Hydrogeological conditions and quality of ground waters in northern Banat,Pannonian basin

Geological relationships, hydrogeology and chemical composition of ground water in northern Banat were studied through the period 2000–2004 using the available background data from published and unpublished sources. Northern Banat is the extreme northeastern part of the Republic of Serbia and a geotectonic part of the vast Pannonian depression. The source of domestic and industrial water supply is only groundwater from artesian and subartesian aquifers of Lower Pleistocene (Q₁¹) and Upper Pleistocene (Pl₃²) sand deposits. The ground water, “peculiar” in chemical composition, is the only source of drinking water in the arid area. A notable variation in the chemical composition of artesian waters within the same geotectonic unit (Pannonian basin), abstracted for municipal water supplies of Kikinda, Novi Knezevac and Djala, has attracted attention of these authors. Our paper attempts to interpret the variation in the chemical composition of ground water and the cause of the variation by the interaction of ground water and rocks forming the aquifers on the case example of the water supply sources for the three mentioned towns. With respect to the depth and lithology of the aquifers, we interpret the varied chemical compositions of waters in the mentioned sources as a consequence of natural factors (geological environment), geological relationships and hydrogeological conditions.     

Some features of mineral waters in Russia

 The Russian Federation has many aquifers and these possess a wide range of chemical compositions. In Russia about 300 mineral water sources have been developed as spas and health resorts. More than 150 of them produce bottled mineral water. A brief historical revue is given. The study of mineral waters in Russia began as far back as the reign of Peter the Great (1682–1725). It has been prolonged by works of many Russian scientists. The details of the chemical composition of the different types of Russian mineral waters and some geological aquifer peculiarities are described. The most widely used classification of mineral waters in Russia is presented. The present condition of these waters and the government standards laid down for their use are described. Examples of different mineral waters are given. Received: 14 April 1998 / Accepted: 8 December 1998     

Interstitial water – sediment geochemistry of N, P and Fe and its response to overlying waters of tropical estuaries: a case from the southwest coast of India

 The concentrations of N, P and Fe in surface sediments and interstitial and overlying (bottom and surface) waters of the Ashtamudi estuary located in the southwest coast of India are reported along with the various chemical species of N (NO₂–N, NO₃–N, NH₃–N and total N) and P (organic P, inorganic P and total P) in interstitial and overlying waters and discussed in terms of the physico-chemical environment of the system. The interstitial water exhibits higher salinity values compared to bottom and surface waters, indicating the coupled effects of salt-wedge phenomena and gravitational convection of more saline-denser marine water downward through surface sediments. N, P and Fe as well as their chemical forms are enriched in the interstitial water compared to bottom and surface waters. However, the dissolved oxygen (DO) shows an opposite trend. The marked enrichment of NH₃–N in the interstitial water and its marginal presence in bottom and surface waters, together with the substantial decrease in the DO concentrations of bottom water and consequent increase in the concentrations of NO₂–N and NO₃–N in interstitial and bottom waters, points to the nitrification process operating in the sediment-water interface of the Ashtamudi estuary. The enrichment of total N, P and Fe in the interstitial water compared to the overlying counterparts and the positive correlation of sediment N, P and Fe with mud contents as well as organic carbon indicate that these elements are liberated during the early diagenetic decomposition of organic matter trapped in estuarine muds. Received: 5 Oktober 1998 · Accepted: 9 February 1999     

Contaminant dispersion at the rehabilitated Mary Kathleen uranium mine, Australia

This study reports on the transfer of contaminants from waste rock dumps and mineralised ground into soils, sediments, waters and plants at the rehabilitated Mary Kathleen uranium mine in semi-arid northwest Queensland. Numerous waste rock dumps were partly covered with benign soil and the open pit mine was allowed to flood. The mineralised and waste calc-silicate rock in the open pit and dumps has major (>1 wt%) Ca, Fe and Mg, minor (>1,000 ppm) Ce, La, Mn, P and S, subminor (>100 ppm) Ba, Cu, Th and U, and trace (<100 ppm) As, Ni, Pb, Y and Zn values. Consequently, chemical and physical weathering processes have acted on waste rock and on rock faces within the open pit, mobilising many elements and leading to their dispersion into soils, stream sediments, pit water and several plant species. Chemical dispersion is initiated by sulfide mineral breakdown, generation of sulfuric acid and formation of several soluble, transient sulfate minerals as evaporative efflorescent precipitates. Radiation doses associated with the open pit average 5.65 mSv year⁻¹; waste dumps commonly have lower values, especially where soil-covered. Surface pit water is slightly acid, with high sulfate values accompanied by levels of U, Cu and Ni close to or above Australian water guideline values for livestock. Dispersion of U and related elements into soils and stream sediments occurs by physical (erosional) processes and from chemical precipitation. Plants growing in the mine void, on waste dumps and contaminated soil display evidence of biological uptake of U, LREE, Cu and Th and to a lesser degree of As, Ni, Pb, Y and Zn, with values being up to 1–2 orders of magnitude above background sites for the same species. Although rehabilitation procedures have been partly successful in reducing dispersion of U and related elements into the surrounding environment, it is apparent that 20 years after rehabilitation, there is significant physical and chemical mobility, including transfer into plants.     

Hydrogeochemical parameters for assessment of groundwater quality in the upper Gunjanaeru River basin,Cuddapah District,Andhra Pradesh,South India

In the management of water resources, quality of water is just as important as its quantity. In order to know the quality and/or suitability of groundwater for domestic and irrigation in upper Gunjanaeru River basin, 51 water samples in post-monsoon and 46 in pre-monsoon seasons were collected and analyzed for various parameters. Geological units are alluvium, shale and quartzite. Based on the analytical results, chemical indices like percent sodium, sodium adsorption ratio, residual sodium carbonate, permeability index (PI) and chloroalkaline indices were calculated. The pre-monsoon waters have low sodium hazard as compared to post-monsoon season. Residual sodium carbonate values revealed that one sample is not suitable in both the seasons for irrigation purposes due the occurrence of alkaline white patches and low permeability of the soil. PI values of both seasons revealed that the ground waters are generally suitable for irrigation. The positive values of Chloroalkaline indices in post-monsoon (80%) and in pre-monsoon (59%) water samples indicate absence of base-exchange reaction (chloroalkaline disequilibrium), and remaining samples of negative values of the ratios indicate base-exchange reaction (chloroalkaline equilibrium). Chadha rectangular diagram for geochemical classification and hydrochemical processes of groundwater for both seasons indicates that most of waters are Ca–Mg–HCO₃ type. Assessment of water samples from various methods indicated that majority of the water samples in both seasons are suitable for different purposes except at Yanadipalle (sample no. 8) that requires precautionary measures. The overall quality of groundwater in post-monsoon season in all chemical constituents is on the higher side due to dissolution of surface pollutants during the infiltration and percolation of rainwater and at few places due to agricultural and domestic activities.     

The geochemical role of phyto- and zooplankton in the extraction of chemical elements from water

This paper provides for the first time comparative assessment of the contents of 70 chemical elements occurring in the aquatic environment in water, phytoplankton, and zooplankton. The assessment was made using modern highly sensitive methods. The studies were performed at Beloyarskoe Reservoir, a manmade freshwater lake situated in the Middle Urals that has been studied in detail. The chemical elements were ranked in groups differing in the accumulation coefficient (AC) values for the phyto- and zooplankton. The comparison revealed that for the vast majority of chemical elements, the AC values were higher in zooplankton (53, or 76%) than in phytoplankton (17, or 24%). The average AC values for zooplankton (∼740 000) exceeded that for phytoplankton (∼68 000) by more than 10 times. It was found that some elements had very high AC values in zooplankton compared to phytoplankton. For instance for Nb, the ratio AC_zoo/AC_phyto was 1 200 000; for B, Ta, Sn, Lu, U, 300 000–500 000; for Sb and Y, 100 000–130 000; for La and Nd, 80 000–85 000; for Mo, Cd, Pr, Gd, Dy, Sc, Se, Bi, 20 000–30 000; and for Pd, Hf, Sm, Sb, Er, As, 10 000–20 000. It is concluded that zooplankton is sometimes more suitable for the biogeochemical indication of the pollution of natural water bodies, because the AC values for most elements are much higher in zooplankton than in phytoplankton and the total plankton. Considering the high assimilability of microelements and radionuclides, the plankton may serve not only as an indication but also as the mean of regulated purification of waterbodies from these elements.     

A methodological approach to water quality assessment in an ungauged basin,Buenos Aires,Argentina

The Reconquista River is one of the most polluted rivers in Latin America. This paper aims at identifying the dynamics of water quality in an area with low or “background” concentrations of pollutants within the Reconquista River system in order to better define levels of pollution in the main system. In order to describe the dynamics of water quality in the background area, we propose a methodology based on flow estimation with the instantaneous unit hydrograph model and on measurements of physical and chemical water variables under different hydrological conditions. Because of high dissolved oxygen and low ammonium and o-phosphate concentrations, the Arroyo Durazno, a tributary stream of the Reconquista River, is defined as a background area. When a storm event begins, the concentration of nitrates and the electrical conductivity diminish. An increase in dissolved organic carbon suggests an important input of carbon from hillslope runoff. The proportion of fulvic and humic acids also increases. On the receding limb of the hydrograph, nitrate concentration was lower than during maximum flow and organic carbon concentration remained high. This behavior, known as the “flushing effect”, suggests that the soluble material accumulated in the drainage area during dry periods is transported to the stream by leaching or “lixiviation” and surface runoff, thus raising solute concentrations during the first few hours of the storm. Water quality changes rapidly, even in background areas, due to its dependence on the flow. The methodology followed in this paper can also be applied to other basins with similar characteristics. Due to the difficulty in defining baseline areas for surface waters, a knowledge of background water quality and its dynamics is essential for understanding pollution trends and anthropogenic impacts on rivers.     

Interaction of acid mine drainage with waters and sediments at the Corona stream, Lousal mine (Iberian Pyrite Belt, Southern Portugal)

This study investigates the geochemical characteristics of the acid mine drainage discharged from the abandoned mine adits and tailing piles in the vicinity of the Lousal mine and evaluates the extent of pollution on water and on the stream sediments of the Corona stream. Atmospheric precipitation interacting with sulphide minerals in exposed tailings produces runoff water with pH values as low as 1.9–2.9 and high concentrations of (9,249–20,700 mg l⁻¹), Fe (959–4,830 mg l⁻¹) and Al (136–624 mg l⁻¹). The acidic effluents and mixed stream water carry elevated Cu, Pb, Zn, Cd and As concentrations that exceed the water quality standards. However, the severity of contamination generally decreases 4 km downstream of the source due to mixing with fresh waters, which causes the dilution of dissolved toxic metals and neutralization of acidity. Some natural attenuation of the contaminants also occurs due to the general reduced solubility of most trace metals, which may be removed from solution, by either co-precipitation or adsorption to the iron and aluminium precipitates.     

Biogenic silica in wetlands and their relationship with soil and groundwater biogeochemistry in the Southeastern of Buenos Aires Province,Argentina

Although phytoliths constitute part of the wetland suspended load, there are few studies focused on the quantification of them in the biogenic silica (BSi) pool. So, the aim of this paper is both to determine BSi content (diatoms and phytoliths) and its relationship with dissolved silica in surface waters, and the influence of soil and groundwater Si biogeochemistry in Los Padres wetland (Buenos Aires Province, Argentina). In the basin of the Los Padres wetland, dissolved silica (DSi) concentration is near 840 ± 232 μmol/L and 211.83 ± 275.92 μmol/L in groundwaters and surface waters, respectively. BSi represents an 5.6–22.1% of the total suspension material, and 8–34% of the total mineralogical components of the wetland bottom sediments. DSi and BSi vary seasonally, with highest BSi content (diatoms specifically) during the spring–summer in correlation to the lowest DSi concentration. DSi (660–917.5 μmol/L) and phytolith (3.35–5.84%) concentrations in the inflow stream are higher than in the wetland and its outflow stream (19.1–113 μmol/L; 0.45–3.2%, respectively), probably due to the high phytolith content in soils, the high silica concentration in the soil solution, and the groundwater inflow. Diatom content (5–16.8%) in the wetland and its outflow stream is higher than in the inflow stream (0.45–1.97%), controlling DSi in this system. The understanding of the groundwater–surface water interaction in an area is a significant element for determining the different components and the role that they play on the local biogeochemical cycle of Si.     

Aquifer chemistry of four high-temperature geothermal systems in Iceland

The deep water feeding wet-steam wells in four high-temperature geothermal areas in Iceland have highly variable salinity as reflected in the chlorine concentrations which vary from 20 to 19000 ppm. Using available values for equilibrium constants, the activities of 26 chemical species involving the major components of the reservoir water have been calculated and quantitative evaluations of solute/ solute, mineral/solute chemical equilibria in these geothermal systems have been made.The unflashed reservoir water is just saturated with calcite. The saline geothermal waters, which represent heated sea-water, are just saturated with anhydrite, but the dilute waters, which are of meteoric origin, are somewhat undersaturated with this mineral. The fluoride mobility is thought to be limited by an ionic exchange reaction where F^? replaces some of the OH^? in the layered silicates. The pH of the unflashed reservoir water is governed by ionic exchange equilibrium in which all the major cations participitate. At a given temperature it seems likely that the activity of one cation fixes the activities of all the other major cations and hydrogen ion. If this is so and we take all the other chemical equilibria which have been demonstrated to exist for granted, it turns out that the major element composition of the unflashed high-temperature geothermal waters is controlled by two independent variables only. These variables are the temperature and the supply to the water of the incompatible element chlorine, incompatible indicating that this element is not incorporated in the geothermal minerals.     

A Geochemical study of the groundwater in the Misli basin and environmental implications

The aim of this study was to determine geochemical properties of groundwater and thermal water in the Misli Basin and to assess thermal water intrusion into shallow groundwater due to over-extraction. According to isotope and hydrochemical analyses results, sampled waters can be divided into three groups: cold, thermal, and mixed waters. Only a few waters reach water–rock chemical equilibrium. Thermal waters in the area are characterized by Na⁺–Cl⁻–HCO₃⁻, while the cold waters by CaHCO₃ facies. On the basis of isotope results, thermal waters in the Misli basin are meteoric origin. In particular, δ¹⁸O and δ²H values of shallow groundwater vary from −10.2 to −12.2‰ and −71.2 to −82‰, while those of thermal waters range from −7.8 to −10.1‰ and from −67 to −74‰, respectively. The tritium values of shallow groundwater having short circulation as young waters coming from wells that range from 30 to 70 m in depth vary from 10 to 14 TU. The average tritium activity of groundwater in depths more than 100 m is 1.59 ± 1.16, which indicates long circulation. The rapid infiltration of the precipitation, the recycling of the evaporated irrigation water, the influence of thermal fluids and the heterogeneity of the aquifer make it difficult to determine groundwater quality changes in the Misli Basin. Obtained results show that further lowering of the groundwater table by over-consumption will cause further intrusion of thermal water which resulted in high mineral content into the fresh groundwater aquifer. Because of this phenomenon, the concentrations of some chemical components which impairs water quality in terms of irrigation purposes in shallow groundwaters, such as Na⁺, B, and Cl⁻, are highy probably expected to increase in time.     

Transport and sediment–water partitioning of trace metals in acid mine drainage: an example from the abandoned Kwangyang Au–Ag mine area, South Korea

Transport and sediment–water partitioning of trace metals (Cr, Co, Fe, Pb, Cu, Ni, Zn, Cd) in acid mine drainage were studied in two creeks in the Kwangyang Au–Ag mine area, southern part of Korea. Chemical analysis of stream waters and the weak acid (0.1 N HCl) extraction, strong acid (HF–HNO₃–HClO₄) extraction, and sequential extraction of stream sediments were performed. Heavy metal pollution of sediments was higher in Chonam-ri creek than in Sagok-ri creek, because there is a larger source of base metal sulfides in the ores and waste dump upstream of Chonam-ri creek. The sediment–water distribution coefficients (K _d) for metals in both creeks were dependent on the water pH and decreased in the order Pb ≈ Al > Cu > Mn > Zn > Co > Ni ≈ Cd. K _d values for Al, Cu and Zn were very sensitive to changes in pH. The results of sequential extraction indicated that among non-residual fractions, Fe–Mn oxides are most important for retaining trace metals in the sediments. Therefore, the precipitation of Fe(–Mn) oxides due to pH increase in downstream sites plays an important role in regulating the concentrations of dissolved trace metals in both creeks. For Al, Co, Cu, Mn, Pb and Zn, the metal concentrations determined by 0.1 N HCl extraction (Korean Standard Method for Soil Pollution) were almost identical to the cumulative concentrations determined for the first three weakly-bound fractions (exchangeable + bound to carbonates + bound to Fe–Mn oxides) in the sequential extraction procedure. This suggests that 0.1 N HCl extraction can be effectively used to assess the environmentally available and/or bioavailable forms of trace metals in natural stream sediments.     

Mineralogical and geochemical investigations of silicate-rich mine waste from a kyanite mine in central Virginia: implications for mine waste recycling

A kyanite mine in central Virginia produces a silicate-rich waste stream which accumulates at a rate of 450,000–600,000 tons per year. An estimated 27 million tons of this waste stream has accumulated over the past 60 years. Grain size distribution varies between 1.000 and 0.053 mm, and is commonly bimodal with modes typically being 0.425 and 0.250 mm and uniformity coefficients vary from 2.000 to 2.333. Hydraulic conductivity values vary from 0.017 to 0.047 cm/s. Mineralogy of the waste stream consists of quartz, muscovite, kyanite and hematite. Muscovite grains have distinct chemical compositions with significant Na₂O content (1.12–2.66 wt%), TiO₂ content (0.63–1.68 wt% TiO₂) and Fe content, expressed as Fe₂O₃ (up to 1.37 wt%). Major element compositions of samples were dominated by SiO₂ (87.894–90.997 wt%), Al₂O₃ (6.759–7.741 wt%), Fe₂O₃ (1.136–1.283 wt%), and K₂O (0.369–0.606 wt%) with other components being <1.000 wt%. Elements of environmental concern (V, Cr, Ni, Cu, Zn, As, Ag, Sn, Sb, Ba, Hg, Tl, and Pb) were detected; however, the concentrations of all elements except Ni were below that of the kyanite quartzites in the region from which the waste is derived. Both major and trace element compositions indicate minimal variation in composition. The waste stream has potential for recycling. Muscovite is suitable for recycling as a paint pigment or other industrial applications. Muscovite and hematite are commonly intergrown and are interpreted to be material where much of the elements of environmental concern are concentrated. Reprocessing of the waste stream to separate muscovite from other components may enable the waste stream to be used as constructed wetland media for Virginia and nearby states. Recycling of this mine waste may have a positive impact on the local economy of Buckingham County and aid in mitigation of wetland loss.     

Geochemical and Sr-isotopic characteristics of stream and spring waters from small-forested catchments at Seto,central Japan

Hydrogeochemical processes controlling surface water chemistry were examined in five small (<1.5 km ²) forested catchments that have contrasting bedrock lithologies of granite, and conglomerate, and are distributed in the southeast of Seto district, central Japan. Watersheds developed on these two bedrocks differ in their ability to neutralize atmospheric acid (pH ~4.5) deposition. The study was conducted to (1) characterize the hydrogeochemical processes controlling surface water chemistry, and (2) to elucidate acidification of spring and stream waters using data from three sampling campaigns conducted from August to October 2000. Stream and spring water solutes fall into two general groups according to concentration: alkaline, relatively high pH (5.2–7.7) and high cation concentrations (HCO ₃ ^-, Cl ^-, base cations), and dilute, low pH (4.2–5.5) waters. Concentrations of trace metals (Al, Ba, Sr) showed a strong negative correlation with pH, suggesting the mobility of these metals in the dissolved load of catchments underlain by Tokai conglomerate. The strontium isotope ratio ( ⁸⁷Sr/ ⁸⁶Sr) of rock and soil, plant, precipitation, and surface water samples was used to identify different reservoirs within the ecosystem. Low Si concentrations in stream and spring waters from the conglomerate area, with a relatively high pool of SiO ₂, >90 (wt%), suggest slow chemical weathering. The dissolved solute concentrations are generally of similar magnitude in stream waters within the catchments of similar bedrock lithology. The high inverse correlation ( r ²=0.72) between pH and SO ₄ ^– concentrations and the high positive correlation ( r ² =0.90) between Ba and SO ₄ ^– concentrations in waters draining Tokai conglomerate suggest that barite (BaSO ₄) is being dissolved in an acidic environment. The three catchments were identified as being sensitive to acidic deposition because the bedrock conglomerate provided little capacity to buffer acidic inputs. The soils from the granite area have a high cation-exchange capacity (CEC an average of 868 µmol/kg), and are nearly ten times greater than the soils from the conglomerate area. Because ion exchange, besides weathering, is the main source that counteracts soil acidification, the sensitivity to further acidification may increase.     

Hydrogeochemical study of the Terme and Karakurt thermal and mineralized waters from Kirşehir Area,central Turkey

The Terme and Karakurt thermal resorts are located in the center of Kirşehir city in central Anatolia. Thermal waters with temperatures of 44–60°C are used for central heating and balneologic purposes. Paleozoic rocks of the Kirşehir Massif are the oldest units in the study area. The basement of the Massif comprises Paleozoic metamorphic schist and marbles which partly contain white quartzite layers of a few tens of cm thickness. The metamorphic schists which are cut by granites of Paleocene age are overlain by horizontally bedded conglomerate, sandstone, claystone, and limestone of upper Paleocene-Eocene age. Among the thermal and cold waters collected from the areas of Terme and Karakurt, those from thermal waters are enriched with Ca–HCO₃ and cold waters are of Ca–Mg–HCO₃ type waters. The pH values of samples are 6.31–7.04 for the thermal well waters, 6.41 for thermal spring, 7.25 and 7.29 for the cold waters, and 7.52 for the Hirla lake water. EC values are 917–2,295 μS/cm for the thermal well waters, 2,078 μS/cm for thermal spring, and 471 and 820 μS/cm for the cold springs. The lowest TDS content is from water of T10 thermal well in the Terme area (740.6 mg/l). The hot and cold waters of Terme show very similar ion contents while the Karakurt hot waters at western most parts are characterized by distinct chemical compositions. There is ion exchange in thermal waters from the T5 (5), T6 (6), T12 (7), and T1 (8) wells in the Terme area. The thermal waters show low concentrations of Fe, Mn, Ni, Al, As, Pb, Zn and Cu. Waters in the study area are of meteoric origin, and rainwater percolated downwards through faults and fractures, and are heated by the geothermal gradient, later rising to the surface along permeable zones. δ¹³C_VPDB values measured on dissolved inorganic carbon in samples range from −1.65 to +5.61‰ for thermal waters and from −11.81 to −10.15‰ for cold waters. Carbon in thermal waters is derived from marine carbonates or CO₂ of metamorphic origin while carbon in cold waters originates from freshwater carbonates.     

Solute geothermometry of springs and wells of the Los Azufres and Las Tres Vírgenes geothermal fields,Mexico

Subsurface reservoir temperatures of two important Mexican geothermal systems (Los Azufres and Las Tres Vírgenes) were estimated by applying all available solute geothermometers for 88 and 56 chemical data measurements of the spring waters and fluids of the deep geothermal wells, respectively. Most of the chemical data for spring water of these two geothermal fields are for HCO₃ water, followed by SO₄ and Cl types. For the Los Azufres geothermal field (LAGF), the reservoir temperatures estimated by Na-K geothermometers for springs of HCO₃ and SO₄ waters, and by Na-Li and Li-Mg geothermometers for Cl water, are close to the average bottom-hole temperature (BHT) of the geothermal wells. However, all reservoir temperatures for spring waters from the Las Tres Vírgenes geothermal field (LTVGF) estimated by all solute geothermometers indicated significantly large differences (low temperatures) compared to the BHT. Evaluation of inferred reservoir temperatures for spring waters of the LAGF and LTVGF suggests that not all springs nor all solute geothermometers provide reliable estimation of the reservoir temperatures. Even though chemical equilibrium probably was not achieved in the water–rock system, Na-K geothermometers for HCO₃ water (peripheral water mainly of meteoric origin with little geothermal component) and SO₄ water (geothermal steam heated) and Na-Li and Li-Mg geothermometers for Cl-rich spring water (fully mature geothermal water) of the LAGF indicated reservoir temperatures close to the BHT. However, in comparison with the geothermometry of spring water of the LAGF and LTVGF, fluid measurements from geothermal wells of these two fields indicated reservoir temperatures in close agreement with their respective BHTs. For the best use of the solute geothermometry for spring water, it is advisable to: (1) chemically classify the springs based on water types; (2) identify and eliminate the discordant outlier observations by considering each water type as a separate sampled population; (3) apply all available solute geothermometers employing a suitable computer program such as SolGeo instead of using some specific, arbitrarily chosen geothermometers; and (4) evaluate the temperatures obtained for each solute geothermometer by considering the subsurface lithology, hydrological conditions, and BHTs or static formation temperatures whenever available.     

Monitoring of the groundwater chemical status in the Azores archipelago (Portugal) in the context of the EU water framework directive

A main challenge associated to EU Water Framework Directive corresponds to groundwater monitoring, both quantitative and chemical. The need for monitoring was also stressed by the Azores Water Plan. Monitoring of the chemical status of groundwater in Azores started in 2003 and has been progressively enlarged to all islands, totalizing 72 springs and 32 wells. A large number of parameters are analysed biannually, as major, minor and trace elements, pesticides and total hydrocarbons, as well as microbial indicators. Spring waters are mainly from HCO₃–Na type; instead water from wells is predominantly from the Cl–Na type, been differences attributed to their respective hydrogeologic framework. Springs discharge mainly from perched-water bodies, been influenced mainly from CO₂ in soils, silicate weathering, and seawater spraying and aerosols. Wells are in basal bodies, therefore subject to seawater intrusion influence, and 9% of Cl analyses made in wells exceed the standard value. Heavy metals, metalloids, hydrocarbons and pesticides all comply with standard values. Agriculture pollution also influences groundwater quality, as revealed by both NO₃ and PO₄ content, been the guide value exceeded respectively in 8 and 9% of the analyses. Despite the discontinuous variation of coliforms over time microbial indicators present an impact on water quality.     

Modeling preferential water flow and solute transport in unsaturated soil using the active region model

Preferential flow and solute transport are common processes in the unsaturated soil, in which distributions of soil water content and solute concentrations are often characterized as fractal patterns. An active region model (ARM) was recently proposed to describe the preferential flow and transport patterns. In this study, ARM governing equations were derived to model the preferential soil water flow and solute transport processes. To evaluate the ARM equations, dye infiltration experiments were conducted, in which distributions of soil water content and Cl⁻ concentration were measured. Predicted results using the ARM and the mobile–immobile region model (MIM) were compared with the measured distributions of soil water content and Cl⁻ concentration. Although both the ARM and the MIM are two-region models, they are fundamentally different in terms of treatments of the flow region. The models were evaluated based on the modeling efficiency (ME). The MIM provided relatively poor prediction results of the preferential flow and transport with negative ME values or positive ME values less than 0.4. On the contrary, predicted distributions of soil water content and Cl⁻ concentration using the ARM agreed reasonably well with the experimental data, with ME values higher than 0.8. The results indicated that the ARM successfully captured the macroscopic behavior of preferential flow and solute transport in the unsaturated soil.     

Hydrogeochemistry of abandoned Pb sulphide mines: the mining district of La Carolina (southern Spain)

The impact of past mining activities on the quality of groundwater and surface water has been investigated in the mining district of La Carolina (southern Spain, province of Jaén), a region characterised by the presence of mineralisations of Pb–Ag, Cu and Fe sulphides and Ba sulphates. The chemistry of waters from flooded galleries, shafts and drainage adits has been compared with that of surface waters in the same area. Generally, waters present neutral pH, since carbonates neutralise the acidity produced by the oxidation of Fe-bearing sulphide minerals in the mine impacted water. Despite of this natural attenuation process, in most of the cases, the mine groundwater is of low quality and shows high dissolved SO₄ (up to 3.7 g/l), Fe and Mn contents (tens to hundreds mg/l), exceeding the limit established by the guidelines of the World Health Organization for drinking water. Generally, the surface waters are of the sulphate calcium–magnesium to magnesium types, with moderate mineralisation. Post-rebound mine waters caused degradation of receiving watercourses in which the Fe contents are usually high, with values close to 3 g/l, and the mineralisation is greater as the channels run down in the mining zone. During dry seasons a considerable increase of salts and metals dissolved in stream waters was found, due to the decreasing contributions by run-off in this semiarid region, whereas the abandoned mine discharges remained practically constant.     

An assessment study of heavy metal distribution within soil in upper course of Zarqa River basin/Jordan

Levels of heavy metals are found in soils and waters of the major tributary valleys of the Jordan Valley. Heavy metal content in soils irrigated by treated waste water were measured for a 40 km reach of Zarqa River. Soil samples from eight different sites along the upper course of this river were analyzed to determine the concentration of selected heavy metals (CO, Cr, Cu, Pb, Ni, Zn). Silt forms the major component of the soils with an average of 54%. Clay fractions show an increase with depth from 17 to 41%. Trends in particle size distribution and metal contents were compared across sample sites. Samples contained moderate to considerable levels of Pb and Ni. Concentrations of Cu and Cr ranged between 33–59 and 65–90 ppm, respectively. These values represent a slight to moderate class of pollution. The concentration of Cr shows a decrease with depth and distance from the waste water plant. Cu, Zn, and Ni show increasing concentrations with depth but Pb and CO do not. The concentrations of the measured heavy metals increases near the waste water treatment plant but decreases with distance from the plant due to precipitation in the stream bed and dilution with stream water. This decline in metal content with distance from the treatment plant suggests that most metals reaching floodplain soils may derive from the same source. Although current metal concentrations are low to moderate, floodplain surface soils in this area should be regarded as a potential source for future heavy metal pollution downstream.