11/22/2023 0 Comments Cobalt 60 warning![]() Reasons for many environmental problems can be attributed to fine to fine sediment which acts as a vector for the transfer and off-site conveyance of nutrients, which, when in concentrated form, can readily act as a pollutant. Against an expanding world population reliant on finite land on which to produce food and offer continuing food security, it is now acknowledged that the accelerated loss of a non-renewable resource such as soil is unsustainable which not only leads to land degradation and reduced food production per se, but also can lead to many environmental problems seemingly unconnected to agriculture and food production. More recently, Imeson reported that global agricultural cropland productivity is diminishing by an average of 5% each year, principally by water-driven soil erosion but undoubtedly exacerbated by modern agricultural practises, whereas others such as Cherlet and Ivits concluded that approximately 24 billion tonnes of fertile soil is lost to erosion and degradation each year, which, they speculate, could lead to a 12% reduction in global food production in the next 25 years. debated that two billion hectares (ha), representing 22.5% of all productive land on Earth, was more degraded than it was in the mid-1940s. In the mid-1980s, for instance, Brown concluded that global soil depletion annually exceeded the amount that could be replenished under natural conditions by around 23 billion tonnes each year. Although inherently difficult to quantitatively express the degree to which land is, or has been, degraded at the global scale, varying authors have offered numerous statistics in an attempt to judge the severity of the problem. The recognition that soil and sediment both represent a vital resource has led to concerns that accelerated soil erosion, along with the concomitant degradation of agricultural land, poses significant threats to sustainable food production to long-term global food security and to the quality of the environment per se. The mobilisation, transportation and deposition of fine sediment (defined here as particles and aggregates <2 mm dia.) by rainfall and surface run-off are natural processes but are often accelerated by certain human activities that include inter alia, deforestation, modern agricultural practises and/or adopting inappropriate land uses. The chapter finally concludes by evaluating the versatility and efficacy of Co-60 as a fine-sediment tracer. ![]() It then outlines some of the notable drawbacks associated with using Co-60, before highlighting refinements and prospects for future work. The chapter then outlines and reviews three ways in which Co-60 has been experimentally applied in varying erosion and sedimentation scenarios where most of the more commonly used tracers would be unsuitable or would lack the level of sensitivity needed to return meaningful data. Some historical background information on previous uses of Co-60 are then provided, and the suite of key environmental characteristics that, from the perspective of studies in hydrology and geomorphology, make Co-60 a potentially attractive candidate for fine-sediment tracing. It then briefly reviews some of the most commonly used tracers in sedimentation studies, before focusing on artificial, gamma-emitting radionuclides, and in particular, on Cobalt-60 (Co-60). Cobalt-60 external beam therapy has recently been incorporated in on-line MR guided radiation therapy programs where it’s ability to generate an MV beam without significantly perturbing the MRI’s magnetic field is a great advantage.The chapter firstly outlines the global crisis concerning accelerated soil erosion, the implications that this could have on longer-term food security and ways that soil loss has been quantified originally through catchment-scale monitoring but with a recent shift toward the use of sediment tracers. Greater specific activity allows for smaller source size and higher energy allows for a more penetrating and more skin sparing field. Compared to other radionuclides used for this purpose (Radium-226 and Cesium-137), 60Co has a greater specific activity and a higher energy. Use in External Beam TherapyĬobalt-60 is the radionuclide of choice for nuclide based external beam radiation therapy. The dose distribution is more dominated by inverse square law than Ir-192 leading to a slightly shallower dose fall off. Compared with Ir-192, Cobalt-60 is more expensive and requires a larger source size for the same dose rate but has the advantage of a longer half life. Use in BrachytherapyĬobalt-60 is was used in brachytherapy in the past but is rarely used today. Co-60 vs Ir-192 radial dose distribution.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |