Uranium in Environmental Samples

Uranium is a radioactive element that occurs naturally in low concentrations (a few parts per million) in soil, rock, and surface and groundwater. 

Needless to say that uranium originating from the nuclear fuel cycle operations is frequently not of natural isotopic composition. However, there are also variations in the isotopic composition of naturally occurring uranium compounds, as mentioned in Chapter 1, with minute differences in the ratio (Hiess et al. 2012), 

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.) 

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Analytical Methods for Determining Uranium in Biological Samples 6-2 Analytical Methods for Determining Uranium in Environmental Samples... 

Additional Analytical Methods for Determining Uranium in Environmental Samples... 

The purpose of this chapter is to describe the analytical methods that are available for detecting and/or measuring and monitoring uranium in environmental media and in biological samples. The intent is not to provide an exhaustive list of analytical methods that could be used to detect and quantify uranium. Rather, the intention is to identify well-established methods that are used as the standard methods of analysis. Many of the analytical methods used to detect uranium in environmental samples are the methods approved by federal agencies such as EPA, DOE, and the National Institute for Occupational Safety and Health (NIOSH). Other methods presented in this chapter are those that are approved by a trade association such as the Association of Official Analytical Chemists (AOAC) and the American Public Health Association (APHA). Additionally, analytical methods are included that refine previously used methods to lower detection limits, and/or to improve accuracy and precision. 

Two types of methods are commonly used for measurement of uranium in environmental samples. The first are field surveys using portable survey instruments, and the second is analysis of samples procured in the field that are returned to the laboratory for quantification. 

Abbasi SA. 1989. Atomic absorption spectrometric and spectrophotometric trace analysis of uranium in environmental samples with N-p-methoxyphenyl-2-furylacrylohydroxamic acid and 4-(2-pyridylazo) resorcinol. Intern J Environ Anal Chem 36 163-172. 

Boomer DW, Powell MJ. 1987. Determination of uranium in environmental samples using inductively coupled plasma mass spectrometry. Anal Chem 59 2810-2813. 

Boulyga, S. F., Becker, J. S., Matusevitch, J. L., and Dietze, H. J. 2000. Isotope ratio measurements of spent reactor uranium in environmental samples by using inductively coupled plasma mass spectrometry. Int J Mass Spectrom 203(1-3), 143-154. 

Karangelos DJ, Anagnostakis MJ, Hinis EP, Simopoulos SE, Zunic ZS (2004) Determination of depleted uranium in environmental samples by gamma-spectroscopic techniques. J Environ Radioact 76 295-310... 

First, we would like to mention a number of general reviews and overviews that are not method speciflc but provide excellent background material for a better understanding of the analytical determination of uranium in environmental samples. 

The analytical methods used for the determination of uranium in environmental samples are basically the standard methods reviewed in brief in Chapter 1. The main differences are in the sample preparation procedures required for the analysis of the variety of environmental samples that include soil of different types, sediments, diverse types of vegetation, water from different sources with a wide range of acidity, salinity, suspended matter, etc. In addition, the environmental samples may include airborne particulate matter, vapors, and gases, as well as special samples involved in the food chain that may affect humans. Einally, the interplay of uranium (and other contaminants) between the environmental compartments—for example, the transfer factors of uranium from soil-to-plant or from vegetation to food products (e.g., free-range grazing cattle) are also part of the media that need to be characterized. 

As seen in the specific examples given later, numerous analytical methods are used for the determination of uranium in environmental samples. The most popular among them are ICPMS and alpha spectrometry, but neutron activation analysis, gamma spectrometry, and XRF are often deployed and even simple spectrophoto-metric (like colorimetric aresnazo-III) techniques are sometimes still used. For the precise determination of total uranium and its isotopic composition, isotope dilution (ID) methods can be used. One example is a comparison of ID-TIMS and ID-SIMS for isotope ratios in soil standards where two separation and preconcentration chromatographic techniques were also compared (Adriaens et al. 1992). 

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. 

Examples of procedures used to characterize uranium in environmental samples of soil, sediments, vegetation, water, and air... 

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