Geomicrobial interactions with other transition metals (chromium, molybdenum, vanadium, technetium), metalloids (polonium), actinides (uranium, neptunium, and plutonium), and the rare earth elements

Chromium is not a very plentiful element in the Earth’s crust, but it is nevertheless fairly widespread. Its average crustal abundance of 122 ppm (Fortescue, 1980) is less than that of manganese. The average concentration in rocks ranges from 4 to 90 mg kg−1, in soil around 70 mg kg−1, in freshwater around 1 µg kg−1, and in seawater around 0.3 µg kg−1 (Bowen, 1979). Higher concentrations in the environment are associated with anthropogenic activities such as mining, metallurgy, and leather tanning (Kamaludeen et al., 2003).