Ca-HCO3 Water Type Research Articles

Hydrogeochemical investigation of Küçük Menderes River coastal wetland, Selçuk–Izmir, Turkey

Kucuk Menderes River forms a rich coastal wetland inside in the Selcuk plain. Three saline/brackish lakes, one swamp and Kucuk Menderes River are these wetlands’ components. Alkaline-slightly alkaline type lakes are recharged from precipitation and karstic springs that discharge from marble-schist and marble-alluvium contacts in the northern and southern parts of the study area. Water types of the wetland are Na–Cl and Na–Ca–Mg–HCO3–Cl in both rainy and dry seasons. Both seawater intrusion and evaporation, as being the sources of the ions, justify the presence of Na–Cl, Na–SO4 and Cl–SO4, in the wetland water. Environmental isotopes were used to identify the relationship between wetland and groundwater in the Selcuk plain. The δ18O and δD composition of wetland area samples have changed between −6.42 to −4.56‰, and −36.40 to −23.80‰, respectively. The lakes and rivers are plotted on the mixing line by slope of 5.2 and these data indicate that wetland is affected from seawater intrusion. The recharge area that was sampled in order to compare the wetland has Ca–HCO3 water type with a neutral-slightly alkaline pH values and the main hydrogeochemical process is weathering the different types of silicates. Iron, manganese and selenium are the dominant minor ions due to the high biological activities and organic matters in the lakes. There are two contamination risks for this wetland: (1) waste disposal site and (2) water treatment plant where the purified waters are released into the river. EC, Al, As, Cd, Cu, Fe and Zn values exceed those of aquatic life standards. In the near future these sites will pose a danger for wetland wild life and surrounding irrigation water suppliers.

Determination of the recharge area and salinization degree of karst springs in the Lamas Basin (Turkey)

The Lamas Basin is an area covering ∼4400 km2 situated on the eastern Mediterranean coast of Turkey covered with highly karstified limestone and dolomitic limestone from the Miocene and Mesozoic age, respectively. Owing to the area’s low karstification basement, groundwater in the karst aquifer circulates deep from the surface towards the springs along the coast as well as to the submarine springs. This study aims working out the salinization level and recharge characteristics of the Lamas Basin using environmental isotopes techniques. In the study, the data collected previously to discover, in general terms, the groundwater characteristics within the area are reanalyzed to fulfil the purpose of the study. In conclusion, it is found that the down gradient karst springs discharging along the Mediterranean coast mostly contain groundwater contributions from higher altitudes with depleted δ18O and δ2H compositions. The δ18O-altitude effect was determined as approximately−0.12 ‰/100 m which may indicate sea-spray intrusion towards inland. As a result, the salinization level of coastal springs changes ranging between 1.2 % and 17.0 %. Owing to the seawater encroachment, Ca–HCO3 water type changes to Na–HCO3 or Na-Cl water by the cation exchange during the dry period. As the unique freshwater potential extends along the coastal area, the groundwater production should be exploited in a way that seawater encroachment is kept at minimum.

Hydrochemical characteristics and pollution potential of Uluova aquifers, Elazig, Turkey

The study area is in the southeastern part of the city of Elazig between 38°17′–38°43′ latitudes and 38°36′–39°07′ longitudes. Formations of Paleozoic, Mesozoic and Cenozoic age comprise confined and unconfined aquifers. Unconfined aquifers are represented by Na-Cl and Na-HCO3 type waters while confined aquifers are characterized by Ca-HCO3, Mg-HCO3 and Na-HCO3 type waters. Due to sodium pollution, as a result of irrigation from waters of Hazar lake in the plain, as well as intense use of artificial fertilizer and improper storage of animal fertilizers, NH4-N, NO3-N and total PO4-P pollution are detected in waters of the unconfined aquifer. Organic material contents in waters of well nos. S27, S29 and S32 completed in the unconfined aquifer are above 3.5 mg/l of Turkish Standard Institute (TSE), (266) standard. In confined aquifers, total PO4-P pollution in four wells and NH4-N pollution in three wells were observed to be above the TSE (266) standard.

Hydrology, hydrogeology and hydrochemistry of wetlands: a case study in Izmir Bird Paradise, Turkey

Izmir Bird Paradise is one of the most valuable wetlands in Turkey, but this area is now being threatened by the drying out of marshes and water pollution. This wetland consists of two ecosystems: fresh- and saltwater. The recharge of marshes is from rainfall, the Gediz River and groundwater from Can Suyu Pond. The water type of the river is Ca–Mg–Na-HCO3–SO4, whereas the groundwater is a Na-Cl water type. The reasons for the drying are long-term drought (evapotranspiration at 894 mm is >> rainfall at 546 mm), and excessive pumping of groundwater and seawater intrusion into Menemen Plain. Therefore, an additional freshwater resource is necessary. This water can be supplied from the limestone levels of Neogene sedimentary rocks in and around Izmir Bird Paradise that have a Ca-HCO3 water type. Water pollution levels were also analysed. In the freshwater ecosystem Cd, Cr, Fe, Mn, Ni, Pb, Sb and Zn values, in the open channel in Izmir Bird Paradise Sb, Fe, Ni and Cd values, and in the river Fe, Pb and Sb values exceed the TSE 266 and EPA 2000 standards probably due to agricultural and industrial sources.

A regional study of saltwater intrusion in southeastern Nigeria based on the analysis of geoelectrical and hydrochemical data.

Vertical electrical sounding (VES) and hydrochemical data have been used to examine the extent of saltwater intrusion into shallow aquifers (depth 0.70). Furthermore, the coastal sites are marked by Ca-Cl and Ca-HCO3 water types whereas Na-Cl dominated both the islands ( at depths greater than 20 m) and the seawater. This gives an indication of seawater contamination. Seawater contamination is also indicated by the results of five assessment parameters as follows: high chloride concentration (>500 mg/l), high saturation index (halite>10–6), high ionic strength (>0.05), low formation resistivity (<25 ohm-m), and low formation factor (<0.05). Two of these parameters (chloride concentration, ionic strength) have been used to compose an assessment scheme with five major classes (AA, BB, CC, DD, EE) corresponding to various degrees of salinity. Generally in the study area, saltwater contamination is a feature of island locations at depths greater than about 20 m. Water within the inland coastal regions is fresh.

Hydrogeochemistry of seepage water collected within the Youngcheon diversion tunnel, Korea: source and evolution of SO4‐rich groundwater in sedimentary terrain

AbstractIn the Youngcheon Diversion Tunnel area, South Korea, 46 samples of tunnel seepage water (TSW) and borehole groundwater were collected from areas with sedimentary rocks (mainly sandstone and shale) and were examined for hydrogeochemical characteristics. The measured SO4 concentrations range widely from 7·7 to 942·0 mg/l, and exceed the Korean Drinking Water Standard (200 mg/l) in about half the samples. The TDS (total dissolved solid) content generally is high (171–1461 mg/l) from more shale‐rich formations and also reflects varying degrees of water–rock interaction. The water is classified into three groups: Ca SO4 type (61% of the samples collected), Ca SO4 HCO3 type (15%) and Ca HCO3 type (24%). The Ca HCO3 type water (mean concentrations=369 mg/l Ca, 148 mg/l HCO3 and 23 mg/l SO4) reflected the simple reaction between CO2‐recharged water and calcite, whereas the more SO4‐rich nature of Ca SO4 type water (mean concentrations=153 mg/l Ca, 66 mg/l HCO3 and 416 mg/l SO4) reflected the oxidation of pyrite in sedimentary rocks and fracture zones. Pyrite oxidation resulted in precipitation of amorphous iron hydroxide locally within the tunnel as well as in high concentrations of Ca (mean 153 mg/l) and Na (mean 49 mg/l) for TSW, and is associated with calcite dissolution resulting in pH buffering. The pyrite oxidation required for the formation of Ca SO4 type water was enhanced by the diffusion of oxygenated air through the fractures related to the tunnel's construction. The subsequent outgassing of CO2 into the tunnel resulted in precipitation of iron‐bearing carbonate. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Geochemical Evolution of Ground Water in the Great Plains (Dakota) Aquifer of Nebraska: Implications for the Management of a Regional Aquifer System

AbstractThe Great Plains (Dakota) aquifer system is one of the most extensive in North America extending from the Arctic Circle to New Mexico, and underlies approximately 94% of Nebraska. In Nebraska, we do not have the physical ground water monitoring data at the scale that is necessary to manage ground water flow systems. However, first‐order management strategies for this regional aquifer can be developed by understanding the geochemical evolution of the ground water. Using major‐ion water chemistry data from 203 wells in 19 counties in eastern Nebraska, reconnaissance δ180, δD, and δ87Sr data, and two geochemical models, PHREEQC and SNORM, we determine that modern meteoric water, NaCl brines from underlying formations, and cold glacial melt water are the primary sources for the water in the Dakota Aquifer. Based on these three water sources and the geochemical evolution of the various water types, the following first‐order management strategies are suggested. In areas where CaSO4 and Ca‐Na SO4 type water occur, Pleistocene‐age glacial meltwater is the source. This water supply is not easily renewable. It is recommended that detailed water resource evaluation be conducted before extensive development occurs. The source of Ca (± Mg) HCO3 type water is from recharge by local precipitation and should be managed to maintain them as a renewable resource. In mixed ground water type areas, the ground water chemistry reflects the interaction of two distinct water types, one of which is meteoric water and the other is either CaSO4 and Ca‐Na SO4‐type water or NaCl‐type water. If the relatively fresh ground water is extracted at a rate that changes the location of the interface between the endmembers, then monitoring changes in water chemistry in a well over time could be used as an early warning system for the onset of potential problems related to overpumping.