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.
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Wigley, T. M. L., & Plummer, L. N. (1976). Mixing of carbonate waters. Geochimica et Cosmochimica Acta, 40(9), 989–995.
Abstract: When mineral solutions of different compositions are mixed, the molalities and activities of individual ions in the mixture are often non-linear functions of their end-member values. This non-linearity is particularly significant in determining mineral saturation levels. Mixtures of saturated solutions may be either undersaturated or supersaturated depending on the end-member compositions and the physical conditions in which end-members and their mixtures exist. In carbonate solutions important non-linear effects occur due to redistribution of carbonate species. In extreme cases this causes mixture pH to be below both the end-member pH values. A simple but precise computer program (WATMIX) has been developed for calculating mixture composition for closed and open system mixing of arbitrary end-members. A number of mixing examples are considered which allow one to isolate three important processes leading to non-linear behaviour: the algebraic effect, the δPCO2 effect, and the ionic strength effect.
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Zhou, X., & Li, C. (1992). Hydrogeochemistry of deep formation brines in the central Sichuan Basin, China. Journal of Hydrology, 138(1), 1–15.
Abstract: Subsurface brines are abundant in the Sichuan Basin, China. Five brine-bearing aquifers have been identified within rocks of Triassic age in the central part of the basin. These are of two types: brine-bearing clastic and brine-bearing carbonate aquifers. Brines in this region have high total dissolved solids and chemical species that are different from those of evaporatively concentrated seawater. Deep formation brines in clastic aquifers, in which evaporites do not exist, are characterized by high concentrations of Ca, Sr, Ba, Br and I, low concentrations of Mg and K, and lack of SO4, and are dominated by the NaCaCl type. Brines in carbonate aquifers, which have interbeds of evaporites, are characterized by high total dissolved solids, low concentrations of Ca, Mg and SO4, and lack of Ba, and are of the NaCl type. The brines in clastic aquifers originate from connate continental sedimentary waters mixed with marine waters; membrane filtration through shales has played an important part in modifying the chemical compositions and increasing the salinity of the brines. Those in carbonate aquifers are bittern marine sedimentary waters, with chemical compositions mainly controlled by precipitation of evaporites.
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Alexakis, D., Gotsis, D., & Giakoumakis, S. (2015). Evaluation of soil salinization in a Mediterranean site (Agoulinitsa district—West Greece). Arabian Journal of Geosciences, 8(3), 1373–1383.
Abstract: Soil salinization is an environmental problem having
significant impacts on the soil–water–plant system. This
problem is more frequent in coastal areas due to seawater
intrusion into the land. Assessing the soil salinization is a
critical issue for the agricultural areas situated in the
Mediterranean basin. This paper examines the deterioration
of soil quality in the cultivated land of a Mediterranean site
(Agoulinitsa district—West Greece). Soil samples were collected
in both pre-irrigation and post-irrigation seasons.
Electrical conductivity (EC), pH and the ions Br−, Ca2+, Cl−,
F−, K+, Li+, Mg2+, Na+, NH4
+, NO2
−, NO3
−, PO4
3− and SO4
2−
were determined by the 1:2 (soil/water ratio on weight basis)
method. The salts which were present in both seasons in the
soils of the area studied are KCl, MgCl2, NaCl, CaSO4 and
K2SO4. The wide spatiotemporal variation of EC in the cultivated
land in both seasons demonstrates that soil salinity is
controlled mainly by seawater intrusion and anthropogenic
factors such as the application of salt-rich water which is
directly pumped from the drainage ditches. Seawater intrusion
provides the affected soil with elevated contents of Ca2+, Cl−,
K+, Mg2+, Na+ and SO4
2−. Classification of the soils by using
criteria given by the literature is discussed. Practices to prevent,
or at least ameliorate, salinization in the cultivated land
of Agoulinitsa district are proposed.
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Di Lorenzo, T., & Galassi, D. M. P. (2013). Agricultural impact on Mediterranean alluvial aquifers: do groundwater communities respond? Fundamental and Applied Limnology/Archiv für Hydrobiologie, 182(4), 271–282.
Abstract: In Mediterranean countries agricultural development heavily depends on groundwater availability due
to arid and semi-arid climate and poor surface-water resources. Agriculture represents one of the most relevant
pressures which generate impacts in alluvial aquifers by means of fertilizers and pesticides usage and groundwater
overexploitation. Until now, very few studies have addressed the ecological response of groundwater fauna to
groundwater contamination and overexploitation due to agricultural practices. We investigated a Mediterranean
alluvial aquifer heavily affected by nitrates contamination and groundwater abstraction stress due to crop irrigation. The aim of this study was to evaluate the sensitivity of groundwater communities to (a) groundwater nitrate
contamination, (b) groundwater abstraction due to irrigation practices, and (c) saltwater intrusion. The present
work suggests that nitrate concentration lower than 150 mg l
–1 is not an immediate threat to groundwater biodiversity in alluvial aquifers. This conclusion must be carefully considered in the light of the total lack of knowledge
of the effects of long-term nitrate pollution on the groundwater biota. Moreover, local extinctions of less tolerant
species, prior to monitoring, cannot be ruled out. Conversely, species abundances in ground water are affected by
groundwater withdrawal, but species richness may be less sensitive. This result is attributable to the disappearance
of saturated microhabitats and to the depletion of fine unconsolidated sediments, reducing the surface available
to bacterial biofilm, which represent the trophic resource for several groundwater invertebrates and where the
main aquifer self-purification processes, such as denitrification, take place. Saltwater intrusion seems not to affect
groundwater species at the values measured in this coastal aquifer.
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