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.     

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.     

Daily ingestion of 232Th, 238U, 226Ra, 228Ra and 210Pb in vegetables by inhabitants of Rio de Janeiro City

The concentrations of the naturally occurring radionuclides 232Th, 238U, 210Pb, 226Ra and 238Ra were determined in the vegetables (leafy vegetables, fruit, root, bean and rice) and derived products (sugar, coffee, manioc flour, wheat flour, corn flour and pasta) consumed most by the adult inhabitants of Rio de Janeiro City. A total of 88 samples from 26 different vegetables and derived products were analyzed. The highest contribution to radionuclide intake arises from bean, wheat flour, manioc flour, carrot, rice, tomato and potato consumption. The estimated daily intakes due to the consumption of vegetables and derived products are 1.9 mBq of 232Th (0.47 microg), 2.0 mBq of 238U (0.17 microg), 19 mBq of 236Ra, 26 mBq of 210Pb and 47 mBq of 228Ra. The estimated annual effective dose due to the ingestion of vegetables and their derived products with the long-lived natural radionuclides is 14.5 microSv. Taking into account literature data for water and milk from Rio de Janeiro the dose value increases to 29 microSv, with vegetables and derived products responsible for 50% of the dose and water for 48%. 210Pb (62%) and 228Ra (24%) were found to be the main sources for internal irradiation.     

Surfactant-based oil dispersant toxicity to developing nauplii of Artemia: effects on ATPase enzymatic system

The paper deals with the toxicity of a surfactant-based oil dispersant to the ATPase activities of two naupliar stages of Artemia (instar I & II). Both instars were exposed to sub-lethal and lethal concentrations derived from acute toxicity data. The chosen concentrations were near to LOECs and NOECs. An eightfold difference indicated between the instars was instar-exposure time dependent. The most prominent effects were the inhibition and the stimulation of Na⁺/K⁺-ATPase and Mg²⁺-ATPase activities, respectively. The cause of these effects was related to the dispersant components, the surfactants. The pattern stimulation/inhibition of Mg²⁺-ATPase and Na⁺/K⁺-ATPase activities could be used to indicate toxic stress by surfactant-based oil dispersants since previous studies with other contaminants have shown different ATPase activity patterns.     

Enhanced transport of pesticides in a field trial with treated sewage sludge

This study was designed to provide high-density data on spatial distribution of three herbicides with different physiochemical characteristics in a sludge-amended and non-amended control field over the course of an irrigation season. The field experiment was carried out on a sandy loam Hamra Red Mediterranean soil (Rhodoxeralf) at Bet Dagan, Israel. After a single 50 mm irrigation event, the mean centers of mass (COM) in the control field were at 15.6, 14.9, and 17 cm for bromacil, atrazine and terbuthylazine, respectively; in the sludge-amended field, mean COMs were at 28.8, 31.2, and 34.1 cm, respectively. After 500 mm of irrigation in the control field, the COM depth distribution of the three pesticides was inversely correlated with octanol-water (Kow) distribution coefficients and soil sorption coefficients (Koc), and positively correlated with aqueous solubilities. After 500 mm irrigation in the sludge-amended field, the mean terbuthylazine COM was at 19.8 cm versus 13.8 cm for the control field, demonstrating a sustained enhanced effect on terbuthylazine transport. Downward transport of atrazine was also enhanced by sludge amendment, albeit less than terbuthylazine. Bromacil was preferentially accumulated in the upper soil layers of the sludge-amended field as compared with the control field after 500 mm irrigation. The enhanced transport of all three pesticides in the sludge-amended field after a single irrigation event is attributed to development of preferential flow pathways around hydrophobic clods of sludge. Enhanced transport of terbuthylazine, and to a lesser extent, atrazine, throughout the irrigation season, is attributed to their transport as complexes with dissolved, colloidal and suspended organic matter derived from sludge degradation.     

Effects of spraying the herbicides 2,4-D and 2,4,5-T on a population of the tortoise Testudo hermanni in southern Greece

A population of the tortoise Testudo hermanni near Olympia in southern Greece was studied by mark-recapture from 1975 to 1984. Part of the site was sprayed with the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) each year from 1980, producing symptoms of poisoning (swollen eyes, fluid discharge from the nose and immobility) in tortoises. Survival rates of tortoises 10 cm or larger were significantly lower in the affected areas, with extra mortality of about 34% year-1, against an annual survival rate of 0.85-0.90 in unaffected areas. Changing population structures showed that juveniles were even more strongly affected, with the proportion of juveniles in samples decreased by half. The population in the sprayed area declined to near zero by 1984, due to mortality rather than to emigration, since more movements were recorded into than out of the affected area. There was no difference in body mass condition between sprayed and unsprayed areas, showing that effects were acute; mortality was not due to starvation from loss of food plants. The scale and pattern of mortality was similar to that from a severe scrub fire; spraying is potentially more catastrophic since often repeated at shorter intervals than burning. Possible physiological mechanisms of death are discussed. The susceptibility of tortoises to 2,4-D and 2,4,5-T (or to associated dioxin impurities) presents a warning for conservation of these late-maturing animals.     

津巴布韦因西扎地区的菲拉布斯河床开采:小型人工采矿的可持续性发展模式

河床开采计划位于因西扎地区的菲拉布斯小镇附近,地处津巴布韦西南部的布拉瓦约东南方大约 100公里的地方 .1990年代中期,这个示范工程由已故的 Jurgen G. Voss教授和他的"津巴布韦大学采矿工程与冶金学系"的工作人员发起,资金支持则由德国技术援助集团 (GTZ)提供 .     

Uranium transport around the reactor zone at Bangombé and Okélobondo (Oklo): examples of hydrogeological and geochemical model integration and data evaluation

The sites at Bangombé and Okélobondo (Oklo) in Gabon provide a unique opportunity to study the behaviour of products from natural nuclear reactions in the vicinity of reactor zones which were active around two billion years ago. The Commission of the European Communities initiated the Oklo Natural Analogue Programme. One of the principal aims was to study indications of present time migration of elements from the reactor zones under ambient conditions. The hydrogeological and hydrochemical data from the Oklo sites were modelled in order to better understand the geochemical behaviour of radionuclides in the natural system, by using independent models and by comparing the modelling outcome. Two modelling approaches were used: M3 code (hydrochemical mixing and mass balance model), developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) and HYTEC (reactive transport model) developed by Ecole des Mines de Paris. Two different reactor zones were studied: Bangombé, a shallow site, the reactor being at 11 m depth, and OK84 at Okélobondo, situated at about 450 m depth, more comparable with a real repository location. This allowed the validation of modelling tools in two different sedimentary environments: one shallow, with a more homogeneous layering situated in an area of meteoric alteration, and the other offering the opportunity to study radionuclide migration from the reaction zone over a distance of 450 m through very heterogeneous sedimentary layers. The modeling results indicate that the chemical reactions retarding radionuclide transport are very different at the two sites. At Bangombé, the decomposition of organic material consumes oxygen and at Okélobondo the oxygen is consumed by inorganic reactions resulting, in both cases, in uranium retardation. Both modelling approaches (statistic with M3 code and deterministic with HYTEC code) could describe this situation. The goal of this exercise is to test codes which can help to describe and understand the processes taking place at the sites, validate the models with in situ data, and thus build confidence in the tools used for future site characterization. Ultimately, this allows identifying and selecting processes and parameters that can be used as input into repository performance assessment calculations and modelling exercises.     

Predicting logP of pesticides using different software

We compared experimental and calculated logP values using a data set of 235 pesticides and experimental values from four different sources: The Pesticide Manual, Hansch Manual, ANPA and KowWin databases. LogP were calculated with four softwares: HyperChem, Pallas, KowWin and TOPKAT. Crossed comparison of the experimental and calculated values proved useful, especially for pesticides. These are harder to study than simpler organic compounds. Structurally they are complex, heterogeneous and similar to drugs from a chemical point of view. They offer an interesting way to verify the goodness of the different methods. Other studies compared several logP predictors using a single set of experimental values taken as a reference. Here we discuss the utility of the different logP predictors, with reference to experimental data found in different databases. This offers three advantages: (1) it avoids bias due to the assumption that one single data set is correct; (2) a given predictor can be developed on the same data set used for evaluation; (3) it takes account of experimental variability and can compare it with the predictor's variability. In our study Pallas and KowWin gave the best results for prediction, followed by TOPKAT.     

Anthropogenic 236U at Rocky Flats,Ashtabula river harbor,and Mersey estuary: three case studies by sector inductively coupled plasma mass spectrometry

236U (t(1/2)=2.3 x 10(7) y) is formed as a result of thermal neutron capture by (235)U. In naturally occurring U ores, where a high neutron flux is present from spontaneous fission of (238)U, (236)U/(238)U atom ratios are approximately 10(-4) ppm. In the natural Earth's crust, unaffected by nuclear fallout, these ratios are expected to be on the order of 10(-8) ppm. Reactor-irradiated U, however, exhibits high (236)U/(238)U atom ratios approaching 10(4) ppm. As a result, the presence of very small quantities of reactor-irradiated U will significantly enhance the "background" (236)U/(238)U atom ratio. When sufficiently elevated (236)U/(238)U ratios are present, the determination of (236)U/(238)U by rapid inductively coupled plasma mass spectrometric (ICPMS) methods is attractive. We have used sector ICPMS at medium resolving power (R=3440) to measure (236)U/(238)U atom ratios with a determination limit of 0.2 ppm. The limiting factors in the measurement are the (235)U(1)H(+) isobar and background signal at m/z 236 arising from the (238)U(+) peak tail. Based upon the analysis of replicates and considerations of possible systematic errors, uncertainties of +/-5% are found for (236)U/(238)U atom ratios of 1-100 ppm. This procedure has been demonstrated in studies of anthropogenic (236)U in the environment at three locations: (a) offsite soils from the vicinity of the Rocky Flats Environmental Technology site (Golden, Colorado, USA); (b) sediments from the Ashtabula River (Ohio, USA); and (c) sediments from the Mersey estuary (Liverpool, UK). In each of these three locations, definite plumes of elevated (236)U/(238)U are identified and characterized. Maximum (236)U/(238)U atom ratios observed in RFETS-vicinity soils, the Ashtabula River, and the Mersey Estuary are 2.8, 140, and 4.4 ppm, respectively.