D.G. Jones

Chemical signatures of the Anthropocene in the Clyde estuary, UK: sediment-hosted Pb, 207/206Pb, total petroleum hydrocarbon, polyaromatic hydrocarbon and polychlorinated biphenyl pollution records

The sediment concentrations of total petroleum hydrocarbons (TPHs), polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), Pb and 207/206Pb isotope ratios were measured in seven cores from the middle Clyde estuary (Scotland, UK) with an aim of tracking the late Anthropocene. Concentrations of TPHs ranged from 34 to 4386 mg kg−1, total PAHs from 19 to 16 163 μg kg−1 and total PCBs between less than 4.3 to 1217 μg kg−1. Inventories, distributions and isomeric ratios of the organic pollutants were used to reconstruct pollutant histories. Pre-Industrial Revolution and modern non-polluted sediments were characterized by low TPH and PAH values as well as high relative abundance of biogenic-sourced phenanthrene and naphthalene. The increasing industrialization of the Clyde gave rise to elevated PAH concentrations and PAH isomeric ratios characteristic of both grass/wood/coal and petroleum and combustion (specifically petroleum combustion). Overall, PAHs had the longest history of any of the organic contaminants. Increasing TPH concentrations and a concomitant decline in PAHs mirrored the lessening of coal use and increasing reliance on petroleum fuels from about the 1950s. Thereafter, declining hydrocarbon pollution was followed by the onset (1950s), peak (1965–1977) and decline (post-1980s) in total PCB concentrations. Lead concentrations ranged from 6 to 631 mg kg−1, while 207/206Pb isotope ratios spanned 0.838–0.876, indicative of various proportions of ‘background’, British ore/coal and Broken Hill type petrol/industrial lead. A chronology was established using published Pb isotope data for aerosol-derived Pb and applied to the cores.

Background exposure rates of terrestrial wildlife in England and Wales

It has been suggested that, when assessing radiation impacts on non-human biota, estimated dose rates due to anthropogenically released radionuclides should be put in context by comparison to dose rates from natural background radiation. In order to make these comparisons, we need data on the activity concentrations of naturally occurring radionuclides in environmental media and organisms of interest. This paper presents the results of a study to determine the exposure of terrestrial organisms in England and Wales to naturally occurring radionuclides, specifically (40)K, (238)U series and (232)Th series radionuclides. Whole-body activity concentrations for the reference animals and plants (RAPs) as proposed by the ICRP have been collated from literature review, data archives and a targeted sampling campaign. Data specifically for the proposed RAP are sparse. Soil activity concentrations have been derived from an extensive geochemical survey of the UK. Unweighted and weighted absorbed dose rates were estimated using the ERICA Tool. Mean total weighted whole-body absorbed dose rates estimated for the selected terrestrial organisms was in the range 6.9 x 10(-2) to 6.1 x 10(-1) microGy h(-1).

Development and application of marine gamma-ray measurements: a review.

The development of instruments to measure gamma radiation in the marine environment, particularly on the sea floor, and the range of uses to which they have been put is reviewed. Since the first steps in the late 1950s, systems have been developed in at least 10 countries with the main thrust occurring in the 1970s. Development has continued up to the present, primarily in Europe and the USA. Marine gamma-ray spectrometers have been used for a range of applications including the mapping of rocks and unconsolidated sediments, mineral exploration (mainly for heavy minerals and phosphorites), sediment transport studies and investigations in relation to discharged and dumped nuclear wastes and at nuclear weapon test sites.

Background dose-rates to reference animals and plants arising from exposure to naturally occurring radionuclides in aquatic environments

In order to put dose-rates derived in environmental impact assessments into context, the International Commission on Radiological Protection (ICRP) has recommended the structuring of effects data according to background exposure levels. The ICRP has also recommended a suite of reference animals and plants (RAPs), including seven aquatic organisms, for use within their developing framework. In light of these propositions, the objective of this work was to collate information on activity concentrations of naturally occurring primordial radionuclides for marine and freshwater ecosystems and apply appropriate dosimetry models to derive absorbed dose-rates. Although coverage of activity concentration data is comprehensive for sediment and water, few, or in some cases no, data were found for some RAPs, e.g. for frogs (Ranidae) and freshwater grasses (Poaceae) for most radionuclides. The activity concentrations for individual radionuclides in both organisms and their habitat often exhibit standard deviations that are substantially greater than arithmetic mean values, reflecting large variability in activity concentrations. To take account of variability a probabilistic approach was adopted. The dominating radionuclides contributing to exposure in the RAPs are (40)K, (210)Po and (226)Ra. The mean unweighted and weighted dose-rates for aquatic RAPs are in the ranges 0.07-0.39 microGy h(-1) and 0.37-1.9 microGy h(-1) respectively.

The distribution of gamma-emitting radionuclides in surface subtidal sediments near the Sellafield plant

Abstract Detailed distributions of total gamma activity, 137 Cs, 106 Ru and 95 Zr + 95 Nb in surface seabed sediments near the Sellafield plant are presented. The results are derived from a towed seabed gamma-ray spectrometer survey in September, 1982. All the distributions are similar, with contours of equal activity parallel to the coast defining a ‘ridge’ of higher activity which is displaced northwards relative to the outfall. This pattern appears to be largely a response to the transport of particle-associated radioeffluent modified in places by the type of seabed sediment present. At greater distance from Sellafield, the uptake of nuclides from solution seems to be more important. Nuclide concentrations decrease with increasing distance from Sellafield; rates of decrease being in the order Zr + Nb > Ru > Cs. This can be related to the levels of the nuclides discharged, their sorption characteristics and their half lives. The pattern of seabed activity seems to have been fairly stable over the period 1978 – 1985, but there is evidence of a small northward shift. Concentrations of 137 Cs and 106 Ru in 1985 were considerably lower than in 1978 or 1982. This is explicable in terms of the fall in discharge levels allied, in the case of Ru, to its short half life and, for Cs, the desorption observed in laboratory experiments. Nuclide ratios in sediment samples yield apparent transit times for the transport of nuclides in the survey area of 1·7 – 3·7 years. These times are generally greater than those obtained from sediments in the more distant Solway Firth and Ravenglass Estuary. It is suggested that they reflect fairly intense bioturbation causing mixing of relatively recent effluent with that from earlier discharges. This is supported by structures observed in X-radiographs of box cores, an abundant burrowing benthos and by interpretations of nuclide profiles and radiocarbon dating of sediment cores by other workers. A lag effect, of up to two years across the survey area, appears to be superimposed on that due to mixing.

Mercury contamination in surface sediments and sediment cores of the Mersey Estuary, UK

Mercury (Hg) is one of the most important heavy metals in estuarine and coastal sediments. This is due to its toxic effect on marine invertebrates and tendency for the methyl-Hg to bio-accumulate up trophic levels, where it can enter humans via the has a highly industrialised and urbanised drainage basin of approximately 5000 km 2. Elevated Hg concentrations (>2 mg/kg) in sediments from the Mersey estuary can be attributed in part to the high density of chemical factories in the Widnes-Runcorn area (Fig. 1). In particular, the alkali, bleaching and detergents industries developed in this area in the mid-19 th century used the Castner-Kellner process for large-scale sodium hydroxide and bleach production. This process required a flowing liquid mercury cathode in an electrolytic reaction cell. Losses and discharges from such plants, plus releases from other industries and domestic coal-burning, will have released many tonnes of Hg to the estuary over several decades. In addition to their anthropogenic metal burden, Mersey estuary sediments are also contaminated with persistent organic pollutants (POPs) sourced from the dockyards, shipping, chemical works, oil refineries and

The distribution of 137Cs in surface intertidal sediments from the Solway Firth

Abstract The distribution of 137 Cs from the Sellafield (Windscale) nuclear fuel reprocessing plant has been examined in detail in the surface intertidal sediments of the inner Solway Firth by means of a hovercraft-borne radiometric survey. With the exception of a belt of relatively active sands to the south of Silloth, caesium distribution is generally consistent with that of fine-grained sediment such that the highest concentrations occur in mud flat and salt marsh sediments which are most extensive in sheltered coastal embayments. 137 Cs activities in July 1980 were typically 2–30 pCi g −1 but locally exceeded 50 pCi g −1 . These levels are considerably lower than those recorded in locations, such as the outer Solway and Ravenglass estuary, which are closer to the Sellafield outfall.

Soil Gas as a Monitoring Tool of Deep Geological Sequestration of Carbon Dioxide: Preliminary Results from the Encana EOR Project in Weyburn, Saskatchewan (Canada)

Publisher Summary Carbon dioxide injection into the EnCana (formerly Pan Canadian) oil reservoir, located south of Weyburn, Saskatchewan, Canada, is being undertaken for enhanced oil recovery (EOR) purposes, while at the same time, the site is being studied for the feasibility of environmental sequestration of this gas. The systematic measurement of soil gas concentration and gas flux at locations above the Phase 1A injection site provides data to construct a baseline of near surface soil gas geochemistry. Data for CO2, CO2 flux, O2, CH4, radon (222Rn), thoron (Tn or radioisotope 22°Rn), and helium, along with other permanent gases, sulphur species, and light hydrocarbons are being collected at yearly intervals for a period of three years, while radon is also being continuously monitored for seasonal and diurnal variations using in situ probes. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) CO2 flux survey measured all 360 points, whereas the initial URS soil gas survey measured 217 points for Rn and Tn, 291 points for field gas chromatography, and 292 sites for laboratory measured gases. The BGS soil gas sampling program completed the southern third of the grid except for 16 sampling sites in the southeast comer that could not be sampled due to a late harvest. The British Geological Survey (BGS), Bureau de Recherches Grologiques et Minieres (BRGM) and INGV also completed gas measurements along 4 profiles. The profiles were defined from anomalies detected during the initial grid sampling, in conjunction with structural data for the immediate area. Natural background levels and concentration distributions have been established for the measured soil gases, and by comparing these results with future data sets, it will be possible to estimate CO2 storage integrity for the reservoir rocks.

Geological controls on radon potential in Scotland

Synopsis 222Rn, a natural radioactive gas produced by the radioactive decay of 238U, accounts for about 50% of the total radiation dose to the average person in the UK. Geology is the most important factor controlling the source and distribution of radon; which has been linked to an increased risk of lung cancer. In order to prevent the public receiving high exposures to radon, it is necessary to identify those areas most at risk. We present results of new mapping of radon potential for Scotland using a method that allows the spatial variation in radon potential to be delineated both within and between geological groupings. The main geological and geochemical associations with moderate to high radon potential areas are described. The highest radon potential values in Scotland are associated with U-rich, highly evolved Siluro-Devonian biotite granite intrusions, notably those clustered within a zone to the west of Aberdeen and at Helmsdale, in Caithness. U mineralization plays a role in areas including the Helmsdale granite and the Middle Old Red Sandstone of the Orcadian Basin. Elevated radon potential is also associated with limestones – where fracture permeability is influential – and with Ordovician–Silurian greywackes. The radon potential of unconsolidated deposits, and how this affects the radon potential of the underlying bedrock, reflects both their permeabilities and their compositions.

Exposure of burrowing mammals to 222Rn.

Estimates of absorbed dose rates to wildlife from exposure to natural background radionuclides are required to put estimates of dose rates arising from regulated releases of radioactivity and proposed benchmarks into context. Recent review papers have estimated dose rates to wildlife from (40)K, and (238)U and (232)Th series radionuclides. However, only one study previous has considered the potential dose rates to burrowing animals from inhaled (222)Rn and its daughter products. In this paper we describe a study conducted at seven sites in northwest England. Passive track etch detectors were used to measure the (222)Rn concentrations in artificial burrows over a period of approximately one year. Results suggest that absorbed dose rates to burrowing mammals as a consequence of exposure to (222)Rn are likely to be at least an order of magnitude higher than those suggested in previous evaluations of natural background exposure rates which had omitted this radionuclide and exposure pathway. Dose rates in some areas of Great Britain will be considerably in excess of incremental no-effects benchmark dose rates suggested for use as screening levels. Such advised benchmark dose rates need to be better put into context with background dose rates, including exposure to (222)Rn, to ensure credibility; although the context will be determined by the purpose of the benchmark and the assessment level.