RADIOCHEMICAL APPROACH TO ENVIRONMENTAL INVESTIGATION OF AQUATIC SYSTEMS
Introduction
Sustainable development and responsible care are imperatives in countries
where, it is possible to conjugate properly development and environmental
protection; this implies:
-introducing advanced technologies to minimise and control emissions in
the environmental compartments
-recovering of the already compromised natural environments.
Environmental Protection - Aquatic systems
The aquatic systems represent the ultimate sink of all wastes dispersed in
fresh waters and in the soil and subsequently are the most potentially
affected bodies of the ecosystem. Sediments play an important role in
defining the features of an aquatic environment; and can directly
influence a wide range of chemical reactions that strongly affect the
composition of the overlying water column. Under suitable, undisturbed
conditions sediments can document the history of past events and allow the
reconstruction of antecedent environmental situations.
The Radiochemical approach
The radiochemical characterisation of sediments in contaminated aquatic
systems has gained increasing interest in as much as this activity is
almost unique to obtain information critical for the environmental
recovery:
-the determination of the inventory of the anthropic fraction of
micropollutants present in the system.
-the identification of the natural background (pre-industrial)
concentration for each single micropollutant.
-the determination of the sediment balance in term of erosion/accumulation
over a given period of time.
-the quantification of intra-basin sediments transport phenomena even at
the seasonal time scale etc.
For this purpose new specific analytical protocol, based on concentration
measurements of some radioisotopes whose initial concentrations in air or
in water is almost constant or well-known, have been prepared and
qualified in our Institute.
The best solution is to carry out a preliminary survey to investigate the
homogeneity of the system; and then to plan a detailed study in accordance
with the intents that are effectively achievable.
Utilisation of Radiochemical data
The general features of the system evolution as concerns
erosion/accumulation of sediments could be derived from the inventory
distribution of radioisotopes (see example in figure). The peculiarity of
the radiochemical procedure is evidenced in the present case for its
independence from a series of disturbing factors normally present in
coastal systems e.g. subsidence and eustacy, which make dubious the
results obtained with the traditional bathymetric measurements. Using
these maps, a detailed chronological reconstruction will be carried out
for each homogeneous area. The aim of this phase is to obtain a
characterisation of sediment profiles as wide as possible, including all
parameters linked to organic and inorganic pollution. This set of data
will allow the detailed reconstruction of the inventories and of the
fluxes of the pollutants. These data are essential for the environmental
recovery of the area.
This methodology, that will be improved to determine the mass balance of
suspended materials exchanged between sea-lagoon coastal systems, has been
already applied for environmental investigations of the Lagoon of Venice
in collaboration with Consorzio Venezia Nuova (MLP-Water Authority of
Venice).
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