Tellurium in the environment: current knowledge and identification of gaps

Tellurium has recently become a ‘technology-critical element' increasingly used in new applications. Thus, potential environmental impacts need to be evaluated. This, in turn, requires knowledge of its typical concentrations in the environment along with better understanding of the chemical processes governing its environmental behaviour. We evaluate the current situation of our understanding of tellurium in the environment and identify the areas where improvements in measurement technology are most needed. The comprehensive evaluation of published data described in this study shows that values for tellurium concentrations in the different environmental compartments are scarce, particularly in the case of natural waters where reliable estimates of tellurium concentrations in seawater and freshwater cannot even be produced. Data in air are even less abundant than for natural water. Concentration data do exist for soils suggesting a predominant geological origin. Some urban soil surveys and lake sediment data close to tellurium contamination sources point to possible effects on the element's distribution as a result of human activity; long-range atmospheric transport remains to be proved. Current knowledge about tellurium behaviour in the environment is strongly hindered by analytical difficulties, with insufficiently low analytical detection limits being the main limitation. For instance, ‘dissolved' concentrations are well below current analytical capabilities in natural water and often require pre-concentration procedures that, for the moment, do not provide consistent results; solid samples require complex mineralisation procedures that often exclude tellurium from routine multielement studies. In general, the use of available measuring techniques is far from straightforward and needs particular expertise. Overcoming the current analytical limitations is essential to be able to progress in the field