Seasonal evolution of gas-phase PCB concentrations in the Venice Lagoon area.

The concentrations of gas-phase PCBs were measured from March 2002 to June 2003 at two sites of the Venice Lagoon and at one site of the Euganei hills. The aims of this study were to evaluate the various gas-phase PCB sources, the spatial and temporal variability of PCB concentrations in the gas-phase that enter the Venice Lagoon atmosphere and the influence of the air temperature on PCB trends. The highest annual average concentration of summation PCBs was observed at the station directly influenced by "urban" sources with values about 3 and 1.5 times higher compared to the concentrations found at the stations where "marine" sources and "not subjected to direct local sources" were respectively sampled from. The temporal trends of summation PCBs concentrations were similar at the three sampling stations corresponding to seasonal temperature changes. Greater concentrations occurred in the summer and first autumn months while the lower ones occurred in late autumn and winter. The temperature dependences were investigated using plots of the natural logarithm of the summation PCBs concentrations vs. reciprocal mean temperatures.

Metals in Mediterranean aquatic species.

Metals such as arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), lead (Pb), vanadium (V), have been determined in species of Mediterranean marine organisms collected from areas supposed to be at background contamination levels. The Inductively Coupled Plasma Mass Spectrometry (ICP-MS) approach was adopted for the determination of all the metals. Arsenic, Cd and Pb determined in the 42 samples, do not exceed the pertinent maximum level except a sample of hake. In wild fish, the concentration range for Cr, Ni, V and Cu was, respectively: 0.07-0.09, 87.6-124, 0.022-0.075 and 0.79-1.74 µg/g fresh weight (fw). The farmed fish samples show concentration levels below the wild fish ones, except for Cr which range at the same levels. Cadmium and Pb show a high sample number under the quantification limit. The elements do not bio-magnify among the species considered and appear to show low variations in relation to organisms' position in the food chain and at sampling sites.

The interactions of cetyltrimethylammonium with mitochondria: an uncoupler or a detergent?

The interactions of cetyltrimethylammonium (CTA) with mitochondria have been investigated. We confirm, as already observed in a previous paper, that this compound behaves as proton carrier (or uncoupler) of the oxidative phosphorylation, but evidences suggest that this compound enhances the membrane permeability to many other compounds such as sucrose. We conclude therefore that CTA as a detergent enhances membrane permeability to all ions including protons. Some evidences are also given that the inhibitory effect of CTA on the mitochondrial respiratory chain is a consequence of the swelling induced.

Study of organic sulphur compounds (DMS, DMSP and CS2) in lagoon ecosystems: the case of the Venice lagoon.

This study of the origin and fate of dimethyl sulphide (DMS) in a particular and complex lagoon ecosystem such as that of the Venice lagoon focuses on the temporal evolutions of DMS concentrations in surface water together with those of dimethylsulphoniopropionate (DMSP), carbon disulphide (CS2), nutrients (nitrate, nitrite, ammonium, phosphate, silicate), sulphate, chlorophyll a, chlorinity, water temperature and phytoplankton (composition and density). Measurements were made from 3 March 1997 to 23 July 1998 at three stations in the central part of the Venice lagoon. The temporal trends of DMS concentration showed an absolute maximum concentration in winter (65 nmol S/l, 19/2/1998, Stn. 1; 119 nmol S/l, 19/2/1998, Stn. 2; 29 nmol S/l, 17/2/1998, Stn. 3) and two relative maxima in the spring-summer period. The spring-summer secondary maxima of DMS concentration were related to the maxima of DMSP and chlorophyll a concentrations and consequently to phytoplanktonic abundance while the winter DMS maximum showed no relation to DMSP or to chlorophyll a suggesting that the production and the fate of DMS could be different for the two periods. According to previous studies the CS2 concentration increased in the spring, achieved its maximum in summer, decreased in autumn and fell to its minimum in winter.

Winter evolution of DMS and DMSP in Venice lagoon water and sediment.

The evolution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) concentrations in the water and sediment of the Venice lagoon were studied together with the concentration of chlorophyll a, temperature and the composition and density of phytoplankton to understand the role of the sediment as a source of DMS during the winter period. The temporal trend of water DMS concentration in this period showed a maximum concentration in February (75.7 nmol S l-1) related to low DMSP and chlorophyll a concentrations but to high phytoplanktonic abundance. The DMS and DMSP concentrations were greater in the sediment than in the water. The temporal trend of DMS concentration in sediment showed a maximum in February (1155 nmol S l-1) related to the maximum of DMS concentration in surface water. These observations suggested that in the winter period DMS could be produced by the conversion of the DMSP present in the bulk water but principally by that present in the sediment (microbiological degradation of DMSP or other sulphur-containing compounds) that subsequently diffuse in water.

Chemometric studies in the Lagoon of Venice, Italy. Annual evolution of sulphur species and relationship to biogeochemical cycles in lagoon water.

During the period March 1997-March 1998 dimethyl sulphide (DMS), dimethylsulphoniopropionate (DMSP) and carbon disulphide (CS2) were determined weekly in the water of the Lagoon of Venice, Italy (at three stations located in the Giudecca Canal, the San Secondo Canal and the Rio di San Nicolò). At the same time, the following hydrological and biological variables were also measured: tide height, temperature, transmittance, fluorescence, pH, salinity, chlorinity, sulphate, ammonia, nitrite, nitrate, phosphate, silicate, chlorophyll a, phaeopigments, phytoplankton (abundance and biomass). Principal component analysis (PCA), applied as a dimension reduction tool, made it possible to summarize multivariate information in a small number of components, which highlighted the relationships between the temporal evolutions of the sulphur compounds with hydrological and biological variables in the seasonal biogeochemical cycle of the lagoon. In particular the overall temporal cycle, which begins with the development of biological activity in late winter and spring, followed by the predominance of degradation processes during the late summer and the remineralization of nutrients in autumn, is clearly described in the plane of the first two principal components, together with the interrelationships between all the relevant variables.

Persistent toxic substances in Mediterranean aquatic species.

Fish and fishery products may represent one of the main sources of dietary exposure to persistent toxic substances (PTSs) such as polychlorinated dibenzodioxins, dibenzofurans, and biphenyls; polybromodiphenyl ethers; organochlorine pesticides; perfluorooctanoic acid and perfluorooctane sulfonate; and inorganic mercury and methyl mercury. In this study, PTS contamination of Mediterranean fish and crustaceans caught in Italian coastal waters was investigated in order to increase the representativeness of the occurrence database for wild species. The objectives were to verify the suitability of regulatory limits for PTSs, identify background concentrations values, if any, and examine the possible sources of variability when assessing the chemical body burdens of aquatic species. Twelve wild species of commercial interest and two farmed fish species were chosen. Excluding methyl mercury, chemical concentrations found in wild species fell generally towards the low ends of the concentration ranges found in Europe according to EFSA database and were quite lower than the tolerable maximum levels established in the European Union; farmed fish always showed contamination levels quite lower than those detected in wild species. The data obtained for wild species seemed to confirm the absence of local sources of contamination in the chosen sampling areas; however, species contamination could exceed regulatory levels even in the absence of specific local sources of contamination as a result of the position in the food web and natural variability in species' lifestyle. A species-specific approach to the management of contamination in aquatic organisms is therefore suggested as an alternative to a general approach based only on contaminant body burden. A chemical-specific analysis performed according to organism position in the food chain strengthened the need to develop this approach.

Determination of polychlorobiphenyls and polycyclic aromatic hydrocarbons in the atmospheric aerosol of the Venice Lagoon.

An analytical method for simultaneous determination of "particle"-associated and "gaseous"-phase concentrations of polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) in atmospheric aerosol samples obtained by high-volume samplers using polyurethane foam adsorbent (PUF) and quartz fibber filters (QFF) has been investigated. Quality control of the analytical procedure was carried out by blank control and by evaluating limits of detection, recoveries, accuracy, and repeatability. The proposed method was subsequently used to determine PAH and PCB in the "gaseous" and "particulate" phases of the aerosols that enter the Venice Lagoon atmosphere. The highest concentrations of sigma PCB and sigma PAH were predominantly in the "gaseous" phase. In both "particulate" and "gaseous" phases the penta-CB congeners dominated total PCB concentrations whereas phenanthrene, fluoranthene, and pyrene dominated the sigma PAH concentrations. Total ("gaseous" plus "particulate") PCB and PAH concentrations were higher at the site directly influenced by the industrial plants but the concentrations in marine aerosol samples were lower by a factor four only and must be taken into consideration when studying the chemical contamination of the Venice Lagoon.

Transport of gas-phase polycyclic aromatic hydrocarbons to the Venice lagoon.

Concentrations of gas-phase polycyclic aromatic hydrocarbons (PAHs) were studied over one year at two sites of the Venice lagoon (designated Marine and Industrial) and at a mainland station (designated Rural) in Italy. Average sigmaPAH concentrations, calculated as sum of 16 PAHs, at Marine are about three and five times lower than those at Industrial and Rural, respectively. The seasonal trends, the temperature-PAH relationship, and principal component analysis indicate that at Industrial and Marine sites several local sources (vehicle and industrial emissions, etc.) could be the PAH sources in the warmer months, whereas in the colder months the main PAH sources could alternate between vehicle emissions and residential heating. At Rural the main PAH sources are: vehicle emissions in the spring and autumn; vehicle emissions, field burning, and wood combustion in the summer; and vehicle emissions and fuel consumption for residential heating in the winter. To evaluate the contribution from different sources to the Venice Lagoon air, horizontal fluxes of PAHs have been obtained. The estimated annual flux of PAHs is about 9 times greater at Industrial (193.5 mg m(-2) y(-1)) than at Marine (20.6 mg m(-2) y(-1)). These results show that study of the chemical contamination of the Venice atmosphere must take into account the PAH flux derived from marine sources as well as the continental input.