Decolorization and partial mineralization of a polyazo dye by Bacillus firmus immobilized within tubular polymeric gel

The degradation of C.I. Direct red 80, a polyazo dye, was investigated using Bacillus firmus immobilized by entrapment in tubular polymeric gel. This bacterial strain was able to completely decolorize 50 mg/L of C.I. Direct red 80 under anoxic conditions within 12 h and also degrade the reaction intermediates (aromatic amines) during the subsequent 12 h under aerobic conditions. The tubular gel harboring the immobilized cells consisted of anoxic and aerobic regions integrated in a single unit which was ideal for azo dye degradation studies. Results obtained show that effective dye decolorization (97.8%), chemical oxygen demand (COD) reduction (91.7%) and total aromatic amines removal were obtained in 15 h with the immobilized bacterial cell system whereas for the free cells, a hydraulic residence time of 24 h was required for an equivalent performance in a sequential anoxic and aerobic process. Repeated-batch experiments indicate the immobilized cells could decolorize C.I. Direct red 80 and reduce medium COD in five successive batch runs with enhanced activity obtained after each consecutive run, thus suggesting its stability and potential for repeated use in wastewater treatment. UV–visible spectrophotometry and HPLC analysis were used to confirm the partial mineralization of the dye. Data from this study could be used as a reference for the development of effective industrial scale biotechnological process for the removal of dyes and their metabolites in textile wastewater

Behaviour of Lead-210 in continental environment: Comparison with stables isotopes of lead

Lead-210 is a natural radioactive isotope and a decay product of the Uranium-238 decay chain found in the natural environment along with Radon-222 and Polonium-210. Lead-210 contribution to the internal exposure of man through ingestion is 20% but represents 70% of the internal exposure of man through inhalation due to the uranium and thorium decay series. Transfer of lead-210 in the environment has been relatively poorly studied when compared to other radionuclides (Caesium-137, Strontium-90, Cobalt-60, Tritium, Carbon-14, etc.) even if we register a recent increase in the number of scientific publications. Therefore, this study reviews experimental data concerning the transfers of Lead-210 in the different compartments (atmosphere, freshwaters, sediments, soils, plants, animals) of continental environments (terrestrial and freshwater) from its natural sources. Moreover, it compares these data with those concerning the stable isotopes of lead. Indeed, stable lead is found in all the terrestrial and freshwater ecosystems but with an important variation in its concentration according to location and sampling type. Such a global contamination of the environment is mainly due to its industrial use. Lead toxicity is coming from its physiological behaviour similar to those of essential elements such as calcium and magnesium. A list of transfer factors for Lead-210 and stable isotopes of lead between the different compartments of the terrestrial and freshwater ecosystems is provided. The main conclusion of this review is that the behaviours of Lead-210 and stable isotopes of lead are quite similar in terrestrial environments although some discrepancies are noted in freshwater environments. The nature of these discrepancies is discussed

Radioecology and Society: A mutual need

Radioecology is defined as the study of the behaviour and effects of ionising radiations and radionuclides in the environment. Until recently, ecosystems were only considered in radioecology as an intermediate compartment between the source of radiation and man. Interest in the effects of ionising radiation and radionuclides on the environment has recently increased because of the surge in the public awareness concerning the different sources of pollution of the environment and their effects on human health, the evolution of paradigm by the ICRP concerning the radiation protection of the environment, and the increase in our knowledge in that specific field of research. Radioecology is now a mature scientific domain which is standing on its own feet. Its maturity can be assessed in different domains: (i) Education: with the appearance and development of masters in Radioecology worldwide, it is becoming a proper teaching domain in Higher Education; (ii) networks of excellence: international collaboration are initiated all over the world; (iii) Regulation: radiation protection of the environment is becoming a major point of concern along with the radiation protection of the public worldwide (ICRP, IAEA, IUR,…) and more specifically in the European Union; (iv) Public concern: the public mind is now open for and in an urgent need for more information about the implications of human activities, and among them those producing and releasing ionising radiations and radionuclides, on his own environment and health, i.e. on his personal feeling of well-being

Modelling Tritium and Carbon 14 in the environment: A biomass-oriented approach

There are many existing models describing the behaviour of carbon 14 and tritium in the environment. There are all quite difficult to handle and data consuming because they are based on the precise description of the different and complex mechanisms of the carbon and hydrogen cycles. A simplified model of transfer in the environment of tritium and carbon 14 is presented. It is based on the following assumptions: (a) the modelled radionuclides have an homogeneous repartition inside the biological compartments considered; (b) transfer flows of such radionuclides are proportional to the biomass changes in all the biological compartments; (c) time evolution of radionuclides isotopic equilibrium is discrete. Such a dynamic approach is based on the use of growth models of biological systems (plants, animals, etc..). From the proposed conceptual model, 2 mathematical models are proposed: a one-pool model (organic carbon for carbon 14) and a two-pool model (organic tritium and tritiated water for tritium)

Dynamics of Carbon 14 in soils: A review

In terrestrial ecosystems, soil is the main interface between atmosphere, hydrosphere, lithosphere and biosphere. Its interactions with carbon cycle are primordial. Information about carbon 14 dynamics in soils is quite dispersed and an up-to-date status is therefore presented in this paper. Carbon 14 dynamics in soils are governed by physical processes (soil structure, soil aggregation, soil erosion) chemical processes (sequestration by soil components either mineral or organic), and soil biological processes (soil microbes, soil fauna, soil biochemistry). The relative importance of such processes varied remarkably among the various biomes (tropical forest, temperate forest, boreal forest, tropical savannah, temperate pastures, deserts, tundra, marshlands, agro ecosystems) encountered in the terrestrial ecosphere. Moreover, application for a simplified modelling of carbon 14 dynamics in soils is proposed.

Impact of micro-organisms on the fate of radionuclides in rhizospheric soils

This book collates a series of contributions which reflect on on-going discussions and provide reviews of the most up-to-date scientific and technical information regarding continental and estuarine environments. It also identifies research themes for the future along with scientific and ethical issues

Bioavailability in the BORIS assessment model

The fifth framework EU project BORIS (Bioavailability Of Radionuclides In Soils: role of biological components and resulting improvement of prediction models) had three scientific objectives. The first was to improve understanding of the mechanisms governing the transfer of radionuclides to plants. The second was to improve existing predictive models of radionuclide interaction with soils by incorporating the knowledge acquired from the experimental results. The last and third objective was to extract from the experimental results scientific basis for the development of bioremediation methods of radionuclide contaminated soils and to apprehend the role of additional non-radioactive pollutants on radionuclide bioavailability. This paper is focused on the second objective. The purpose of the BORIS assessment model is to describe the behaviour of radionuclides in the soil-plant system with the aim of making predictions of the time dynamics of the bioavailability of radionuclides in soil and the radionuclides concentrations in plants. To be useful, the assessment model should be simple and use only a few parameters, which are commonly available or possible to measure for different sites. The model shall take into account, as much as possible, the results of the experimental studies and the mechanistic models developed in the BORIS project. The adopted approach was to introduce in the assessment model a quantitative relationship between bioavailability of the radionuclides in soil and the soil properties. To do this an operational definition of bioavailability was proposed. Here, operational means experimentally measurable, directly or indirectly, and that the bioavailability can be translated into a mathematical expression. This paper describes the reasoning behind the chosen definition of bioavailability and how it was used in the assessment model

De toekomst van Israel

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