R. Donazzolo

Heavy metal contamination in surface sediments from the Gulf of Venice, Italy

Abstract The authors studied surface sediments from 102 stations in four areas of the three port entrances to the Lagoon of Venice, examining the relationships between textural character, mineralogical composition, and Hg, Pb, Cd, Cu, Ni, Cr, Zn, Co and Fe content. Heavy metal distribution allowed boundaries to be fixed between polluted and nonpolluted zones. While the Cavallino area is not polluted, very high concentrations of Zn, Pb and Hg in the two central areas, facing the Lido and Malamocco port entrances, respectively, suggest that wastes mainly from industrial production of zinc are present. High concentrations of Cr in the southern part of the Chioggia area are probably due to tannery wastes reaching the sea from the Brenta river.

Historical development of the Venice lagoon contamination as recorded in radiodated sediment cores

Abstract Three cores (length 60 cm, i.d. 10 cm) collected in the most contaminated area of the lagoon of Venice (Italy) were sectioned (14, 12 and 15 sections each respectively) and analysed. Concentrations of heavy metals (Hg, Pb, Cd, Co, Cu, Zn, Cr, Ni, Fe), organic carbon, total nitrogen and total phosphorus were determined. Eh and pH profiles are discussed. Background (pre-industrial) levels for metals were estimated from the deepest sections. The principal component analysis performed on the metal concentrations, normalized on the backgrounds, revealed that two components can account for 99% of the variability. The first clearly represents the mercury pollution, the second weights the contribution of zinc and, to a lesser degree, of other metals (Cd, Cu, Co, Pb) to a contamination mainly caused by discharges of industrial tailings. Radiodating of two cores permitted us to reconstruct the historical evolution of the sediment pollution as related to the development of specific activities in the industrial zone of Porto Marghera. Total phosphorus and organic carbon accumulation was significant in the upper 10–20 cm of the cores.

Heavy metal content and lithological properties of recent sediments in the Northern Adriatic

Heavy metal (Hg, Pb, Cd, Cu, Cr, Ni, Co, Zn and Fe) concentrations, textural characters and mineralogical compositions have been determined on 246 surface sediment samples from the Northern Adriatic Italian sea area. The relationship between the heavy metals content and the pelite (< 63 μm fraction) percentage has been studied. All the metals resulted accumulated in the fine fraction with the following percentages (Hg, 95%; Zn, 86%; Pb, 82%; Cu, 79%; Cd, 74%; Ni, 70%; Cr, 65%; Co, 65% and Fe, 64%). The specific surface area has been measured on 44 samples and correlated to metal values. A fairly good (50% and more variation explained) linear correlation co-efficient has been found for Ni and Cu in the entire area, less significant correlation for other metals. In order to discriminate between natural and anthropogenic origin the metal concentrations on the whole sediment has been normalized on the basis of the pelite percentage. In the areal distributions drawn with the corrected values, zones contaminated by industrial discharges have been identified mainly in front of the lagoon of Venice.

Macroinvertebrate communities and sediments as pollution indicators for heavy metals in the river Adige (Italy)

Abstract Sediments and macrobenthos communities sampled in the tract of the River Adige in the province of Verona and in the main tributaries Fibbio and Alpone are the subject of a study aiming at evaluating contamination by heavy metals (Hg, Cd, Cu, Zn, Pb, Cr, Ni, Co and Fe). Pollutant concentrations were found to be related to sediment grain size composition, organic carbon content of sediments and to macrobenthos community composition. Two samplings, carried out in the low-water periods preceding and following the spring-summer floods, established that such floods had a considerable effect on the river, by causing sediment renewal and mobilizing pollutants that became more available to macrobenthos. Sediments were found to be good pollution indicators, as they accumulate all metals. Macrobenthos preferentially bioaccumulate some metals (Cu, Zn) and help in detecting acute contamination by showing concentrations higher than sediments for some metals (Hg, Cr) in certain stations. On the basis of the relative concentrations determined in the stations, some information was derived on contamination sources: in particular very high concentrations of Cr were found in sediments and macrobenthos due to pollution caused by leather tanning industries, together with a considerable amount of mercury, probably due to paper industries.

The role of alkaline phosphatase in the sediments of Venice Lagoon on nutrient regeneration

Abstract Potential alkaline phosphatase activity and nutrient concentration have been determined in the seawater, interstitial water and sediments of the most polluted area in the Venice Lagoon, at 6 stations, during three cruises performed in the October/November 1982 period, when a minimum phytoplankton standing crop existed. The relationships between parameters were established by linear regression analysis. The results clearly indicate the important role of alkaline phosphatase (APA) in phosphorus regeneration. Indeed, APA appears to be a good indicator of the degree of nutrient regeneration occurring in surface sediments on a global basis. In the Venice Lagoon a significant nutrient release from the sediments to the overlying lagoon water takes place. This process appears to be at least as important as external contributions in both establishing and controlling the concentration of the nutrients in lagoon waters.

Combined preparative and analytical use of normal-phase and reversed-phase high-performance liquid chromatography for the determination of aliphatic and polycyclic aromatic hydrocarbons in sediments of the Adriatic sea

Abstract High-performance liquid chromatography (HPLC) has been used for the preparative separation of environmentally relevant aliphatic and polycyclic aromatic hydrocarbons (PAHs), and for quantifying PAHs. Normal-phase HPLC was employed as a fractionation step, whereas the quantitative determination of the PAHs was accomplished by using reversed-phase HPLC. In both cases, GC and GC/MS were used as confirmatory techniques. The concentrations of twelve unsubstituted PAHs in sixteen surface and deeper sediments, taken from the northern and central Adriatic Sea, are reported, together with an evaluation of their dependence upon the percentages of fine material and total organic carbon.

Heavy metal pollution studies by resuspension experiments in Venice Lagoon

Abstract A mechanical device for sediment resuspension has been used in Venice Lagoon for sampling extremely thin surface sediment layers, allowing the characterization of the top few tenths or hundredths of a millimetre. The age of the resuspended layer was estimated at two sampling stations from the sedimentation rate to be about 2 weeks. Zinc and iron were determined (nitric acid extraction) in particles of the resuspended layers and in the corresponding underlying sediments. Lower metal concentrations were detected in sediments (43–323 μg/g for Zn and 9200–17400 μg/g for Fe) with respect to resuspended particles (63–424 μg/g for Zn and 12,200–25,400 μg/g for Fe). The remarkable concentration decreases of zinc (both in resuspended particles and in sediments) from the inner areas of the lagoon (Porto Marghera) seaward, can be attributed to the decreasing effects of industrial pollution. The relatively high concentrations of iron observed in areas far from Porto Marghera, can be explained by the contribution of runoff waters or by contamination from nearby polluted sediments. Higher metal concentrations in resuspended particles were observed in April than in February (1987). Concentration increases for zinc (from 7 to 91%) were more substantial than for iron (from not significant to 42%). Zinc uptake by plankton, followed by deposition of residual organic materials onto the sediment surface is suggested as an explanation of the higher metal concentrations detected in April. These results reflect the particular features of the proposed technique, which, at least for cohesive and fine grained sediments, seems to be promising for future applications in studies both on the tracing of metal pollution sources and on the migration processes of these contaminants between sediment and overlying water.

DDT and PCBs in sediments of the Venice gulf

Abstract The concentrations of ?DDT and PCBs in surface sediments collected in the Gulf of Venice are reported. The contribution of the lagoon and of the rivers to sea sediment contamination is discussed. Fresh waters reaching the sea through the lagoon or directly from rivers are responsible for relatively high ?DDT concentrations. The Porto Marghera industrial zone located in the inner border of the lagoon is probably the main PCB source. Two transport mechanisms have been identified: mobilization of suspended solids by tidal movements and direct dumping of industrial tailing and/or dredged materials from the lagoon canals.

Influence of waste waters from the city of Venice and the hinterland on the eutrophication of the lagoon

Four seasonal samplings of lagoon waters were carried out during successive phases of high and low tide at stations located within Venice and its surroundings to monitor various physico-chemical parameters (pH, redox potential, temperature), salinity, nutrient concentrations (nitrogen, phosphorus, carbon compounds) and bacteria (total coliform bacteria). Salinity was used as a parameter for estimating the hydrographic distance from the Adriatic Sea, and for grouping stations into five homogeneous areas. A negative correlation was found between salinity and the concentrations of nutrients. Gradients of increasing concentrations of nutrients were observed at increasing hydrographic distance from the sea. The contributions to eutrophication of fresh waters entering the lagoon from the hinterland and of waste waters from the city have been estimated and found to be comparable. Some necessary interventions for the restoration of the lagoon are suggested.

Contamination by chlorinated hydrocarbons (DDT, PCBs), in surface sediment and macrobenthos of the river Adige (Italy)

Surface sediments and macrobenthos communities have been employed as contamination indicators for halogenated hydrocarbons (DDT and PCBs) in the river Adige and its tributaries Fibbio and Alpone in the province of Verona. Two sampling campaigns were carried out, before and after the spring-summer floods, to determine the effects of this event on the contamination of the river. The halocarbons in the sediment were found to be associated with the fine fraction (< 53 μm) and organic carbon. From the relative concentrations of contaminants determined at various sampling stations, some information has been obtained on the sources.