Florida's ground water quality monitoring program: background hydrogeochemistry

The purpose of this report is to present the results of the initial quantification of background water quality in each of the state's major potable aquifer systems. Results are presented and interpreted in light of the influencing factors which locally and regionally affect ambient ground-water quality. This initial data will serve as a baseline from which future sampling results can be compared. Future sampling of the Network will indicate the extent to which Florida's regional ground-water resources are improving or declining in quality. (Document has 378 pages.)

Hydrogeochemistry of formation water in relation to overpressures and fluid flow in the Qikou Depression of the Bohai bay basin, China

The Qikou Depression is the largest hydrocarbon bearing depression in the western part of the Bohai bay basin, dominated by fan delta and lacustrine strata with volcanic and volcaniclastic rocks. In this study, the formation pressures and hydrochemistry of the formation water in the Qikou depression are investigated. It is found that a significant overpressure occurs in the Dongying (Ed) Formation and the first member (Est), the second member (Es2), the third member (Es3) of the Shahejie Formation. The pressure coefficients commonly range from 1.2 to 1.6 with the highest pressure coefficient being 1.7. The analysis of hydrochemistry data shows that the whole depression is dominated by NaHCO3 water type. The concentration of total dissolved solid (TDS) ranges from 2.13 to 53.16 g/L and shows a distinct vertical variation of salinity and ion ratios. High salinity water (TDS> 10 g/L) occurs below a depth of 2500 m, which coincides with the presence of the overpressured system. However, the increasing trend of TDS is diminished below 3500 m because the generation of organic acids in Qikou Depression is inhibited in the presence of overpressure. The analysis of the relationship among different ions indicates that the present-day characteristics of the formation water result from the albitization of feldspar and the dissolution of sodium-rich silicate minerals and halite in the different hydrochemical and pressure systems. (C) 2009 Elsevier B.V. All rights reserved.

Hydrogeochemistry and Arsenic Contamination of Groundwater in the Haor Basins of Bangladesh

Hydrogeochemical relationships and the level of arsenic (As) contamination of groundwater in the Haor Basin, a low-lying, semi-natural, region of remnant wetland environs to the northeast of Bangladesh, were studied to assess the As biogeochemical cycling. Most of the shallow and deep tubewells in the study area are contaminated with As (2-331 mu g/l). The relatively higher proportions of Na+ (8-156 mg/l) in groundwater suggest a mixing of connate marine water with freshwater aquifer. Non-significant association between As and PO43- has been found. Highly significant (P <0.001) relationship of As with DOC in groundwater indicates biodegradation of organic matter, creating an overall reducing environment in the aquifer sediments, which facilitates the release of As in the groundwater. The inverse As-Fe, As-Mn, As-Ca and As-Mg relationships in groundwater could be related to the precipitation of Fe-, Mn-, Ca-and Mg-minerals.

Hydrogeochemistry of surface and spring waters in the surroundings of the CO2 injection site at Hontomín–Huermeces (Burgos, Spain)

In this paper the very first geochemical and isotopic data related to surface and spring waters and dissolved gases in the area of Hontomín–Huermeces (Burgos, Spain) are presented and discussed. Hontomín–Huermeces has been selected as a pilot site for the injection of pure (>99%) CO2. Injection and monitoring wells are planned to be drilled close to 6 oil wells completed in the 1980s for which detailed stratigraphical logs are available, indicating the presence of a confined saline aquifer at the depth of about 1500 m into which less than 100,000 tons of iquid CO2 will be injected, possibly starting in 2013. The chemical and features of the spring waters suggest that they are related to a shallow hydrogeological system as the concentration of the Total Dissolved Solids approaches 800 mg/L with a Ca2+(Mg2+)-HCO3− composition, similar to that of the surface waters. This is also supported by the oxygen and hydrogen isotopic ratios that have values lying between those of the Global and the Mediterranean Meteoric Water Lines. Some spring waters close to the oil wells are haracterized by relatively high concentrations of NO3− (up to 123 mg/L), unequivocally suggesting an anthropogenic source that adds to the main water–rock interaction processes. The latter can be referred to Ca-Mg-carbonate and, at a minor extent, Al-silicate dissolution, being the outcropping sedimentary rocks characterized by Palaeozoic to Quaternary rocks. Anomalous concentrations of Cl−, SO42−, As, B and Ba were measured in two springs discharging a few hundred meters from the oil wells and in the Rio Ubierna. These contents are significantly higher than those of the whole set of the studied waters and are possibly indicative of mixing processes, although at very low extent, between deep and shallow aquifers. No evidence of deep-seated gases interacting with the Hontomín–Huermeces waters was recognized in the chemistry of the disolved gases. This is likely due to the fact that they are mainly characterized by an atmospheric source as highlighted by the high contents of N2, O2 and Ar and by N2/Ar ratios that approach that of ASW (Air Saturated Water) and possibly masking any contribution related to a deep source. Nevertheless, significant concentrations (up to 63% by vol.) of isotopically negative CO2 (<−17.7‰ V-PDB) were found in some water samples, likely related to a biogenic source. The geochemical and isotopic data of this work are of particular importance when a monitoring program will be established to verify whether CO2 leakages, induced by the injection of this greenhouse gas, may be affecting the quality of the waters in the shallow hydrological circuits at Hontomín–Huermeces. In this respect, carbonate chemistry, the isotopic carbon of dissolved CO2 and TDIC (Total Dissolved Inorganic Carbon) and selected trace elements can be considered as useful parameters to trace the migration of the injected CO2 into near-surface environments.

Applying reactive models to column experiments to assess the hydrogeochemistry of seawater intrusion: optimising ACUAINTRUSION and selecting cation exchange coefficients with PHREEQC

Three sets of laboratory column experimental results concerning the hydrogeochemistry of seawater intrusion have been modelled using two codes: ACUAINTRUSION (Chemical Engineering Department, University of Alicante) and PHREEQC (U.S.G.S.). These reactive models utilise the hydrodynamic parameters determined using the ACUAINTRUSION TRANSPORT software and fit the chloride breakthrough curves perfectly. The ACUAINTRUSION code was improved, and the instabilities were studied relative to the discretisation. The relative square errors were obtained using different combinations of the spatial and temporal steps: the global error for the total experimental data and the partial error for each element. Good simulations for the three experiments were obtained using the ACUAINTRUSION software with slight variations in the selectivity coefficients for both sediments determined in batch experiments with fresh water. The cation exchange parameters included in ACUAINTRUSION are those reported by the Gapon convention with modified exponents for the Ca/Mg exchange. PHREEQC simulations performed using the Gains-Thomas convention were unsatisfactory, with the exchange coefficients from the database of PHREEQC (or range), but those determined with fresh water – natural sediment allowed only an approximation to be obtained. For the treated sediment, the adjusted exchange coefficients were determined to improve the simulation and are vastly different from those from the database of PHREEQC or batch experiment values; however, these values fall in an order similar to the others determined under dynamic conditions. Different cation concentrations were simulated using two different software packages; this disparity could be attributed to the defined selectivity coefficients that affect the gypsum equilibrium. Consequently, different calculated sulphate concentrations are obtained using each type of software; a smaller mismatch was predicted using ACUAINTRUSION. In general, the presented simulations by ACUAINTRUSION and PHREEQC produced similar results, making predictions consistent with the experimental data. However, the simulated results are not identical to the experimental data; sulphate (total S) is overpredicted by both models, most likely due to such factors as the kinetics of gypsum, the possible variations in the exchange coefficients due to salinity and the neglect of other processes.

Ecohydrology, evapotranspiration and hydrogeochemistry of carbonate mangrove wetlands

Coastal environments can be highly susceptible to environmental changes caused by anthropogenic pressures and natural events. Both anthropogenic and natural perturbations may directly affect the amount and the quality of water flowing through the ecosystem, both in the surface and subsurface and can subsequently, alter ecological communities and functions. The Florida Everglades and the Sian Ka'an Biosphere Reserve (Mexico) are two large ecosystems with an extensive coastal mangrove ecotone that represent a historically altered and pristine environment, respectively. Rising sea levels, climate change, increased water demand, and salt water intrusion are growing concerns in these regions and underlies the need for a better understanding of the present conditions. The goal of my research was to better understand various ecohydrological, environmental, and hydrogeochemical interactions and relationships in carbonate mangrove wetlands. A combination of aqueous geochemical analyses and visible and near-infrared reflectance data were employed to explore relationships between surface and subsurface water chemistry and spectral biophysical stress in mangroves. Optical satellite imagery and field collected meteorological data were used to estimate surface energy and evapotranspiration and measure variability associated with hurricanes and restoration efforts. Furthermore, major ionic and nutrient concentrations, and stable isotopes of hydrogen and oxygen were used to distinguish water sources and infer coastal groundwater discharge by applying the data to a combined principal component analysis-end member mixing model. Spectral reflectance measured at the field and satellite scales were successfully used to estimate surface and subsurface water chemistry and model chloride concentrations along the southern Everglades. Satellite imagery indicated that mangrove sites that have less tidal flushing and hydrogeomorphic heterogeneity tend to have more variable evapotranspiration and soil heat flux in response to storms and restoration. Lastly, water chemistry and multivariate analyses indicated two distinct fresh groundwater sources that discharge to the phosphorus-limited estuaries and bays of the Sian Ka'an Biopshere Reserve; and that coastal groundwater discharge was an important source for phosphorus. The results of the study give us a better understanding of the ecohydrological and hydrogeological processes in carbonate mangrove environments that can be then be extrapolated to similar coastal ecosystems in the Caribbean.

Characterization of groundwater chemistry under the influence of lithologic and anthropogenic factors along a climatic gradient in Upper Cauvery basin, South India

Hydrogeological and climatic effect on chemical behavior of groundwater along a climatic gradient is studied along a river basin. `Semi-arid' (500-800 mm of mean annual rainfall), `sub-humid' (800-1,200 mm/year) and `humid' (1,200-1,500 mm/year) are the climatic zones chosen along the granito-gneissic plains of Kabini basin in South India for the present analysis. Data on groundwater chemistry is initially checked for its quality using NICB ratio (<+/- 5 %), EC versus TZ+ (similar to 0.85 correlation), EC versus TDS and EC versus TH analysis. Groundwater in the three climatic zones is `hard' to `very hard' in terms of Ca-Mg hardness. Polluted wells are identified (> 40 % of pollution) and eliminated for the characterization. Piper's diagram with mean concentrations indicates the evolution of CaNaHCO3 (semi-arid) from CaHCO3 (humid zone) along the climatic gradient. Carbonates dominate other anions and strong acids exceeded weak acids in the region. Mule Hole SEW, an experimental watershed in sub-humid zone, is characterized initially using hydrogeochemistry and is observed to be a replica of entire sub-humid zone (with 25 wells). Extension of the studies for the entire basin (120 wells) showed a chemical gradient along the climatic gradient with sub-humid zone bridging semi-arid and humid zones. Ca/Na molar ratio varies by more than 100 times from semi-arid to humid zones. Semi-arid zone is more silicaceous than sub-humid while humid zone is more carbonaceous (Ca/Cl similar to 14). Along the climatic gradient, groundwater is undersaturated (humid), saturated (sub-humid) and slightly supersaturated (semi-arid) with calcite and dolomite. Concentration-depth profiles are in support of the geological stratification i.e., not approximate to 18 m of saprolite and similar to 25 m of fracture rock with parent gneiss beneath. All the wells are classified into four groups based on groundwater fluctuations and further into `deep' and `shallow' based on the depth to groundwater. Higher the fluctuations, larger is its impact on groundwater chemistry. Actual seasonal patterns are identified using `recharge-discharge' concept based on rainfall intensity instead of traditional monsoon-non-monsoon concept. Non-pumped wells have low Na/Cl and Ca/Cl ratios in recharge period than in discharge period (Dilution). Few other wells, which are subjected to pumping, still exhibit dilution chemistry though water level fluctuations are high due to annual recharge. Other wells which do not receive sufficient rainfall and are constantly pumped showed high concentrations in recharge period rather than in discharge period (Anti-dilution). In summary, recharge-discharge concept demarcates the pumped wells from natural deep wells thus, characterizing the basin.

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

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

塔克拉玛干沙漠地球化学研究

The Taklamakan Desert, lying in the center Tarim Basin of sourthern Xinjiang, is the largest sand sea in China and well known in the world as its inclemency. For understanding the formation and evolution of the Taklamakan Desert, it is very important to identify the provenance of aeolian sediments in the extensive dune fields, but the opinions from earlier studies are quite different. In this study, we examined the major- and trace-element compositions, mineral compositions and grain-size distributions of some Quaternary aeolian and nonaeolian sediments collected from the Taklamakan Desert, together with the variation of chemical and mineralogical compositions of different grain-size fraction. At the same time, we also studied the chemistries of some natural water samples (river water and groundwater) with the items of TDS, pH, Alkalinity, conductivity and major cation and anion compositions. Our results of analysis show some significant opinions as follow: Most of the frequency-distribution curves of grain size of dune sand samples are simgle peak, but that of the river and lacustrine sediment are most double peak or multi-peak. The grain-size distribution of dunefield sand changed gradually from north to south with the major wind direction in large scale, but there are many differences in regional scale. The major, REE, trace element compositions and mineral compositions are very different among the coarse, fine fraction and bulk samples due to the influence of grain-size. Most of the fine fractions are geochemically homogenous, but the coarse fractions and bulk samples are heterogenous. All the surface and ground waters are limnetic or sub-salty, their chemical compositions are mainly controlled by rock-weathering and crystallization- evaporation processes, and mainly come from the evaporate, while the contributions of the carbonate and silicate are little, excluding the influence on oasis water by carbonate. The mineral compositions of selected samples are stable, mainly composed of the strongly resistant mineral types. The mineral maturity of them are more immature at whole compared with other sandy sediments in the world, and they have experienced less degree of chemical weathering and recycling, being lying in the early stage of continental weathering. Among these sediments, the river sediments are relatively primitive. The sources of these sediments are maybe mainly terrigenous, silicic and subaluminous/ metalunious rocks, such as the granodiorite and its metamorphic rock. The geochemical compositions of dunefield sand are similar with those of the river sediments and dune sands near the river way; There are not only the resemblances but also the differences on geochemistry and granularity between north and south dunesands; The sediments from same section have different age but same trace-element compositions; The sediments from the south edge of Tarim Basin are all somewhat geochemically similar with the palaeo-river-sediment on the south edge of studying area. The REE data support the idea that the south dunesands are a little older than the north dunesands, and the tectonic settings of source area are mainly active continental margin based on the major-element compositions, so they indicate that the sediment of Taklamakan Desert maybe come mainly from the rock-weathering production of north part of the Kunlun Mountains. Compared with the sands of other dune field in north of China, the sands of the Taklamakan Desert are distinct by REE composition, but similar with the Luochuan loess, center China, and the two sandy dusts of Beijing, eastern China.

关中盆地东部浅层地下水水化学与CFC年龄研究

Hydrochemistry, isotope and CFCs were used to determine groundwater transport in the eastern part of the Guanzhong Basin. In this paper, we systematically collected water samples and measured major ions, 2H-18O and CFCs in surface water and shallow groundwater. Groundwater in this region can be divided into three categories based on total dissolved solids (TDS): fresh water with TDS < 1g/L, brackish water with TDS between 1～3g/L, and saline water with TDS > 3g/L. Saline water is mainly located in the north of the Wei River, and saline groundwater is not in the south. Tributaries in the south of the Wei River and underlain groundwater had similar 2H-18O values, indicating a close hydraulic connection between them. Tributaries in the north of the Wei River characterized certain extent of evaporation, and 2H-18O values deviated to a differing extent between surface water and groundwater, indicating that surface water in the north bank of the Wei River has little hydraulic connection with underlain groundwater. The CFCs age of groundwater from the piedmont recharge area was young, and became older toward the Wei River valley. Vertically, the CFCs age of groundwater increased with well depth. The shallow groundwater is mainly composed of young water with ages < 60 years and old water with ages > 60 years. Young water is in a larger proportion. The NO3-N concentration positively correlates with the CFC-12 concentration in the groundwater, which indicates that young water is subjected to be contaminated. Keyword: Guanzhong Basin , shallow groundwater, isotope, CFC

Evolução hidrogeoquímica das águas sulfúreas de Entre-os-Rios: avaliação preliminar

O principal objectivo desta dissertação foi avaliar a evolução hidrogeoquímica das águas minerais de Entre‐os‐Rios, para uma melhor compreensão do modelo hidrogeológico conceptual deste sistema hidromineral. Desta forma, foram coligidos diversos dados hidroquímicos, quer das nascentes clássicas (Torre, Curveira, Ardias, Arcos Esquerda e Arcos Direita), quer do furo Barbeitos. Foram compiladas e analisadas oitenta análises hidroquímicas no período 1938‐2012, incluindo características organolépticas (cheiro, cor e turbidez), diversas propriedades físico-químicas (temperatura, pH, condutividade eléctrica, sulfuração, etc), os principais catiões e aniões (bicarbonato, fluoreto, sódio, lítio, etc) e os elementos vestigiários (chumbo, tungsténio, boro, etc). Além disso, foram integrados os dados históricos disponíveis de finais do século XIX e inícios do século XX. Foram igualmente reunidos e discutidos alguns dados isotópicos (oxigénio‐18, deutério e trítio). O recurso hidromineral de Entre‐os‐Rios está condicionado pela litologia e pelas condições tectónicas. As análises químicas revelaram que as águas minerais de Entre‐os‐Rios apresentam uma estabilidade química nos últimos 100 anos. Estas águas são orto‐ a hipertermais, fracamente mineralizadas, de reacção alcalina, sulfídricas, bicarbonatadas sódicas, carbonatadas e muito fluoretadas. Estas características são claramente distintas das águas normais da região. As águas de Entre‐os‐Rios são muito semelhantes às águas minerais de S. Vicente e, em diversos parâmetros, bastante diferentes das águas minerais das Caldas da Saúde. Os dados isotópicos permitiram concluir que as águas de Entre‐os‐Rios têm uma origem meteórica, com um tempo de residência longo no sistema aquífero, e que são, muito provavelmente, submodernas, com uma recarga anterior a 1952. Na região de Entre‐os‐Rios coexistem três sistemas aquíferos, um sistema granítico superficial, livre e um sistema livre a semi‐confinado, ambos com circulação de águas normais, e um sistema aquífero granítico, profundo, confinado, com circulação de água mineral.

An Integrated Hydro geological Study of the Muvattupuzha River Basin, Kerala, India

The present investigation on the Muvattupuzha river basin is an integrated approach based on hydrogeological, geophysical, hydrogeochemical parameters and the results are interpreted using satellite data. GIS also been used to combine the various spatial and non-spatial data. The salient finding of the present study are accounted below to provide a holistic picture on the groundwaters of the Muvattupuzha river basin. In the Muvattupuzha river basin the groundwaters are drawn from the weathered and fractured zones. The groundwater level fluctuations of the basin from 1992 to 2001 reveal that the water level varies between a minimum of 0.003 m and a maximum of 3.45 m. The groundwater fluctuation is affected by rainfall. Various aquifer parameters like transmissivity, storage coefficient, optimum yield, time for full recovery and specific capacity indices are analyzed. The depth to the bedrock of the basin varies widely from 1.5 to 17 mbgl. A ground water prospective map of phreatic aquifer has been prepared based on thickness of the weathered zone and low resistivity values (<500 ohm-m) and accordingly the basin is classified in three phreatic potential zones as good, moderate and poor. The groundwater of the Muvattupuzha river basin, the pH value ranges from 5.5 to 8.1, in acidic nature. Hydrochemical facies diagram reveals that most of the samples in both the seasons fall in mixing and dissolution facies and a few in static and dynamic natures. Further study is needed on impact of dykes on the occurrence and movement of groundwater, impact of seapages from irrigation canals on the groundwater quality and resources of this basin, and influence of inter-basin transfer of surface water on groundwater.

An integrated study on the hydrogeology of Bharathapuzha river basin, South West coast of India

The present work deals with the An integrated study on the hydrogeology of Bharathapuzha river basin ,south west coast of india. To study the spatial and temporal behaviour of the groundwater system of the Bharathapuzha river basin.To discover the sub-surface parameter by ground resistivity surveys.T o determine the groundwater quality of the Bharathapuzha river basin for the different seasons {pre monsoon and post monsoon with reference to the domestic and irrigational water quality standards.Present study will provide a good database on the hydrogeological aspects within the river basin.The study area covers l7 block Panchayats. Of these, Chitoor block is ‘over exploited’, Kollengode, Trithala, and Palakkad are ‘critical’ in category and Kuttippuram and Sreekrishnapuram blocks are ‘semi critical’ in terms of groundwater development.Comparison of Geomorphology map with drainage map shows that the geomorphology has a clear control on the drainage net work of the basin. The structural hill area shows a highest drainage network, where as pediment shows lowest drainage network.There are many discontinuous lineament in the Bharathapuzha river basin which can be connected by a straight line.Ground water flow directions are generally towards the western portions of the study area. From the northern region Water flows towards the central and also water from the eastern and southern side confluences at the centre and move towards western side of the basin.The positive correlation of transmissivity and storativity values show good aquifer conditions exists in the present study area .