G. Queirazza

Intercomparison of five methods for the determination of trace metals in sea water

Abstract Trace elements (Mn, Fe, Co, Zn, Ni, Cu and Cr) were preconcentrated from sea water by retention on Chelex-100 resin, APDC/8-quinolinol complexation followed by extraction with 4-methyl-2-pentanon or Freon-113, or coprecipitation with Mg(OH) 2 or Fe(OH) 2 . After consideratin of analytical blanks, extraction efficiency, precision preconcentration factor, and suitability for operation on board ship, the best results were obtained by preconcentrating Mn, Fe, Co, Zn, Ni and Cu on Chelex-100 resin and coprecipitation of chromium(III) and (VI) with Fe(OH) 2 . Graphite-furnace atomic absorption spectrometry and inductively-coupled plasma atomic emission spectrometry were used for the final measurements. The accuracy of the method was tested by using the reference sea water sample NASS-1.

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.

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.

Plutonium concentration in sediment cores collected in the Mediterranean Sea

As is well known, the determination of plutonium isotopes in the marine environment is of great importance to calculate the contamination due to the nuclear industry and to better understand sedimentation processes. In the last 20 years sea sediment cores have been collected in different areas of the Mediterranean Sea by four Italian research teams. The sampling depth ranged from 50 to 2800 m and the core lengths were 10–30 cm. The radioanalytical procedures were based on plutonium separation by anion exchange resins or by extraction chromatography with Microthene-TOPO; plutonium electroplating was performed before α-spectrometry. The final chemical yields were determined by spiking with 236Pu or 242Pu. In some cases 238Pu could be detected. As far as the vertical profiles are concerned, no significant subsurface maxima resulted for the cores collected at greatest depth; on the contrary interesting peaks were found for cores collected at 50–100 m depth.

In-flow speciation of copper, zinc, lead and cadmium in fresh waters by diffential-pulse anodic stripping voltammetry: Part I. Optimization of filtration and enrichment steps

Abstract An automatic system for the in situ determination of dissolved Cu, Zn, Pb and Cd in fresh waters, composed of a filtration unit, a separation and enrichment unit and electrochemical unit for differential-pulse anodic stripping voltammetry, was investigated. The filtration and enrichment units were designed to establish the most effective experimental conditions for the measurement of metal concentration at environmental levels. The system was built for installation in a buoy equipped with a facility for radiotransmission of obtained data.

Environmental studies at pre-operational and operational stages of nuclear power plants in Italy: chemical and radioanalytical implications

The criteria currently adopted by the Italian Electricity Board (ENEL) to assess the capacity of the aquatic environment to receive radioactive liquid discharges from nuclear power plants are described. The behaviour of radionuclides and their stable isotopes in coastal seawater, in the presence of suspended matter, and sediments was studied at Montalto di Castro, where a nuclear power plant is being constructed. The environmental concentrations of dissolved elements that might be discharged by a reactor were determined. Large fractions of the total trace elements in seawater were found, by ultrafiltration techniques, to be associated with the finest particle fraction (m.m. < 1000). Most of the elements could be leached from the particulates with 0.3 M hydrochloric acid. This indicates that the leachable elements may become available to organisms. Distribution coefficients (particulate/water) were determined. Investigations of Cs-137 concentrations in various sediments showed Cs-137 to have a preference for sandy-clay. The concentrations of trace elements in pore water were also determined. Similar studies were carried out in the Po river system after scheduled releases of low-level radioactive liquid waste. Concentration factors for Co-60, Mn-54 and Zn-65 in fish, aquatic plants and molluscs are reported. The concentrations of radionuclides found in the sediments, the aquatic plants, and fish were low and in most cases indistinguishable from the background. The aim of these studies is to obtain adequate knowledge of the ability of the environment to accept radioactive liquid wastes without being harmed.

Radioanalytical procedures for the separation and determination of alpha, beta and X emitters in environmental samples of a nuclear power plant before decommissioning

Abstract Before any Nuclear Power Plant decommissioning action it is often necessary to evaluate the environment radiological state (zero point). In this paper some radioanalytical techniques are described for the separation and determination of alpha [ 238 Pu and 239(240) Pu], beta ( 90 Sr, 63 Ni and 241 Pu) and X emitters ( 55 Fe, 59 Ni) in foodstuffs, soils, river and sea sediments, sands and liquid effluents together with the relevant corrosion suspended particulated matter. All the results of the investigation are also reported and discussed.

Radionuclide Partitioning between Water and Suspended Matter: Comparison of Different Methodologies

Abstract In nuclear environmental impact studies, radionuclide partitioning between water and suspended matter is an important process that affects both the geochemical transport and the biological availability of the isotopes. The radionuclide partitioning between water and suspended matter is usually described in terms of distribution coefficients (Kd values), which exhibit a great variability in natural water bodies. In this paper the Kd values for some elements, obtained using different experimental methodologies, are presented both for a riverine and a marine coastal ecosystems. The effect of some parameters as particulate load and total element concentration on the Kd values is investigated within the range of environmental variability. Many measurements of Kd in field are performed on the Po river water (Northern Italy) following the Chernobyl accident. The preferential association of radionuclides with different suspended matter (grain-size types) is given.

Methodological approach to the evaluation of diffusion coefficients of radionuclides in marine coastal sediments

Abstract The migration of radionuclides from seawater to bottom sediments may induce accumulation of radioactivity in the bottom. Different mechanisms contribute to the transport of radionuclide solutes through pore water and across the water-sediment interface. The aim of the present paper was to evaluate the diffusive contribution to radioactivity transport. Diffusion coefficients for a number of radionuclides in marine coastal sediments, collected in the Mediterranean sea, were measured in an experimental arrangement the more similar to natural stationary seawater-bottom sediment conditions. Measured diffusion coefficients for the different radionuclides were statistically treated to search similarities and/or meaningful differences. Results indicate that the experimental set-up is quite important to obtain reliable diffusion coefficients.