly evaluating H⁺ ion consumption and other relevant consequences. The results for both CCS and VCS show that H⁺ ion consumption, increase in positive surface charge and increase in soluble Al are all characterized by a rapid step followed by a slow one. The higher the content of free Fe oxides in the soil, the larger the increase in positive surface charge and in H⁺ ion consumption in the initial rapid step. This is due mainly to protonation on external surfaces. The gradual increase in positive surface charge in the slow step for the 3 VCSs is a result of H⁺ ion diffusion to the reactive sites of Fe–OH on internal surfaces. The very low content of free Fe oxides on internal surfaces of the 2 CCSs render a negligible increase in positive surface charge in the slow step. For the 3 VCSs, the gradual consumption of H⁺ ions in the slow process is the result of protonation, Al dissolution and/or transformation into exchangeable acidity. For the 2 CCSs, however, the gradual consumption is mainly the result of Al dissolution and/or transformation into exchangeable acidity. The time-dependent Al dissolution from both VCS and CCS is influenced by several factors such as mineral components, solubility and dissolution rates of the soils, and H⁺ ion concentration in soil suspensions.     

Biogeochemistry of trace metals (Mn, Sr, Rb, Ba, Cu, Zn, Pb and Cd) in a river-wetland-lake system (Balaton Region, Hungary)

Mn, Sr, Ba, Rb, Cu, Zn, Pb and Cd concentrations have been measured seasonally in the water and deposited sediments of the system comprising: Zala river (main input) — Lakes Kis-Balaton 1 and 2 (small artificial lakes created in a former bay of Lake Balaton) — Keszthely bay (hypertrophic part of Lake Balaton). The concentrations of the trace elements together with pH, alkalinity, dissolved cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), dissolved inorganic ligands (Cl^–, SO₄ ^2–), particulate Al, Ca, inorganic and organic carbon are used to assess the contamination of the study area and biogeochemical processes controlling trace element concentrations. Thermodynamic speciation calculations have also been utilized to enhance our understanding of the system. In the sediments Rb, Ba, Cu and Zn concentrations were mainly controlled by the abundance of the aluminosilicate fraction. Strontium was mainly associated with the calcium carbonate fraction. The aluminosilicate fraction constitutes a major sink for Mn and Cd but the concentration of these elements are also strongly related to calcite precipitation. The main processes that control the dissolved distribution of trace elements in the Balaton system were: solid phase formation (carbonate) for Mn; coprecipitation with calcite for Sr, Ba, Rb and possibly Mn and Cd; adsorption/desorption processes (pH dependent) for Zn and Pb; solubilization of Mn and precipitation of Cd and Cu in reed covered wetland areas where anoxic conditions were probably existing during the warm season. A preliminary budget of atmospheric and river input to Lake Balaton has also been outlined. Although Lake Balaton, is subjected to anthropogenic inputs mainly from agricultural and domestic activities, their impact on trace element concentrations in the Balaton system is very limited due to the efficiency of removal processes (i.e. adsorption and co-precipitation) and to high sedimentation rates and strong sediment re-suspension. Anthropogenic inputs are only detected for Pb.     

Tectonic-hydrothermal pegmatites

The Kiawa pegmatites, New Mexico, are thought to have formed by the process outlined in part I of this paper, i.e., by the reaction, Quartz + Muscovite + (Na⁺, K⁺) Perthite + H⁺.The pegmatites and country rocks were mapped and sampled in detail and geochemical data were obtained by spectrochemical analysis of separated minerals for 17 major and trace elements.Structural compatibility with the model is demonstrated by the occurrence of the pegmatites in structurally low pressure zones. Geochemical evidence indicates that quartz and muscovite, the raw materials for the reaction, were available before formation of the pegmatites. The distribution of major and trace elements in the minerals of the pegmatites and country rocks supports the model. Elements that were released by major reactions are found in secondary minerals in the country rocks and/or in pegmatite minerals. The distribution of barium in the minerals is that which would be predicted from its known geochemical behavior. Geologic evidence suggests that the pegmatites formed synkinematically during regional metamorphism.Other features of the Kiawa pegmatites, such as albitization, structural control of element distributions, and possibly an older generation of pegmatites, are shown to be in accord with the proposed model. Certain features of the pegmatites are not amenable to a magmatic explanation.     

Distribution of trace elements in fracture fillings from the “Mina Fe” uranium deposit (Spain) by sequential leaching: implications for the retention processes

Sequential leaching methods have been used to determine the mineralogical distribution of some trace elements for environmental purposes, such as radiological contamination of soils and sediments, bioavailability studies and natural analogues of deep geological radwaste disposals. In this context, a 7-step-sequential leaching protocol is applied to Fe(III)–U(VI)-rich fracture filling materials from the oxidised zone of the “Mina Fe” U deposit to identify and evaluate the main sinks of natural nuclides and other analogue trace elements, since it is crucial in the performance assessment of a nuclear waste repository.After a careful characterisation of the samples, the analytical data from each leaching step were statistically analysed and then interpreted in light of the mineralogical and geochemical features of the samples. Precise knowledge of the mineralogical distribution of trace elements by sequential leaching methods is quite complex, mainly due to cross-contamination throughout the different steps of the experiments. Thus, the results obtained suggest that U is retained as U-minerals, mainly oxides, closely associated with crystalline Fe-oxyhydroxides. Though Ce and La also form independent compounds, such as Ce oxides and La–Nd phosphates, they are mainly retained by the amorphous Mn-oxyhydroxides. However, the crystalline Mn-oxyhydroxides are the main sink for Ni and crystalline Fe-oxyhydroxides mainly retain P.     

Geochemical estimation of the potential danger of waste rocks from the Veduginskoe deposit

Using a series of analytical and experimental methods, a predictive estimate was obtained for the possible environmental impact of the waste rocks of the Veduginskoe gold deposit. All samples of the country rocks were analyzed for major and 13 trace elements. This allowed us to demonstrate that the accumulation of elements in the water phase (water and weak acid extracts) is not always correlated with their contents in the solid material but controlled by their chemical speciation in the water-rock system. The dynamics of 20-week leaching of a series of contrasting rock samples supported the plausibility of criteria selected for their differentiation: the filtrates of one group remained neutral to weakly alkaline up to the end of experiments, whereas an “acid mine drainage” was produced in the other group. Acid sulfate solution with high contents of Fe, Al, and heavy metals can also accumulate Be, As, and Hg. However, the slightly alkaline solutions that have not received proper attention during environmental protection operations may transport elements with specified maximum permissible concentrations (MPC): anion-forming Sb, As, and Mo; amphoteric Be; and supertoxic Hg.     

西沙石岛西科1井生物礁碳酸盐岩地球化学特征

对西科1井生物礁碳酸盐岩样品进行了地球化学(常量组分、微量及稀土元素含量等)分析, 旨在探讨生物礁的形成演化以及所记录的环境变化信息.结果表明: 西科1井岩心在井深36 m附近存在地球化学参数的显著变化, 暗示该深度是一处重要的地层界面或环境突变界面.岩心中的常量组分可以分为3类组合: 以CaO为主, 辅以K₂O的原生碳酸岩组分, 该组分对应的主要造岩矿物是方解石, 代表了未经白云岩化的生物礁原生碳酸盐沉积; 以MgO为主, 辅以Na₂O和P₂O₅, 代表了白云岩化作用中的富集组分, 反映了相对封闭的泻湖环境; 以SiO₂为主, 加以Al₂O₃、TiO₂、Fe₂O₃和MnO, 代表造礁生物对这些组分的富集作用, 但不能排除火山组分少量混入的可能性.相对于全球第四纪碳酸盐岩、上陆壳及页岩的平均值, 岩心碳酸盐岩中大部分微量元素和稀土元素含量都较低.岩心中氧化还原敏感性微量元素(RSE)含量较低, 指示岛礁发育过程中大部分时期处于氧化环境条件下, 而RSE含量在岩心中的大幅波动体现出氧化/还原环境的交替变化.微量元素含量、ΣREE、ΣLREE、ΣHREE、LREE/HREE、δCe、δEu等地球化学指标在岩心中的分布与岩心样品的矿物组成无明显的相关性, 说明成岩作用和白云岩化作用并没有造成微量和稀土元素含量及特征指标的明显变化.      

Impact of termite activity on soil environment: A perspective from their soluble chemical components

An investigation on varied types of termite mounds relative to the nearby soils that are not inhabited by the termites in different places of Cameroon show that the activity of the termites is increasing the contents of most major and some trace elements in the termite mounds, except for Si and sometimes Fe, Mn, Na and K. These released elements are relocated into newly formed mineral phases that are dissolved by either H₂O or dilute HCl leachings. The Ca and Mn released by the termite activity testify for crystallization of Ca-Mg carbonates and phosphates as well as of Fe oxy-hydroxides and/or Mn hydroxides. Termite activity also induces an increase in the lanthanide contents, the mound materials being especially enriched in light lanthanides relative to the corresponding soils without termite activity. The shapes of the patterns support precipitation of Mn-Fe oxy-hydroxides and Ca carbonates-phosphates. The increased amounts of Eu and Ce linked to termite activity seem to relate to the occurrence of reducing agents that are released by the termites, modifying Eu⁺³ into Eu⁺² and Ce⁺⁴ into Ce⁺³, favoring in turn selective incorporation of Eu⁺² and Ce³⁺ in the new phases of the termite mounds. Another consequence of the termite activity is the precipitation of H₂O and HCl extractable phases having low Sr/Ca ratios. Even if the K/Rb values of the termite mounds are typical for common soil-forming silicate minerals, their relocation by an inorganic process alone does not explain an abnormally high ratio in the H₂O leachable mineral phases. It was also shown that the main source for K and Rb of the dissolved phases is not only the interlayer site of clay particles, but also nutrients immobilized in and by the termites.     

Internal consistency of a water analysis and uncertainty of the calculated distribution of aqueous species at 25°C

Many water analyses contain more than the minimum number of analytical determinations needed to calculate the distribution of species at ~ 25°C. The speciation of a water that contains $\text{n}$ cations and ligands other than H⁺ and OH^? can be calculated if just $\text{n}$ analytical determinations are available. In the frequent case where $\text{n + 1}$ (or more) determinations are available, one can calculate from the speciation a value for the ($\text{n + 1}$)th variable. The comparison between this computed value and its analytical counterpart (not used in calculating the speciation) constitutes a test for internal consistency among the $\text{n + 1}$ determinations that make up the whole analysis.Application of this test requires knowing the uncertainties of the calculated speciation and of the value computed for the ($\text{n + 1}$)th variable from the speciation. Such uncertainties have been ignored in previous algorithms, but have been determined herein by a Monte Carlo method of error propagation which is very well suited to systems of nonlinear algebraic equations.By comparing the titration alkalinity against the alkalinity calculated from the speciation, several published analyses for which the cation/anion balance is < 3% can be shown to be internally inconsistent. Such analyses may be unsuitable for geochemical calculations (water/rock interaction, estimation of reservoir temperatures, etc.).Several existing speciation algorithms disregard the possibility that the analytical data used as input are internally inconsistent.     

Dissolution kinetics of galena in acid NaCl solutions at 25—75 °C

Experiments on dissolution kinetics of galena were performed in 1 mol l⁻¹ NaCl solutions at pH 0.43–2.45 and 25–75 °C. When the dissolution reaction is far from equilibrium, a linear relation exits between the dissolution rate, r, and the H⁺ ion activity, [H⁺]. The rate law for galena dissolution is given by the following equation: r=k[H⁺]. With respect to H⁺, the dissolution reaction is in the first order. The apparent rate constant, k, has values of 2.34×10⁻⁷ mol m⁻² s⁻¹ at 25 °C, 1.38×10⁻⁶ mol m⁻² s⁻¹ at 50 °C, and 7.08×10⁻⁶ mol m⁻² s⁻¹ at 75 °C. The activation energy of dissolution reaction is 43.54 kJ mol⁻¹. The mechanism of dissolution is suggested to be surface chemical reaction, and the rate determining step is the dissociation of the Pb–S bond of the surface complex, which releases Pb²⁺ into the solution.     

Compositional evolution of grossular garnet from leucotonalitic pegmatite at Ruda nad Moravou, Czech Republic; a complex EMPA, LA-ICP-MS, IR and CL study

Five distinct paragenetic, morphological and compositional types of grossular garnet (G1, G2, G3, G4, G5) were distinguished within the individual (sub)units of the zoned leucotonalitic pegmatite cutting serpentinized lherzolite with rodingite dikes at ??ár near Ruda nad Moravou, Staré Město Unit, Northern Moravia. Detailed study using Electron Microprobe Analysis, Laser Ablation Inductively Coupled Plasma Mass Spectrometry, Cathodoluminiscence and Infrared Spectroscopy revealed distinct compositional trends in major, minor and trace elements. The contents of Fe³⁺, Mn, Mg and Ti increase from early garnet (G1) in the outermost grossular subunit through the interstitial garnet (G2) in the leucocratic subunit to graphic intergrowths of quartz+garnet (G3) in the coarse-grained unit. Then these constituents decrease in inclusions of garnet (G4) from the blocky unit and large crystals of garnet (G5) from the quartz core. Some trace elements (V, Ni, Y) exhibit the same trends, only Be evidently increases in garnet from border zone to the centre. Fluorine has negative correlation with Fe³⁺ as well as some trace elements (Ta, Pb). Concentrations of H₂O in garnets, up to 0.22 wt.% H₂O, are comparable with spessartine-almandine garnets from the Rutherford No. 2 pegmatite, Virginia, and grossular garnets from high-temperature calc-silicate rocks (skarns). Water contents correlate positively with Fe³⁺, but inversely with F. The use of water contents in garnet to elucidate the fluctuations of activity of H₂O during the pegmatite formation is only limited; the incorporation of hydrous defects seems to be controlled instead by crystal-structural constraints. However, the sum of all volatile components (H₂O + F) increases about twice from the outermost subunit to the centre of the pegmatite body.     

Identification of hydrogeochemical processes and pollution sources of groundwater resources in the Marand plain,northwest of Iran

The main aims of the present study are to identify the major factors affecting hydrogeochemistry of groundwater resources in the Marand plain, NW Iran and to evaluate the potential sources of major and trace elements using multivariate statistical analysis such as hierarchical clustering analysis (HCA) and factor analysis (FA). To achieve these goals, groundwater samples were collected in three sampling periods in September 2013, May 2014 and September 2014 and analyzed with regard to ions (e.g., Ca²⁺, Mg²⁺, Na⁺ and K⁺, HCO₃ ^?, SO₄ ^2?, Cl^?, F^? and NO₃ ^?) and trace metals (e.g., Cr, Pb, Cd, Mn, Fe, Al and As). The piper diagrams show that the majority of samples belong to Na–Cl water type and are followed by Ca–HCO₃ and mixed Ca–Na–HCO₃. Cross-plots show that weathering and dissolution of different rocks and minerals, ion exchange, reverse ion exchange and anthropogenic activities, especially agricultural activities, influence the hydrogeochemistry of the study area. The results of the FA demonstrate that 6 factors with 81.7% of total variance are effective in the overall hydrogeochemistry, which are attributed to geogenic and anthropogenic impacts. The HCA categorizes the samples into two clusters. Samples of cluster C1, which appear to have higher values of some trace metals like Pb and As, are spatially located at the eastern and central parts of the plain, while samples of cluster C2, which express the salinization of the groundwater, are situated mainly westward with few local exceptions.     

Speciation of trace metals in leachate from a MSWI bottom ash landfill

Trace metal concentrations and speciation were determined in leachate from a municipal solid waste incinerator bottom ash landfill both experimentally and by thermodynamic model calculations. Total dissolved Cr, Sb and W concentrations determined directly by ICP-MS were up to two orders of magnitude higher than that determined upon preconcentration by anin-situ solid phase extraction technique based on 8-HQ cation exchanger which indicates oxyanion complex formation of these metals in the leachates. Speciation modeling suggests that a similar difference for Cu is caused by organic complexation. Lead and Zn concentrations determined by both methods were fairly comparable but very low, in the range 4–60 nmol l⁻¹. The low mobility of both metals can be modeled by assuming adsorption onto Fe-oxyhydroxides oxycoprecipitation with Ca-silicate hydrate phases. The resulting high retardation coefficients between 500 and 800 indicate that scavenging by these secondary weathering products in the MSWI bottom ash deposit can cause an efficient immobilization of both Pb and Zn.     

An EFTEM/HRTEM high-resolution study of the near surface of labradorite feldspar altered at acid pH: evidence for interfacial dissolution-reprecipitation

Using an approach combining high-resolution and energy-filtered transmission electron microscopy (HRTEM and EFTEM), we have studied with Å to nm-spatial resolution the interfacial region that delimits the near-surface altered zone and non-altered labradorite feldspar after dissolution under acid pH conditions. The interface is characterized by extremely sharp and spatially coincident changes in structure and chemistry. The 500-nm-thick altered zone is depleted in interstitial cations (Ca, Na, K) and Al, a framework element, whereas it is enriched in H, O, and Si. Modeling H⁺-alkali interdiffusion within a 500-nm-thick altered zone shows that volume interdiffusion cannot reproduce the sharp chemical interfaces measured by EFTEM. Based on these new data, we propose that the near-surface altered zone is a result of interfacial dissolution-reprecipitation, and not of preferential leaching of cations and interdiffusion with H⁺. This implies an intrinsic dissolution process that is stoichiometric, where the breaking of bonds and release of interstitial cations and framework elements (Al, Si, and O) to solution occur contemporaneously at equal relative rates from the original fluid–mineral interface.     

Groundwater contamination in parts of Nalgonda district,Telangana, India as revealed by trace elemental studies

The present paper deals with major and trace elements geochemistry of the groundwater from Nalgonda district, Telangana. The study area is very important in terms of anthropogenic activity like rapid industrial, urban development, pesticides, pharmaceutical, granite polishing and agro based industries. Inductively coupled plasma mass spectrometer (ICPMS) was employed to determine the concentration of trace elements in collected groundwater samples (bore well). These probe elements were further categorized as toxic elements (Pb, As, Cd, and V), alkaline earths (Sr and Ba), alkali metals (Li, Rb), transition metals (Cr, Mo and Ni), metallic elements (Cu, Fe, Zn, Al, Co), and other non-metallic elements (Se and Si). The groundwater quality was examined in perspective of Indian as well as World Health Organization drinking water standards. Based on the analytical results, groundwater in the study area is found to be slightly alkaline in nature and very hard, the average abundance of the major cations and anions is in the order of Ca⁺<Na⁺<Mg⁺<K⁺ and Cl^-<HCO₃ ^?<CO₃ ^?<SO₄ ^?<NO₃ ^?<F^– respectively. The dominant hydro chemical facies of groundwater is Na⁺ - HCO ₃ ^– – Cl^– and Na⁺ - Cl^– – HCO^– ₃ types.The results of trace elements shows that concentration of Pb, As, Cd, V in collected samples exceeding the desirable limits, and in the case of alkaline, alkali, transition, non-metallic elements, seventy per cent of the samples crossed the desirable limits, but all metallic elements viz. Cu, Fe, Zn, Al, Co is within the limits as per Indian as well as World Health Organizations drinking water standards. Factor analysis results shows that seven factors emerged as a significant contributor to the groundwater contamination is about 65.32 per cent. The spatial variation maps decipher trace elemental concentrations both geogenic and anthropogenic origin, by three zones i.e. ‘low’, ‘moderate’ and ‘high’ of the study area based on environment using Arc-GIS. High concentrations of trace elements are indicative of phenomenal rise in chemical composition and likely to have its origin from silicate weathering reactions and dissolution/precipitation processes supported by rainfall and anthropogenic activities, indiscriminate use of fertilizers/pesticides, and disposal of waste and sewage, release of reactive pollutants into the atmosphere by industries. Hence, this work is of immense societal benefit in terms of prevailing human health hazards in the study area with a direct relevance to such industrially populated regions elsewhere.     

Time and the crystallization of apatite in seawater

Carbonate fluorapatite has been synthesized in seawater in an experiment of nearly 10-years duration. The addition of phosphate to seawater whose fluoride concentration had been increased to 7.6 mg/l brought about an initial amorphous phosphate precipitate. After 20 months, a crystalline magnesium phosphate phase developed within the amorphous phosphate. Crystallization of apatite, which occurred during the last 3 years of the experiment, was accompanied by dissolution of the crystalline magnesium phosphate phase.The MgO content of the apatite (1.9 percent) is high in comparison to Tertiary and older apatite but similar to some young apatite; the CO₂ content (3.6 percent) is medium, and the fluorine content (2.2 percent) is low but again similar to some young apatite. The hydroxyl ion (OH^?) likely fills the need for additional fluorine-position atoms. The mole ratio of Ca plus substituent elements to P plus substituent elements (1.50) is low in comparison to the expected ratio of 1.67. The substitution of the hydronium ion (H₃O⁺) for Ca may account for this difference.The synthesis of apatite in seawater demonstrates that the factor of time overcomes the well known inhibiting effect of magnesium upon the crystallization of apatite. It also implies that given an adequate supply of phosphate, apatite can form in most ocean environments and likely plays a major pan in the control of the phosphate content of seawater.     

LA-ICP-MS微区原位准确分析含水硅酸盐矿物主量和微量元素

通过描述一种利用LA-ICP-MS准确测定含水硅酸盐矿物主量元素和微量元素含量的多外标、无内标分析方法.总结出该方法基于矿物化学计量式计算含水硅酸盐矿物中挥发分的相对含量,再将全部分析元素归一化到总金属氧化物含量(100%减含水量)的原理,利用多种天然成分的岩石标准玻璃(如MPI-DING玻璃和USGS玻璃)作为外标进行校正计算.利用该方法对角闪石、绿帘石、电气石和透闪石等含水硅酸盐矿物进行了分析,并与利用电子探针和微钻(直径300 μm)取样溶液-ICP-MS分析的结果进行了对比研究.研究结果表明:对于组成均一的主量元素的分析结果与电子探针分析数据一致,相对偏差集中在5%以内.除了那些分布异常不均一的元素(在300 μm尺度上),对微量元素的分析结果与溶液-ICP-MS分析结果具有很好的一致性,二者之间的相对偏差大部分集中在10%以内.研究结论为采用归一化校正策略,选择MPI-DING和USGS玻璃作为外标,利用LA-ICP-MS微区分析方法可以准确测定含水硅酸盐矿物中的主、微量元素含量.      

Geochemistry of dissolved and particulate elements in the major rivers of China (The Huanghe,Changjiang, and Zhunjiang rivers)

The relationship between the geochemistry of dissolved and particulate materials and geographic conditions was investigated. Samples of water and suspended particulate matter were collected from five locations in three of the major rivers of China (the Huanghe, Changjiang, and Zhunjiang rivers). Because these rivers generally flow parallel to latitudes and flow through diverse geologic and climate zones, they provide excellent opportunities for comparisons of solute transport. The geochemistry of these rivers is influenced strongly by climate. The low discharge of the Huanghe River influences the character of the major ionic materials (Cl^?+SO₄ ^2? and Na⁺+K⁺) as well as the high degree of mineralization within the system. Dissolved concentrations of both major ions and trace elements are lower in the southern reaches of the rivers. The highly mobile ions, such as, Na⁺ and Ca²⁺, are depleted from the suspended particulate material in the southern regions, while the relatively immobile ions of Al, Fe, Ti, Mn, and trace metals are concentrated within the suspended mateiral. The relative mobility of some elements as measured by the Dissolved Transport Index (DTI) changes with climate. The geology of the area drained by the rivers has a major influence on the geochemistry in areas of similar climate. Lowest leaching rates in the southern climates occur in areas dominated by granite, which is resistant to weathering. The composition of both cations and anions among the three tributaries of the Zhujiang River are dependent on the rocks that dominate each eregion. Some particulate forms of the rare earth elements are present in the highest concentrations in regions dominated by granite. The DTI calculated for the major rivers in China are much smaller than those computed for other major rivers of the world. The low concentration of heavy metals in the particulate material suggests that pollution in the rivers of China is less serious than in rivers of other industrialized countries.     

Evaluation of aquifer environment under Hazaribagh leather processing zone of Dhaka city

Hazaribagh is a densely populated area of Dhaka city where about 185 leather processing industries have been operating and discharging solid and liquid wastes directly to the low-lying areas, river and natural canals without proper treatment. The area is covered by alluvial deposits of Holocene age and is underlain by Pleistocene Madhupur clay. The Dupi Tila Formation of Mio-Pliocene age underlain by this yellowish gray to brick red clay bed serves as the main water-bearing aquifer of Dhaka city. To assess the environmental degradation as well as the groundwater environment, major anions, cations and heavy metals of water samples, heavy metals and organic carbon content of sediment samples were analyzed in this study. Analyses of tannery effluent detect high concentration of Na⁺, Mg²⁺, Cl⁻ and SO ₄ ²⁻ followed by Ca²⁺, NH ₄ ⁺ and K⁺ with remarkable contents of some trace elements, mainly Cr, Fe, Mn, S, Ni and Pb. Higher accumulations of Cr, Al and Fe are observed in topsoil samples with significant amounts of Mn, Zn, Ni and Cu. Concentrations of ions and all the investigated trace elements of sampled groundwater were within the maximum allowable limit for drinking water of the Department of Environment, Bangladesh (DoE), and World Health Organization (WHO). However, excessive concentrations of Cr, Pb, etc., have already been reported in the shallow groundwater (10–20 m) of the area. Due to excessive withdrawal the vulnerability of groundwater contamination in deeper parts cannot be avoided for the future.     

Groundwater Chemistry of the Mornag Aquifer System in NE Tunisia

The present paper investigates hydrochemical processes and water quality in the Mornag aquifer in NE Tunisia. Groundwater samples were collected during a field campaign, and were analysed for major and trace elements. The collected waters have a chemical facies rich in Ca²⁺, Na⁺ and Cl^-. Piper diagram shows a progressive increase in chloride ions along with increasing salinity. Saturation indexes calculated by using PHREEQC (USGS) show that the Mornag waters are slightly saturated with respect to carbonates (calcite and dolomite), while undersaturated with respect to gypsum, halite and other evaporitic minerals. The current composition of waters takes place via dissolution of halite and Ca-sulfates, where the increase in calcium is partially balanced by possible calcite precipitation. The relevant recorded pollutant is nitrate, which was likely dispersed from agricultural soils, while heavy metals were generally far below values of pollution thresholds, indicating no influence by mining activity.