Development of natural conditions in constructed wetlands: Biological and chemical changes

The main objectives of this study were to determine the biogeochemical chan ges taking place in wetlands constructed on coal mine spoil, and to determi ne the rate at which these constructed wetlands would develop the ecologica l characteristics of natural wetlands. In 1992 a multicell wetland was cons tructed. The cells were lined with two coal mine spoil types and one topsoi l. In 1993, the cells were planted with cattail (Typha latifolia), maidenca ne (Panicum hemitomon), pickerelweed (Pontederia lanceolota), and soft stem bulrush (Scirpus validus). Pickerelweed spread most rapidly followed by ma idencane and bulrush. Cattail did not establish uniformly but spread in an irregular manner. There was no difference in plant establishment between th e topsoil or the two mine spoils. The pH of the most acidic spoil increased by more than one unit after flooding. Organic matter content fluctuated in all three substrates from year to year. The concentration of the nutrient and metal elements increased after flooding. Extractable Al, Fe, and Mn inc reased more than other elements. The data presented here indicate that, exc ept for organic matter accumulation, these constructed wetlands have taken on the botanical and biogeochemical characteristics of natural wetlands wit hin 3-4 years. (C) 1999 Elsevier Science B.V. All rights reserved.