Maurizio Bonardi

Heavy metal pollution in central Venice lagoon bottom sediments: evaluation of the metal bioavailability by geochemical speciation procedure.

Bottom sediments of the central area of the Venice Lagoon (Italy) and some lagoon canals, chosen as an anaerobic reference environment, were analyzed by a sequential extraction procedure for Cr, Cu, Ni, Pb, Zn, Mn, and Fe. Bio-Available Phases (BAPs) and Non-Bio-Available Phases (NBAPs) have been determined in the Malamocco-Marghera Canal, to define the significant level of heavy metal contamination of the sediment. Relationships among metal distributions with Fe/Mn oxides/hydroxides and sulfides were determined in both environments, using statistical methods. The central lagoon area shows low pollution and a balanced influence of all the sediment components in the metal complexing processes, mostly due to the manganese and iron matrices. The inner canals are very polluted with heavy metals strongly bonded to H2S that form highly insoluble compounds, as demostrated through the correlation analysis. The authors suggest different procedures for lagoon restoration due to the different sediment behaviours, i....

Ancient and modern salt marshes in the Lagoon of Venice

Abstract The Lagoon of Venice was formed during the Late Holocene transgression and anthropogenic remains are common within its sedimentary sequences. This study is based on the foraminiferal association of 58 samples from 7 cores obtained from salt marshes north of Venice. Below horizons of lagoonal origin, these samples reveal the presence of faunas with Trochammina inflata (Montagu) and Helenina anderseni (Warren) which indicate conditions that are characteristic of present-day salt marshes. Foraminiferal faunas can identify the different lagoonal environments and indicate the relative position of the various horizons with respect to sea level. Faunas obtained from the lower section of the cores are analogous to present-day assemblages and they indicate, below a transgressive phase, the existence of buried ancient salt marshes occupied by human settlements. The absolute age of these horizons indicates that the establishment of human settlements is much older than previously thought and that the average rate of Holocene relative sea level rise for the last 5000 years is of the order of 1.2 mm/yr. The formation of these salt marshes, and their subsequent submergence, occurred with rates of accretion and subsidence markedly variable and with occasional erosional phases. This study also shows that, within the present lagoonal environment, together with erosional processes there are areas of accumulation with the formation of new salt marshes.

Benthic foraminifera as proxies of pollution: The case of Guanabara Bay (Brazil)

Due to economic importance of Guanabara Bay, a multidisciplinary approach was adopted to investigate 88 surficial sediment samples in order to use the benthic foraminifera as indicators for the characterization of environmental variations. Grain-size analyses indicate that bottom sediments of the inner part of the bay are mainly muddy while those close to the entrance of the bay are sandy. Geochemical data show high concentration of heavy metals mainly in the northern region of the bay. Micropalaeontological analyses indicate the boundaries of the areas with the highest concentration of heavy metals. The dominant benthic foraminifera in the bay are Ammonia beccarii and Buliminella elegantissima, taxa capable of differentiating the presence of pollutants of different sources. B. elegantissima, in particular, has shown to be an indicator of anthropogenic pollution. The study highlights the worsening of environmental conditions since 2000 and those areas of the bay in need of a priority recovery.