Hydrogeochemical, isotopical and ecotohicological approach to the Paranhos spring galleries catchworks from Porto urban area (nw Portugal)

This multidisciplinary study presents the preliminary results of the hydrogeochemical, isotopical and ecotoxicological analyses performed to assess the nature and suitability for use of groundwater from the Paranhos’ spring galleries catchworks. These springs constituted for more than five centuries one of the main water supplies to Porto city. For the characterisation of the underground area (ca. 3km extension and a-25m of depth), constituted mainly by granitic rocks, the following tools were applied: i) subsurface geological and geotechnical mapping and; ii) hydrogeological, isotopical and ecotoxicological techniques. Surface and subsurface fieldwork surveys were first carried out to identify major tectonic accidents responsible for groundwater circulation paths and to assess lithological and structural heterogeneity. Hydrogeological fieldwork campaigns were then performed, and in situ determinations included: temperature (°C), pH and electrical conductivity (uS/cm). Several sampling sites were subsequently established, based on the surface activities located on the course of the springs, and water samples were collected for hydrogeochemical, isotopical and ecotoxicological analyses. All the water samples have been analysed for major element concentration. The isotopic techniques employed included d2H and d18O. For ecotoxicological evaluation standard acute bioassays with Daphnia magna were performed. For each sample, two 48h-LC5o bioassays were simultaneously performed: one with PH correction and the other without pH correction. In each bioassay, five concentrations of groundwater were prepared by dilution of the original sample with ASTM hard water. The hydrogeochemical analyses showed a nitrate and sulphate-enriched composition for these groundwaters, probably resulting from intense urbanisation, sewer leakage and some agricultural practices. Concerning the ecotoxicological analyses, no mortality was observed in any of the tests performed. The results obtained in this study suggest that part of Porto urban groundwater could be suitable for irrigation uses, but additional tests must be carried out to verify its compliance with existing standards of water quality. Specifically, geoenvironmental and ecotoxicological studies are required to assess potential variations in water composition and toxicity associated with seasonal changes in climate and human activities.

Palavras-chave

Groundwater Porto urban area hydrogeochemistry isotope hydrology Daphnia magna bioassays

URI

http://hdl.handle.net/10400.22/32317

Citação

Afonso, M. J., Chaminé, H. I., Guimarães, L., Marques, J. M., Carreira, P., Costa, I., Teixeira, J., Carvalho, J. M., Guilhermino, L., Fonseca, P. E. & Rocha, F. T. (2006, july 12-14). Hydrogeochemical, isotopical and ecotohicological approach to the Paranhos spring galleries catchworks from Porto urban area (nw Portugal). In Beleza, B. (Ed.) Conferência internacional sobre a água - IWC 2006. (pp.213-222). Porto, Portugal.

Editora

ISEP - Instituto Superior de Engenharia do Porto

Coleções

ISEP – DEG – Artigos

Licença CC

Sem licença CC

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