Bonardi, Maurizio

We report on the results of an experiment of in situ bioremediation by forced aeration, carried out in the Arsenale Vecchio shipyard dock basin of the Venice Lagoon, Italy. The experimental area is characterized by its limited size and reduced boat traffic. The forced aeration technique chosen for the oxygenation of the highly polluted bottom sediments and of the water column above does not obstruct harbor activities and is unique due to its innovative use of a system of porous pipes laid on the bottom sediments. The general recovery of the polluted shipyard dock basin resulted in the documented return of small fish to the area as an indication of a less polluted environment. Most important the bioremediation of the water body above the bottom sediment favours, with time, the formation of a clean natural sediment capping over the bottom contaminated sediments. Post-experiment control after fifteen months of aeration with no extra oxygen added, shows the presence of clean light grey sediments with no foul septic smell, deposited over the polluted bottom sediments. The experiment has indicated that oxygenation by porous pipe forced aeration could represent a cost effective and environmentally feasible way for the recovery of shallow marine and fresh water systems, in situations where other techniques may not be economically and/or environmentally feasible.

Vengono riportati i risultati di uno studio mineralogico condotto sui sedimenti sabbiosi tardo quatemari sottostanti il cordone litorale veneziano compreso tra la foce del Fiume Brenta a Sud e quella del Sile a Nord. Sono stati analizzati 170 campioni indisturbati, provenienti da 18 sondaggi terebrati a carotaggio continuo fino a 25-30 m sotto il piano campagna. L'analisi mineralogica è stata eseguita su un minimo di 200 grani per campione utilizzando una microsonda elettronica (EPMA) equipaggiata con uno spettrometro a dispersione di energia (EDS). L'elaborazione dei dati analitici ha evidenziato una netta differenza di composizione mineralogica tra le sabbie di deposizione continentale tardo-pleistocenica e quelle di deposizione marino-Iagunare olocenica e la possibilità di discriminarle con la sola quantificazione dei principali componenti, quali: quarzo, feldspati, calcite, dolomite, miche e clorite. Questa marcata differenza di composizione mineralogica può quindi essere utilizzata per una migliore definizione del limite Pleistocene/Olocene, in particolare nelle situazioni in cui il caratteristico livello guida di argille sovraconsolidate, noto come caranto, è assente per erosione o per mancata formazione. L'elaborazione statistica dei dati analitici ha evidenziato inoltre che la composizione mineralogica media varia, sia con la profondità che areai mente, dal settore meridionale del litorale a quello settentrionale. Le variazioni mineralogiche verticali sono state attribuite all'evoluzione temporale degli ambienti deposizionali, principalmente legati alle variazioni climatiche degli ultimi 25.000 anni, mentre quelle areali, tra i due settori litoranei, sono dovute soprattutto alle differenze petrografiche delle aree di provenienza dei sedimenti. I sedimenti sabbiosi depositati durante l'ultima fase glaciale tardo-pleistocenica presentano una composizione mineralogica media abbastanza omogenea, mentre quelli di deposizione post-glaciale mostrano variazioni ben marcate. This paper reports the results of a mineralogical investigation on 170 sand samples from 18 boreholes, 25-30 m deep and representative of Upper Quaternary sand sediments underlying the sandy littoral bar that separates the Lagoon of Venice from the open Adriatic Sea. A minimum of 200 grains, per sample, randomly chosen, have been analyzed using an Electron Microprobe (EPMA) equipped with an Energy Dispersion Spectrometer (EDS). The statistical elaboration of the analytical data indicates that the percentages of quartz, feldspars, carbonates, mica and chlorites for the sediments of the continental depositional environments are quite different from those of marine-Iagoonal environments. The mineralogical differentiation of sand sediments and their detailed characterization can be used to more accurately define the Holocene/Pleistocene boundary, particularly in those areas of the lagoon where the limit is not represented by the overconsolidated clay layer, typical of the last Pleistocene continental sedimentation, locally known as caranto. The average mineralogical composition also shows vertical and lateral variations. Generally, vertical variations are linked to changes in depositional environment conditions mainly due to climatic changes during the past 25,000 years. The lateral variations between the northern and southern areas of the Venetian littoral are related to the petrology of the source areas of sediments, the carbonate-rich Tagliamento, Piave, Sile, Adige and Brenta Rivers basins and the silicate-rich Po River basin from north to south, respectively. This study highlights that the average mineralogical composition of sands deposited during the last stage of the Wűrmian glaciation is relatively homogeneous while sand deposited during the post-glacial Flandrian transgression, shows very distinct variations.

Negli ultimi decenni le previsioni della tendenza futura del clima globale e dei suoi effetti indotti sulle aree costiere, come ad esempio le variazioni del livello del mare, gli alluvionamenti e la desertificazione, sono state oggetto di diversi studi con risultati spesso contrastanti che hanno generato accesi dibattiti scientifici, economici e politici. I vari scenari forniti generalmente sono realizzati con modelli di previsione molto complessi basati su dati input provenienti da misure di parametri ambientali che tuttavia, per una migliore validazione e calibrazione, necessitano anche di parametri indiretti di tipo paleoclimatico-ambientale. Lo studio delle successioni sedimentarie fornisce informazioni essenziali sia sulle variazioni paleoclimatiche che sui loro effetti sull'ambiente. In particolare le variazioni climatiche verificatesi su scala globale negli ultimi 25.000 anni sono rappresentative sia di periodi climatici principali con caratteristiche estreme (ultima glaciazione würmiana e postglaciale olocenico) sia di eventi secondari piu' brevi e meno intensi (ad es. periodi freddi dell'Eta' del Ferro e del Medioevo) ma estremamente significativi in quanto confrontabili per durata ed intensita' con gli scenari di previsione. Di seguito vengono riportati degli esempi di alcuni modelli di cicli sedimentari correlati alle variazioni paleoclimatiche per cinque aree soggette a differenti processi evolutivi: il litorale e la Laguna di Venezia, lo Yangtze River delta, il South Yellow Sea, il Lingdingyang Estuary Zhujiang ed il South China Sea.

The results of a study to determine the geochemical, mineralogical, magnetic and textural characteristics done on Late-Quaternary sediments from drill cores from the South Yellow Sea (core H106) and the Yangtze River Delta (core LA) (China) are reported. The Late-Pleistocene continental sedimentation is represented by clayey silt and hard clay layers, while the marine Holocene sediments consist mainly of clay (H106) and sand and clay layers (LA).

The effects of global climatic changes that occurred since the last Quaternary glaciation are recognizable in the stratigraphic sequences from several coastal zones in different locations around the world. The paleoevolution of the Northern Adriatic Sea and the Yellow Sea during the last 25,000 years has been characterized by several similar episodes of climatic changes. We report on the effects of climatic changes on the mineralogical composition and textural characteristics of clay and sand sedimentations in these paleoenvironments that are geographically far apart, correlating regional paleoclimatic changes with the mineralogical composition variations of sand and clay sequences. The mineralogical investigation has evidenced an increase of Quartz and Feldspar percentages and a decrease of Calcite and Dolomite during colder periods. Two depositional events, the hard clay layers and the cemented sand formations, that carry the imprints of the climatic conditions during their diagenesis are here reported and described. The hard clay layers represent the last continental sedimentation deposited during the Upper Pleistocene. The compactness of these clay layers is probably due to a long exposure to a cold and very dry climate. The water inside cemented sands studied were found under and outside of the Venice Lagoon and are similar to the beachrock formations presently found in tropical regions in intertidal zones. These cemented sands are remnants of ancient shorelines and witnesses of warm climate events.

The coastal areas are transition zones where land and ocean processes interact and play a critical role. Here, several factors may trigger environmental disasters or increases hydrogeological hazard. More than half of the global population lives in the 60 km wide coastal zone and the resources for populations, such as freshwater and food, depend on the critical relationships between land and sea and their variations due to both natural and anthropogenic causes. In particular, climate changes and stresses induced by human activities, e.g. pollution, engineering interventions for dams, flood control, canalization, deforestation, urbanization, agriculture and freshwater withdrawals, cause the degradation and the ravage of the habitat. In the new millennium the management of the use of coastal areas is focussed on the integration of the monitoring systems which have to provide data and information for decision support system-based actions. In 2008 the project “An integrated monitoring and management approach of hydrologic processes in coastal ecosystems for the understanding of the relationship between continental and marine waters in the Yantai (China) and in Venice (Italy) areas” started under the umbrella of the bilateral scientific and technological agreement between the National Research Council of Italy and the Chinese Academy of Sciences. The project is carried out by the Institute of Marine Sciences of Venice and the Institute of Coastal Zone Research for Sustainable Development of Yantai. This project aims at understanding the complex relationship between continental and marine groundwater, i.e. the salt water intrusion, in two coastal areas, the Laizhou Bay (Shandong Province) in the southern Bohai Sea (China) and the Venice Lagoon (Italy). In this work we report an overview of the salt water contamination process in the two study areas and some preliminary results on a survey carried out in the Venice Lagoon, which goal was to test seismic and geoelectrical surveys for the detection of buried morphological features, such as high-permeable sandy paleo-channels, that can enhance the flow of saline water from the lagoon-sea to the inland.

ABSTRACT The imprints of paleoevolutionary processes that affected the Venice lagoon and its littoral during the Late-Quaternary can be found in the sand and c/ay layers underlying the Venetian basin. Sedimentological characteristics of the Late-Pleistocene and Holocene sand and clay sedimentation during the past 25-30.000 years, before the human impact, in the lagoon of Venice, are reported. The multidisciplinary investigation of clay and sand sediments and the development and application of new analytical techniques and methodologies, allowed the detailed mineralogical, geochemical and textural characterization of the recent sediments. The new data obtained not only may contribute to better understand the paleoevolutionary events that took place in the Venetian basin and the impact of the paleoclimatic variations on the depositional environments, but also they may be used as a sediment natural reference base for a more accurate quantification of the pollution level in the bottom sediments of the lagoon of Venice. RIASSUNTO Gli strati di sabbia e di argilla sottostanti il bacino veneziano conservano le tracce dei processi paleoevolutivi che hanno influenzato la laguna di Venezia ed il suo litorale. Lo studio multidisciplinare dei sedimenti sabbiosi ed argillosi depositatisi durante gli ultimi 25-30.000 anni, prima dell'impatto antropico, e lo sviluppo ed utilizzo di nuove metodologie analitiche, hanno permesso una caratterizzazione mineralogica, geochimica e tessiturale dettagliata dei sedimenti recenti. I nuovi dati ottenuti possono non solo contribuire a meglio comprendere gli eventi paleoevolutivi succedutisi nel bacino veneziano e l'impatto delle variazioni paleoclimatiche sugli ambienti deposizionali, ma possono anche servire come base naturale di riferimento per una più accurata quantificazione dei livelli di inquinamento dei sedimenti di fondo soggetti ad antropizzazione della laguna di Venezia.

RIASSUNTO Questo lavoro riporta l'applicazione del rilevamento geomorfologico attraverso misure plano-altimetriche e batometriche ad alta risoluzione per differenti problematiche ambientali in due aree costiere: la Laguna di Venezia e lo stagno costiero di Orbetello. La programmazione di un piano di gestione e salvaguardia degli ecosistemi ha richiesto, per la laguna di Venezia, il monitoraggio delle tendenze evolutive' dei principali elementi morfologici, mentre per Orbetello la naturalizzazione di alcune casse di colmata. I rilevamenti topografici e batimetrici di dettaglio sono stati effettuati sia mediante strumenti e metodologie tradizionali sia mediante GPS in modalità statica-differenziale e cinematica-differenziale che ha permesso la visualizzazione dei dati in tempo reale ottenendo un diretto controllo delle misure. Queste metodologie, per il rilevamento topografico di alcuni limiti ed elementi morfologici inaccessibili,sono state integrate dal telerilevamento con foto aeree mentre, per la progettazione degli interventi di modella mento delle casse di colmata,dalla mappa tura dei sedimenti superficiali. Infine, la valutazione dei tassi erosivi e deposizionali, è stata effettuata sia con rilevamenti topografici stagionali sia con il confronto di una serie storica di cartografie e di foto aeree. ABSTRACT Environment management plans for lagoonal ecosystems require highly detailed geomorphological maps that cannot be obtained with the standard topographical survey. High resolution topographic and bathymetric measurements were carried out in the Lagoon of Venice and in the Lagoon of Orbetello (ItaIy) both with traditional methods and instrumentation and with DGPS (Differential Global Positioning System) in static and kinematic differential modes, with the purpose of providing the ecosystem management plans for the two lagoons, with detailed geomorphological data. For the Lagoon of Venice the detailed topographic and bathymetric surveys were required for the recognition and quantification of erosion and/or deposition processes active in the Venetian basin survey. The comparison of topographic and bathymetric surveys, since 1931, of aerial photographs and of all available information on the geomorphology of the area, has allowed the recognition and quantification, on a decadal scale, of the rate and trend of erosion and sedimentation and has made it possible to de fine those morphological boundaries impossible to survey due to the inaccessible soft mud. Three field measurements done during the 1996-1997 period have made possible the identification of the present erosion rate in a selected area of a salt marsh subjected to wave action. For the Lagoon of Orbetello very low scale topographic measurements were needed for the "naturalization" of manmade mud flats and salt marshes. The naturalization plan of five artificial islets, made with dredged sediments, required the detailed topographic measurements at very low scale of all the morphological elements in order to recreate a natural environment for a rich transitory, nesting or permanent bird life. In addition, sever l small creeks have been dredged for improve the hydrodynamics of the lagoon and the water exchallge between shallows in the 111art made islets and the main channels and to protect the bird life by making it inaccessible for man and other predacious animals. Overall the combination of traditional survey methods with DGPS and the use of all in house developed software has proved to be very efficient for producing the required for detailed topographic and bathymetric maps of the two study areas. Furthermore the study has provided the management plans for the two different ecosystems with geomorphological data otherwise not available.

The results of a detailed study on the sediments representative of the boundary area from the Late-Pleistocene and the Lower-Holocene sedimentations are reported. Mineralogical, granulometric and geochemical investigations have been carried out to characterize the clay-rich samples taken along the littoral bar and representative of the continental and marine sedimentations. Particular attention was devoted to the study of the overconsolidated clay layer considered to be the last continental deposit before the Holocene (Flandrian) transgression and interpreted as a paleosol.

ABSTRACT The effect of global climatic changes that occurred since the last Würmian glaciation is recognizable in the stratigraphic sequences of the Pleistocene-Holocene boundary zone from several coastal areas in different locations around the world. This study gives the results of mineralogical, chemical, and textural investigations of about fifty samples of the hard clay layers and the clay layers above and below underlying the Venice littoral. This hard clay layer, locally known as caranto, from few centimeters to few meters thick, represents the Holocene/Pleistocene boundary and it carries the marks of climate changes that characterized the last phase of the Pleistocene and the early part of the Holocene. The very dry climate during a period of very limited sedimentation and a long subaerial exposition, desiccated, compacted and oxidized the clay previously deposited, to form the overconsolidated clay level (caranto). RIASSUNTO Gli effetti delle variazioni climatiche succedutesi, su scala globale, a partire dall'ultima glaciazione würmiana sono riconoscibili nelle sequenze stratigrafiche in varie località costiere sparse in tutto il mondo. In questo studio vengono riportati i risultati preliminari di una indagine sulle caratteristiche mineralogiche, geochimiche e tessiturali di circa cinquanta campioni di un livello di argilla sovraconsolidata e degli strati argillosi sopra e sottostanti, lungo il litorale veneziano. Questo strato di argilla sovraconsolidata, noto come "caranto", con spessore variante da pochi centimetri ad alcuni metri, rappresenta il limite Olocene/Pleistocene e conserva gli effetti dei cambiamenti climatici che hanno caratterizzato l'ultima fase del Pleistocene e quella iniziale dell'Olocene. Il clima freddo e molto arido, durante un periodo di sedimentazione molto limitata e la prolungata esposizione subaerea hanno determinato l'essiccamento, la compattazione e l'ossidazione dell'ultima sedimentazione continentale argillosa, sino a formare quel livello sovraconsolidato che e' noto col nome locale di caranto.