14C and 210Pb in NE atlantic sediments: Evidence of biological reworking in the context of radioactive waste disposal

Scavenging by the seabed and by sedimentary particles in the deep ocean may have a significant effect on the removal of artificial radionuclides released to the water column as a result of radioactive waste disposal operations. Biological activity in the upper layers of the sediment column will enhance the rate of removal for those particle-reactive radionuclides with a short half-life relative to the turnover time of the upper mixed layer. For longer-lived radionuclides the rate of sediment accumulation will determine the ultimate rate of removal.The rate of sediment accumulation and extent of biological mixing of deep-sea sediment from three areas of the NE Atlantic Ocean have been investigated using ¹⁴C and ²¹⁰Pb data. Treatment of the radiocarbon with a simple box model provided estimates of sedimentation rate (ω), mixed layer depth (L), mixed layer age (T_ML) and the age of material arriving at the surface (T₀), which were broadly similar to previously published values from other ocean basins. Box cores from the Iberia Abyssal Plain, Madeira Abyssal Plain and from the NEA low-level radioactive waste dumpsite yielded sedimentation rates in the range 0.8 to 2.2 cm ky^?1 over the upper 16–25 cm. Continuous particle mixing appears to be taking place to a depth of 4 to 6 cm below the present sediment-water interface. Closely spaced vertical sampling of core 161-2 for ²¹⁰Pb allowed a biodiffusion coefficient (D_B) to be calculated (4 × 10^?9cm²s^?1), treating bioturbations as a diffusive term and sedimentations as an advective term in a simple mathematical model. In general, values of D_B in deep ocean sediments fall within the range 1–10 × 10^?9cm²s^?1, two orders of magnitude lower than nearshore values. From a review of published data it is concluded that biological mixing takes place extensively in the deep ocean; it appears to be fairly constant on a basin-wide scale and amenable to incorporation in mathematical models of radionuclide behaviour in the water column.     

Distributional 234,238U, 226Ra, 210Pb and 210Po in soil

A soil profile from 0 to 90 cm was collected in an undisturbeded area of Cape Cod, Massachusetts. Five centimeter increments of the profile were analyzed for ^234,238U, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po. The factors affecting the activity distribution of these naturally-occurring radionuclides are discussed for this particular soil type.     

Environmental and climatic signals from stable isotopes in Anatolian tree rings, Turkey

Dendrochronological and oxygen–carbon isotopic analysis was conducted on tree rings collected at two different elevations from three different regions in western Anatolia, Turkey. Tree rings were sampled from Anatolian black pines (Pinus nigra Arn. subsp. pallasiana (Lamb.) Holmboe) of at least 200?years old through an N–S transect covering Bolu-Mengen (north), Kütahya–Simav, and Antalya–Alanya (south) forests. Cellulose was extracted from 5-year blocks of tree rings from lower to upper altitudes in each region. Dendrochronological site chronologies were built for each of the 6 sites, and response to climate was evaluated. The long-term δ¹³C chronologies comprising the period 1800–2008 strongly decline by an average of 2.5‰ from the mid-twentieth century, which corresponds with the commencement of industrialization in Turkey. Oxygen isotope (δ¹⁸O) time series show dominantly low undulations, although some high-frequency variations of up to 6‰ are also observed. As a result of latitude and continent effects, oxygen isotope values of tree rings show an average of 3‰ increase from south (Antalya) to the north (Bolu). Correlations between carbon isotope ratios yield high positive values indicating that industrial pollution exerts a major control on the δ¹³C systematics of the studied trees. Corrected δ¹³C ratios are mostly represented by strong positive responses to variations in temperature and precipitation, whereas δ¹⁸O and summer temperature/precipitation are negatively correlated. Tree-ring widths and δ¹⁸O display similar responses to the temperature and sensitivity to the climatic impact of historic volcanic eruptions, and changes in the solar irradiance record are also detected in other high-resolution paleoclimate archives for the region.     

Biotic, temporal and spatial variability of tritium concentrations in transpirate samples collected in the vicinity of a near-surface low-level nuclear waste disposal site and nearby research reactor

The results of a 21 month sampling program measuring tritium in tree transpirate with respect to local sources are reported. The aim was to assess the potential of tree transpirate to indicate the presence of sub-surface seepage plumes.Transpirate gathered from trees near low-level nuclear waste disposal trenches contained activity concentrations of ³H that were significantly higher (up to ∼700 Bq L⁻¹) than local background levels (0-10 Bq L⁻¹). The effects of the waste source declined rapidly with distance to be at background levels within 10s of metres. A research reactor 1.6 km south of the site contributed significant (p < 0.01) local fallout ³H but its influence did not reach as far as the disposal trenches.The elevated ³H levels in transpirate were, however, substantially lower than groundwater concentrations measured across the site (ranging from 0 to 91% with a median of 2%). Temporal patterns of tree transpirate ³H, together with local meteorological observations, indicate that soil water within the active root zones comprised a mixture of seepage and rainfall infiltration. The degree of mixing was variable given that the soil water activity concentrations were heterogeneous at a scale equivalent to the effective rooting volume of the trees. In addition, water taken up by roots was not well mixed within the trees. Based on correlation modelling, net rainfall less evaporation (a surrogate for infiltration) over a period of from 2 to 3 weeks prior to sampling seems to be the optimum predictor of transpirate ³H variability for any sampled tree at this site.The results demonstrate successful use of ³H in transpirate from trees to indicate the presence and general extent of sub-surface contamination at a low-level nuclear waste site.     

Cesium-137 contamination of oak (Quercus petrae Liebl.) from sub-mediterranean zone in South Bulgaria

This study focuses on the cesium-137 (¹³⁷Cs) contamination in grass and in different compartments of oak trees growing in ecosystems, located in the zone with sub-mediterranean climate in South Bulgaria, characterized with high summer temperatures, low precipitation and often periods of drought. In 2008, three experimental sites - PP1, PP2, PP3 - were sampled in oak ecosystems from Maleshevska Mountain at 900 m above sea level. Samples from grass species and oak tree leaves, branches with different diameter, wood disks and bark were analyzed for ¹³⁷Cs activity with γ-spectrometry. The soil-to-plant transfer factor (TF) values for ¹³⁷Cs were estimated differentiating different tree compartments. Our findings showed relatively high activity concentrations of ¹³⁷Cs in oak trees even 22 years after the Chernobyl accident. The grass under oak was less contaminated compared with the oak trees. The different organs of oak trees could be distinguished according to the ¹³⁷Cs contamination as follows: bark > branches (d < 1 cm) > leaves > branches (d > 3 cm) > wood. The relatively higher contamination of bark compared with the new-formed biomass suggested that a significant part of ¹³⁷Cs was accumulated as a result of direct adsorption at the time of the main contamination event. The TF values obtained and the presence of ¹³⁷Cs in the branches, leaves and in the wood formed after 1986 confirmed that 22 years after the contamination, the main mechanism of ¹³⁷Cs entrance in tree biomass was the root uptake.     

The application of fucus vesiculosus as a bioindicator of 60Co concentrations in the Danish Straits

The occurrence of ⁶⁰Co in the Danish Straits is investigated by applying the seaweed Fucus vesiculosus as a bioindicator. In order to describe different dispersion situations, three areas have been studied separately: the North Sea, where it is possible to measure ⁶⁰Co from sources in France and/or the UK; the Kattegat, where the sources are the Swedish nuclear power plants Ringhals and Barsebäck; and the Sound, where the initial mixing of the release from Barsebäck takes place. A power function can be estimated for the Kattegat and the Sound describing the content of ⁶⁰Co in Fucus as a function of distance from Barsebäck. Problems of uncertainty related to differences in environmental parameters are discussed and new investigations to improve the use of Fucus as a bioindicator are suggested.     

Uptake and loss of 134Cs and 60Co by the Baltic bivalve Macoma baltica in a laboratory microcosmos

Accumulation and clearance of ¹³⁴Cs and ⁶⁰Co by the Baltic bivalve Macoma baltica were experimentally investigated in a laboratory microcosmos. The nuclides were added to the water and the activities in bivalve flesh, shell, feces and sediment were determined at regular intervals. The uptake was quite rapid, 40% (Cs) and 55% (Co) of the final steady state values being attained after 24 h. The subsequent releases were also rapid, 50% (Cs) and 40% (Co), of the accumulated activity being lost within 6 days. The experiments demonstrated that the major intake route following short-term releases of activity will be from the water column and that the close relationship between activity in water and organism can thus be used for predictive purposes without the complication of radionuclide uptake from contaminated sediments. However, for longer periods, the subsequent intake of sediments will generate a significant exposure pathway for this deposit-feeding bivalve.     

85Kr atmospheric concentration in Bratislava from 1980 to 1983

A cryogenic-chromatographic method for determination of ⁸⁵Kr in the atmosphere is presented. Sampling of the air on the activated-charcoal, chromatographic separation of Krypton from the other air components and radioactivity measurement are described in details. The activity of ⁸⁵Kr is measured by small proportional counters with sensitive volumes of 5 and 10 cm³. Results of the measurements of ⁸⁵Kr air concentration in Bratislava from 1980 to 1983 are presented and compared with other ⁸⁵Kr data measured in Europe.     

南京紫金山马尾松树轮δ13C对气候变化响应敏感性的研究

树木年轮宽度指标在气候重建中发挥了重要的作用,可是在温暖湿润的地区,利用树木年轮宽度重建古气候遇到了困难。因此寻找其他代用指标就成为一项急迫而重要的任务。一些研究发现,树轮稳定碳同位素可以发挥重要的作用。但是,是否所有的树种的树轮碳同位素对气候的响应都同样的敏感,还需要通过大量的研究分析工作来验证。为了了解温暖湿润的亚热带季风区马尾松树轮δ13C对气候响应的敏感性,选取了南京紫金山的两个马尾松树盘,进行了树轮δ13C的分析,建立了1939~2002和1955~2002年两个树轮δ13C变化序列。与降水、温度、相对湿度、光照时数、风速等气候指标进行了相关分析。结果表明：（1）马尾松树轮δ13C对于气候的响应是敏感的,可以作为气候变化的代用指标;（2）坡向对于马尾松树轮δ13C对气候的响应敏感性也有一定的影响,树轮δ13C平均值西南坡比东南坡高,西南坡比东南坡对月平均最低和最高温度的响应更敏感;（3）紫金山马尾松树轮δ13C与该地区生长季（尤其是夏、秋季）的月平均气温、月平均最高气温和日照时数呈正相关,而与月平均最低气温、降水量、空气相对湿度呈负相关     

Areal distribution of 129I in west cumbrian solis

¹²⁹I has been released during operations at the BNFL nuclear fuel reprocessing plant at Sellafield in west Cumbria over the past thirty years with about 95% being discharged into the sea and 5% into the atmosphere. Soil samples have been taken within a 40 km radius of Sellafield to determine the extent to which the ¹²⁹I is deposited in the immediate vicinity of the plant. The ¹²⁹I content has been determined by a sensitive neutron activation technique and levels in soil were found to be elevated above global levels in all samples. The areal distribution of ¹²⁹I was consistent with direct deposition following release to the atmosphere from Sellafield and the relationship between ¹²⁹I activity and the distance from Sellafield was of a form predicted by atmospheric dispersion models. The absence of any observable return of ¹²⁹I from the sea has implications for assessments of dose.     

Tree bark — sensitive biotest for environment acidification

The Niepo?omice Forest, a large forest complex (11,000 ha), situated about 20 km from a large steel mill and about 40 km from the city of Cracow was the object of study. Sulphur dioxide emitted by the steel mill and the city has already caused acidification of the environment of the Niepo?omice Forest. The degree of such acidification was estimated using tree bark as a bioindicator. The pH value and buffer capacity were determined for three tree species — Quercus robur, Tilia cordata and Pinus sylvestris. The bark of all trees showed acidic reaction ranging from pH 2.2 to 4.7. Difference in pH of bark were found between various localities. The bark of examined species was much more acidic in the western part in the Niepoo?mice Forest than in the eastern part of the forest complex. The buffer capacity of bark also differs in various localities increasing with SO₂ concentration in the air. A good correlation between acidification of tree bark and the concentration of SO₂ in the air of Niepo?omice Forest was found; therefore tree bark may be regarded as a good bioindicator and recommended for practical use to estimate the degree of air pollution. The procedure of sampling and analysis of tree bark is described in detail.     

Determination of 99Tc, 63Ni and 121m+126Sn in the marine environment

Four artificially produced radionuclides (${}^{99}\text{Tc, t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 2·15 × 10}{}^5\text{y;}{}^{63}\text{Ni, t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 93 y}$ and ${}^{\mathrm{121m+126}}\text{Sn, t}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 55·5 y}$) have been analyzed in sediments and organisms from the marine environment. The samples were obtained from the vicinities of nuclear energy facilities, at sites of nuclear weapon tests and at sites remote from both of these locales. The activities of these nuclides per unit dry weight are remarkably similar at the first two of the above areas but are usually detectable only with difficulty, if at all, in the third area. Techniques for sample treatment and measurement are given.     

Environmental fate and distribution of technetium-99 in a deciduous forest ecosystem

The aims of the present research are to describe the uptake of ⁹⁹Tc by trees intercepting contaminated groundwater from a radioactive waste storage site, to identify the major ⁹⁹Tc pools within the woodland ecosystem and to assess the relative mobility of ⁹⁹Tc in the existing element cycle. Technetium in the groundwater freely passed through a dialysis membrane with a molecular weight exclusion limit of approximately 3500 amu and ⁹⁹Tc in the groundwater chromatographed on Biogel P-2 in a manner similar to pertechnetate anion (TcO₄⁻). Reducing conditions and organic associations at the study site were probably responsible for the relatively large amount (83–92%) of the ⁹⁹Tc that was nonextractable from soil by 0·01 m CaCl₂. More than one-third of the ⁹⁹Tc was released from the soil by oxidizing reagents, indicating the presence of chemically reduced forms. The highest average ⁹⁹Tc concentrations in vegetation were found in herbaceous plants (18 530 pCi g⁻¹ dry wt). Although ⁹⁹Tc was progressively accumulated over the growing season in tree leaves, average concentrations in tree wood and twigs were equal to or greater than concentrations in leaves. Tree wood was the major above-ground pool for ⁹⁹Tc because of the high concentrations in wood as well as the large amount of wood relative to other biomass at the site. Technetium was not easily leached from the trees by rainfall and was not readily extractable from forest floor leaf litter by water. The relative importance of return pathways for ⁹⁹Tc to the forest floor was leaf fall>stemflow >throughfall, indicating that ⁹⁹Tc was conserved by the trees. Snails and millipedes from the leaf litter layer concentrated technetium 20- and 16-fold, respectively, above levels found in the soil. Pertechnetate was rendered less bioavailable after ingestion by a leaf litter macroinvertebrate (Porcellio sp.) common to the study site.     

Communities of trees along a tropical forest restoration gradient

Increasing rates of deforestation in tropical forests have been linked to agriculturalists. A critical concern generating debate is how well communities of trees recover into a more species rich ecosystem after restoration planting. The aim of the study was to evaluate the pattern of recovery of communities of tree, assess the influence of Acanthus pubescens, Lantana camara and Pennisetum purpureum, on the recovery as well as how restoration planting facilitates recruitment of other native tree seedlings along a gradient of forest restoration in Kibale National Park, Uganda after evictions of illegal settlers. We studied six restoration forests ranging in age from 3 to 16 years, naturally regenerating and three primary forests. Our results showed that recovery with natural regeneration was more effective than restoration planting although the latter enhanced recruitment of other native tree seedling. Tree recovery was generally correlated with age so that species density and diversity increased although at different rates. A reverse pattern was found for dominance but no clear pattern was found for tree density (individual/ha). Communities of tree showed directional patterns of change however community composition were still distinct among the different forests. A. pubescens, L. camara and P. purpureum negatively correlated with species density, tree density and diversity but a positive correlation was found for dominance. Restoration planting can reestablish forests with high species density, tree density and diversity, but this is dependent on age and the extent of the herbs, grasses and shrubs cover in tropical forests.     

Carbon stock variation of Pinus roxburghii Sarg. Forest along altitudes of Garhwal Himalaya, India

The present study was undertaken in Pinus roxburghii forest along three different altitudes i.e., 1100, 1300 and 1500 meter above mean sea level of Garhwal Himalaya to understand the effect of altitudes on carbon stocks (live trees and soil) in Pinus roxburghii forest. Tree density of this forest ranged between 590 tree ha^?1 (upper altitude) to 640 tree ha^?1 (lower altitude). The highest total carbon density (TCD) of above and belowground carbon was 66.33 ± 29.92 Mg ha^?1 at lower altitude followed by 57.64 ± 16.75 Mg ha^?1 in middle altitude and 52.92 ± 6.52 Mg ha^?1 in upper altitude. Soil organic carbon was highest (33.20 ± 2.77 Mg ha^?1) at lower altitude followed by middle (22.61 ± 7.17 Mg ha^?1) and upper altitude (12.65 ± 6.10 Mg ha^?1). Total carbon stock (trees + soil) of Pinus roxburghii forest was maximum (99.53 Mg ha^?1) at lower altitude and minimum (65.57 Mg ha^?1) at upper altitude.     

Mutagenicity of a bipyridylium herbicide in an N2-fixing cyanobacterium Nostoc muscorum

The herbicide diquat (1,1′-ethylene-2,2′-bipyridylium ion) is toxic and lytic to Nostoc muscorum. A reverse mutation (from het^?nif^? auxotrophy to het⁺nif⁺ prototrophy), a forward mutation (for streptomycin [St]-resistance), and an auxotrophic mutation (carbon-auxotrophy through methylamine [MA]-resistance) have been obtained with a dose of diquat permitting about 20% or 50% survival. Similar mutation frequencies were obtained through induction with MNGG (N-methyl-N′-nitro-N-nitrosoguanidine).     

CO2 dispersion around two PWR nuclear power plants in Brazil

Atmospheric air samples were taken within 3 km from power plants encompassing five different distances and wind directions. Samples were taken between 2002 and 2005 aiming to evaluate the environmental ¹⁴C enrichment due to the operation of Brazilian nuclear power plants. The sampling system consisted of a pump connected to a trapping column filled with a 3 M NaOH solution. The trapped CO₂ was analyzed for ¹⁴C by using a single stage accelerator mass spectrometry (SSAMS).     

Extraction of fallout 210Pb from soils and its distribution in soil profiles

Natural fallout ²¹⁰Pb may be extracted from soils with hot, dilute nitric acid without extracting significant quantities of ²¹⁰Pb produced by decay of radon in the soil. This method was used to determine the distribution of fallout ²¹⁰Pb in the profiles of nine New Zealand soils. The measured levels were similar to equilibrium cumulative depositions calculated from deposition records. The results indicate that these soils have quantitatively retained fallout ²¹⁰Pb, with 75–100% of it being concentrated in the top 10 cm of soil. This permanent retention of fallout lead by soils suggests that accumulation of lead in the upper soil layer is likely in areas of aerosol lead pollution.     

Distribution and ratios of Cs and K in control and K-treated coconut trees at Bikini Island where nuclear test fallout occurred: effects and implications

Coconut trees growing on atolls of the Bikini Islands are on the margin of K deficiency because the concentration of exchangeable K in coral soil is very low, ranging from only 20 to 80 mg kg⁻¹. When provided with additional K, coconut trees absorb large quantities of K and this uptake of K significantly alters the patterns of distribution of ¹³⁷Cs within the plant. Following a single K fertilization event, mean total K in trunks of K-treated trees is 5.6 times greater than in trunks of control trees. In contrast, ¹³⁷Cs concentration in trunks of K-treated and control trees is statistically the same while ¹³⁷Cs is significantly lower in edible fruits of K-treated trees. Within one year after fertilization (one rainy season), K concentration in soil is back to naturally low concentrations. However, the tissue concentrations of K in treated trees stays very high internally in the trees for years while ¹³⁷Cs concentration in treated trees remains very low in all tree compartments except for the trunk. Potassium fertilization did not change soil Cs availability.