Distribution of arsenic compounds in Mytilus galloprovincialis of the Venice lagoon (Italy).

Samples of Mytilus galloprovincialis collected in different sites of the Venice lagoon (Italy) were investigated for total arsenic concentrations by ICP-AES and for single arsenic species by HPLC-ICP-MS. For this purpose, an analytical procedure for the sensitive and efficient speciation of the arsenic species As(III), As(V), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenobetaine (AB), arsenocholine (AC), and four arsenosugars was optimised. The total arsenic and the single arsenic species were determined in both the hepatopancreas (digestive gland) and the remaining soft tissues in order to verify the different arsenic accumulation in the body parts of mussels. Arsenic compounds were extracted from the mussels with a methanol/water mixture; the extracts were evaporated to dryness, redissolved in water, and chromatographed in an anion-exchange column, a Hamilton PRP-X100. Only small quantities or traces of inorganic arsenic were detected in the mussels. The majority of arsenic compounds detected in the extracts were organic species, with a predominance of arsenobetaine and of an arsenosugar. In addition, a greater arsenic accumulation in the digestive glands of mussels was observed.

Speciation of heavy metals in sediments of the lagoon of Venice collected in the industrial area.

In this study a procedure of sequential extraction of metals from sediments was applied to samples from the lagoon of Venice. Compared to the measurement of total concentrations, the knowledge of metal partitioning among sediment phases can help in estimating the risk posed by metal polluted sediments and give information on contamination sources and on the factors that influence metal enrichment in sediments. The results permitted to estimate for each metal the percentage of the total content that could be potentially remobilized from sediments, owing to changes in environmental conditions. The immediately available fraction represented in general a low proportion of the total content. An important proportion of most metals (except for Zn, Cd and Cu) was associated to residual phases and therefore was not expected to be released under the normal environmental conditions. The large amounts of metals bound to Fe-Mn oxides/hydroxides confirmed the strong scavenging efficiency of this phase. The carbonate phase was the preferential associative form for Pb, Cd and Zn, whereas Cu was bound in prevalence to the organic matter/sulphide phase.