Date of Award
Master of Science
Wetlands and streams provide many ecosystem services, yet many of these services have been lost during the process of surface mining. It is often not practical to avoid wetlands and streams, and newer technologies such as large draglines have made it possible to mine through large perennial streams and their associated riparian wetland systems. Laws such as the Surface Mining Control and Reclamation Act and Clean Water Act require the restoration of these systems in approximately the same location and configuration as before mining, but do not address the long-term replacement of function. In Perry County, Illinois, three stream segments of Bonnie Creek, Galum Creek, and Pipestone Creek and their associated riparian wetland systems were among the largest ever restored following surface mining. The research objective was to determine whether or not function was restored in the three aforementioned streams and riparian wetlands following surface mining reclamation. Wetland soil properties, vegetation, and hydrology at study sites along Bonnie and Galum Creeks were compared to that of nearby natural wetlands and across a chronosequence of soil age. Water quality was assessed [alkalinity, chloride (Cl), fluoride (Fl), iron (Fe), manganese (Mn), zinc (Zn), nitrate (NO3), sulfate (SO4), total dissolved solids (TDS), and total suspended solids (TSS)] in the three restored streams for post restoration trends over time and along the length of the restored channels. Deep basins, called incline pits, were located inline of all three restored channels and are unique to streams restored on surface mines. Stream samples were collected above and below incline pits during storm events to evaluate their ability to reduce sediment concentrations. Two types of wetlands were found at the mine site: mined planned wetlands (MPWs) that had deeper water and fewer or no trees, and mined bottomland forested wetlands (MBFWs) with more shallow water depths and many trees. Significant differences were found between the two wetland types among soil properties, vegetation, and hydrology. Unlike most studies comparing wetlands restored on non-mined sites to natural wetlands, SOM, C, N, and C/N ratio in the surface 15 cm in the MBFWs were not significantly different from the natural wetlands, indicating restoration of function. Plant taxa richness was higher in both mined wetland types than in the natural wetlands at lower elevation sample points where inundation was seasonal. Overall, the mined wetlands also retained water within 30 cm of the surface for more time than the natural wetlands. However, not all function was fully regained in the mined wetlands. Several soil properties were significantly different in the mined wetlands compared to the natural wetlands. SOM, N and the C/N ratio was significantly lower in the 15-30 cm depth, and in the surface 15 cm of the lower elevation samples of the MPW. Soil texture was significantly different in the MPW. There was more sand and less silt. Plan taxa richness was also lower in the higher elevation sample points of the MPW due to the presence of the invasive Phragmites australis. Few trends were found in the soil properties across a chronosequence of soil age. Only pH showed a significant negative linear trend in both mined wetland types across soil age. Assessment of the water chemistry of the restored streams showed that for some parameters, water quality remained stable or improved with distance or time along the restored streams. However, along Bonnie and Galum Creek, a significant positive trend was seen by length of relocated channel in SO4, Fe, Mn, Zn, TDS, conductivity, and Cl. On the other hand, at Pipestone Creek, significant negative trends were evident in TDS, Mn, water temperature, conductivity, and SO4 levels over time or along the length of the relocated channel. Trends along the length of the Pipestone Creek were only found in monitoring conducted twenty years after the channel relocation was complete. Sediment concentration above and below the incline pits inline of Bonnie and Galum Creek were not significantly different based on the sampling of two storm events. An additional input from an agricultural drainage ditch to the Bonnie Pit increased sediment concentrations at the downstream sample point counteracting the reductions that were seen in the Galum pit. Research on the mined stream and riparian systems indicated that reclamation of wetlands and streams to a stable or condition similar to a natural system is possible and sets a standard for future mining operations to follow. However, several shortcomings were identified. Reduced levels of SOM and soil N in the MPWs in the surface 15 cm of the lower sample points may have been the result of longer periods of inundation that reduced nitrification and vegetation recruitment. SOM, soil N, and the C/N ratio in the 15-30 cm depth were lower in the mined wetlands suggesting that these properties take longer to recover at deeper depths, but the significant linear trend in pH show that soil in the deeper strata is changing with time. Invasion by P. Australis reduced taxa richness suggesting that invasive plants are still a problem even more than twenty years after restoration. In addition, the increase in conductivity and SO4 downstream of a visible seep in Bonnie Creek highlight the potential for contaminated groundwater to affect surface water. More consideration should be given to reclaiming not just the surface and subsoils, but also the deeper water bearing strata to ensure that surface water chemistry is not impacted by mining.
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