INFLUENCE OF ACID-RAIN AND OZONE ON SOIL HEAVY-METALS UNDER LOBLOLLY-PINE TREES - A FIELD-STUDY

A field growth chamber study was conducted to determine the effects of ozone and simulated acid rain (SAR) on soil heavy metals. Loblolly pi ne (Pinus taeda L.), grown in open-top chambers, was exposed to three concentrations of ozone (charcoal filtered air with 0.026 mu L O-3 L(- 1), and two non-filtered treatments in which ozone concentrations were 0.074 mu L L(-1) and 0.147 mu L L(-1), respectively) and two levels o f SAR (pH 3.5 and 5.2). Ozone was applied for 12 h d(-1) for 9 months and acid rain deposition was 125 mm event(-1). After 9 months exposure , soil pH, organic matter and DTPA-extractabIe heavy metals (Cd, Pb, Z n, Mn, Fe, Cu) were determined on soil samples collected from exposed chambers at two depths (0-15 cm and 15-30 cm). Simulated acid rain dec reased the original soil pH. The concentrations of Cd, Pb and Mn at SA R pH 3.5 were significantly higher than at SAR pH 5.2. Ozone did not a ffect Zn, Fe and Cu, but a significant interaction between pH and O-3 On Mn, Pb and Cd was observed. Due to the poor drainage capacity of th is soil, leaching of heavy metals was not observed.