Uranium anthropogenic sources

Many coastal ecosystems have elevated levels of metals and radionuclides (14). Anthropogenic sources of stable isotopes of metals include sewage disposal plants, electroplating plants, and mining and dredging operations sources of radioactive isotopes include effluents from nuclear power plants and submarines, medical establishments, and uranium ore mining. The pollution from most of these operations results from routine or accidental discharges and are either continuous or episodic. 

Radiation Energy conversion is the largest anthropogenic source of radiation through the disposal of wastes from nuclear stations and the mining of uranium (see Table 3). 

Tracers serve as a dye with which to follow the circulation of ocean waters. There are conventional ocean tracers such as temperature, salinity, oxygen, and nutrients. There are stable isotope tracers such as oxygen-18, carbon-13, and there are radioactive tracers both naturally occurring (such as the uranium/thorium series, and radium), and those produced both naturally and by the bomb tests (such as tritium and carbon-14). The bomb contributions from the latter two are called transient tracers, as are the CFCs, because they have been in the atmosphere for a short time. This implies an anthropogenic source and a nonsteady input function. 

FIGURE 3.1 A schematic presentation of the transport of uranium from the natural and anthropogenic sources, through the environment leading to human exposure. (From Winde, F., Uranium pollution of water A global perspective on the situation in South Africa, Inaugural Lecture Presented at the North-West University, Vaal Triangle Campus, South Africa, February 22, 2013. With permission.)... 

Uranium occurs naturally in variable concentrations in all soils, minerals, rocks and waters. It can also be derived from several anthropogenic sources. Uranium is weakly radioactive and human exposure to the element has long been considered to pose a radiological as well as toxic hazard (WHO, 2004 2008 Smedley et al., 2006). This dissolved toxic radioactive metal may poison drinking water sources and the food chain via contaminated surfaces and groundwater. In recent years, there has been increasing concern that the chemical effects of uranium may also pose a potential hazard to exposed populations. However, there are few if any epidemiological studies that have been able to demonstrate any resultant harm, even in occupational contexts (The Royal Society, 2001). 

The anthropogenic sources of radioactivity in the environment include the testing of nuclear weapons and radioactive material handling, especially in nuclear power plants. In the explosion of atomic bombs or in nuclear reactors, a complex mixture of different radionucHdes is produced, namely uranium plutonium Pu, caesium Cs (half-Hfe of 30 years), strontium Sr (half-life of 28 years), cobalt Co (half-Hfe of 5.3 years), caesium Cs (half-Hfe of 2 years), ruthenium Ru (half-Hfe of 1 year) and iodine 1 (half-Hfe of 8 days). A number of other radionucHdes result from an atomic explosion by coUision of neutrons with the atoms of elements that are contained in the casing of the non-explosive parts of the atomic bomb. For example, these activation products include zinc Zn (half-Hfe of 245 days). 

There are essentially three sources of radioactive elements. Primordial nuclides are radioactive elements whose half-lives are comparable to the age of our solar system and were present at the formation of Earth. These nuclides are generally referred to as naturally occurring radioactivity and are derived from the radioactive decay of thorium and uranium. Cosmogenic nuclides are atoms that are constantly being synthesized from the bombardment of planetary surfaces by cosmic particles (primarily protons ejected from the Sun), and are also considered natural in their origin. The third source of radioactive nuclides is termed anthropogenic and results from human activity in the production of nuclear power, nuclear weapons, or through the use of particle accelerators. 

The main interest in the analysis of uranium in environmental samples is its effect as radioactive toxic heavy metal on the flora and fauna and assessment of the potential risk to human life directly or through the food chain. Natural uranium is present in practically all types of environmental samples—plants, soil, water bodies, and even air. In addition, anthropogenic activities related mainly to releases and discharges from the uranium fuel cycle may contaminate nearby areas, and that pollution may spread by wind and water action to considerable distances from the source. In order to assess the uranium content in the environment, representative samples need to be gathered (see Frame 3.2)—a task that is much more complicated than generally expected due to the variability of the sampled media. 

In order to distinguish between exposure to uranium from natural sources and anthropogenic origins, the isotopic composition of uranium must be determined. Such a method using sector field ICPMS for measurement of and... 

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