The potential use of storm water and effluent from a constructed wetland for re-vegetating a degraded pyrite trail in Queen Elizabeth National Park, Uganda
|Authors||Osaliya, R.; Kansiime, F.; Oryem-Origa, H.; Kateyo, E.|
|Year of Publication||2011|
|Type of Publication||Journal Article|
|Journal||Physics and Chemistry of the Earth, Parts A/B/C|
During the operation of the Kilembe Mines (copper mining) a cobaltiferous stockpile was constructed, which began to erode after the closure of the mines in the early 1970s. The erosion of the pyrite stockpile resulted in a large acid trail all the way to Lake George (a Ramsar site). The acid trail contaminated a large area of Queen Elizabeth National Park (QENP) resulting in the death of most of the shallow-rooted vegetation. Processes and conditions created by storm water and effluent from a constructed wetland were assessed for vegetation regeneration in the degraded QENP pyrite trail. Cynodon dactylon, Imperata cylindrica and Hyparrhenia filipendula dominated the regeneration zone (RZ) where storm water and effluent from a constructed wetland was flowing; and the adjacent unpolluted area (UP) with importance value indices of 186.4 and 83.3 respectively. Typha latifolia and C. dactylon formed two distinct vegetation sub-zones within the RZ with the former inhabiting areas with a higher water table. Soil pH was significantly higher in the RZ, followed by UP and bare pyrite trail (BPT) at both 015 cm and 1630 cm depths. Soil electrical conductivity was not significantly different in the RZ and BPT but significantly higher than that in UP for both depths. For 015 cm depth, RZ had significantly higher concentrations of copper than BPT and UP which had similar concentrations. Still at this depth (015 cm), the unpolluted area had significantly higher concentrations of total phosphorus and total nitrogen than the regeneration zone and the bare pyrite trail which had similar concentrations. The RZ dominated by Typha had significantly higher concentrations of TP and TN compared to the RZ dominated by Cynodon. The concentrations of NH4N were significantly lower in Typha regeneration zone than in CRZ at 015 cm depth but similar at 1630 cm depth. At 1630 cm depth, concentrations of copper were significantly higher in the regeneration zone followed by the bare pyrite trail and the unpolluted zone. The concentration of lead in the regeneration zone and bare pyrite trail were similar but significantly higher in the unpolluted zone. Concentrations of TP and TN were significantly higher in unpolluted zone, followed by regeneration zone and bare pyrite trail. Storm water and effluent from a constructed wetland enhanced the revegetation process by modifying soil pH, making plant growth nutrients available and by providing a steady supply of moisture necessary for plant growth. T. latifolia and C. dactylon which seem to have tolerance of high concentrations of metals were the dominant species in the regeneration zone. If storm water and effluent supply continues, the aforementioned vegetation will colonize the pyrite trail and will eventually protect QENP and Lake George from metal contamination.