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Fig. 9 Results obtained for six of the standard acute bioassays performed with samples from Paranhos and Salgueiros groundwater, collected during the 2006 campaign in the Arca d’Agua masonry reservoirs, the granitic gutter pipe (white symbols) and the rock discontinuities (black symbols)

Figure 9 Results obtained for six of the standard acute bioassays performed with samples from Paranhos and Salgueiros groundwater, collected during the 2006 campaign in the Arca d’Agua masonry reservoirs, the granitic gutter pipe (white symbols) and the rock discontinuities (black symbols)

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Fig. 1 Regional hydrogeological setting from Porto City (geological background revised from Carrington da Costa and Teixeira 1957; COBA 2003; Chaminé et al. 2003a). Regional hydrogeological units and related features in the Porto area (lower part of the figure)
Fig. 1 Regional hydrogeological setting from Porto City (geological background revised from Carrington da Costa and Teixeira 1957; COBA 2003; Chaminé et al. 2003a). Regional hydrogeological units and related features in the Porto area (lower part of the figure)
a very complex groundwater flow regime. In the less- weathered granite, the flow path is mainly related to the discontinuities set systems, whereas in the more heavily weathered material or soil-like granite, the ground acts more like a porous medium (Fig. 3). Hydrogeochemistry To understand how human activities may interfere with the chemical composition of these groundwaters, 23 sampling points were selected (see Fig. 3). The results of the phys- ico-chemical analyses of local groundwater samples are presented in Table 1. Sampled waters are mainly slightly acidic with a median pH value of 6.8 (pH values ranged from 5.1 to 7.9). Electrical conductivity (EC) measurements ranged from 369 to 604 uS/cm, indicating the presence of medium mineralised waters. The chemical signatures of these samples may be divided into two groups: (1) most of the waters from Arca d'Agua masonry reservoirs and those flowing along the granitic gutter pipe are of SO,—Ca-type and (2) waters percolating through the rock discontinuities Sampled waters are mainly slightly acidic with a median
a very complex groundwater flow regime. In the less- weathered granite, the flow path is mainly related to the discontinuities set systems, whereas in the more heavily weathered material or soil-like granite, the ground acts more like a porous medium (Fig. 3). Hydrogeochemistry To understand how human activities may interfere with the chemical composition of these groundwaters, 23 sampling points were selected (see Fig. 3). The results of the phys- ico-chemical analyses of local groundwater samples are presented in Table 1. Sampled waters are mainly slightly acidic with a median pH value of 6.8 (pH values ranged from 5.1 to 7.9). Electrical conductivity (EC) measurements ranged from 369 to 604 uS/cm, indicating the presence of medium mineralised waters. The chemical signatures of these samples may be divided into two groups: (1) most of the waters from Arca d'Agua masonry reservoirs and those flowing along the granitic gutter pipe are of SO,—Ca-type and (2) waters percolating through the rock discontinuities Sampled waters are mainly slightly acidic with a median
Table 1 Physico-chemical data for water samples collected during the fieldwork campaigns (2005 and 2006 Site description: ar Arca d "Agua masonry reservoirs, g granitic gutter pipe, r rock discontinuities, n.d. not determinec
Table 1 Physico-chemical data for water samples collected during the fieldwork campaigns (2005 and 2006 Site description: ar Arca d "Agua masonry reservoirs, g granitic gutter pipe, r rock discontinuities, n.d. not determinec
Concerning the irrigation guidelines limits imposed by the Portuguese law, these waters have EC and SAR (sodium adsorption ratio) values below those limits, 1,000 p1S/cm and 8, respectively. Nevertheless, since the majority of the sam- ples exceed 50 mg/L for nitrate, this means that more sensitive cultures can be affected by these high levels of nitrate. Portuguese law, these waters have EC and SAR (sodium
Concerning the irrigation guidelines limits imposed by the Portuguese law, these waters have EC and SAR (sodium adsorption ratio) values below those limits, 1,000 p1S/cm and 8, respectively. Nevertheless, since the majority of the sam- ples exceed 50 mg/L for nitrate, this means that more sensitive cultures can be affected by these high levels of nitrate. Portuguese law, these waters have EC and SAR (sodium
waters of the same group. These two outlayers could be attributed with a di bonate concentration in these two water samples could be explained slighter water-rock interaction (e.g. plagioclase hydroly- sis). In t wastewat NO; and to a mixing process of infiltrated meteoric waters fferent underground flow path. The lower bicar- by local granitic heterogeneities, inducing a he waters from rock discontinuities as a whole, ers should be considered as typical sources of Cl, SO,. Leakage from sewerage systems could also be an im portant factor, since most of these infrastructures may be deteriorated and so they are not leakproof (see Eiswirth 2002; Barrett 2004; Taylor et al. 2004; Burn et al. 2007). Coancernino the icatanic annrnach renrecentative anal
waters of the same group. These two outlayers could be attributed with a di bonate concentration in these two water samples could be explained slighter water-rock interaction (e.g. plagioclase hydroly- sis). In t wastewat NO; and to a mixing process of infiltrated meteoric waters fferent underground flow path. The lower bicar- by local granitic heterogeneities, inducing a he waters from rock discontinuities as a whole, ers should be considered as typical sources of Cl, SO,. Leakage from sewerage systems could also be an im portant factor, since most of these infrastructures may be deteriorated and so they are not leakproof (see Eiswirth 2002; Barrett 2004; Taylor et al. 2004; Burn et al. 2007). Coancernino the icatanic annrnach renrecentative anal
Fig. 6 6'°O versus 6°H signatures of the groundwater samples from Paranhos spring galleries. The Global Meteoric Water Line (GMWL: 67H = 8 65'80 + 10 in Craig 1961) and the Local Meteoric Water Line were plotted as reference (LMWL: 57H = 7.260 + 4.98; °° = 0.67; n = 30)
Fig. 6 6'°O versus 6°H signatures of the groundwater samples from Paranhos spring galleries. The Global Meteoric Water Line (GMWL: 67H = 8 65'80 + 10 in Craig 1961) and the Local Meteoric Water Line were plotted as reference (LMWL: 57H = 7.260 + 4.98; °° = 0.67; n = 30)
Fig. 7 Evolution pattern of 3H and 6'°O contents along spring collection chambers for 2005 (a) and 2006 (b) fieldwork campaigns On the other hand, the decrease in the tritium activity found in 2006 (in all water samples) can be attributed to the presence of older groundwater entering the system due to the lack of precipitation during the preceding years (see Fig. 8). This hypothesis seems to be corroborated by the extremely low *H content in samples from the spring Besides, one can also identify a decrease in the 3H values between the 2005 and 2006 campaigns. The highest
Fig. 7 Evolution pattern of 3H and 6'°O contents along spring collection chambers for 2005 (a) and 2006 (b) fieldwork campaigns On the other hand, the decrease in the tritium activity found in 2006 (in all water samples) can be attributed to the presence of older groundwater entering the system due to the lack of precipitation during the preceding years (see Fig. 8). This hypothesis seems to be corroborated by the extremely low *H content in samples from the spring Besides, one can also identify a decrease in the 3H values between the 2005 and 2006 campaigns. The highest
Fig. 8 5'%O versus 7H scatter diagrams for water samples collected during 2005 (a) and 2006 (b) fieldwork campaigns
Fig. 8 5'%O versus 7H scatter diagrams for water samples collected during 2005 (a) and 2006 (b) fieldwork campaigns
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