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Assessment of nutrient enrichment and heavy metal pollution of headwater streams of Bulawayo, Zimbabwe
Physics and Chemistry of the Earth, Parts A/B/C ( IF 3.7 ) Pub Date : 2020-08-05 , DOI: 10.1016/j.pce.2020.102912
N. Siziba , T. Mwedzi , N. Muisa

The continuing degradation of riverine ecosystems by the discharge of poorly treated and untreated urban-wastewater (together referred to as partly treated urban-wastewater in this study) is a major problem in developing countries. This study assessed water and sediment quality of headwater streams radiating from the Bulawayo area including Umguza and Khami Rivers that drain wastewater from the City. Seventeen study sites were a priori selected from different land use types: City sites (5 sites), downstream communal sites (4), upstream communal sites (3) and for reference five sites were selected upstream of the City within the buffer zones of protected areas. Water and sediment samples were collected during the hot-wet, cold-dry and hot-dry seasons from these site categories and were analysed for selected physicochemical water parameters and heavy metals. The City sites were the most degraded as indicated by significantly highest levels of dissolved oxygen deficiency, embeddedness by particulates, turbidity, conductivity, total dissolved solids (TDS), salinity, total nitrogen (TN) and total phosphorus (TP) and chemical oxygen demand (COD) (ANOVA, p < 0.05). The City sites were also salinised. Principal component analysis (PCA) revealed that urban-wastewater was the major factor explaining the dissimilarity of the studied site clusters and the results also suggested that the sources of heavy metals in the study area were diffuse. Degradation of studied sites by urban-wastewater signifies negative health risks to biodiversity and humans particularly the downstream rural communities. Therefore, priority must be on interventions to ensure improvement of the quality of urban-wastewater discharged from City of Bulawayo to the environment.

更新日期:2020-08-05
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