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Author |
Di Lorenzo, T.; Galassi, D.M.P. |
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Title |
Agricultural impact on Mediterranean alluvial aquifers: do groundwater communities respond? |
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Journal Article |
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Year |
2013 |
Publication |
Fundamental and Applied Limnology/Archiv für Hydrobiologie |
Abbreviated Journal |
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Volume |
182 |
Issue |
4 |
Pages |
271-282 |
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Keywords |
alluvial aquifers, groundwater, stygobiont, nitrate, overexploitation |
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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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E. Schweizerbart'sche Verlagsbuchhandlung |
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1863-9135 |
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Call Number |
THL @ luqianxue.zhang @ DiLorenzo2013 |
Serial |
43 |
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Author |
Sarker, M.M.R.; Van Camp, M.; Islam, M.; Ahmed, N.; Walraevens, K. |
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Title |
Hydrochemistry in coastal aquifer of southwest Bangladesh : origin of salinity |
Type |
Journal Article |
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Year |
2018 |
Publication |
Environmental Earth Sciences |
Abbreviated Journal |
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Volume |
77 |
Issue |
2 |
Pages |
20 |
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Keywords |
Hydrochemistry,Stable isotope,Seawater intrusion,Coastal aquifer,Bangladesh,DAR-ES-SALAAM,SEAWATER INTRUSION,DELTA PLAIN,GROUNDWATER,DRINKING,TANZANIA,DROUGHT,COMPLEX |
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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. |
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1866-6280 |
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THL @ christoph.kuells @ Sarker2018 |
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194 |
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