Concentration and Speciation of Copper and Chromium Adjacent to Chromated Copper Arsenate (CCA) Treated Lumber Fence Posts.

Chromium (Cr) and Copper (Cu) are ubiquitous in soils as a result of anthropogenic and geogenic processes.  The fate of Cr and Cu in the environment is largely governed by their speciation, which is influenced by soil physiochemical properties.  This study investigated the influence of soil physiochemical properties and landscape position on Cr and Cu concentration and speciation in soils adjacent to Chromated Copper Arsenate (CCA) treated lumber fence posts. Concentration gradients showed elevated total Cu adjacent to the three fence posts, which decreased with increasing distance from the posts. In addition, higher concentrations of Cu were found in surface soil samples than the subsoil samples, possibly due to enhanced weathering of the CCA treated posts at the surface. Concentrations of Cu were similar among the Maury and Donerail silt loam, however, they were closer to the background concentration in the Newark silt loam, a partially hydric soil, indicating mobility of the metals. No elevation in Cr concentration was apparent in soil adjacent to CCA posts, indicating limited mobility of Cr from CCA posts. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy indicates Cu(II) complexes with soil organic matter in surface soils with a greater degree of Cu-mineral complexation in subsoil horizons. Overall, the use of CCA treated lumber as a metal source can help determine how soil properties influence mobility and speciation of Cr and Cu across the soil landscape.