Investigation of Chromium Sources in the Groundwater of Thiva, Greece

Chromium (Cr) is a heavy metal that naturally occurs in the Earth’s crust, and can be found in groundwater in either the trivalent, Cr(III), or in the hexavalent, Cr(VI), form. While Cr(III) is considered an essential trace element for the human body, Cr(VI) is potentially dangerous for human health although the type and intensity of the effect are still being investigated. The widespread use of chromium in industrial applications along with careless waste disposal practices has in many cases resulted in serious soil and groundwater contamination. Until recently, this was considered the only Cr(VI) source in groundwater, although new research has shown that relatively high levels of Cr(VI) can also be attributed to natural processes. This mainly occurs in areas where the levels of naturally occurring Cr(III) are high and natural oxidation processes convert Cr(III) to Cr(VI). Such phenomena take place in several areas worldwide, including Greece. Naturally occurring high contents of Cr(III) in ultramafic rocks and serpentinites of ophiolite complexes may by oxidized and converted to Cr(VI) by natural oxidants under favorable environmental conditions. The area of the current study is Thiva, located in central Greece, where industries and agriculture co-exist. In addition, the existence of ophiolite complexes in the geological background of the area constitute potential natural chromium sources. This is the second part of an ongoing research study which intends to investigate the potential origin of chromium in the groundwater of this area. The study further investigate the presence of chromium in the topsoil of two locations in the Thiva region where elevated Cr(VI) concentrations have been previously measured.