Assessment of Soil Degradation in a Palustrine Wetland and the Implication on its Water Purification Potential

Abstract

This study determined the extent of degradation of soils in Khubelu wetland in Lesotho and the impact this may have on its water purification potential. Seventy-two soil samples were collected at different sites and depths around the wetland and characterised for different properties. The values of these properties were then used to determine the chemical degradation index (CDI) of the wetland soils. The soils were non-saline as reflected by the electrical conductivity (EC) values (<0.25 mS/cm), mostly acidic (4.5 < pH < 5.22) with moderate organic matter content (2.06–3.9 %). These soil properties varied with depth and from upstream to downstream of the wetland. Values for soil CDI were 3.42, 3.25 and 3.06 for soils from upstream, midstream and downstream of the wetland, respectively, indicating a decrease in soil degradation from upstream to downstream. The dominance of emergent vegetation in the Khubelu wetland may indicate a potential to get rid of sediments in influents into the wetland but the soil characteristics may present a challenge with regards to the removal of nutrients and organic and inorganic pollutants from these influents. The characteristics of the soils and the extent of soil degradation present some challenges in the performance of the Khubelu wetland as a water purification system especially with regards to nutrients and organic and inorganic pollutants.