## 3 Results and Discussion
### Bottom Sediment Characterization  
The in situ pH and ORP measurements in the bottom sediment exhibited a consistent pattern across the sampling sites. The pH values were 6.09 at S1, 6.59 at S2, and 6.52 at S3. The corresponding ORP values were \(-\)219.67 mV at S1, \(-\)206.07 mV at S2, and \(-\)217.30 mV at S3. The analysis also highlighted the significant presence of organic matter (OM) in the bottom sediment, with notably high concentrations at S2 (25.74%) and S3 (23.43%). Organic matter refers to the sediment component derived from the decay of plant material, microorganisms, and other biological residues. OM is crucial in wetland environments as it influences various biogeochemical processes, including nutrient cycling, metal binding,and pollutant degradation. High levels of OM indicate a rich organic environment, which supports microbial activity and contributes to the wetland's ability to remediate AMD by enhancing microbial processes that can neutralize pollutants and improve water quality. The elemental composition of the bottom sediment samples from each site was determined using XRF analysis and was found to be relatively consistent across the wetland. The weight percentages (\(\%\)\(w\)/\(w\)) of key elements such as Al, Fe, Mn, and S in their oxidized forms are detailed in Table 3. A uniform pattern was observed at all three sites, following the sequence: Al\({}_{2}\)O\({}_{3}\) > Fe\({}_{2}\)O\({}_{3}\) > SO\({}_{3}\) > MnO. This stability in terms of the elemental composition highlights the uniform distribution of these elements within the wetland's sediment, which is essential for understanding the sediment's role in the overall ecosystem function and its capacity to treat AMD. Student's \(t\)-test was used to compare the means of the bottom sediment characteristics between S1 and S3 of the wetland, as detailed in Table 3. Given the substantial distance between S1 and S3, ample time and space are provided for biogeochemical reactions to occur, potentially leading to significant changes in the sediment composition. However, the analysis showed no statistically significant differences (\(p\) > 0.05) between S1 and S3 in terms of the pH, ORP, organic matter percentage (OM%), and elemental composition. In contrast, the sediment texture analysis revealed a significant difference (\(p\) < 0.05) between these sites. As particles enter the wetland, they undergo aggregation, flocculation, and sedimentation, settling into the bottom soil [3]. This sedimentation process ensures continuous interaction between the surface water particles and the wetland bottom sediment [6]. Ultimately, water and soil particles combine and settle to form the bottom sediment layer [7]. Characterizing the bottom sediment is crucial for understanding the functioning of natural wetlands and the dynamics of pollutants, which is fundamental for effective wetland management and restoration [63; 64]. In previous studies on constructed wetlands designed to treat mine and industrial effluent, the sediment pH and ORP measurements ranged from 6.4 to 7.1 and 384 to \(-\)261 mV, respectively. These findings are consistent with the current study's results [65; 66]. Wetland bottom sediment is often characterized by high organic matter content, as observed at S2 and S3 in this study [3]. This high organic matter content is due to the balance between carbon fixation and loss, which occurs at different rates under anaerobic conditions in satu