Trace metals used as natural markers for discriminating some karstic freshwaters near Trieste (Italy)

Some heavy metals have been determined using voltammetry in freshwaters forming part of a karstic hydrological system (the Timavo River, north of Trieste), during attempts to characterize and discriminate the different sources of the springs. The trace elements can be considered natural markers, with lead appearing to be the most discriminating variable. Non parametric statistics and cluster analysis were used to estimate the significance of the determined parameters with respect to the considered ecosystem.     

An improved index for monitoring metal pollutants in surface sediments

An approach for defining the quality of surface sediments of limited areas in terms of heavy metal contents is proposed. Sediments were taken on a bi‐dimensional mapping, for checking possible different sources of pollution in the case study, a harbour zone. Non residual metals were determined by ICP‐AES in cold diluted hydrochloric acid leachates of sediments. An “enrichment factor”;, r, can be computed for each metal: metals with r values exceeding unity can be considered as indicators of metal pollution. A “total enrichment factor”;, R, was proposed in order to assess the degree of pollution of sediments for each site. R is an adimensional value that accounts for the presence of metals that exceed threshold values determined by background concentrations.     

The seasonal distribution of dissolved inorganic nitrogen and phosphorous in the lagoon of Venice: a numerical analysis

This paper investigates the seasonal evolution of the spatial distributions of dissolved inorganic nitrogen and phosphorus, in relation to the estimation of the N and P loads, which were obtained in the framework of the DRAIN project. Such investigation is carried out by using a 3D reaction-diffusion model which has been calibrated against salinity data and then used for obtaining the most likely scenario of the spatial and seasonal distribution of DIN and DIP. The consequences of different management policies are also discussed, in relation to the current Italian legislation, which sets quality standards for both DIN and DIP in the lagoon of Venice.     

Metal Pollution Assessment of Surface Sediments Along a New Gas Pipeline in the Niger Delta (Nigeria)

Chromium, nickel, copper, zinc and cadmium were determined in sediments of the Niger Delta (Nigeria) in order to discriminate between natural metal sources and anthropogenic ones. Surface sediments were collected at seven sites along a new gas pipeline near Port Harcourt, between the New Calabar River and the Bonny River towards Bonny town. Chemical characterisation is obtained by hydrofluoric–nitric acid digestion procedure, providing the ‘total’ (‘residual’) metal contents. Information about the anthropogenic metal fraction was obtained by cold diluted hydrochloric acid extraction procedure. This ‘labile’ acid soluble fraction of metals, perhaps due to relatively recent inputs in the sediments, constitutes the fraction more likely to be available to marine organisms, and furnishes a first evaluation of the possible toxicity of sediments of this sensitive ecosystem. Zinc appears to be the most available of all the heavy metals: its ‘labile’ fraction attains 40–50% of the ‘total’ zinc in sediment. Sites near Port Harcourt city are the most contaminated. All the examined metals are one order of magnitude below the respective values proposed as a limit for toxicity and are comparable with those observed by other authors in similar Niger Delta areas. Some anomalous data found near Port Harcourt city suggest that zinc and cadmium are the metals that require further monitoring. Their anthropogenic source could be derived from urban and industrial sewage.     

Nutrient distribution in locations of the Gulf of Trieste (northern Adriatic sea) suspected of pollution

Nutrients (ammonium‐nitrogen, nitrite, nitrate, orthophosphate and dissolved silica) as well as some chemical‐physical parameters (temperature, pH, salinity, dissolved oxygen and total suspended matter) were determined in filtered seawater samples taken at the surface, at middle depth and at the bottom, in 6 open‐sea locations of the Gulf of Trieste (northern Adriatic Sea) close to pipeline exits that discharge wastewaters from treatment plants. The collected data allow a comparison of the quality of these open‐sea waters with coastal waters and constitute a reference for successive monitoring in these locations suspected of pollution. A multivariate statistical analysis by the principal component method shows that the considered ecosystem can be modeled with two factors: the first one is referenced to the marine environment, in particular to the decomposition of the organic debris in deep water; whereas the second factor is referenced to the input of freshwaters in the Gulf, driving nitrates from agricultural lands.