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Results are presented for a study of manmade and natural radionuclides in north east Atlantic continental shelf and slope sediments to the west of Scotland. The data are interpreted in the context of sediment mixing and accumulation processes and are used to establish the westward extent of contamination of the sediment system. Offshore shelf and slope sediments were found to have post-glacial sedimentation rates of the order of 1 cm ky(-1) but nearshore sediments had much higher accumulation rates of the order of 0.1 cm y(-1). Surface mixed layer depths of up to 6 cm were observed and non-local mixing affected most of the slope sediments, resulting in advective transport of surface sediment to depths of up to 10 cm. Biodiffusion coefficients for offshore shelf and slope sediments were dominantly in the range 10(-8) to 10(-9) cm2 s(-1). The study confirmed that seawater contaminated with Sellafield waste radionuclides is dominantly entrained to the east of 7 degrees W and, consistent with this, higher levels of Sellafield derived radionuclides were confined to nearshore sediments, with lower levels to the west of 7 degrees W. 238Pu/(239,240)Pu data indicated that Sellafield contributed 75-91% of the total plutonium in coastal sediment but only about 4-8% of the total in slope sediments. By analogy, it can be concluded that a similar situation will apply to other contaminants in seawater entering the north east Atlantic via the North Channel.

The well characterised temporal trend in the 206 Pb/ 207 Pb atom ratio of atmospheric lead deposition in Scotland during the 20th century was used to investigate the surface integrity of several cores collected by different methods from Flanders Moss ombrotrophic peat bog, central Scotland, during 1996–2001. Based on 206 Pb/ 207 Pb profile comparisons, in conjunction with identified 210 Pb radionuclide inventory deficits for two of the cores, it was deduced that 25 ± 7 yrs worth of material was missing from the more seriously affected core. After allowing for an appropriate vertical offset based on 206 Pb/ 207 Pb profile matching, the subsequent matching of profiles of titanium, lead, sulfur, arsenic, iron, phosphorus and manganese in three cores for which total concentration data were available was excellent. Without such offset correction, erroneous conclusions could have been drawn concerning the recent historical record of anthropogenic lead and arsenic deposition, the position of the redox boundary, which controls geochemical cycling and enrichment of iron, and the nutrient recycling status of manganese and phosphorus in the near-surface vegetation. Topographic, vegetative and coring (both device and operator) influences may have been responsible, thus endorsing the use of reliable, multiple core sampling and the use of lead isotope ratio profiles, supplemented by appropriate radionuclide data, in both assessing and ensuring the surface integrity of peat cores.

The basic concept of deep geological disposal of high-level radioactive waste is to isolate the waste from the human environment for the long term. Because the Japanese islands are located in a geologically active area, geological phenomena such as exhumation and fault activity must be considered by any safety assessment connected with deep geological disposal. The Tono Uranium Deposit, central Japan, has been affected by such geological phenomena during the interval since its formation, and so it is a suitable analogue for evaluating how this might be done. The present natural analogue study of the Tono Uranium Deposit (Tono Natural Analogue Project) was started in 2001 with the main aim of studying a so-called ‘worst-case scenario’ for performance assessment (PA). The project involved characterizing the geology, hydrogeology, geochemistry and microbiology of the deposit and obtaining quantitative information about specific times in the past, as a means for developing, and building confidence in, conceptual and numerical models. This project applied systems analysis, which has been widely undertaken in PAs of deep geological isolation. Systems analysis involves a systematic identification, classification and screening of features, events and process (FEPs) that occur or have occurred in and around the deposit. Based on the site data, important FEPs were identified.

Data from the Tono Uranium Deposit of central Japan were used to develop an improved approach for simulating uranium migration and retardation, while taking into account both long-term environmental changes and uncertainties in data. Based upon extensive field and laboratory investigations, conceptual and numerical models for environmental perturbations, including uplift, subsidence and faulting, were constructed. Model development was based on a novel adaptation of a safety assessment methodology that previously has been applied to radioactive waste repositories. A ‘reference scenario’ was developed using a systems analysis approach. This scenario is a best estimate of how the geological system and the uranium deposit reached their present states and includes descriptions of all major environmental perturbations. Uranium is mobilized from the uppermost Toki granite under relatively oxidizing conditions, and is then transported by groundwater into overlying sedimentary rocks. There, reducing conditions promote uranium deposition. A specially designed numerical model simulated the main features of this scenario. Many simulations were performed to identify key uncertainties to which the timing of ore deposition and uranium distribution are sensitive. A key finding is that retardation of U by processes other than precipitation of discrete U minerals, most probably sorption on solid phases, contributes significantly to the stability of the ore deposit. Sorption could potentially be important for confining the U within the sedimentary rocks in spite of environmental changes such as exhumation and seismic pumping. The approach could be used elsewhere, to assess the safety of deep geological high-level radioactive waste (HLW) disposal. A related application would be at potential future waste disposal sites, to prioritize site characterization so that the most safety-relevant uncertainties are reduced. There are also possible applications in other fields, most notably to assess the implications of alternative ore genetic models.

We provide evidence of rapid, recent environmental change in two lakes in the highlands of central Mexico. Multiple sediment cores were obtained from Lago de Zirahuen (Michoacan) and Laguna de Juanacatlan (Jalisco). Analysis of diatom assemblages, magnetic susceptibility, and metal concentrations was carried out, with the chronology provided by 210Pb dating, 14C dating, and tephrochronology. There is evidence of catchment disturbance during the colonial period in both basins, but the most striking feature at both sites is the rapid change in diatom assemblages during the last 20 y, indicating the onset of eutrophication. Limnological data from Lago de Zirahuen support this interpretation, although none are available from Laguna de Juanacatlan. Paleolimnology is a powerful tool in tracking recent change, particularly in the absence of regular limnological monitoring programs. These lakes appear to be highly sensitive to changes in catchment exploitation, which must be considered in future drainage basin management.

As part of a wider investigation of the biogeochemistry and fate of Pb deposited from the atmosphere at Glensaugh, a rural upland catchment in N.E. Scotland, the concentration and isotopic composition of Pb were determined in four thinly sectioned monolith cores (25 cm) of peat collected at altitudes of 426--434 m from different faces of Thorter Hill and in a series of 21 10-cm unsectioned cores of peat and organic-rich soil along a transect from near the top (434 m) to the bottom (224 m) of the catchment. Depth profiles of Pb concentration and (206)Pb/(207)Pb ratio were similar for the longer cores. Subsurface Pb maxima (238--489 mg kg(-1)) typically occurred below (206)Pb/(207)Pb minima (1.123-1.134). One core was (210)Pb-dated and had a fairly constant (206)Pb/(207)Pb value of 1.170 from mid-19th century to ca. 1930, followed by a decline (attributable to the increasing influence of Australian Pb of much lower (206)Pb/(207)Pb ratio) to 1.134 by the early 1990s, and then a rapid increase to 1.160 by 2002, after the phased withdrawal of leaded petrol. The fluxes of Pb increased from 15 mg m(-2) year(-1) in the late 19th century to a peak of 60 mg m(-2) year(-1) ca. 1960, before declining steadily to 3.6 mg m(-2) year(-1) by the beginning of the 21st century. Some 40% of the anthropogenic Pb in the core had been deposited prior to 1900. The mean anthropogenic Pb inventory of the four longer cores was 7.4+/-1.5 g m(-2), of which approximately 70% occurred in the top 10 cm, in good agreement with the inventories of the shorter cores collected above 400 m. These inventories are higher than those of the industrial central belt of Scotland, probably because of enhanced deposition at altitude. This is consistent with the derived average (210)Pb flux of 198+/-11 Bq m(-2) year(-1), which is twice that of typical UK (210)Pb deposition and the rainfall for the site. The past deposition of Pb at Glensaugh, including that from sources (e.g., smelting, coal combustion) other than leaded petrol, has clearly been considerable. Even since the introduction of leaded petrol ca. 1930, car-exhaust emissions may have accounted for no more than 35% of the Pb deposited.

The ship that the oceanographer Dr William Speirs Bruce used on the Scottish National Antarctic Expedition, 1902–04, was originally a sealer named Hekla, built in Norway in 1872. In 1889 the Norwegian skipper Ragnvald Knudsen explored the northeast coast of Greenland between latitudes 74° and 75°, and in 1891–92 the ship was used by the Danish naval officer, Lieutenant C. Ryder, to explore the inner recesses of Scoresby Sund, finally visiting Angmagssalik. In 1902, re-named Scotia and captained by Tam Robertson from Peterhead, she sailed to the Weddell Sea under the leadership of Bruce. The southern winter of 1903 was spent at Laurie Island in the South Orkney Islands, and in March–April 1904 the party discovered 150 miles of previously unknown coastline of the Antarctic continent, reaching a farthest south of 74°01′S, 22°00′W. An extensive programme of marine survey and biological research was carried out. Back in the UK, Bruce sold the ship, and she returned to sealing, based in Dundee until appointed to be the first international North Atlantic Ice Patrol ship after the tragedy of Titanic. The Great War caused her to become a freighter in the English Channel area until she caught fire and was burnt out on a sandbank in the Bristol Channel on 18 January 1916.

The intertidal biota from Parton beach, close to the Sellafield nuclear fuel reprocessing plant, were all found to be enriched in radiocarbon relative to ambient background. The degree of enrichment appears to reflect the positions of the biota in the food chain once the dilution in seaweed from atmospheric uptake is taken into account. Close to the low-water mark, the order was mussels > limpets > anemones winkles > seaweed. The same order was observed close to the high-water mark, except that anemones were absent from this area. The activities in the biogeochemical fractions of the water column reflect the fact that discharges are primarily in the form of dissolved inorganic carbon (DIC), which is subsequently transferred to the particulate organic carbon (POC) and, to a lesser extent, the dissolved organic carbon (DOC), and finally, the particulate inorganic carbon (PIC). Analysis of intertidal sediment suggests that there is likely to be a gradual increase in the specific activity of 14C in the inorganic component of this material as Sellafield contaminated organisms die and their shells are ground down by natural processes.

Lago de Zirahuen (19° 26′ N, 101° 44′ W) lies within a montane basin in highland Michoacan, Mexico at 2075 m a.s.l. The lake basin has high recreational value and is promoted as a tourist attraction. Four short (

Prior to 1984, the reported marine 14C discharges from Sellafield were estimates: 0.2 TBq per annum from 1952 to 1969 and 1 TBq per annum until 1984 when measurements commenced. The relationship between the net excess 14C activity in annually collected Nori (Porphyra umbilicalis) seaweed samples and the annual discharges (estimated and measured) implies that the discharges were not as constant as the estimates. Based on the relationship between post-1984 measured discharges and the excess 14C in the seaweed, two simple empirical models were used to re-calculate the discharges between 1967 and 1984. Gamma-spectrometry measurements on the seaweed also indicate that Porphyra is a sensitive indicator of changes in discharge of other radionuclides, brought about by the introduction of new waste clean-up technologies within Sellafield.

The Sellafield nuclear fuel reprocessing plant on the northwest coast of England is the largest source of anthropogenic radiocarbon to the UK coastal environment. In a mid-1990s study of 14C distribution around the UK coast, the pattern of dilution with increasing distance from Sellafield appeared to be perturbed by anomalously high 14C activities in marine biota in the coastal environment of northeast England. This present study was undertaken during 1998 and 1999 to determine whether this 14C enhancement was due to Sellafield or the nuclear power plants on the east coast. Seawater, seaweed (Fucus sp.), and mussel (Mytilus edulis) samples that were collected from the vicinity of the Torness and Hartlepool advanced gas-cooled reactor (AGR) nuclear power stations were all enhanced above the contemporary regional background activity derived from natural production and atmospheric nuclear weapons testing. We used previously published dilution factors and transfer times for 99Tc between Sellafield and various points on the UK coast to determine likely Sellafield-derived 14C contributions to the activities at the nuclear power plant sites. The results suggest that the activities observed at Torness, which are only marginally enhanced above the natural background activity, are possibly due to discharges from Sellafield; however, the significant 14C enhancements at Hartlepool are not Sellafield-derived. Furthermore, since both reactors have the same fundamental design, the low activities at the Torness AGR imply that the activities at Hartlepool are not from the AGR, suggesting that there is an input of 14C to the marine environment in the vicinity of Hartlepool which is probably non-nuclear-power related. However, there is no other authorized site in the area that could account for the observed 14C enrichments; therefore, further research is required to ascertain the source of this 14C.

An epidemiologic study of index and family infectious mononucleosis and adult Hodgkin's disease (HD): Evidence for a specific association with EBV+ve HD in young adults. Infectious mononucleosis (IM) is an established risk factor for Hodgkin's disease (HD). A substantial minority (33%) of cases of HD have. Epstein-Barr virus (EBV) DNA within the malignant cells (are EBV+ve). It is unclear whether risk after IM applies specifically to EBV+ve HD. We report the results of a population-based case-control study of HD in adults (n = 408 cases of classical H D, 513 controls) aged 16-74 years; the case series included 113 EBV+ve and 243 EBV-ve HD. Analyses compared total HD, EBV+ve HD and EBV-ve HD with the controls and EBV+ve HD with EBV-ve HD cases using, mainly, logistic regression. Regression analyses were adjusted for gender, age-group and socioeconomic status, and were per formed for the whole age range and separately for young (< 35 years) and old adults ( greater than or equal to 35 years); formal tests of effect modification by age were included. For the young adults, reported 1M in index or relative was strongly and significantly associated with EBV+ve HD when compared to controls (odds ratio [OR] = 2.94, 95% confidence interval [Cl]: 1.08-7.98 and OR = 5.22, 95% Cl: 2.15-12.68, respectively). These results may be interpreted as indications that late first exposure to EBV increases risk of HD, especially in young adults; this applies primarily to EBV+ve HD. (C) 2003 Wiley-Liss, Inc.

In response to the increased use of catalytic convertors in motor vehicle exhausts systems, recent studies, employing GF–AAS or ICP–MS analysis of platinum group elements (PGEs), have identified a significant increase of Pt and Pd concentrations in road dust and roadside soils leading to concern over potential effects on human health. After deposition, the PGEs are subject to various physical and chemical transformations, potentially resulting in migration into other environmental compartments i.e. soils, the aquatic system and biota. However, the processes involved are poorly understood and the reactivity, bioavailability, and speciation of the PGEs are ill defined. In contrast to environmental studies, in geochemical research, Isotope Dilution ICP–MS (ID ICP–MS) has primarily been used for the quantification of Pt, providing a significant improvement in accuracy by allowing removal from the analyte solution of elements which could potentially give isobaric interference in the mass spectra. In the present work, an ID ICP–MS analytical technique with a detection limit of 0.1 μg kg−1 has been used for determination of concentrations of Pt in road dust samples from west central Scotland. The study highlights potential interference problems that may occur in analysis of Pt in environmental matrices using ICP–MS. Initial application of ID ICP–MS in a study of roadside environments in west central Scotland has revealed significantly enhanced concentrations of Pt, within the range 13–335 μg kg−1, in road dust samples from a trunk road and motorway, representing a significant increase relative to surface soils in this area that are remote from roads, which have Pt concentrations of less than 1.0 μg kg−1. In contrast, lower levels of contamination of 1.8–11.8 μg kg−1 were observed for dust samples from residential areas, in the town of East Kilbride.

A review of information that can be provided from measurements made on natural and anthropogenic radionuclide activities in human skeletal remains has been undertaken to establish what reliable information of forensic anthropological use can be obtained regarding years of birth and death (and hence post-mortem interval (PMI)). Of the anthropogenic radionuclides that have entered the environment, radiocarbon (14C) can currently be used to generate the most useful and reliable information. Measurements on single bones can indicate whether or not the person died during the nuclear era, while recent research suggests that measurements on trabecular bone may, depending on the chronological age of the remains, provide estimates of year of death and hence PMI. Additionally, 14C measurements made on different components of single teeth or on teeth formed at different times can provide estimates of year of birth to within 1–2 years of the true year. Of the other anthropogenic radionuclides, 90Sr shows some promise but there are problems of (1) variations in activities between individuals, (2) relatively large analytical uncertainties and (3) diagenetic contamination. With respect to natural series radionuclides, it is concluded that there is no convincing evidence that 210Pb dating can be used in a rigorous, quantitative fashion to establish a PMI. Similarly, for daughter/parent pairs such as 210Po/210Pb (from the 238U decay series) and 228Th/228Ra (from the 232Th decay series), the combination of analytical uncertainty and uncertainty in activity ratios at the point of death inevitably results in major uncertainty in any estimate of PMI. However, observation of the disequilibrium between these two daughter/parent pairs could potentially be used in a qualitative way to support other forensic evidence.

In recent years, the most common technique for radiocarbon dating of deep-ocean sediments has been accelerator mass spectrometry (AMS) analysis of hand-picked planktonic foraminifera (forams). Some studies have exposed age offsets between different sediment size fractions from the same depth within a core and this has important implications when establishing a chronological framework for palaeoceanographic records associated with a particular sediment component. The mechanisms generating the age offsets are not fully understood, a problem compounded by the fact that the fraction defined as “large” varies between different studies. To explore this problem, we dated samples of hand-picked forams from two Biogeochemical Ocean Flux Study (BOFS) cores, for which the presence of an offset between the bulk carbonate and >150 μm foraminiferal calcite had already been demonstrated. The presence of a constant age offset between bulk carbonate and coarse fraction material at the two BOFS sites has been confirmed, but the magnitude of the offset is dependent on whether a simple size-separation technique or hand-picking of well-preserved forams is applied. This may be explained if the selection of well preserved forams biases the sample towards those specimens that have spent least time in the surface mixed layer (SML) or have undergone less size selective mixing. Modeling of the 14C profiles demonstrates that SML depth and sediment accumulation rates are the same for both the bulk and coarse sediment fractions, which is consistent with the hypothesis that size-selective mixing is responsible for the age offset.

Since the early 1950s, the Sellafield nuclear fuel reprocessing plant in Northwest England has released radiocarbon into the Irish Sea in a mainly inorganic form as part of its authorized liquid effluent discharge. In contrast to the trend in which the activities of most radionuclides in the Sellafield liquid effluent have decreased substantially, 14C discharges have increased since 1994–95. This has largely been due to a policy change favoring marine discharges over atmospheric discharges. 14C is radiologically important due to its long half life, mobility in the environment, and propensity for entering the food chain. Current models for radionuclide dispersal in the Irish Sea are based on a reversible equilibrium distribution coefficient (kd), an approach which has been shown to be inadequate for 14C. Development of predictive models for the fate of Sellafield-derived 14C requires a thorough understanding of the biogeochemical fluxes between different carbon reservoirs and the processes controlling the net flux of 14C out of the Irish Sea, through the North Channel. In this study, both an empirical and a halving time approach indicate that close to 100% of the 14C that is discharged from Sellafield is dispersed beyond the Irish Sea on a time-scale of months in the form of DIC, with little transfer to the PIC, POC, and DOC fractions, indicating that the “dilute and disperse” mechanism is operating satisfactorily. This is consistent with previous research that indicated little transfer of 14C to Irish Sea sediments. While significant 14C enhancements have been observed in the biota of the Irish Sea, this observation is not necessarily in conflict with either of the above as the total biomass has to be taken into account in any calculations of 14C retention within the Irish Sea.

Regularly increasing radiocarbon age–depth profiles and near-constant sediment composition with depth have demonstrated that sediment accumulation has been relatively constant during the late Holocene at two north-east Atlantic sites on Rockall Bank and Feni Drift (UK Benthic Boundary Layer Experiment sites). In such a quasi-steady state situation, the geochemical responses to early diagenesis of the redox-sensitive elements Cd, Mn, Mo, Re, Se and U are readily discerned through changes in element concentrations with depth. Collectively, a colour change in the sediments, surficial MnOx-enriched layers and 210Pbexcess profiles allow an estimate of the mean position of the oxic–post-oxic boundary in the sediments at both sites. This boundary is situated deeper than the 210Pbexcess surface mixed layer but shallower than the 14C surface mixed layer which represent mixing on 102 and 103 year time scales, respectively. This implies that the well-defined surface MnOx enrichment and its associated 226Ra and Mo fractions must have been efficiently recycled first by downwards mixing into anoxic conditions, and then by subsequent reduction and diffusive migration back up into oxic conditions. This occurs in

Radiocarbon age offsets between foraminifera and bulk carbonate samples were investigated in a sediment core from the western Rockall Plateau in the North East Atlantic. Within the surface mixed layer (SML), foraminifera (forams) ages were significantly younger than those of the bulk sediment at corresponding depths. Below the SML, no significant offset was observed between the two, which is in contrast to previous studies. The absence of an offset below the SML may be the result of advective biological mixing dominating over diffusive mixing in the SML, or the foram size fraction being below the threshold at which size selective mixing becomes active. Within the SML, the sampling strategy may bias the collection of forams towards the youngest specimens at each depth.

Bioturbation and Holocene sediment accumulation are quantified in the three experimental areas of the Benthic Boundary Layer (BENBO) programme by means of the natural radionuclides 14C and 210Pb and the artificial radionuclides 137Cs and 241Am. The Holocene accumulation rates, determined by the radiocarbon method, are 4.4 and 6.5 cm kyr−1 at sites B (Rockall Plateau, 1100 m water depth) and C (Feni Drift, 1925 m water depth), respectively. Accumulation at site A, situated between Feni Drift and Porcupine Bank at 3570 m water depth, was interrupted by an erosional event in the mid-Holocene, which removed 0.25 m or more of the uppermost sediment present at that time. The estimated accumulation rate since that event is 2.1 cm kyr−1. Different estimates of surficial bioturbation mixing depths at site B are returned by the 210Pbexcess and 14C methods, with the former indicating

The sediments of the north eastern basin of the Irish Sea contain substantial quantities of contaminant radionuclides, including long-lived actinides, as a consequence of the disposal, from 1952 to the present, of low-level liquid radioactive waste from the Sellafield nuclear fuel reprocessing plant. Onshore transfer of contaminated sediment has resulted in deposition of Sellafield waste radionuclides in intertidal, floodplain and beach environments of this area, with the highest levels of contamination occurring in fine-grained saltmarsh and estuarine deposits. As a result both of reductions in the quantities of radionuclides discharged and of physical dispersion of the contaminated offshore sediment, radionuclide concentrations in sediment deposited in these coastal environments have gradually decreased since the late 1970s. However, the rate of decrease has declined significantly as the contaminant radionuclides have become increasingly dispersed in the offshore sediments and concentrations in the coastal sediments have tended towards those of the offshore sediment. Further reductions in the concentrations of long-lived radionuclides in coastal sediments will therefore depend upon longer-term processes such as re-dissolution or dispersion of the contaminated sediment out of the north eastern basin of the Irish Sea. Results are presented here for a study of radionuclide concentrations in bulk surface sediment and separated size fraction samples of sediments from the Irish Sea and the North Channel. The study reveals that the contaminant radionuclides are dominantly associated with clays and silts in the north eastern basin of the Irish Sea but that at other sampling locations, on a mass balance basis, associations with coarser sediment are often of equal or greater importance. Linear correlations between radionuclide concentrations and comparison of activity ratios with those of the Sellafield discharge suggest that there has been limited dispersion of particles of diameter less than 20 μm from the north eastern basin to other parts of the Irish Sea. The specific activities and the total quantities of radionuclides involved are relatively small, but such a mechanism is nevertheless important in determining the long-term environmental fate of the actinides, which will in turn influence the long-term dose commitment arising from the Sellafield discharge.

The use of concentration profiles of lead and other contaminant metals in 210 Pb-dated ombrotrophic peat cores for reconstruction of historical trends in atmospheric deposition has become relatively well established. However, uncertainty remains over the validity of the assumption of post-depositional immobility of lead in peats. In particular, a number of studies have suggested that in saturated peat systems, lead is subject to diagenetic remobilisation and redistribution, with the result that 210 Pb and lead profiles do not provide a historical record of deposition. Results are presented here for lead concentrations, inventories and stable isotope ratios and for 210 Pb activities in two peat cores from locations close to the Glasgow industrial area in west-central Scotland. Contrasting biogeochemical conditions prevailed at the two sampling sites, with one being unsaturated and ombrotrophic while the other was saturated and minerotrophic. The results for the ombrotrophic peat core were compatible with information from other peat and lake sediment core studies, data for archived herbage samples and with known historical trends both in industrial activity and in the use of lead as an additive to petrol, giving a high degree of confidence in the 210 Pb chronology and implied record of deposition. This provides strong support for the suggestion that lead is immobile in such systems. In contrast, the lead concentration profile and stable isotope data for the minerotrophic peat provided apparent temporal variations that were inconsistent with other studies and known historical trends, confirming that the saturated peat core did not provide a record of atmospheric deposition. This observation is consistent with the suggestion that lead is subject to diagenetic remobilisation and redistribution in saturated peats.

An ombrotrophic peat core from west-central Scotland was subjected to multi-element analysis and 210Pb dating in order to estimate historical trends in atmospheric deposition of contaminants. The inferred depositional flux of ash (total inorganic material) exhibited small, transient increases from as early as the mid 18th century, followed by a larger increase from the mid 19th century to a pronounced maximum approx. 1960. A significant decrease was observed from the peak ash deposition of 29.2 g m−2 year−1 to the contemporary level of 11 g m−2 year−1, although this is still an order of magnitude greater than the pre-industrial value of 1 g m−2 year−1. Depositional fluxes of a wide range of elements (scandium, copper, arsenic, antimony, samarium, cobalt, bromine, lanthanum and lead) also exhibited major increases from the mid 19th century and peak values in the mid 20th century (approx. 1940–1950). Aluminium, cerium and bromine also showed evidence of transiently increased deposition as early as the mid 18th century. Normalisation of the concentrations of individual elements to that of aluminium confirmed that the peak depositional fluxes in the mid 20th century were not due to increased re-deposition of soil minerals from the atmosphere, but were attributable to other sources of contamination including heavy industry, coal burning and vehicle exhaust emission. Nevertheless, re-deposited soil minerals were estimated to constitute an important fraction of the ash, with peak input at the start of the 20th century and subsequent deposition at a relatively constant level, about half that of the maximum flux. Excellent agreement was observed between the inferred trends in contaminant deposition and the known history of industrial development of the area.

Prior to this study, almost no up-to-date information was available on the ‘background’ level of 14C present in the water and biota of the UK coastal marine environment. The weighted mean 14C activity derived from the lowest activities of dissolved inorganic carbon (DIC) and biota for sites which are remote from potential sources is 247·6±1·0 Bq kg-1 carbon. This is proposed as the best estimate of the natural/weapons testing ‘background’ for 1995 and should be subtracted from the activity derived for any sample to establish the excess due to UK anthropogenic inputs. 14C activities in the DIC component of seawater and a range of marine biota are significantly enhanced above the expected ‘background’ value in the environment around the British Nuclear Fuels plc reprocessing plant at Sellafield, Cumbria, NW England and Amersham International plc, Cardiff, Wales. The enrichments around Sellafield are largely confined to the NE Irish Sea while those at Cardiff are confined to the Severn Estuary. The dose from 14C to the Sellafield seafood-consuming critical group (

Sir Ernest Shackleton bought the Norwegian sealer Foca 7 in 1921 for his third Antarctic expedition and renamed it Quest. He died aboard the ship in South Georgia in January 1922, but Frank Wild took over the leadership and completed the expedition after the delayed start. The vessel returned to Norwegian ownership in 1923 but kept the name Quest. In the 1920s and 1930s, in-between sealing voyages, she was chartered out for various scientific or hunting expeditions, mostly to S valbard or the east coast of Greenland, during which many well-known explorers trod her decks, including Gunnar Isachsen, Gino Watkins, Augustine Courtauld, John Rymill, Count Eigil Knuth, Lawrence Wager, H.W. Ahlmann, Gaston Micard, Paul-Emile Victor, and John Giaever. Vital assistance was given in rescuing the survivors of the Italian airship Italia in 1928, of the Danish ship Teddy in 1924, and of several sealers at different times. Many sailors owed their lives to this little ship, which was owned by the Schjelderup family and for most years captained by Ludolf Schjelderup, who gained international fame as an expert ice pilot. On one occasion, 1936–37, the vessel overwintered at Loch Fyne in northeast Greenland. In April 1940, when the Germans invaded Norway, Quest was sealing off Newfoundland. Allied naval forces took possession of her and she was used in various capacities in Canada, Bermuda, and UK coastal waters for the rest of the war. After the war, she once again returned to the sealing business under Norwegian ownership until finally coming to grief in the ice just north of Newfoundland and sinking on 5 May 1962.

A sediment core from the southern basin of freshwater Loch Lomond, Scotland, was thinly sectioned at 3 mm intervals and analysed for radiocaesium, present as a result of fallout from the atmospheric nuclear weapons’ testing programme of the 1950s and 1960s and from the Chernobyl reactor accident of April 1986. The high-resolution sampling enabled much improved resolution of peaks from weapons testing fallout and Chernobyl and led to the estimation of a sedimentation rate (30·9 mg cm -2 y -1 ) for which the uncertainty was a factor of five times less than that of a previous study based on a 1 cm sampling frequency. Further potential advantages of high-resolution sampling in distinguishing possible influences upon the vertical distribution of radiocaesium in sediments are discussed.

This paper describes a study of the geochemical associations of Sellafield waste radionuclides in saltmarsh sediments from south-west s]Scotland. The contaminant radionuclides are transported to this environment in association with particulate material and 137Cs was found to be predominantly (80-98%) non-extractable. In the case of 239+240Pu there was a redistribution from the oxalate extractable oxide fraction to the pyrophosphate extractable organic fraction as a consequence of on-shore transfer of contaminated sediment. The relatively aggressive nature of the chemical extractants required to remove the radionuclides from the sediments suggests that they were in a form which was unlikely to result in their being released into the aquatic environment or taken up by plants. Plutonium had a greater potential mobility or bioavailability than Cs. Values of KD for the desorption of 137Cs from the sediment by freshwater, groundwater and seawater were all approximately 105 L kg-1, confirming its immobility in this environment. The desorption KD values for stable 133Cs were all approximately 106 L kg-1, so the stable Cs did not have a significant influence on the radiocaesium in this sediment.

Alpha/beta separation is achieved by the use of pulse shape discrimination (PSD), calibrated by quantifying event misclassification at any given setting for pure α and β emitters. Previous studies have shown that the degree of misclassification is affected by quenching, but with no attempt made to understand the causes for this phenomenon. This study examines the potential effects of β energy and quench on PSD calibration. PSD was shown to be energy dependent, with misclassification increasing with β event energy. Therefore, PSD calibration requires the use of a β emitter with the same energy distribution as is present in the sample, or a restricted region of interest should be employed. For gross α/gross β analysis of samples containing unknown β emitters, a stepwise calibration procedure is proposed for both PSD and efficiency calibration. Quenching by carbon tetrachloride, nitromethane and 9 M hydrochloric acid was shown to affect PSD by suppression of the delayed component of the scintillation pulse, although to variable extents, and therefore having a range of effects on misclassification. Acetone quenching had little impact on PSD. Standard quench calibration procedures using either carbon tetrachloride or nitromethane are inappropriate for applications utilising α/β separation by PSD. Instead, a quench calibration procedure based on overspiking samples encompassing a range of quench conditions is recommended. The influence of oxygen quenching on PSD was investigated through purging samples with either oxygen or nitrogen. PSD was found to be unaffected by the small amounts of oxygen normally dissolved in the diisopropylnaphthalene based cocktail used in this study.

The reconstruction of historical trends in atmospheric deposition of contaminant metals by use of their concentration profiles in accumulating, ombrotrophic peat deposits, in conjunction with radionuclide-derived chronologies, is subject to uncertainty because of potential post-depositional mobility both of the radionuclides and of the contaminant metals. Results are presented here for a study of the distribution of 210Pb, Pb, stable Pb isotopes and radiocaesium in the unsaturated, surface zone of ombrotrophic peat deposits in three contrasting locations in Scotland. 210Pb chronologies are derived and the implied historical variations in atmospheric depositional fluxes and atom ratios of contaminant Pb are considered, along with total inventories, relative to known historical trends in input and proximity to heavily populated, industrial areas. Similarly, radiocaesium concentration profiles, activity ratios and inventories are considered in the context of the 210Pb chronologies and known inputs. It is concluded that the historical trends in the depositional flux and stable Pb atom ratio of contaminant Pb derived on the basis of the 210Pb chronologies are in good agreement with known temporal variations in these parameters, consistent with post-depositional immobility of Pb under the conditions investigated here. The study confirms that the high degree of mobility of radiocaesium in organic soils renders it of little value in providing chronological information, but suggests that the presence of small amounts of mineral matter may restrict this mobility.

The distribution and Inventories of Pb in the sediments of Loch Tay have been strongly influenced by inputs from past Pb mining activity, as demonstrated by correlation with the characteristic 206Pb/207Ph signature of the Tyndrum ore deposit. A major depositional event, perhaps associated with the cessation of Pb mining in the area, has been dated at 1906–1928 by the 210Pb method. Zinc and Cu have been influenced to a lesser extent by mining, as shown by comparison with inventories in Loch Lomond. Profiles of As, Mn and Fe have been affected by post-depositional diagenetic remobilisation processes. The results serve as a benchmark, with Au mining set to commence at Cononish, near Tyndrum, in 1996.

The ship Fox, built in Aberdeen in 1855 as a yacht, was used by Francis Leopold McClintock on his successful search for relics of Sir John Franklin's lost expedition. She was then chartered for one summer for Allen Young and John Rae to survey a route for a trans-Atlantic cable via the Faeroes, Iceland, and Greenland, after which she was in the services of the Kryolith Mine og Handelsselskabet, based at Ivigtut, southwest Greenland, for many years. In 1905, under charter, she made a historically significant voyage to Thule in northwest Greenland. After this she was owned by the Kongelige Grønlanske Handel and used for coastal freighting, until in 1912 she was condemned and abandoned in Qeqertarsuaq (Godhavn) Harbour, where remnants may be seen today.

Plutonium-239,240 activities in seawater from the north-east Irish Sea, collected in January 1992, were in the range of 0.17–4.30 mBq l−1 in solution and 7.2–62.3 Bq kg−1 in suspended particulates. The 238Pu:239,240Pu activity ratios for the soluble fraction were consistent with those of the underlying sediments but inconsistent with contemporary discharges from Sellafield, indicating that most of the plutonium in solution was derived from re-dissolution from the sediment. The activity ratios for the particle associated material were more variable, but again, on average, typical of the sediments. The annual loss of 239,240Pu from the north-east Irish Sea in solution was estimated to be 1.19 TBq and that associated with suspended particulates to be 0.11 TBq. From this, a halving time of 350 years for the loss of 239,240Pu activity from the sediment by dissolution was determined. A similar treatment of 137Cs data yielded an annual loss of 86 TBq in solution and a halving time of 23 years. Calculations using a numerical model of the Irish Sea yielded similar estimates of current loss rates and permitted the estimation of total cumulative losses from the Irish Sea by advection through the North Channel of 7.9 TBq of 238Pu, 48 TBq of 239,240Pu 2.6 × 104 TBq of 137Cs.

Radiocarbon is an important constituent of the low level, liquid, radioactive effluent discharged from the Sellafield nuclear fuel reprocessing plant in northwest England, but despite the fact that it gives the highest collective dose commitment of all the nuclides in the waste, its behavior in the Irish Sea is poorly defined. There is therefore a clear requirement for an improved understanding of 14C behavior in the Irish Sea, to assist with dose evaluation modeling and definition of the mixing and accumulation characteristics of the sediment in this area. In this context, results are presented here for a temporal study of 14C activities in four geochemical fractions of seawater and in a sediment core from the vicinity of the Sellafield effluent outfall. Clear 14C enrichments in the dissolved inorganic carbon (DIC) and particulate organic carbon (POC) components of seawater were observed, with temporal trends in activity that were related to variations in the Sellafield discharge. Smaller, but nevertheless detectable, enrichments were also observed for particulate inorganic carbon (PIC) and dissolved organic carbon (DOC) in the seawater. The distribution of 137Cs and 241Am revealed that the sediment core could be classified into three zones in which the intensity of mixing decreased discontinuously with depth. Bulk carbonate 14C analyses of the core demonstrated the presence of glacial or pre-glacial carbonate in the system, but failed to show any evidence of contaminant 14C input or provide information on sediment accumulation processes. In contrast, analysis of bulk organic matter from the sediment provided clear evidence of the recent perturbation of a well mixed system by input of younger material, consistent with the recent input of contaminant 14C from Sellafield and possibly weapons testing fallout.

Interleukin-10 (IL-10) plays a key role in regulating proinflammatory immune responses to infection but can interfere with pathogen clearance. Although IL-10 is upregulated throughout HIV-1 infection in multiple cell subsets, whether this is a viral immune evasion strategy or an appropriate response to immune activation is unresolved. Analysis of IL-10 production at the single cell level in 51 chronically infected subjects (31 antiretroviral (ART) naïve and 20 ART treated) showed that a subset of CD8(+) T cells with a CD25(neg) FoxP3(neg) phenotype contributes substantially to IL-10 production in response to HIV-1 gag stimulation. The frequencies of gag-specific IL-10- and IFN-γ-producing T cells in ART-naïve subjects were strongly correlated and the majority of these IL-10(+) CD8(+) T cells co-produced IFN-γ; however, patients with a predominant IL-10(+) /IFN-γ(neg) profile showed better control of viraemia. Depletion of HIV-specific CD8(+) IL-10(+) cells from PBMCs led to upregulation of CD38 on CD14(+) monocytes together with increased IL-6 production, in response to gag stimulation. Increased CD38 expression was positively correlated with the frequency of the IL-10(+) population and was also induced by exposure of monocytes to HIV-1 in vitro. Production of IL-10 by HIV-specific CD8(+) T cells may represent an adaptive regulatory response to monocyte activation during chronic infection.

Typhoid infection causes considerable morbidity and mortality worldwide, particularly in settings where lack of clean water and inadequate sanitation facilitate disease spread through faecal-oral transmission. Improved understanding of the pathogenesis, immune control and microbiology of Salmonella Typhi infection can help accelerate the development of improved vaccines and diagnostic tests necessary for disease control. S. Typhi is a human-restricted pathogen; therefore animal models are limited in their relevance to human infection. During the latter half of the 20th century, induced human infection ("challenge") studies with S. Typhi were used effectively to assess quantitatively the human host response to challenge and to measure directly the efficacy of typhoid vaccines in preventing clinical illness. Here, the findings of these historic challenge studies are reviewed, highlighting the pivotal role that challenge studies have had in improving our understanding of the host-pathogen interaction, and illustrating issues relevant to modern typhoid challenge model design. © 2014.

Bentonite is one of the more safety-critical components of the engineered barrier system in the disposal concepts developed for many types of radioactive waste. It is used due to its favourable properties (including plasticity, swelling capacity, colloid filtration, low hydraulic conductivity, high retardation of key radionuclides) and its stability in relevant geological environments. However, bentonite is unstable under alkaline conditions and this has driven interest in low-alkali cements (leachate pH of 10–11). To build a robust safety case, it is important to have supporting natural analogue data to confirm understanding of the likely long-term performance of bentonite. In Cyprus, the presence of natural bentonite in close proximity to natural alkaline groundwaters permits the zones of potential bentonite/alkaline water reaction to be studied as an analogy of the potential reaction zones in the repository. Here, the results indicate minimal volumetric reaction of bentonite, with production of a palygorskite secondary phase.

Stable lead isotope data can yield information on the geochemical origins of lead and on its relative contributions from sources such as coal burning, mining, smelting, and car-exhaust emissions. This extremely detailed 206Pb/207Pb profile for dated bottom sediments in Loch Lomond, Scotland, shows the trends clearly related to the varying nature and extent of anthropogenic lead inputs after 1630. In particular, a significant decline in the 206Pb/207Pb ratio of excess lead during 1929−1991 is attributable to the introduction and use of (206Pb-depleted) leaded petrol since the 1920s. This accounts, however, for just 24−53% of the excess lead deposited since 1929 and ≤19% of the total excess lead inventory. Deposition of lead from industrial (and domestic) activities has predominated overall and, on an annual basis, until at least the mid-1950s.

Diffusion of contaminants from fractures into the interconnected wall-rock porosity is an important retardation process in geosphere transport. Contaminant immobilization can also be achieved at a redox front, owing to contrasting solubilities of reduced and oxidized species along with sorption and coprecipitation on secondary phases produced at the front. Here, a natural analogue study is presented that demonstrates the applicability of these concepts to potential sedimentary host formations for a high-level radioactive waste repository in Switzerland. The existence of matrix diffusion to at least 0.08 m into the wall rock (the full length of the profile examined) is demonstrated on the basis of mineralogical and porosimetric evidence, pore-space geometry and disequilibria in the 238 U-and 232 Th-decay series. Radioactive disequilibria are due to at least two distinct processes, namely pervasive 234 U and 228 Ra leaching throughout the rock along with U deposition around the redox fronts.

Four Northeast Atlantic cores which exhibited well-correlated linear progressions of conventional radiocarbon age with depth were analysed to provide 230 Th excess profiling data. The current evaluation of marine radiocarbon data suggests that conventional radiocarbon ages consistently underestimate true time. This deficit progressively increases from 4 to 22 ky BP. As a result, steady-state sediment accumulation rate models based on conventional radiocarbon ages are expected to be in error by up to 17%, dependent on the period over which the estimates are made. When proxy timescales from the radiocarbon and 230 Th excess data for the four cores are compared over periods between 0–11.5 and 0–18.2 ky BP, the trend of cumulative time derived from the 230 Th excess profiling data is shown to be consistent with the expected trend of conventional radiocarbon age vs the best current estimate of true time. This agreement supports the use of 230 Th excess as a tracer for detailed estimates of changing deep-sea sediment accumulation fluxes.