Tellurium in the environment: A critical review focused on natural waters, soils, sediments and airborne particles

Tellurium is usually present at very low concentrations in environmental samples, which makes it a challenging element to measure in complex matrices. It exists mainly as Te(IV) and Te(VI) in natural waters and geological samples and its geochemistry is often compared to that of selenium, its upper neighbor in the periodic table of the elements. More than 145 papers that are related to tellurium in freshwaters, marine and estuarine systems, soils and sediments and air particulate maters, as well as various analytical techniques associated to this element, have been reviewed. Concentrations of total dissolved tellurium in open oceans are usually less than 2 ng/L (∼16 pM) and can increase by approximately one order of magnitude in non polluted freshwaters. Most tellurium compounds are considered toxic. Except from samples collected close to sources of contamination, tellurium concentrations in soils and sediments are normally at the low ppb (μg/g) level. In tellurium speciation studies, pre-concentration steps are often required in the analytical protocols. In fact very few studies have reported tellurium speciation in solid samples. Total tellurium reported in studies on aerosols and air particulates is usually below the ng/m3.