|
|
Gat, J. R. (1980). The relationship between surface and subsurface waters: water quality aspects in areas of low precipitation / Rapport entre les eaux de surface et les eaux souterraines: aspects des propriétés caractéristiques de l’eau dans les zones à précipitation faible. Hydrological Sciences Bulletin, 25(3), 257–267.
Abstract: In the temperate and semiarid environment the salinity of both surface and subsurface(meteoric) waters is dominated by the weathering products of soil and aquifer minerals, since even surface waters have a history of subsurface flow. In the desert environment, in contrast, surface flows are more superficial and their chemistry dominated by the aeolian salinity. This has both a marine input and
a contribution from recycled salinity from surface accumulation of evaporitic minerals. Both these sources have chloride (and to a lesser extent sulphate) as the dominant anion.
|
|
|
|
Pacheco, F. A. L., & Szocs, T. (2006). “Dedolomitization reactions” driven by anthropogenic activity on loessy sediments, SW Hungary. Applied Geochemistry, 21(4), 614–631.
Abstract: In the Szigetvár area, SW Hungary, shallow groundwaters draining upper Pleistocene loess and Holocene sediments are considerably contaminated by domestic effluents and leachates of farmland fertilizers. The loess contains calcite and dolomite, but gypsum was not recognized in these sediments. The anthropogenic inputs contain significant amounts of Ca and SO4. The Ca from these anthropogenic inputs is promoting calcite growth, with concomitant consumption of carbonate alkalinity, undersaturation of the system with respect to dolomite, and dolomite dissolution; in brief, is driving “dedolomitization reactions”. Geochemical arguments supporting the occurrence of “dedolomitization reactions” in the area are provided by the results of mass balance and thermodynamic analyses. The mass balances predicted the weather sequence dolomite\textgreatercalcite\textgreaterplagioclase\textgreaterK-feldspar, at odds with widely accepted sequences of weatherability where calcite is the first mineral in the weathering sequence. The exchange between calcite and dolomite can be a side effect of “dedolomitization reactions” because they cause precipitation of calcite. The thermodynamic prerequisites for “dedolomitization reactions” are satisfied by most local groundwaters (70%) since they are supersaturated (or in equilibrium) with respect to calcite, undersaturated (or in equilibrium) with respect to dolomite, and undersaturated with respect to gypsum. The Ca vs. SO4 and Mg vs. SO4 trends are also compatible with homologous trends resulting from “dedolomitization reactions”.
|
|
|
|
Qi, H., Ma, C., He, Z., Hu, X., & Gao, L. (2019). Lithium and its isotopes as tracers of groundwater salinization: A study in the southern coastal plain of Laizhou Bay, China. Sci Total Environ, 650(Pt 1), 878–890.
Abstract: In the southern coastal plain of Laizhou Bay, due to intensive exploitation of groundwater since the early 1970s, the shallow aquifer has been severely influenced by saltwater intrusion, which causes the extraction to shift from shallow to deeper aquifer changing the hydrogeological condition greatly. This study was conducted to investigate the groundwater salinization using hydrochemistry and H, O and Li isotope data. Dissolved Li shows a linear correlation with Cl and Br in seawater, brine and saline groundwater indicating the marine Li source, whereas the enrichment of Li in surface water, brackish and fresh groundwater is impacted by dissolution of silicate minerals. The analyses of hydrochemistry and isotopes (H, O and Li) indicate that brine originated from seawater evaporation, followed by mixing processes and some water-rock interactions; shallow saline groundwater originated from brine diluted with seawater and fresh groundwater; deep saline groundwater originated from seawater intrusion. The negative correlation of δ(7)Li and Li/Na in surface water, brackish and fresh groundwater is contrary to the general conclusion, indicating the slow weathering of silicate minerals and hydraulic interaction between surface water and shallow groundwater in this area. The analyses of hydrochemistry and isotopes (Li, H and O) can well identify the salinity sources and isotope fractionation in groundwater flow and mixing, especially groundwater with high TDS. As both mixing with saltwater and isotope fractionation can explain the combination of high δ(7)Li and low TDS in brackish groundwater, isotope fractionation may limit their use in recognizing salinity sources of groundwater with low TDS.
|
|
|
|
Sarker, M. M. R., Van Camp, M., Islam, M., Ahmed, N., & Walraevens, K. (2018). Hydrochemistry in coastal aquifer of southwest Bangladesh : origin of salinity. Environmental Earth Sciences, 77(2), 20.
Abstract: In the coastal region of Bangladesh, groundwater is mainly used for domestic and agricultural purposes, but salinization of many groundwater resources limits its suitability for human consumption and practical application. This paper reports the results of a study that has mapped the salinity distribution in different aquifer layers up to a depth of 300 m in a region bordering the Bay of Bengal based on the main hydrochemistry and has investigated the origin of the salinity using Cl/Br ratios of the samples. The subsurface consists of a sequence of deltaic sediments with an alternation of more sandy and clayey sections in which several aquifer layers can be recognized. The main hydrochemistry shows different main water types in the different aquifers, indicating varying stages of freshening or salinization processes. The most freshwater, soft NaHCO3-type water with Cl concentrations mostly below 100 mg/l, is found in the deepest aquifer at 200-300 m below ground level (b.g.l.), in which the fresh/saltwater interface is pushed far to the south. Salinity is a main problem in the shallow aquifer systems, where Cl concentrations rise to nearly 8000 mg/l and the groundwater is mostly brackish NaCl water. Investigation of the Cl/Br ratios has shown that the source of the salinity in the deep aquifer is mixing with old connate seawater and that the saline waters in the more shallow aquifers do not originate from old connate water or direct seawater intrusion, but are derived from the dissolution of evaporite salts. These must have been formed in a tidal flat under influence of a strong seasonal precipitation pattern. Long dry seasons with high evaporation rates have evaporated seawater from inundated gullies and depressions, leading to salt precipitation, while subsequent heavy monsoon rains have dissolved the formed salts, and the solution has infiltrated in the subsoil, recharging groundwater.
Keywords: Hydrochemistry,Stable isotope,Seawater intrusion,Coastal aquifer,Bangladesh,DAR-ES-SALAAM,SEAWATER INTRUSION,DELTA PLAIN,GROUNDWATER,DRINKING,TANZANIA,DROUGHT,COMPLEX
|
|
|
|
Stigter, T. Y., van Ooijen, S. P. J., Post, V. E. A., Appelo, C. A. J., & Carvalho Dill, A. M. M. (1998). A hydrogeological and hydrochemical explanation of the groundwater composition under irrigated land in a Mediterranean environment, Algarve, Portugal. Journal of Hydrology, 208(3), 262–279.
Abstract: In the Campina de Faro, in the south of Portugal, agricultural practices have a large impact on groundwater composition. These practices involve pumping of water for irrigation from combinations of large diameter, shallow wells (noras) and small diameter, deep boreholes (furos). Excess irrigation water returns to the aquifer and mixes with water from the regional groundwater flow system. This irrigation return flow is concentrated by strong evapotranspiration and by flushing of fertilisers. The concentration increase induces cation exchange, whereby Ca on the soil exchanger is replaced by Na. The mixing in the aquifer allows application of a mixing cell model which may then be used to calculate transmissivities from the Cl mass balance. The calculations are complicated by the time-variant behaviour of Cl and the method is adjusted to calculate the change of chloride in time. Results from the calculations appear to be in good agreement with hydrochemical observations.
|
|
