Abstract: In anaerobic soils of wetlands, Mn is highly available to plants because of the decreasing redox potential and pH of flooded soil. When growing adjacent to each another in wetland forests, water tupelo (Nyssa aquatica L.) had 10 times greater leaf manganese concentration than bald cypress (Taxodium distichum [L.] Richard). This interspecific difference was examined over a range of manganese-enriched soil conditions in a greenhouse experiment. Water tupelo and bald cypress seedlings were grown in fertilized potting soil enriched with 0, 40, 80, 160, 240, 320, and 400 mg Mn/L of soil and kept at saturated to slightly flooded conditions. Leaf Mn concentration was greater in water tupelo than bald cypress for all but the highest Mn addition treatment. Growth of water tupelo seedlings was adversely affected in treatments greater than 160 mg Mn/L. Total biomass of water tupelo in the highest Mn treatment was less than 50% of the control. At low levels of added Mn, bald cypress was able to restrict uptake of Mn at the roots with resulting low leaf Mn concentrations. Once that root restriction was exceeded, Mn concentration in bald cypress leaves increased greatly with treatment; that is, the highest treatment was 40 times greater than control (4,603 vs 100 < mu >g/g, respectively), but biomass of bald cypress was unaffected by manganese additions. Bald cypress, a tree that does not naturally accumulate manganese, does so under manganese-enriched conditions and without biomass reduction in contrast to water tupelo, which is severely affected by higher soil Mn concentrations. Thus, bald cypress would be less affected by increased manganese availability in swamps receiving acidic inputs such as acid mine drainage, acid rain, or oxidization of pyritic soils.

Abstract: This paper summarises the performance of minewater-treatment schemes which are operated under the Coal Authority's National Minewater Treatment Programme. Commonly-used design criteria and performance indicators are briefly discussed, and the performance of wetland systems which are operated by the Coal Authority is reviewed. Most schemes for which data are available remove more than 90% iron, and average area-adjusted iron-removal rates range from 1.5 to 5.5 g Fe/m(2). d. These values, which are based on performance calculations, can be distorted by several factors, including the practice of maximising wetland areas to make best use of available land. Removal rates are limited by influent iron loadings, and area-adjusted iron-removal rates should be used with caution when assessing wetland performance. Sizing criteria for all types of treatment system might be refined if more detailed data become available.