Publication Date:
2020-10-16
Description:
Urban lakes have become increasingly important in the
planning of urban ecology, green infrastructure and green areas
in European cities. This paper describes the chemical, isotope and
microbial features of Lake Bullicante, a small artificial lake located
within the urban area of the city of Rome. It has an anthropogenic
origin due to excavation works that intercepted the underlying
aquifer, giving rise to a water body. The lake area is 7.000 m2, with
a maximum depth of 7 m and located on the distal deposits of the
Alban Hills Volcanic District in an area named “Acqua Bullicante”
(i.e. Bubbling Water), where degassing phenomena were historically
recorded. The proximity of this volcanic district motivated the
study on Lake Bullicante as a potential open-air laboratory to
trace possible degassing phenomena in a highly urbanized area. A
preliminary geochemical and microbial sampling survey was carried
out in winter 2018. Samples were collected along a vertical profile
of the lake from the surface to the maximum depth. Major, minor,
trace elements, dissolved gases and stable isotopes (δD-H2O, δ18OH
2O, δ13C-CO2) were analyzed, along with the analysis of 87Sr/86Sr
ratio. The microbial community characteristics were analysed by
epifluorescence microscopy (CARD-FISH) and flow cytometry. The
chemical composition and water isotopes suggest that lake water
has a meteoric origin and is related to a Ca-HCO3 shallow aquifer
hosted in volcanic rocks. This is confirmed by both the 87Sr/86Sr
ratio of lake water, which falls in the range of values of Alban Hills
volcanites, and the chemical-isotopic composition of neighboring
wells. A relatively high concentration of dissolved CO2, its isotopic
signature (d13C-CO2 20‰ V-PDB), and the high content in organic
matter (DOC 10-30 mg/L) suggest for the lake a eutrophication state
with denitrification also occurring. Considering the relatively high
concentrations of dissolved CO2, an external input of carbon dioxide
cannot be completely excluded and as a consequence, not even the
hypothesis of mixing processes between biotic and inorganic CO2.
This makes further investigations necessary especially during the
summer, when the lake is stratified. A summer survey could be also
useful to better understand the microbial processes into the lake,
its eutrophication evolution and health status, and to plan eventual
proper remediation strategies, providing important tools to the local
administration and stakeholders to improve, protect and preserve
this ecological niche.
Description:
Published
Description:
436-449
Description:
6A. Geochimica per l'ambiente e geologia medica
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article