BackgroundDue to fast urban expansion and increased industrial activities, large quantities of solid and liquid wastes contaminated by trace metals are released into the environment of the Addis Ababa city, most often untreated. This study was conducted to investigate spatial distribution, seasonal variations and ecological risk assessment of selected trace metals (Cd, Cr, Cu, Fe, Mn, Pb, Ni and Zn) in the surface sediments from Akaki River catchment and Aba Samuel reservoir, Central Ethiopia.MethodsTwenty-two surface sediment samples were collected, digested using the Mehlich-3 procedure and analyzed quantitatively using inductively coupled plasma optical emission spectrometer.ResultsThe trace metals occurred in varying concentrations along the course of the sampling stations. The decreasing order of trace metal concentrations in the dry season was: Mn > Fe > Pb > Cr > Zn > Ni > Cu > Cd and in the rainy season was Mn > Fe > Pb > Cr > Ni > Zn > Cu > Cd. Little Akaki River contained a higher load of trace metals than the other regions, which is due to the existence of most of the industrial establishments and commercial activities. Relatively lower levels of trace metals were recorded at Aba Samuel reservoir due to the lower residence time of the sediment (reservoir rehabilitated recently). Ecological risk assessment using USEPA sediment guidelines, geo-accumulation index, contamination factor and pollution load index revealed the widespread pollution by Cd and Pb. These were followed by Mn, Ni and Zn.ConclusionThe concentrations of Pb, Cd, Mn, Ni and Zn in sediments were relatively greater and at levels that may have adverse biological effects to the surrounding biota. Therefore, regular monitoring of these pollutants in water, sediment and biota would be required.

中文翻译：

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埃塞俄比亚中部 Akaki 河集水区和 Aba Samuel 水库表层沉积物中痕量金属的分布和生态风险评估

背景由于城市的快速扩张和工业活动的增加，被微量金属污染的大量固体和液体废物被释放到亚的斯亚贝巴市的环境中，而且通常未经处理。本研究旨在调查中部 Akaki 河集水区和 Aba Samuel 水库表层沉积物中选定痕量金属（Cd、Cr、Cu、Fe、Mn、Pb、Ni 和 Zn）的空间分布、季节变化和生态风险评估。埃塞俄比亚。方法收集了 22 份表层沉积物样品，使用 Mehlich-3 程序进行消解，并使用电感耦合等离子体发射光谱仪进行定量分析。结果在采样站的过程中，痕量金属以不同的浓度出现。干季微量金属浓度递减顺序为：Mn>Fe>Pb>Cr>Zn>Ni>Cu>Cd，雨季为Mn>Fe>Pb>Cr>Ni>Zn>Cu>Cd。小赤木川的微量金属含量高于其他地区，这是由于大多数工业设施和商业活动的存在。由于沉积物的停留时间较短（最近修复的水库），在 Aba Samuel 水库记录到的痕量金属含量相对较低。使用美国环保署沉积物指南、地质累积指数、污染因子和污染负荷指数进行的生态风险评估揭示了广泛的 Cd 和 Pb 污染。其次是 Mn、Ni 和 Zn。结论 Pb、Cd、Mn、沉积物中的 Ni 和 Zn 含量相对较高，并且可能对周围生物群产生不利的生物影响。因此，需要定期监测水、沉积物和生物群中的这些污染物。