Measuring anthropogenic impacts on an industrialised coastal marine area using chemical and textural signatures in sediments: A case study of Augusta Harbour (Sicily, Italy).

From the early 1950s until the late 1970s, Augusta Bay (Sicily, Italy) served as a major European (petro) chemical hub. It thereafter began a progressive decline as several crude oil refining and industrial plants closed due to the transfer of production cycles to other sites around the globe. As a result of the rapid and relatively uncontrolled post-WWII development of the site, several environmental studies identified significant contamination in sediments around the southernmost sector of the bay. The pollution was mainly due to barium (Ba) and mercury (Hg), attributable to the former chlor-alkali plant (1958-2003), and polychlorobiphenyls (PCBs) and hexachlorobenzene (HCB). The present study focuses on understanding the broad legacy of pollution across the whole harbour by systematically analysing 10 sediment cores collected in 2008 for contaminant concentration profiles of Hg, Ba, PCBs, HCB and grain-size variations. Pre-industrial environmental geochemical background conditions were identified using data from the deeper parts of cores. The results show that contamination has affected the entire harbour area to varying degrees, and this has allowed identifying contamination transfer, based on decreasing concentrations and related depths in the sediment cores from the southernmost sector to the central and northern area. A recent finding by the current researchers is that the construction of the dam/breakwater in the early 1960s, that largely coincided with the start of industrial inputs, led to the trapping of fine terrestrial sediment inside the harbour, particularly in the central and northern area. This trapped sediment provides a granulometric time marker in those cores. The presence of highly contaminated sediments inside the harbour represents a significant future liability unless remedial action is applied to remove the worst of the polluted sediment.

Pre-concentration of naturally occurring radionuclides and the determination of (212)Pb from fresh waters.

A novel technique has been developed for determining the (212)Pb activity of fresh waters. This is of interest to environmental monitoring programmes that utilise gross α-activity methods to screen for anthropogenic radionuclides. The contribution from (212)Pb varies, and is difficult to experimentally measure due to its relatively short half-life (t(½) = 10.6 h) and low environmental activity (<0.1 Bq l(-1)). The use of a three-stage technique that encompasses a unique form of pre-concentration, separation and analysis by liquid scintillation counting allows a lower detection limit of 0.006 Bq l(-1) with a chemical yield of 92.5 ± 5.6%. The measurement can be obtained within 7 h of sample collection, and is calculated using the radioactive decay of (212)Bi. Other naturally occurring radionuclides may also be extracted using the pre-concentration stage of the technique, with efficiencies above 90% at a range of pH values.

Activity determination and nuclear decay data of (113m)Cd.

The radionuclide (113m)Cd was extracted from a Cd component, which has been irradiated in a research reactor during its routine operation. A validated separation procedure was then used to obtain a (113m)Cd solution of high radiochemical purity. The solution was measured by means of liquid scintillation counting for activity determination. To this end, the CIEMAT/NIST efficiency tracing method as well as the triple-to-double coincidence (TDCR) counting technique were used. Measurements in a low-background gamma-ray spectrometer were applied to identify any potential photon-emitting impurities and to measure the 263.7 keV photons from the isomer transition. A gamma emission probability of 0.01839(29)% was determined for this line. The liquid scintillation measurements were also used to evaluate the half-life of (113m)Cd. The decay was followed for about 11 months and a half-life T(1/2)=13.97(13) years was obtained.

Short-lived variations in the background gamma-radiation dose.

Sudden increases in the background gamma-radiation dose may occur due to the removal of (222)Rn and (220)Rn progeny from the atmosphere by wet deposition mechanisms. This contribution has been measured using a Geiger-Muller detector at the Atomic Weapons Establishment (Aldermaston, UK) during July 2005-April 2006. The results are approximated by a log-normal distribution and there were nine separate occurrences of the gamma-radiation dose exceeding 125% of the geometric mean value. The increases were associated with periods of heavy rainfall, although no correlation was evident between the dose rate and the amount of rainfall, as increased rainfall dilutes the activity further rather than increasing its atmospheric removal. The events were preceded by periods of fine weather and atmospheric stability that allow for the build-up of (222)Rn and (220)Rn progeny. Similar increases in gamma-radiation dose have been measured at a nearby monitoring station situated approximately 11 miles from Aldermaston. Increases in gamma-radiation dose during heavy rainfall have also been observed throughout the UK, that followed the trajectory of an air mass. All events decreased to typical values within 1-2 h as the water permeated into the ground below and the radioactivity decayed away.

Effective desorption of tritium from diverse solid matrices and its application to routine analysis of decommissioning materials.

Tritium extraction from materials is most commonly carried out using oxidative thermal desorption in purpose-built furnace systems and typically involves trapping the product in a water bubbler which is sampled for measurement using liquid scintillation counting (LSC). The performance of perhaps the most widely used commercial system, the Raddec Pyrolyser, has been evaluated for a broad range of sample types. Several parameters that were expected to affect tritium desorption and recovery were systematically studied. These included sample heating rates and end-point temperatures, carrier/oxidant gas flows, catalyst temperature, bubbler trapping and carry-over/memory effects. A catalyst such as platinised-alumina is used to ensure the quantitative oxidation of volatile combustion products to HTO and CO(2). This also ensures that the trapped decomposition products do not colourise the bubbler solutions that are subsequently sampled for LSC. Tritium evolution profiles were determined for a range of sample types and were obtained by systematically changing bubblers at a set of progressively increasing temperatures. These experiments showed the maximum heating temperature and total combustion time required for the complete recovery of tritium from samples was dependent on the sample matrix types and the (3)H form. These evolution profiles need only be determined once and are readily transferable to other Pyrolyser systems. For example tritiated water is rapidly liberated from samples at temperature around 100 degrees C whereas (3)H substituted for structural H in organic species can require a temperature in excess of 300 degrees C to be released. Higher temperatures (up to 900 degrees C) are needed to liberate (3)H originating from neutron capture reactions on trace Li or B within a material (e.g. reactor graphite or concrete). The furnace system investigated is highly effective at extracting tritium and (14)C from all sample types studied (soil, sediment, biota, wood, metal, plastic, concrete, graphite, etc.) and overall it demonstrates high and reproducible recoveries.

Spatial distribution of (241)Am, (137)Cs, (238)Pu, (239,240)Pu and (241)Pu over 17 year periods in the Ravenglass saltmarsh, Cumbria, UK.

Ninety five surface scrape samples were collected at the Ravenglass saltmarsh and analysed for radionuclides by alpha spectrometry ((238)Pu and (239,240)Pu), gamma spectrometry ((241)Am and (137)Cs) and liquid scintillation counting ((241)Pu). Both (241)Am and (137)Cs activities are compared with those reported by Horrill [1983. Concentrations and spatial distribution of radioactivity in an ungrazed saltmarsh. In: Coughtrey, P.J. (Ed.), Ecological Aspects of Radionuclide Release. British Ecological Society Special Publication No. 3. Blackwell, Oxford, pp. 119-215.] Significant decreases in activities for both radionuclides were observed which is caused by the declining levels of discharges from the Sellafield nuclear reprocessing plant since the 1980s. It has been concluded that the spatial distribution of these radionuclides are controlled by the tidal currents and the clay contents in the sediments. There is evidence of surface erosion of the saltmarsh and redistribution of radionuclides in the saltmarsh using isotopic ratios of measured Pu.

Effective determination of the long-lived nuclide 41Ca in nuclear reactor bioshield concretes: comparison of liquid scintillation counting and accelerator mass spectrometry.

The routine application of liquid scintillation counting to (41)Ca determination has been hindered by the absence of traceable calibration standards of known (41)Ca activity concentrations. The introduction of the new IRMM (41)Ca mass-spectrometric standards with sufficiently high (41)Ca activities for radiometric detection has partly overcome this although accurate measurement of stable Ca concentrations coupled with precise half-life data are still required to correct the certified (41)Ca:(40)Ca ratios to (41)Ca activity concentrations. In this study, (41)Ca efficiency versus quench curves have been produced using the IRMM standard, and their accuracy validated by comparison with theoretical calculations of (41)Ca efficiencies. Further verification of the technique was achieved through the analysis of (41)Ca in a reactor bioshield core that had been previously investigated for other radionuclide variations. Calcium-41 activity concentrations of up to 25 Bq/g were detected. Accelerator mass spectrometry (AMS) measurements of the same suite of samples showed a very good agreement, providing validation of the procedure. Calcium-41 activity concentrations declined exponentially with distance from the core of the nuclear reactor and correlated well with the predicted neutron flux.

Characterization of the NIST seaweed Standard Reference Material.

The National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) for seaweed was developed through an interlaboratory comparison with 24 participants from 16 countries. After evaluating different techniques to calculate certified values for the radionuclides, the median method was found to be the most representative technique. The certified values were provided for 13 radionuclides and information values were given for 15 more radionuclides. Results for the natural decay series showed disequilibrium in both the uranium and thorium series.

A novel approach for the rapid decomposition of Actinide resin and its application to measurement of uranium and plutonium in natural waters.

A rapid and robust procedure is described for the decomposition of Actinide resin permitting the routine application of this resin as a preconcentrator. Although the classical Fe(OH)3 precipitation is effective in scavenging actinides, the need for careful handling to recover the sticky precipitate makes the new method much more attractive. The known difficulty of decomposing Actinide resin, which is required prior to the subsequent separation of adsorbed actinides, is innovatively overcome by using a borate fusion attack. This procedure effectively solves the normally encountered problem by safely and speedily decomposing the resin in minutes rather than hours. The alternative and apparently simpler technique of direct ashing of the Actinide resin is not used since it leads to a residue that is not readily leachable. The new technique has been incorporated into a procedure for the isolation of Pu and U from natural water samples and their subsequent quantification by alpha spectrometry. The efficiency of loading of the elements onto Actinide resin has been tested using both batch and column-based approaches. The integrated method involving Actinide resin preconcentration, borate fusion, anion and UTEVA chromatography and electrodeposition provides limits of detection of 0.001 BqL(-1) and chemical recoveries in excess of 80% from groundwater and seawater samples as large as 5L. Comparative data, presented for the analysis of independently analysed river, borehole and surface run-off waters using both the described procedure and other competing techniques, show very good agreement.

Penetration of tritium (as tritiated water vapour) into low carbon steel and remediation using abrasive cleaning.

The UKAEA Winfrith site is in a phase of accelerated decommissioning and de-licensing which will generate significant volumes of metal wastes some of which may be suitable for disposal as exempt wastes. If contamination is present, it is often confined within the surface layers of the metal. The UKAEA Winfrith site operates a shot-blast facility (WACM) that removes paint and surface contamination from low carbon steel enabling surface contaminated painted metal to be processed and therefore certified as exempt. A study was conducted to determine whether tritium (as tritiated water vapour) has penetrated into the metal to levels exceeding the Radioactive Substances Act (1993), Substances of Low Activity (SoLA) Exemption Order criteria, and whether processing via the WACM removes sufficient tritium contamination that the SoLA Exemption Order criteria can be met. The results of sampling and analysis show that the tritium is mainly held in the paint or outer 40 microm layer of the metal and that processing through the WACM removes these layers along with sufficient tritium to meet the SoLA Exemption Order criteria.

Records of change in salt marshes: a radiochronological study of three Westerschelde (SW Netherlands) marshes.

Three salt marshes on a 50-km transect along the north bank of the Westerschelde Estuary were investigated to determine whether salt marshes in the estuary had responded to shipping channel modifications in recent decades. Marsh accretion rates were estimated mainly from 137Cs profiles with further evidence from 241Am because changes in both rate of deposition and nature of the accreting material precluded use of standard 210Pb(excess) dating models. The 137Cs profiles usually show peaks corresponding to atmospheric deposition from the 1963 fallout maximum and sometimes from the Chernobyl accident, although intervening enhanced 137Cs activities derived from the nuclear reprocessing marine discharges of Sellafield and La Hague are clearly discernible. In all three marshes (Ritthem at the mouth of the estuary and Zuidgors and Waarde at 20 and 45 km upstream), a marked, near-coincident change in the rate of accumulation and in the grain size of material deposited occurred around 1980. This may be related to a combination of channel deepening and straightening operations undertaken in the mid-1970s and/or natural changes in winter wave climate.

Radiochemical determination of 241Am and Pu(alpha) in environmental materials.

Americium-241 and plutonium determinations will become of greater importance over the coming decades as 137Cs and 241Pu decay. The impact of 137Cs on environmental chronology has been great, but its potency is waning as it decays and diffuses. Having 241Am and Pu as unequivocal markers for the 1963 weapon fallout maximum is important for short time scale environmental work, but a fast and reliable procedure is required for their separation. The developed method described here begins by digesting samples using a lithium borate fusion although an aqua regia leachate is also effective in many instances. Isolation of the Am and Pu is then achieved using a combination of extraction chromatography and conventional anion exchange chromatography. The whole procedure has been optimized, validated, and assessed for safety. The straightforwardness of this technique permits the analysis of large numbers of samples and makes 241Am-based techniques for high-resolution sediment accumulation rate studies attractive. In addition, the technique can be employed for the sequential measurement of Pu and Am in environmental surveillance programs, potentially reducing analytical costs and turnround times.

The uptake of iron-55 by marine sediment, macroalgae, and biota following discharge from a nuclear power station.

Significant quantities of 55Fe, an activation product of stable iron, have been released into the environment following the atmospheric testing of nuclear weapons (mainly in the 1950s and 1960s) as well as through authorized discharges of radioactivity from nuclear power and reprocessing sites. Although some studies have been performed on the behavior of weapons' fallout-derived 55Fe in the environment and subsequent impact on humans, little has been published on the behavior of 55Fe released as a point source discharge from nuclear sites. This study presents data on the concentration and temporal variation of 55Fe in fucoid seaweeds, shellfish, crab, and lobster collected from Weymouth Bay and adjacent coastal areas, southern England. These areas have received authorized discharges of radionuclides originating from the operation of a now-decommissioned steam-generating, heavy water-type reactor at AEE Winfrith. The highest activities of 55Fe are found associated with marine sediments collected near the discharge pipeline and a rapid decline occurs away from the pipeline. This is consistent with rapid sorption of 55Fe by the sediment, and the data show there is only limited reworking and remobilization. Activities of 55Fe in biota generally decreased over time, due to a reduction in the amount of 55Fe discharged. The variation of 55Fe activity, revealed from the monthly sampling of seaweed, does not reflect the short-term fluctuations seen in the patterns of discharged 55Fe activity. Although discharges of 55Fe from AEE Winfrith exceeded other radionuclides, the radiological impact on local seafood consumers is considerably less than for other key radionuclides such as 60Co and 65Zn but of comparable magnitude to the global average population dose arising from fallout-derived 55Fe.

Toxic gas generation from plastic mattresses and sudden infant death syndrome.

Microbial generation of toxic gases from antimony, arsenic, or phosphorus in compounds used as fire retardants in cot mattresses has been proposed as a cause of sudden infant death. To test this hypothesis, 23 polyvinyl chloride mattress samples from cot death cases were incubated on malt agar plates until good microbial growth was obtained. Silver nitrate and mercuric chloride test papers were then inserted and the colour reactions recorded. The predominant organism, recovered from all mattresses tested, was not, as claimed in earlier work, the fungus Scopulariopsis brevicaulis, but a mix of common environmental Bacillus spp. Test paper colour changes occurred whenever bacterial growth was present, but these reactions also occurred in control tests in which no mattress material was present on the plates. Chemical and instrumental analyses of exposed test papers showed that the colour reactions were not due to deposits of antimony, arsenic, or phosphorus. Our findings do not support the hypothesis that toxic gases derived from antimony, arsenic, or phosphorus are a cause of sudden infant death. More sulphur was found in test papers exposed in plates containing bacterial growth than in those without such growth. This result suggests that the test paper reactions were due to the generation of sulphur-containing compounds during bacterial growth on the agar medium.