Geostatical modelling of salt-water aquifer pollution due to evaporite-domes leaching in the Maragota area
Ribeiro, L. (1999). Geostatical modelling of salt-water aquifer pollution due to evaporite-domes leaching in the Maragota area. Natuurwet. Tijdschr. 79(1-4): 80-84
In: Natuurwetenschappelijk Tijdschrift. L. Walschot/Natuur- en Geneeskundige Vennootschap: Gent. ISSN 0770-1748, more
Also appears in:
De Breuck, W.; Walschot, L. (Ed.) (1999). Proceedings of the 15th Salt-Water Intrusion Meeting Ghent (Belgium), 25-29 May 1998. Natuurwetenschappelijk Tijdschrift, 79(1-4). Natuurwetenschappelijk Tijdschrift: Gent. 307 pp., more
In the south of Portugal, saline contamination may occur due to evaporite-domes leaching. The study of this diffuse pollution has been neglected in the past in spite of the extension of the hazardous areas and of the serious problems for human health. Furthermore, as the phenomenon occurs near the coast the problem can be wrongly evaluated in those aquifers where some saline contamination is caused by sea-water intrusion. In order to evaluate the extension of this phenomenon and the causes of this pollution in the Maragota area (Algarve region) we have performed a complete non-parametric geostatistical analysis of chloride-concentration data and of geophysical anomalies obtained during a proton-magnetometer survey. The study encompassed the following phases: 1) several thresholds and indicators of the saline variable were built, and a structural analysis was performed; 2) conditional probabilities according to the distance, i.e. the probabilities that exceed a specific threshold when entering the domain of a lower threshold, were calculated on the basis of the ratios between the cross-variograms of two indicators and their simple variograms; 3) for decision purposes, isoprobability contour maps of the chloride content exceeding a specific threshold value were drawn; 4) a comparative analysis of the detected magnetic anomalies with the saline anomalies has clearly pointed to the saline deposits as the most plausible groundwater-pollution source.
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