Assessment of mixing between shallow and thermal waters using geochemical and environmental isotope tracers (N Portugal): a review and reinterpretation

• Type: Article in International Scientific Journal
• Date: 2014

Authors

Marques, J.M. (Author) Other; Matos, C. (Author) Other; Carreira, P.M. (Author) Other; Marques, Jorge Espinha (Author) FCUP; Teixeira, José (Author) FLUP; Chamine, Helder I. (Author) Other

Journal

Title: Environmental Earth Sciences

Vol. 72

Pages: 2557-2567

ISSN: 1866-6280

Publisher: Springer Nature

Indexing

ISI Web of Knowledge - 3 Citations

Scopus - 3 Citations

Scientific classification

FOS: Natural sciences > Earth and related Environmental sciences

CORDIS: Natural sciences

Other information

Authenticus ID: P-009-TTP

DOI: 10.1007/s12665-014-3162-4

Abstract (EN): Caldas de Moledo thermal (27-46 A degrees C) spring and borehole waters issue in the region of the famous Port Wine vineyards, in the Douro River valley (Northern Portugal). The most abundant lithotypes are lower Cambrian metasedimentary rocks, Variscan granitoids and aplite-pegmatitic veins. The thermal waters are characterised by pH a parts per thousand 9.0, TDS ranging from 200 to 350 mg/L, and belong to the HCO3-Na facies indicating that the reservoir rock should be mainly granite. Since the local Spa is strongly dependent on water quality, the effects of mixing between local shallow cold groundwaters and deep thermal waters have been properly investigated. In the SO4 (2-) (mg/L) versus delta O-18 (aEuro degrees vs. V-SMOW) diagram we can observe that some of the thermal springs show evidences of mixing (higher SO4 (2-) concentrations) with local meteoric waters infiltrated at lower altitude sites (enriched delta O-18 signatures), showing the "altitude effect" in the isotopic composition of the recharge waters. Similar trends can be found in the K+, NO3 (-), Ca2+ and Na+ (mg/L) versus delta O-18 (aEuro degrees vs. V-SMOW) diagrams. It should be stated that SO4 (2-), K+ and Ca2+ are present in the fertilizers and fungicides used in the vineyards in the northern part of the country. Up to now, the thermal waters from boreholes used in the local Spa do not show evidences of mixing with shallow groundwaters contaminated with agrochemicals. The results obtained so far indicate that in the near future, special attention should be put on the possible occurrence of diffuse agricultural contamination (related to the Port Wine vineyards) in the thermal spring waters.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11