Analysing radionuclide content in soil samples and radiological risks in the clayey material surrounding of the “Zbegovi” deposit, Donje Crniljevo, Serbia

This paper presents the results of analyses of radionuclide content in the samples of the surrounding soil and clayey material of ?Zbegovi? open-pit mine in Donje Crniljevo, Serbia. Samples from 78 sites were collected and prepared. The activity concentrations were determined for radionuclides: 238U, 232Th, 40K, 226Ra, and 137Cs. The mean values obtained are as follows: 23 Bqkg?1, 89 Bqkg?1, 372 Bqkg?1, 56 Bqkg?1, and 11 Bqkg?1, respectively. Concentrations of 238U, 40K, and 226Ra in the studied area do not deviate from the values obtained for the soil in Serbia. The concentration of 232Th in the studied area is slightly higher relative to average values for soil, and slightly lower compared to similar deposits of clayey material in the world. Measurements performed showed that the open-pit mine of clayey material is completely uncontaminated surface as far as 137Cs is concerned, while there are sites where measured 137Cs concentrations are significantly higher, which is due to topographic differences and inhomogeneous surface contamination of land after the Chernobyl accident. To assess the radiological risks in the observed area, the following indices were determined: absorbed dose rate, annual outdoor effective dose, absorbed dose for biota, excess lifetime cancer risk outdoors as well as external radiation hazard index. The mean value of the estimated absorbed dose rate in the given area amounts to 80.1 nGyh?1, and the annual outdoor effective dose ranges from 46.9 to 134 Sv. Absorbed dose rate for biota in the studied area is 1.31 10?4 Gyd?1. The mean excess lifetime cancer risk outdoors for the population is 3.8 10?4, and t he mean value of the external radiation hazard index obtained in this study is 0.48, which is consistent with the world average. A low dose of radiation will not pose a risk to the population and biota in the studied area.

Multiple roles of clays in radioactive waste confinement – introduction

Geological disposal provides the safe long-term management solution for higher-activity radioactive waste. The development of a repository (or geological disposal facility) requires a systematic and integrated approach, taking into account the characteristics of the waste to be emplaced, the enclosing engineered barriers, and the host rock and its geological setting.Clays and clayey material are important in the development of many national geological disposal systems. Clays exhibit many interesting properties, and are proposed both as host rocks and as material for engineered barriers. Whatever their use, clays present various characteristics that make them high-quality barriers to the migration of radionuclides and chemical contaminants. As host rocks, clays are, in addition, hydrogeologically, geochemically and mechanically stable over geological timescales (i.e. millions of years).

Clay-induced DNA double-strand breaks underlay genetic diversity, antibiotic resistance and could be a molecular basis for asbestos-induced cancer

Some natural clays and synthetic nanofibres present in the environment have a severe impact on human health. After several decades of research, the molecular mechanism of how asbestos induce cancers is not well understood. Different fibres, including asbestos, can penetrate the membrane and introduce DNA in both, bacterial and eukaryotic cells. Incubating Escherichia coli with sepiolite, a clayey material, and asbestos under friction forces, both fibres cause double-strand breaks in bacteria. Since antibiotics and clays are used together in animal husbandry, the mutagenic effect of these fibres might constitute a pathway to antibiotic resistance due to the friction provided by peristalsis of the gut from farm animals in addition to the previously proposed horizontal gene transfer. Moreover, we raise the possibility that the same mechanism could generate bacteria diversity in natural scenarios with a role in the evolution of species. Finally, we provide a new model on how asbestos may promote mutagenesis and cancer based on the observed mechanical genotoxicity.

Investigation and mitigation of a failure at the Taxiarches canal of Mornos aqueduct

The sudden soil fracture and failure at the Taxiarches canal of Mornos Aqueduct of the Athens Water Supply and Sewerage Company (EYDAP SA), took place approximately 540m after the exit of Elikonas tunnel and resulted in failure and displacement of the canal segments along an 80m long section. Due to the failure the water supply was interrupted and two extensive gullies, spaced 75m apart, were created by the water outflow. The water discharge resulted in subsoil erosion and transportation of vast masses of geomaterial and two of the canal segments downhill. The debris flow destroyed part of Prodromos-Saranti Road, swapping along olive cultivations and causing extensive damage to Saranti settlement. The failure of the canal occurred in an area of steep morphology, at the front of an overthrust, within tectonic breccia and calcareous-clayey material of chaotic structure and reduced mechanical properties, vulnerable to erosion. The boundaries of the main fracture were defined by the thrust geometry. Τhe study of permanent remedial measures included excavation of a cut in the natural slope on the uphill side of the failure, construction of a bypass pipe founded on bedrock and of an anchored pile wall with pre-stressed anchors on the downhill side of the new pipe, excavation and removal of the temporary fill and finally construction of a reinforced fill for rehabilitation of the slide area.

Waste glass as additive to clayey material in subgrade and embankment of road pavement

In this paper the possibility of using waste glass in road construction is discussed. Samples of clay material with the addition of waste glass were subjected to a series of laboratory geotechnical tests performed at the Laboratory of Geotechnics at the Faculty of Civil Engineering and Architecture in Nis. The obtained results were compared with criteria defined in the document ?General technical requirements for road construction?. On this basis, the conclusions on the suitability of this mixture for the intended purpose are given.