Chromium Chemical Speciation In Pedogenic Iron Nodules From Santa Cruz, California.

Drinking water contamination of hexavalent chromium(Cr) in several U.S. major cities was recently brought to our attention by California Environmental working group. While the current remediation methods and water treatment systems can be re-visited to improve the water quality, there are numerous indigenous Cr contamination sources that continue to pose threats to human and ecological health in the U.S. In this study, we investigated the chemical speciation and spatial distribution of Cr in Fe nodules and its relation to Fe mineralogy at a marine terrace soil chronosequence northwest of Santa Cruz, California. Iron nodules (0.5 to 25 mm) are abundant in the terraces at depths < 1m, and nodules are naturally high in Cr due to weathering of ultramafic rocks particularly rich in serpentine. The results of synchrotron based X-ray microprobe/XRD and X-ray absorption spectroscopy analysis will be discussed.