Determination of Uranium-Bearing Samples in Terms of Possible Contamination, Arikli Uranium Region, Çanakkale, Turkey

Radioactive mineralization sites and related exploration activities threaten the ecosystems of surrounding areas. Nowadays, this is an issue of concern to many countries. Natural and artificial factors cause the dispersion of radioactive isotopes from the sites and increase the likelihood of contamination in the surrounding area. It is observed that the isotopes may be liberated, transported and precipitated under certain oxidation conditions and can accumulate in different regions and this process may even lead to secondary mineralization under appropriate conditions. Over time, these accumulations and transport environments may act as secondary sources and damage human and environmental health. The radioisotope distribution varies continuously among landscape components (e.g. rock, soil, groundwater and surface water). As an example, groundwater interacts with rocks, leaches radioisotopes and then influences the chemical composition of the surface water and soils. Sampling strategy is one of the most important issues in contamination research. Methods which are suitable for one environment may be quite inappropriate for another. For example, the mechanisms of formation of uranium deposits vary widely and hence the geochemical signature of the deposits also vary. Therefore, careful measurements and analyses are needed to understand the geological and physical structure of the area before cost-effective analyses. Generally, for the determination of the radioactive element distribution originating from an exploration site, the easiest and cheapest step is to carry out outdoor absorbed gamma dose rate measurements (OAGDR). The distance between the measurement points should be adjusted according to the detector range and the integration time. As a result of the gamma measurement values, the target area can be reduced. For example, if erosion is dominant in the area, drawing the borders along the hilltops, gives the advantage of understanding the flow of elements. The catchments of the exploration sites should be investigated first, but measurements should also be taken in neighbouring catchments to effect comparison of the results and assess the risk of contamination. Then, the next step is geochemical analysis of the samples. Geochemical parameters such as pH, electrical conductivity, organic matter, carbonate and clay contents, and oxidation state help to evaluate the migration patterns. Proper GIS operations and the use of maps such as lithology, topography, soil type, land cover, erosion, hydrology, flow accumulation, run-off, etc., can significantly reduce the number of samples required. Statistical analyses such as homogeneity test of univariate distributions, bivariate scatter plots, multivariate cluster analysis and principal component analysis are used to separate populations in the dataset which may indicate various geochemical processes. For the case study reported in the present work, which was conducted in the Arikli uranium region, a methodology was developed which included geochemical, radiometric and GIS based landscape analysis for the determination of uranium-bearing samples to assess the possible uranium-related contamination.