stefano guerzoni | International Marine Centre (original) (raw)

Papers by stefano guerzoni

Organohalogen compounds, 2004

Zenodo (CERN European Organization for Nuclear Research), Feb 23, 2009

Comparison of 1927, 1970 and 2002 bathymetric surveys in the Lagoon of Venice was used to reconst... more Comparison of 1927, 1970 and 2002 bathymetric surveys in the Lagoon of Venice was used to reconstruct historical changes in sedimentation. A detailed GIS-based analysis of the charts revealed the timing and pattern of geomorphic changes and allowed calculation of sediment deposition and erosion for the lagoon as a whole and each of its four sub-basins: Treporti, Lido, Malamocco and Chioggia. Two main developments are discernible from comparative observation of the areal distribution of the main elevation ranges: the collapse of the saltmarshes, which decreased by more than 50%, from 68 km2 in 1927 to 32 km2 in 2002, and the progressive deepening of the lagoon, with a huge increase in the area of subtidal flats (between-0.75 and-2.00 m depth), from 88 to 206 km2 during the same period. On the whole, the lagoon showed a clear-cut shift in the most frequent elevation (modal depth) from a value of-0.62 m in 1927 to-0.88 m in 2002. The deepening of the lagoon affected mostly the lagoon sub-basins south of the town of Venice, where modal depth increased from-0.65 m to-1.12 m in Lido, from-0.64 to-1.75 m in Malamocco and from-0.39 m to-0.88 m in Chioggia. Large changes in lagoon morphology were caused by human-induced subsidence, the dredging of navigation channels between 1927 and 1970, and intense natural erosion enhanced by sediment re-suspension due to Manila clam fishing between 1970 and 2002. There was a net loss of about 110 Mm3 of sediments from the lagoon, most of which (73 Mm3, ca.70%) was in the earlier period. A significant amount was lost by dredging and direct disposal outside the system, either on land or at sea, and there was a net loss of 39 Mm3 from the lagoon to the sea through the inlets, at an annual rate of 0.5 Mm3. Comparison of erosion rates in the two periods highlighted an alarming acceleration, from a net sediment loss of 0.3 Mm3y-1 in the period 1927-1970 to 0.8 Mm3y-1 in 1970-2002. Deterioration caused a shift from a highly differentiated lagoon morphology in the 1930s to a sediment-starved and subsidence-dominated structure in the 1970s, and from there to the high-energy and marinelike lagoon of today. The results demonstrate the potential application of GIS to reconstructing the recent chronology of sediment distribution and improving our understanding of the geomorphic processes shaping the seafloor, while providing insight into the possible impacts of environmental changes brought on by natural and anthropogenic forcing

Sedimentology, Jan 25, 2011

A comparative study was performed of three instruments used to measure the grain-size distributio... more A comparative study was performed of three instruments used to measure the grain-size distribution of thirty sediment samples from shallow lagoonal flats: the hydrometer, the Sedigraph 5000 and the CIS-1. The hydrometer and Sedigraph are based on sedimentation whilst the CIS-1 uses time of transition. The percentage of the samples accounted for by the <8 µm fraction were not affected by the technique used, but this was not the case with the clay fraction (<2 µm). Due to its relative independence from the analytical method applied, the <8 µm fraction can be used in ternary diagram classifications. This fraction also has an environmental significance in coastal lagoons in terms of hydrodynamics, organic enrichment and macrozoobenthos assemblages. The linear relationships obtained in this study may provide useful operational indications for similar studies.

Environment International, Sep 1, 2005

First available data on atmospheric fallout were provided by sampling monthly bulk depositions in... more First available data on atmospheric fallout were provided by sampling monthly bulk depositions in four sites inside the Lagoon of Venice (550 km 2). Sampling was carried out monthly during the period July 1998-July 1999, in one site near an industrial area (Porto Marghera; site D), another site in the city of Venice (site A), and the remaining two in the southern-and northernmost ends of the Lagoon (Valle Figheri, site C; Valle Dogà site B). The following determinations were carried out for each samples: pH, conductivity, grain-size, particulate load, and dissolved nutrients (N, P). Samples were then subdivided into soluble

Water Science and Technology, Oct 1, 1993

In the period 1957-77 a part of 100-200 tons of mercury as industrial waste was discharged into a... more In the period 1957-77 a part of 100-200 tons of mercury as industrial waste was discharged into a 10 km2 lagoon (“Pialassa Baiona”) connected to the Ravenna harbor and the Northern Adriatic Sea (Italy). Extremely high levels of Hg (up to 160 µg/g) were found in surface sediments, but the maximum values (up to 1114 µg/g) were detected in subsurface layers, down to 80 cm, close to the industrial source, and values of 1-2 µg/g were recorded in the fore-harbor, outside the lagoon. The calculation of total Hg budget in sediments gave 38 tons of Hg being stored within a contaminated area of 15 km2. The redistribution of polluted sediments would seem to be due mainly to the tidal action; more than 80% of the total Hg discharged is confined in 10% of the area, i.e. in the southern ponds close to the input point. The time necessary for a restoration of the area was estimated by using different approaches of accumulation rate calculations (210Pb, Hg peak). It appears that 40-50 years would be needed to clean the surface sediments of the Ravenna lagoon from the mercury contamination. We suggest that remedial plans should be focused on the southern ponds.

Deep-sea Research Part Ii-topical Studies in Oceanography, 1997

Data are presented for a number of parameters for aerosols and rainwaters collected at a station ... more Data are presented for a number of parameters for aerosols and rainwaters collected at a station on Sardinia. The findings are interpreted with special reference to Saharan dusts, and are compared to other data on these dusts obtained from a variety of sites around the Mediterranean Sea. At the Sardinia site the particle size distribution of the Saharan outbreaks exhibits a bimodal structure, the two modes being between 1 and 2 µm and 20-25 µm. The presence of giant particles strongly affects the deposition velocities of the Saharan aerosols. Source markers for the Saharan dusts are palygorskite, kaolinite, calcite, dolomite and rounded quartz grains. The input of Saharan dust has important effects on the chemistry of the Mediterranean aerosols. These include: (i) increases in the atmospheric concentrations and sea surface fluxes of crust-controlled trace metals (e.g.; Al, Fe); (ii) decreases in the EFcrust values of non-crust-controlled trace metals (e.g.; Cu, Zn and Pb) in the aerosols, and (iii) changes in the solid state speciation of Cu, Zn, and Pb, which decrease their solubilities in sea water. The Saharan dusts also affect the composition of rainwater by raising the pH, following the dissolution of calcium, and by decreasing the solubility of trace metals such as Cu, Zn and Pb. Wet deposition controls the flux of Saharan dust to the Mediterranean Sea, but dry deposition can also be important. The dust transport occurs in the form of "pulses", and the annual dust flux can be controlled by few episodes of Saharan outbreaks; e.g. sometimes a single outbreak can account for 40-80 % of the flux. Saharan dust deposition fluxes range from 2 to 25 g m-2 (average; ≅ 10) in the W Mediterranean between 39° and 42° N, between 6 and 46 g m-2 (avg. ≅ 20) in the E Mediterranean, and 0.4 to1.0 g m-2 over the Alps on continental Europe. The present day Saharan dust fluxes (≈ 1 mg cm-2 yr-1) account for about 10-20% of the recent deep-sea sedimentation in the Western Mediterranean (3-15 mg cm-2 yr-1).

Environmental science and technology library, 1996

At two remote coastal sites in Sardinia, the two major soluble and insoluble components of aeroso... more At two remote coastal sites in Sardinia, the two major soluble and insoluble components of aerosols and rainwater collected were seasalt (avg. rain = 61 µg g−l; aerosol = 19 µg m−3) and minerals (avg. rain = 13 µg g−1; aerosol = 9 sg m−3). While seasalt content was more or less similar, a three to seven times higher mineral concentration was found in Saharan (SAH) as compared to background (BKG) samples. Mean wet mass flux in Sardinia for the period 1990–1995 was 3 g m−2 yr−1, and wet-to-dry deposition ratio was highly variable (0.8–2.2). Particulate scavenging ratios (SR) were calculated separately for BKG and SAH samples giving values of 600 and 1800, respectively.

Springer eBooks, 2005

This paper reviews work on the role of Saharan dust as a contribution of various chemical to the ... more This paper reviews work on the role of Saharan dust as a contribution of various chemical to the Mediterranean basin. Both the magnitude and the mineralogical composition of atmospheric dust inputs indicate that eolian deposition is an important (50%) or even dominant (>80%) contribution to sediments in the offshore waters of the entire Mediterranean basin. The Mediterranean Sea is a semi-enclosed basin, that receives substances sporadically from the arid region of the Sahara desert. We considered the location and strength of source areas, the transport paths of material away from the desert, the number of Saharan dust transports per year, the way to be dust is deposited (wet and dry mode), the fluxes of Saharan dust, the nature of the material, and the contribution of nutrients to the sea surface. Estimates of atmospheric inputs to the Mediterranean and some coastal areas are reviewed. Model data for nutrients indicate that the atmosphere delivers the nitrogen and one-third of total phosphorus to the entire basin. Measured data in sub-basins, such as the Western Mediterranean and Eastern Medieterranean indicate an even greater proportions of atmospheric versus riverine input. New production supported by atmospheric nitrogen deposition ranges from 2-4 g C m-2 yr-1 , whereas atmospheric phosphorus deposition appears to support less than 1 g C m-2 yr-1. In spite of the apparently small contribution of atmospheric depositionto overall production in the basin it has been suggested that certain episodic phytoplankton blooms are triggered by atmospheric deposition of N, P or Fe. Iron fluxes may be important in determining the nature and quantity of carbon fluxes from Fe-rich areas (like MED Sea), in addition to Fe-poor areas such as the extant Southern Ocean. A geophysiological model shows that iron removal from the photic zone does occur at a much higher rate than the conventional biological pump can account for and that this might release the risk of excessive phosphate scavenging.

Polycyclic Aromatic Compounds, Jun 11, 2007

Studies have revealed the potential risks to which human health and ecosystems are exposed in the... more Studies have revealed the potential risks to which human health and ecosystems are exposed in the Venice Lagoon, due to the atmospheric deposition of persistent pollutants such as trace metals and organic compounds. A total of seventy-seven atmospheric bulk deposition samples were collected monthly from April 2002 to December 2004, from three sites located in the cities of Mestre and Venice, and inside the industrial area of Porto Marghera. Samples were analysed by HRGC/HRMS for polycyclic aromatic hydrocarbon (PAH) content. Spatial variations of atmospheric fallout were investigated, and source identification was attempted using diagnostic ratios and multivariate statistical analysis. Different conditions were recorded, with three anthropic signatures: i) industrial, mainly affected by local industrial sources and diesel engine emissions, ii) urban, mostly influenced by high traffic density, especially petrol car emissions and iii) lagoonal, characterised by diesel emissions from boat engines and oil burning, with random transport of industrial emissions.

Diversity

Several factors contributed, over time, to the Mediterranean monk seal’s sharp population decline... more Several factors contributed, over time, to the Mediterranean monk seal’s sharp population decline. Despite the relative disappearance of documented breeding sub-populations, sightings have been collected, in recent decades, from most of the species’ former habitat. The conservation of this endangered marine mammal should also encompass those areas. We conducted our research along the coast of Salento (South Apulia, Italy) as a case study. To collect data on monk seal presence in the area, expected to be characterized by low numbers, we combined three different methodologies: a questionnaire to fishermen, interviews with witnesses of sightings, and a historical review of the species’ presence. The different methodologies allowed us to collect 11 records of recent sightings (after 2000) and 30 records of historical encounters (before 2000), highlighting that the species was already rare in Salento over the last century. Most of the historical information was concentrated between 1956 ...

In order to detect the source of error in LOI determinations and to correct differences with CNH ... more In order to detect the source of error in LOI determinations and to correct differences with CNH data, we analysed more than 70 sediment samples collected from the tidal flats of the Lagoon of Venice. Three different leaching procedures (LOI350, at 350°C for 16 hours; LOI450, at 450°C for 4 hours; and LOI550, at 550°C for 3 hours) were analysed and compared with total organic carbon (TOC), total carbonates (TC) and grain-size composition.

Bathymetric map of the Lagoon of Venice, reference date 2002 (CRS EPSG:3004). ... more Bathymetric map of the Lagoon of Venice, reference date 2002 (CRS EPSG:3004). Original data, provided by Magistrato alla Acque di Venezia, were elaborated by Sarretta et al., as described in the article "Sarretta A, Pillon S, Molinaroli E, Guerzoni S, Fontolan G. 2010. Sediment budget in the Lagoon of Venice, Italy. Continental Shelf Research 30 : 934–949. DOI: 10.1016/j.csr.2009.07.002". An open access version of the article can be downloaded from: http://dx.doi.org/10.6084/m9.figshare.810481</p