The atmospheric deposition of dioxins and furans (PCDD-Fs), dioxin-like polychlorobyphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and hexachlorobenzene (HCB) was determined in the Lagoon of ...Venice. Sampling was carried out monthly, for a total of 13 months (July 1998-July 1999) using "bulk" samplers (passive collectors of wet and dry depositions) at four sites, inside the lagoon and close to its edge. Calculated PCDD-F loadings to the Lagoon turned out to be quite homogeneous, their range being approximately 10-20 ng m-2 y-1, whereas in the station located close to the industrial zone of Porto Marghera the value was approximately 50 ng m-2 y-1. PCB deposition in the industrial fallout sampling site and in the city centre of Venice was approximately 2500 ng m-2 y-1, that is, almost five times higher than the values measured at the northern and southern lagoon stations. HCB annual loading (approximately 8000 ng m-2 y-1) was almost six times higher in the industrial zone than in the other sites (approximately 1500 ng m-2 y-1). PAH loadings in the city centre of Venice and at Porto Marghera were 314 and 389 micrograms m-2 y-1, respectively. The amount of 2,3,7,8-TCDD equivalents (TEQ) of PCDD-Fs and PCBs in the Venice and Porto Marghera bulk depositions was compared with the guideline value of 15 pg m-2 d-1 for dioxins in depositions proposed by De Fré et al. (1998). Moreover, as some of the effects which drive the risk assessment of dioxin-like compounds were also observed after exposure to other molecules, the TEQs of PAHs and HCB were also calculated: nine out of 13 samples exceeded the guideline value. Lastly, an atmospheric emission source related to vinyl chloride monomer production, which may affect atmospheric deposition on the whole Lagoon, is reported in the industrial zone of Porto Marghera.
Se estudian los ostrácodos de 99 muestras de sedimentos superficiales de laguna de Venecia. La biocenosisse concentra en el margen lagunar interno, próximo a la desembocadura de corrientes fluviales. ...Las especies presentes permiten delimitar 3 asociaciones salobres, dominadas por
Cyprideis torosa, y una asociación marina transportada (
Pontocythere turbida). Los principales parámetros que controlan la presencia/ausencia de estos microorganismos son la salinidad, el gradiente hidrodinámico lagunar, el contenido en nutrientes y el tipo de sustrato. Su distribución es muy similar a la observada en otros medios lagunares italianos.
Les ostracodes de la lagune de Venise ont été étudiés à partir d'un échantillonnage relevant de 99 prélévements réalisés sur le sédiment du surface. C'est dans la zone lagunaire interne, à proximité de petits chenaux, que les formes vivantes sont les mieux representées. La microfaune existante délimite trois associations lagunaires, caractérisées par l'abondance de
Cyprideis torosa, et une association marine déplacée (
Pontocythere turbida). La salinité, l'hydrodynamique lagunaire, le matériel nutritif et la nature du substrat sont les facteurs susceptibles d'influer sur la répartition des ostracodes. Cette distribution est comparable à celle que l'on connaît actuellement dans d'autres milieux lagunaires voisins.
In the Venice lagoon, ostracods from 99 recent samples were studied. The biocoenosis is more abundant in the inner margin, near some little channels. The microfaunal analysis delimited three estuarine associations, with numerous valves of
Cyprideis torosa, and one marine association (
Pontocythere turbida). Salinity, hydrodynamics, nutrients and substrate are the main factors which control the distribution of these microorganisms. This distribution is very similar in other recent lagoons of Italy.
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