Chromium Geochemistry in a Wetland Environment

Cooling tower water ranging between 7 to 18 mg/L of Cr(VI) was released to a stream channel entering a wetland at Los Alamos National Laboratory, New Mexico, USA from 1956 to 1972. The wetland contains between 5700 and 27,000 kg total Cr mainly as Cr(III), with a median mass of 11,000 kg total Cr, representing 21 to 49% of the total Cr. Chemical analyses conducted on wetland sediments show that 97.3 to 99.9% of the Cr is stable as Cr(III). Mass balance calculations confirm that there are sufficient concentrations of Fe(II) along with the organic-rich sediments to maintain Cr(III) stability within the wetland.