SUSPENDED MATTER PROPERTIES AND ITS ROLE IN POLLUTANT TRANSFER FROM THE RIVER TO THE SEA - CASE-STUDY - ADIGE RIVER ADRIATIC SEA

Suspended matter and bottom sediments have been investigated in the Adige River estuary (Northern Adriatic Sea) and their role in the heavy metals transfer from land to sea. The observed similarity of the geochemical and mineralogical composition between the riverine suspended matter and the marine sediments just at the Adige mouth reveals that most of the riverborne suspended particles settle in the prodelta area together with the associated heavy metals. Among the various toxic elements examinated, chromium has a peculiar behaviour, which indicates the man's influence on its biogeocycle. © 1986

The role of suspended matter in the biogeochemical cycles in the Adige River estuary (Northern Adriatic Sea)

Suspended matter and sediments from the Adige River mouth were analysed in an attempt to elucidate the transfer of heavy metals from the river to the sea. The vertical profile of grain-size spectra of suspended matter in front of the river mouth has shown that the riverine particles are limited to the upper brackish layer. Particulate matter was found to have a large specific surface area, up to 20 m2 g-1 in the estuarine sample. High quantities of quartz and phyllosilicates (micas and clay minerals) were found in the riverine suspended matter. The quartz content of the suspended matter from the brackish layer was found to be diminishing and with the organic matter becoming the essential component (22%). Higher levels of trace metals were usually detected in suspended matter samples (40 ppm Ni, 200 ppm Cr, 60 ppm Pb, 100 ppm Cu, 320 ppm Zn, and 0·9 ppm Cd) than in sediments. The observed similarity of physico-chemical, mineralogical and geochemical characteristics of riverine suspended matter and recent marine sediments, indicates that most of the riverborne particulate matter is deposited in the proximity of the Adige River mouth. The peculiar characteristics of the chromium level (high bulk concentration and its abundance in the organic fraction of the particular matter) when compared to the other trace metals, indicates the anthropogenic influence on its biogeocycle. © 1987

Sediment properties and their influence on the geochemical composition in the Lagoon of Venice.

The grain-size distribution, mineralogical composition, heavy mineral assemblages, surface area and concentration of major and trace elements have been determined for bottom sediments from a restricted zone of the Lagoon of Venice, which is of environmental concern. The interpretation of various parameters and their inter-relationships has been done using several statistical procedures. The most common sediments are day silts, typical of a low energy environment. Their fine grain-size favours the uptake of trace elements. Three mineralogical assemblages with specific areal distributions have been identified, both from the provenance of detrital materials and from the depositional conditions. The predominance of semistable and unstable heavy minerals was observed. Some heavy minerals were also recognized as tracers of the rivers reaching the lagoon in the past. The surface area appears to be related to the presence of fine particles and/or clay minerals. The abundance of major elements reflects the mineralogical composition. The trace element distribution shows two zones with different contamination, referable to industrial and municipal discharges. The relationships between heavy metals concentrations and sediment properties are variable. The main role was played in some cases by the fine grain-size and surface area, and in other cases by day minerals

Geochemistry of recent sediments in the Lagoon of Venice.

Geochemical researches have been carried out on bottom sediments subdivided in two levels (0-2 cm; 3-10 cm). The top sediments differ from deeper ones for some significant elements, such as Al, K, Fe, Mg and P, Zn, Pb, Cd. To evaluate the anthropogenic contribution, the heavy metals contents detected in two levels were discussed. -from Author