BIOGEOCHEMICAL CHARACTERISTICS OF WETLANDS DEVELOPED AFTER STRIP-MINING FOR COAL

Since the costly practice of toxic spoil burial and topsoil replacemen t during surface mine reclamation are mandated by law, it has become f easible to consider creation of constructed wetlands for wildlife habi tat as an alternative mined land reclamation practice on active or aba ndoned mine sites. This is also a novel approach for metigation of los t natural wetland in the past. Implementation of this concept will req uire proper baseline information from the biogeochemical properties of constructed wetlands developed on surface mined sites. Baseline data were collected from two wetlands developed on strip mined sites in Ala bama. We took samples from each wetland in April and September 1992. S ince the naturalization of these wetlands with regard to the spatial v ariabilities within each wetland were the main objective of this work, a natural wetland developed on undisturbed soil was sampled at the sa me time so that it could be used as a reference to wetlands developed on disturbed soils. The natural wetland was dominated by cattail (Typh a latifolia) and smartweed (Polygonum sp.) while the dominant emergent vegetation of the stripmined site wetlands was bulrush (Scirpus sp.) and cattail. The pH of the mineral and organic substrate in the natura l wetland ranged from 7.7 to 7.8 while in the mined-site wetlands, pH ranged from 6.7 to 7.4. Dry soil adjacent to mined site wetlands had p Hs of 4.1 and 5.0, compared to 6.5 for dry soil adjacent to the natura l wetland. Higher levels of extractable clacium (Ca), magnesium (Mg), potassium (K), sodium (Na), aluminum (Al), iron (Fe), manganese (Mn), and zinc (Zn) were measured in April than September for all wetlands. Metal concentrations did not show any consistent trend among the wetla nds or within each wetland. The results of this study indicated that c onstructed wetlands developed on lands strip mined for coal will gain biogeochemical characteristics similar to those of natural wetlands re gardless of the initial chemical characteristics of the mined spoil ma terials. However, more studies with regard to the direct comparison of constructed versus natural wetlands at different locations is warrant ed.