W. Martinotti

Geochemical cycling of heavy metals in a marine coastal area : benthic flux determination from pore water profiles and in situ measurements using benthic chambers

Concentrations of the heavy metals Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn were measured in sea water, suspended matter, sediments and pore water samples collected in a coastal area of the middle Tyrrhenian Sea. Concentration factors between pore water (extracted from the first centimeter of the sediments) and the overlying sea water (taken 30 cm above the sea bed) were less than 1 for Cr, Cu and Pb, 1–10 for Cd and Ni, 10–100 for Fe and Co, 100–1000 for Mn, and 1–100 for Zn.

Soluble and particulate metals in the Po River : factors affecting concentrations and partitioning

Fourteen metals (Ca, Mg, Al, Fe, Mn, Ba, As, Cd, Co, Cr, Cu, Ni, Pb and Zn) were monitored over a 2-year period in the waters of the lower Po River. Concentrations in the dissolved and particulate phases were measured, thus constructing a large database on metal variability. The influence of flow and solid transport on dissolved, particulate and total metal concentrations is discussed. In addition to flow rate and solid content, biological processes seem to be one of the main factors affecting concentrations in the dissolved phase, while the inorganic components of solids seem to control metal concentration in suspended matter. Data on partitioning of metals between the dissolved and particulate phases are presented, together with related information on the affinity sequence of metals for the particulate phase, and the influence of solid load on the modes of metal transport.

Dissolved and particulate transport of arsenic and chromium in the Po River (Italy)

The modes of transport of arsenic and chromium have been investigated, as part of a larger study, on the most important Italian river, the Po. Dissolved, particulate and total concentrations are reported and compared with reference background values. The main factors affecting dissolved concentrations appear to be two interrelated variables, flow and suspended matter concentration, and biological activity. The predominant dissolved species were found to be As(V) and Cr(VI). The ratio between oxidized and reduced species appears in the case of arsenic to be significantly influenced by iron and manganese oxides (Fep and Mnp); the ratio for chromium shows no significant dependence on particulate manganese concentration (Mnp), possibly because its effect is masked by other variables (H2O2 and Fe2+) connected with photochemical reactions. Particulate transport was found to be more important for chromium than arsenic. As and particularly Cr concentrations in suspended matter are strongly influenced by major particulate components including Fep, Alp and Mgp. It is suggested that adsorption is probably not the only mechanism responsible for Crp levels; the presence of mixed CrFe or CrMg hydroxides may better explain this dependence. Previously published laboratory work supports the existence and role of these hydroxides in natural waters. The dissolved fraction of total transport was found to be strongly dependent on suspended matter concentration for As and Cr and equations describing this dependence are proposed.

The NEVALPA project: A regional network for fog chemical climatology over the PO Valley basin

Abstract This paper describes the NEVALPA network, aimed at the study of fog water chemical composition in the Po Valley (northern Italy), its variability and the contribution of fog droplets to the total chemical deposition in the valley. The NEVALPA network is comprised of seven sites representative of the whole Po river basin. The results of the fog campaign carried out during the fall-winter season 1992–1993 are presented here. Higher fog occurrence was recorded in the central and eastern part of the valley, with January being the month with the overall highest fog frequency. An overall high pollutant loading of fog droplets was measured at all locations of the network with a maximum value of fog water ionic strength of 78,500 μeq l −1 at a liquid water content of 45 mg m−3. NH4+, SO42− and NO3− were the major components of fog water, accounting on average for 91 ± 4% of total ionic strength. Overall, the acid content of fog water in the Po Valley was not high, although pH values as low as 3 were sometimes recorded. The median pH value of fog water increased from west to east, with maximum values in the central part of the valley. Median ionic concentration values in the different stations differ within a factor of 2, an indication of the relative homogeneity of pollution throughout the Po Valley during the fall-winter season. No definite seasonal trend of fog water chemical composition was observed at any of the sites.

In-flow speciation of copper, zinc, lead and cadmium in fresh waters by square wave anodic stripping voltammetry Part II. Optimization of measurement step

Abstract The measurement unit of an automatic system for in situ determination of dissolved Zn2+, Cd2+, Pb2+ and Cu2+ in fresh waters with square wave anodic stripping voltammetry (SWASV), is described. The effect of supporting electrolyte solution concentration, pre-electrolysis potential, metal deposition time and thickness of the Hg-film was studied by means of a full factorial experimental design and the significativity levels were determined by a multifactorial ANOVA. Subsequently, the parameters were optimized by using a sequential modified simplex method. Under the so found experimental conditions, the effects of foreign ions and of dissolved oxygen have been investigated, the stability of calibration curves have been studied and the detection limits determined.

C, N and Their Stable Isotopes in Suspended and Sedimented Matter from the Po Estuary (Italy)

C and N content, C/N (atomic) ratio, and C and N isotopic composition (Δ13C and δ15N) were determined on suspended particulate matter and sediment samples obtained from riverine, estuarine and marine environments in two cruises (September 1995 and March 1996) in the Po estuary (Italy). Isotopic tracers of C and N, reported for the first time for this environment, gave information on sources of organic matter and their distributions. An end-member mixing model based on δ13C values was applied to estimate the relative importance of riverine and marine sources of organic matter in suspended particulate matter and sediments.

Distribution of As, Cr and V species in the Po-Adriatic mixing area, (Italy)

Abstract The distribution of dissolved and participate concentrations of As, Cr and V was investigated in the mixing area of the Po river in five surveys over the period March 1992-March 1995. The data obtained indicate noticeable contamination of coastal waters of the northern Adriatic with Cr but not As or V. Total dissolved concentrations for As and V were comparable with oceanic levels but were higher by a factor of 4 for Cr. These results suggest either low anthropogenic inputs of As and V, from terrigenous and atmospheric sources, or efficient removal mechanisms. The investigated metals had low reactivity during freshwater-seawater mixing and the distribution of concentrations in the dissolved and solid phases suggests that the dilution process is the main factor controlling the transport of these metals to the sea in low-to-medium solid transport conditions. Further investigations are required to elucidate the behavior of these metals during high solid transport conditions. Significant changes in the speciation of As occurred during the transition between the two end-member matrices. In the coastal waters of the northern Adriatic, the arsenite fraction in winter, and the arsenite and dimethylarsinate fractions in summer increased with respect to riverine waters. Changes in the speciation of chromium were minor, but also showed a small increase in reduced species in marine waters.

Contribution of the Lambro River to the total pollutant transport in the Po watershed (Italy)

Major ionic components and pollutants including the elements As, Cd, Co, Cr, Cu, Ni, Pb, Zn, Fe and Mn and some organic compounds (anionic surfactants and organohalogenated compounds) were monitored in the middle and lower stretches of the Po River and in its most polluted tributary, the Lambro River. Variations in major ions and pollutant levels between the main river system and its tributary clearly indicate that anthropogenic activities in the watershed have markedly influenced the environmental quality in the Lambro, heavily affecting concentrations of potentially toxic metals and organics as well as those of major ions (mainly Na+ and Cl−). Metal concentrations were measured in both the dissolved and particulate phases of the Lambro and Po. Metals in the Lambro compared to the corresponding levels in the Po showed either a preferential enrichment in one of the two phases or comparable increasing factors (ICF) in both phases. With reference to more toxic elements, ICF were found to be higher in the particulate phase for Cd, Cu and Cr while they appeared comparable for Pb and Zn. Differences in the modes of metal transport between the main river system and its tributary were significant for Cu and Cd, in particular, and were interpreted on the basis of differences in water redox conditions and solid composition. Data collected allowed the polluting contribution of the Lambro discharge to the overall Po watershed to be evaluated.

Determination of cerium, yttrium and thorium in environmental samples

A method for the determination of Ce, Y and Th in sea water, pore water, suspended matter, sediments and biota is reported. The method involves a double coprecipitation with Mg(OH)2 and CaC2O4 to pre-concentrate Ce, Y and Th from sea and pore water and acid digestion in open vessels to solubilise sediments, suspended matter and biota. The measurement was performed by inductively coupled plasma atomic emission spectrometry. Radiotracers (144Ce, 88Y and 228Th) were used in different steps to check the chemical yield of the method. Detection limits of 44 ng g–1(0.005 ng ml–1) for Ce, 0.62 ng g–1(0.0003 ng ml–1) for Y and 15 ng g–1(0.003 ng ml–1) for Th in biota and sediments (water) were obtained. Results for the determination of Ce, Y and Th in sea water, pore water, suspended matter, sediments and biota for samples collected in the Tyrrhenian Sea are given. High concentration factors and recoveries were obtained for Ce, Y and Th in various marine environmental samples. Larger sample volumes can be used to increase the concentration factors and to improve the detection limits.

C and N stable isotopes and trace metals in selected organisms from the river Po delta

Abstract Carbon and nitrogen stable isotopes and trace metals (Hg, Cd, Cr, Ni, Cu, Pb, Zn) were measured in benthic organisms from the marine area outside the Sacca del Canarin lagoon in the Po delta. The results of δ 13 C and δ 15 N determinations permitted the reconstruction of the foodweb composed of filter-feeders, deposit feeders, fish predators and scavengers. Significant interspecies differences in metal concentrations were found and are discussed in relation to feeding habits and trophic level.