Metal Deposition in Baldcypress Tree Rings: Nickel, Copper, Chromium, Manganese and Iron Margaret S. Devall 1, Leonard B. Thien 2, and George C. Flowers 2 1 USDA Forest Service, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneville, MS 2 Tulane University, New Orleans, LA

Methods Cypress trees cored along bayou and reference area and chronology developed 5-year increments ground and pressed into pellets X-ray fluorescent spectrometer used to analyze samples Concentrations presented in spatial and temporal dimensions

Results First, levels of metals presented with respect to proximity to point source Second, history of pollution documented

Mean level of Ni is 6.6 at Stations 0-60 and 4.5 at Stations

Mean level of Cu is 2.4 at Stations 0-60 and 2.8 at Stations

Mean level of Cr is 6.6 at Stations 0-60 and 7.4 at Stations

Mean level of Mn is 20.2 at Stations 0-60 and 29.1 at Stations

Mean level of Fe is 674 at Stations 0-60 and 652 at Stations

Conclusions Metal mobility and availability are different in wetland soils. Sulfate in the brackish water is reduced to sulfide and reacts with metals to form precipitates. The sediments are highly polluted but precipitates are stable as long as reducing conditions are maintained. Fe and Mn are more soluble and available to plants in the reduced state. This may account for their higher concentration in the tree rings.

Conclusions Waterlogged soil, circumneutral to basic pH, and acid volatile sulfides from brackish lake water are the cause of relatively low levels of metals in tree rings in spite of heavily polluted soil. Recently the levels of all metals in Stinking Bayou and levels of Cr, Mg and Fe in Bayou Trepagnier, likely due to urbanization.