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Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale
Plesso Scienze della Terra
Parco Area delle Scienze 157/A
43124 Parma
Address: Università di Parma
Dipartimento di Scienze Chimiche, della Vita e della Sostenibilità Ambientale
Plesso Scienze della Terra
Parco Area delle Scienze 157/A
43124 Parma
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The temporal variability of microbial communities in two springs fed by the same aquifer system, but discharging up- and down-gradient of two low-permeability fault zones, was analysed using a 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)-based approach. At both springs, a remarkable temporal variation in PCR-DGGE profiles was detected throughout the observation period. When comparing the PCR-DGGE profiles of the two springs, a synchronous evolution over time was observed. Moreover, the per cent of PCR-DGGE bands common to both springs progressively increased from early (23%) to late recharge (70%), only to decrease once more in late recession (33%). Considering the results of the hydrogeological and isotopic investigations and EC measurements, the results of biomolecular analyses demonstrate that, at the study site, compartments straddling the analysed fault zones have microbial interconnections, despite the existence of low-permeability fault cores.
investigations (18O,δ2H). The input signal (rainwater) was compared with the isotopic content
of a 35-meter groundwater vertical prof ile, over a 1-year period. Within the studied aquifer,
recharge and f low are diffuse in a well-connected f issure network.
At the test site, the comparison between input and groundwater isotopic signals illustrates that
no eff icient mixing takes place in the whole unsaturated zone, between the fresh inf iltration
water and the stored water.
When analysing the stable isotope composition of groundwater, signif icant variations were
observed above the threshold elevation of 1062 m asl, while a nearly constant composition was
observed below the same threshold. Thus, temporal variations in stable isotope composition
of rainwater are completely attenuated just in the deeper phreatic zone.
On the whole, taking into consideration also the results of previous studies in the same area,
the investigations showed that physical characteristics of the carbonate bedrock, as well as
aquifer heterogeneity, are factors of utmost importance in inf luencing the complete mixing of
water. These f indings suggest a more complex scenario at catchment scale.
The research demonstrated that, in carbonate aquifers where low-permeability faults cause the aquifer system to be compartmentalized, high-altitude temporary springs may be recharged by groundwater. In such settings, neither surface water infiltration in karst systems nor perched temporary aquifers play a role of utmost importance. The rare (once or a few time a year) activation of such springs is due to the fact that groundwater unusually reach the threshold head that allows the spring to flow. The activation of the studied high-altitude temporary spring also depended on relationships between a low-permeability fault core and a karst system that locally interrupts the low-permeability barrier. In fact, when the hydraulic head did not reach the karst system, the concentrated head loss within the fault core did not allow the spring to flow, because the groundwater entirely flowed through the fault towards the downgradient compartment. Copyright 2009 John Wiley & Sons, Ltd."
The results showed that the investigated siliciclastic deposits and marly-clayey-calcareous successions may allow significant groundwater discharge from carbonate aquifers. Thus, they do not everywhere behave as aquitard, contrary to the previous model. Instead, groundwater flows through the upper part of these successions, where stress release fracturing enhanced rock permeability in the near-surface bedrock. Thus, these successions may locally be a new groundwater source within the southern Apennine chain. Copyright 2009 John Wiley & Sons, Ltd."
All investigations revealed the formation of a non-permanent halocline at the experimental site, whose thickness and shape varies over time. Variations in thickness and shape are influenced by infiltration pro- cesses. Three main types of Electrical Conductivity (EC) profiles were found during the research period. In the high-flow period, the EC profile consisted of a transition layer and a nearly homogeneous higher salin- ity groundwater layer, and no mixed layer was observed. A nearly-homogeneous mixed layer was detected in the low-flow period, excluding the late recession when the EC profile was characterized by a higher salinity groundwater layer and a negligible transition layer. The EC profile through the transition layer was approximately symmetric and linear, probably due to a velocity shear across this layer. The velocity shear was probably caused by the difference in opening-porosity detected between the upper and lower carbonate bedrock through geophysical investigations.
The investigated phenomenon is due to water that infiltrates very close to the observation well. In fact: (a) the isotopic composition of the lower salinity groundwater layer in early recharge 2007/2008 (d18O = -8.12‰; d2H =- 49.92‰) is very close to the composition of rainwater collected in the same per- iod near the observation well (d18O = -8.19‰; d2H = -51.35‰); (b) the CDIC composition in the lower salinity groundwater layer (-15,96‰) is very close to the composition (-15.77‰) in the infiltration water collected at the bottom of the soil medium, close to the observation well; (c) the lower salinity groundwater layer is characterized by significant concentrations of acetate (up to 4.5 mg/L) as well as the saturated paste extracts obtained only from the soil medium collected close to observation well (up to 110 mg/L); (d) in the lower salinity groundwater layer acetate-assimilating bacteria belonging to Betaproteobacteria and Bacteroidetes were found, further supporting that this groundwater layer signif- icantly interacts with the soil medium described above. Similar mean 3H contents in local rainwater (4.6 TU), in the lower salinity groundwater layer (4.5 TU), in the higher salinity groundwater layer (4.5 TU) and in spring water (4.4 TU) clearly show that the halocline formation is not influenced by dif- ferences in residence times.
Ó 2009 Elsevier B.V. All rights reserved.
The taxonomic classification of fecal indicators detected in spring water samples was performed using API20 galleries. Fecal enterococci were also identified by means of 16S rRNA gene sequencing. The topsoil of pyroclastic origin significantly retains both thermotolerant coliforms and fecal enterococci. Results of column tests carried out in soil blocks collected randomly within the test site suggest that Escherichia coli was more retained than Enterococcus faecalis, even though this difference is statistically significant in only two out of six soil samples. Thus, a non-uniform difference in retention is expected at field scale. This suggestion is in agreement with the results of
the microbiological monitoring. In fact, fecal enterococci were a more reliable indicator than thermotolerant coliforms for detecting contamination at both seasonal springs of the aquifer system, while no significant differences were
observed at the perennial spring."
The present study has been focused on the refinement of protection measures for carbonate aquifers in central-southern Italy, taking into consideration their hydrogeological features and the results of several years of experimental researches in different test sites.
In these aquifers a good protection can be obtained by integrating the D.L. 152/2006 with specific solutions. The integrative measures can be synthesized as follows: (a) introduction of new protection zones, (b) identification of criteria for delimiting zones IIa, (c) introduction of the concept of “developing protection zones”, and (d) use of “dynamic” protecting measures, when polluting human activities are already existent within the protection zones.
The “map of land use restrictions” has been identified as the graphic core of a GIS-based sDSS which will aid decision-makers to protect the water resources against pollution.
"
aquifer and (b) when the karst system is partially located within a saturated medium. The effectiveness of the updated method has been experimentally verified by comparing the vulnerability values with the results of a hydrogeological and microbiological study at a test site."
schematized by several authors. In the test site, the contrast in permeability at the bottom of the epikarst does not cause retention of percolation and storage of water in a perched temporary aquifer within the uppermost portion of the carbonate medium. Because of the high fracture density and good interconnection of openings within the underlying limestone, the percolation is diffuse also below the epikarstic zone, as well as the groundwater flow. The ‘funnelling’ effect into larger shafts does not play an important role on the hydrogeological behaviour of the aquifer.
some fault zones, as a function of groundwater level fluctuations."
The temporal variability of microbial communities in two springs fed by the same aquifer system, but discharging up- and down-gradient of two low-permeability fault zones, was analysed using a 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)-based approach. At both springs, a remarkable temporal variation in PCR-DGGE profiles was detected throughout the observation period. When comparing the PCR-DGGE profiles of the two springs, a synchronous evolution over time was observed. Moreover, the per cent of PCR-DGGE bands common to both springs progressively increased from early (23%) to late recharge (70%), only to decrease once more in late recession (33%). Considering the results of the hydrogeological and isotopic investigations and EC measurements, the results of biomolecular analyses demonstrate that, at the study site, compartments straddling the analysed fault zones have microbial interconnections, despite the existence of low-permeability fault cores.
investigations (18O,δ2H). The input signal (rainwater) was compared with the isotopic content
of a 35-meter groundwater vertical prof ile, over a 1-year period. Within the studied aquifer,
recharge and f low are diffuse in a well-connected f issure network.
At the test site, the comparison between input and groundwater isotopic signals illustrates that
no eff icient mixing takes place in the whole unsaturated zone, between the fresh inf iltration
water and the stored water.
When analysing the stable isotope composition of groundwater, signif icant variations were
observed above the threshold elevation of 1062 m asl, while a nearly constant composition was
observed below the same threshold. Thus, temporal variations in stable isotope composition
of rainwater are completely attenuated just in the deeper phreatic zone.
On the whole, taking into consideration also the results of previous studies in the same area,
the investigations showed that physical characteristics of the carbonate bedrock, as well as
aquifer heterogeneity, are factors of utmost importance in inf luencing the complete mixing of
water. These f indings suggest a more complex scenario at catchment scale.
The research demonstrated that, in carbonate aquifers where low-permeability faults cause the aquifer system to be compartmentalized, high-altitude temporary springs may be recharged by groundwater. In such settings, neither surface water infiltration in karst systems nor perched temporary aquifers play a role of utmost importance. The rare (once or a few time a year) activation of such springs is due to the fact that groundwater unusually reach the threshold head that allows the spring to flow. The activation of the studied high-altitude temporary spring also depended on relationships between a low-permeability fault core and a karst system that locally interrupts the low-permeability barrier. In fact, when the hydraulic head did not reach the karst system, the concentrated head loss within the fault core did not allow the spring to flow, because the groundwater entirely flowed through the fault towards the downgradient compartment. Copyright 2009 John Wiley & Sons, Ltd."
The results showed that the investigated siliciclastic deposits and marly-clayey-calcareous successions may allow significant groundwater discharge from carbonate aquifers. Thus, they do not everywhere behave as aquitard, contrary to the previous model. Instead, groundwater flows through the upper part of these successions, where stress release fracturing enhanced rock permeability in the near-surface bedrock. Thus, these successions may locally be a new groundwater source within the southern Apennine chain. Copyright 2009 John Wiley & Sons, Ltd."
All investigations revealed the formation of a non-permanent halocline at the experimental site, whose thickness and shape varies over time. Variations in thickness and shape are influenced by infiltration pro- cesses. Three main types of Electrical Conductivity (EC) profiles were found during the research period. In the high-flow period, the EC profile consisted of a transition layer and a nearly homogeneous higher salin- ity groundwater layer, and no mixed layer was observed. A nearly-homogeneous mixed layer was detected in the low-flow period, excluding the late recession when the EC profile was characterized by a higher salinity groundwater layer and a negligible transition layer. The EC profile through the transition layer was approximately symmetric and linear, probably due to a velocity shear across this layer. The velocity shear was probably caused by the difference in opening-porosity detected between the upper and lower carbonate bedrock through geophysical investigations.
The investigated phenomenon is due to water that infiltrates very close to the observation well. In fact: (a) the isotopic composition of the lower salinity groundwater layer in early recharge 2007/2008 (d18O = -8.12‰; d2H =- 49.92‰) is very close to the composition of rainwater collected in the same per- iod near the observation well (d18O = -8.19‰; d2H = -51.35‰); (b) the CDIC composition in the lower salinity groundwater layer (-15,96‰) is very close to the composition (-15.77‰) in the infiltration water collected at the bottom of the soil medium, close to the observation well; (c) the lower salinity groundwater layer is characterized by significant concentrations of acetate (up to 4.5 mg/L) as well as the saturated paste extracts obtained only from the soil medium collected close to observation well (up to 110 mg/L); (d) in the lower salinity groundwater layer acetate-assimilating bacteria belonging to Betaproteobacteria and Bacteroidetes were found, further supporting that this groundwater layer signif- icantly interacts with the soil medium described above. Similar mean 3H contents in local rainwater (4.6 TU), in the lower salinity groundwater layer (4.5 TU), in the higher salinity groundwater layer (4.5 TU) and in spring water (4.4 TU) clearly show that the halocline formation is not influenced by dif- ferences in residence times.
Ó 2009 Elsevier B.V. All rights reserved.
The taxonomic classification of fecal indicators detected in spring water samples was performed using API20 galleries. Fecal enterococci were also identified by means of 16S rRNA gene sequencing. The topsoil of pyroclastic origin significantly retains both thermotolerant coliforms and fecal enterococci. Results of column tests carried out in soil blocks collected randomly within the test site suggest that Escherichia coli was more retained than Enterococcus faecalis, even though this difference is statistically significant in only two out of six soil samples. Thus, a non-uniform difference in retention is expected at field scale. This suggestion is in agreement with the results of
the microbiological monitoring. In fact, fecal enterococci were a more reliable indicator than thermotolerant coliforms for detecting contamination at both seasonal springs of the aquifer system, while no significant differences were
observed at the perennial spring."
The present study has been focused on the refinement of protection measures for carbonate aquifers in central-southern Italy, taking into consideration their hydrogeological features and the results of several years of experimental researches in different test sites.
In these aquifers a good protection can be obtained by integrating the D.L. 152/2006 with specific solutions. The integrative measures can be synthesized as follows: (a) introduction of new protection zones, (b) identification of criteria for delimiting zones IIa, (c) introduction of the concept of “developing protection zones”, and (d) use of “dynamic” protecting measures, when polluting human activities are already existent within the protection zones.
The “map of land use restrictions” has been identified as the graphic core of a GIS-based sDSS which will aid decision-makers to protect the water resources against pollution.
"
aquifer and (b) when the karst system is partially located within a saturated medium. The effectiveness of the updated method has been experimentally verified by comparing the vulnerability values with the results of a hydrogeological and microbiological study at a test site."
schematized by several authors. In the test site, the contrast in permeability at the bottom of the epikarst does not cause retention of percolation and storage of water in a perched temporary aquifer within the uppermost portion of the carbonate medium. Because of the high fracture density and good interconnection of openings within the underlying limestone, the percolation is diffuse also below the epikarstic zone, as well as the groundwater flow. The ‘funnelling’ effect into larger shafts does not play an important role on the hydrogeological behaviour of the aquifer.
some fault zones, as a function of groundwater level fluctuations."
Hydrogeological and geophysical investigations demonstrated the existence of epikarstic horizons, up to 10 m thick. Epikarst formation, evolution and thickening are enhanced by thickness, texture and permeability of pyroclastic soil that often overlies
carbonate rocks in southern Italy, as well as by land use. Nevertheless, the hydrogeological behaviour of the epikarst is different from that schematized by several authors in classic karst aquifers. The small size (<1 m3) of rock blocks and the high
number of sub-vertical discontinuity sets imply a high and diffuse infiltration through the fractured rock mass at the epikarst bottom. Thus, the contrast in permeability at the bottom of the studied epikarstic zones does not cause retention of percolation and storage of water in perched temporary aquifers within the uppermost portion of the carbonate medium. The “funnelling” effect into larger shafts does not play an important role on the
hydrogeologic behaviour of the aquifer, and the epikarst does not significantly influence the recharge function of the carbonate aquifer at basin scale, as well as the transport of contaminants from the ground towards the groundwater."