An overview of the effect of organic matter on soil-radiocaesium interaction: implications in root uptake

This paper aims to give an overview of the effect of organic matter on soil-radiocaesium interaction and its implications on soil-to-plant transfer. Studies carried out after the Chernobyl accident have shown that high 137CS soil-to-plant transfer persists in organic soils over years. In most of these soils, the specific sites in clays control radiocaesium adsorption, organic compounds having an indirect effect. Only in organic soils with more than 95% of organic matter content and negligible clay content does adsorption occur mostly on non-specific sites. After a contamination event, two main factors account for the high transfer: the low solid-liquid distribution coefficient, which is due to the low clay content and high NH4+ concentration in the soil solution, and the low K+ availability, which enhances root uptake. The estimation of the reversibly adsorbed fraction, by means of desorption protocols, agrees with the former conclusions, since it cannot be correlated with the organic matter content and shows the lack of specificity of the adsorption in the organic phase. Moreover, the time-dependent pattern of the exchangeable fraction is related to soil-plant transfer dynamics.     

Radioactive contamination in the Arctic--sources, dose assessment and potential risks

Arctic residents, whose diets comprise a large proportion of traditional terrestrial and freshwater foodstuffs, have received the highest radiation exposures to artificial radionuclides in the Arctic. Doses to members of both the average population and selected indigenous population groups in the Arctic depend on the rates of consumption of locally-derived terrestrial and freshwater foodstuffs, including reindeer/caribou meat, freshwater fish, goat cheese, berries, mushrooms and lamb. The vulnerability of arctic populations, especially indigenous peoples, to radiocaesium deposition is much greater than for temperate populations due to the importance of terrestrial, semi-natural exposure pathways where there is high radiocaesium transfer and a long ecological half-life for this radionuclide. In contrast, arctic residents with diets largely comprising marine foodstuffs have received comparatively low radiation exposures because of the lower levels of contamination of marine organisms. Using arctic-specific information, the predicted collective dose is five times higher than that estimated by UNSCEAR for temperate areas. The greatest threats to human health and the environment posed by human and industrial activities in the Arctic are associated with the potential for accidents in the civilian and military nuclear sectors. Of most concern are the consequences of potential accidents in nuclear power plant reactors, during the handling and storage of nuclear weapons, in the decommissioning of nuclear submarines and in the disposal of spent nuclear fuel from vessels. It is important to foster a close association between risk assessment and practical programmes for the purposes of improving monitoring, formulating response strategies and implementing action plans.     

Temporal trends for 99Tc in Norwegian coastal environments and spatial distribution in the Barents Sea

The objective of this study was to reassess 99Tc transit times and transfer factors, from Sellafield to northern Norway, and to determine the extent of 99Tc migration to the Barents Sea. Filtered seawater samples were collected on a monthly basis from Hilles?y, northern Norway, and in February 1999 from the Barents Sea. Results showed an increase in levels of 99Tc at Hilles?y where activity concentrations have increased from a baseline of 0.2-0.4Bq m(-3) to a maximum of 1.6 Bq m(-3). A transit time of 42 months and a transfer factor of 6Bq m(-3) per PBq a(-1) have been derived, using cross-correlation analysis. The current study predicts that future levels are unlikely to increase dramatically over the levels observed in 1998. Levels of 99Tc in the Barents Sea ranged from 0.2 Bq m(-3) to 1.1 Bq m(-3) showing the influence of new 99Tc inputs by early 1999.     

Environmental radiological impact associated with non-uranium mining industries: a proposal for screening criteria

Niobium, phosphate, coal and gold mining facilities have been selected as case studies with the aim of identifying possible sources of radiological impact during and after cessation of industrial operations. The results have shown that acid drainage, as well as chemical processing of mineral ores, constitute relevant impact indicators for present-day and future scenarios. The possible use of solid wastes abandoned at the end of the operations represents a long-term radiological concern. Therefore, it is necessary that Brazilian legislation for environmental licensing be revised taking into account the potential environmental and radiological impacts caused by these industries and establishing remedial procedures for waste storage areas in the existing sites. The indicators developed and procedures carried out can be used in screening for decisions on the adoption of regulatory requirements for practices at such types of installations.     

Intercomparison of INAA and ICP-MS results for thorium determination in Pakistani diet

A pilot study on ingestion and organ content of trace elements of importance in radiological protection was to be carried out in Pakistan. Baseline analytical data on daily dietary intake of thorium was to be measured using Instrumental Neutron Activation Analysis (INAA) technique. To determine the accuracy and reliability of our technique, some samples were measured in Pakistan using INAA and in Japan using Inductively Coupled Plasma-Mass Spectrometry. For intercomparison of results overall mean Z-scores were calculated. The results showed validity of our technique. Mean value of 232Th concentration in Pakistani diet samples using INAA technique is 0.0062 +/- 0.0028 microg/g and with ICP-MS technique is 0.0069 +/- 0.0032 microg/g.     

Study of a predictive methodology for quantification and mapping of the radon-222 exhalation rate

We propose a new methodology for predicting areas with a strong potential for radon (222Rn) exhalation at the soil surface. This methodology is based on the Rn exhalation rate quantification, starting from a precise characterisation of the main local geological and pedological parameters that control the radon source and its transport to the soil/atmosphere interface. It combines a cross mapping analysis of these parameters into a geographic information system with a model of the Rn vertical transport by diffusion in the soil. The rock and soil chemical and physical properties define the entry parameters of this code (named TRACHGEO) which calculates the radon flux density at the surface. This methodology is validated from in situ measurements of radon levels at the soil/atmosphere interface and in dwellings. We apply this approach to an area located in western France and characterised by a basement displaying a heterogeneous radon source potential, as previously demonstrated by lelsch et al. (J. Environ. Radioactivity 53(1) (2001) 75). The new results obtained show that spatial heterogeneity of pedological characteristics in addition to basement geochemistry--must be taken into account to improve the mapping resolution. The TRACHGEO forecasts explain the Rn exhalation variability on a larger scale and in general correlate well with in situ observations. Moreover, the radon-prone sectors identified by this approach generally correspond to the location of the dwellings showing the highest radon concentrations.     

Changes in soil quality and below-ground carbon storage with conversion of traditional agricultural crop lands to bioenergy crop production

Berm-isolated (0.5 ha) plots have been used since 1995 to quantify changes in soil and water quality with conversion from agricultural to bioenergy crops. Soil quality improvements, including increases in soil carbon storage, have occurred on sites planted to woody or herbaceous species, and no-till corn compared with tilled corn or cotton. Initial increases in soil carbon occurred within the upper 10 cm of the soil profile. Soil carbon on plantings of switchgrass, no-till corn, and sweetgum with a cover crop between the rows increased over the first 3 years. Soil carbon decreased by 6% on the sweetgum plantings without a cover crop and remained lower through the fifth growing season. Overall, the greatest increases in below ground carbon storage have occurred primarily within the upper 40 cm. Former land use, growth characteristics, management practices, and soil characteristics appear to be the primary factors determining the timing, depth. and extent of changes in soil carbon storage for bioenergy and no-till crops.     

Use of pyrolysis molecular beam mass spectrometry (py-MBMS) to characterize forest soil carbon: method and preliminary results

The components of soil organic matter (SOM) and their degradation dynamics in forest soils are difficult to study and thus poorly understood, due to time-consuming sample collection, preparation, and difficulty of analyzing and identifying major components. As a result, changes in soil organic matter chemical composition as a function of age, forest type, or disturbance have not been examined. We applied pyrolysis molecular beam mass spectrometry (py-MBMS), which provides rapid characterization of SOM of whole soil samples. to the Tionesta soil samples described by Hoover, C.M., Magrini, K.A., Evans, R.J., 2002. Soil carbon content and character in an old growth forest in northwestern Pennsylvania: a case study introducing molecular beam mass spectrometry (PY-MBMS). Environmental Pollution 116 (Supp. 1), S269-S278. Our goals in this work were to: (1) develop and demonstrate an advanced, rapid analytical method for characterizing SOM components in whole soils, and (2) provide data-based models to predict soil carbon content and residence time from py-MBMS analysis. Using py-MBMS and pattern recognition techniques we were able to statistically distinguish among four Tionesta sites and show an increase in pyrolysis products of more highly decomposed plant materials at increasing sample depth. For example, all four sites showed increasing amounts of older carbon (phenolic and aromatic species) at deeper depths and higher amounts of more recent carbon (carbohydrates and lignin products) at shallower depths. These results indicate that this type of analysis could be used to rapidly characterize SOM for the purpose of developing a model, which could be used in monitoring the effect of forest management practices on carbon uptake and storage.     

Bioavailability of calcium from sweetpotato and soy flour supplemented diets in hamsters

The bioavailability of calcium from two varieties of sweetpotatoes and supplementation of sweetpotatoes with soy flour was investigated in hamsters using plasma calcium concentration and femur calcium content as indicators. Five different diets were fed to five groups of animals for 28 days. There was no significant difference in plasma calcium concentrations of hamsters in all the diet groups. However, the femur calcium content of hamsters with transgenic sweetpotato flour (TSPF) and parent nontransgenic (from which transgenic was produced) sweetpotato flour (NTSPF) diets was significantly higher than that of the transgenic sweetotato flour supplemented with soy flour (TSPF + SF) and parent nontransgenic sweetpotato flour supplemented with soy flour (NTSPF + SF) diets. The relative bioavailability of calcium from the control (100%), TSPF+SF (30%), NTSPF+SF (23%), TSPF (57%) and NTSPF (46%) indicated that sweetpotatoes could be the better source of calcium, however, supplementation with soy flour might reduce the bioavailability of calcium.     

The influence of nitrogen deposition,competition and desiccation on growth and regeneration of Racomitrium lanuginosum (Hedw.) brid

Racomitrium lanuginosum shoot growth was studied under the combined effects of N deposition (0, 20, 40 and 60 kg N ha(-1) year(-1)). competition with Festuca ovina, and a drought pre-treatment. Moss regeneration from shoot fragments was also investigated. Growth was initially stimulated at the 60 kg N level. However, after 6 months, growth was lower in all N treatments than in the 0 kg N control. Reductions in shoot growth first became apparent in the pre-desiccated moss, while moss shoots grew longer when surrounded by a F. ovina canopy. Optimum regeneration occurred at 20-40 kg N on bare soil, and at 0-20 kg N under a F. ovina canopy. These results suggest that current N deposition in upland Wales is already detrimental to growth of this species, and to regeneration under certain conditions. This species may be affected under predicted climatic scenarios of increased summer drought in Britain.