article · ENVIRONMENTAL SYSTEMS RESEARCH
Rapid urban expansion and industrial growth in Addis Ababa generate substantial untreated waste containing trace metals. Surface sediment samples from twenty-two sites across the Akaki River catchment and Aba Samuel reservoir in Central Ethiopia were evaluated for cadmium, chromium, copper, iron, manganese, lead, nickel, and zinc across dry and rainy seasons. Manganese and iron showed the highest concentrations across both seasons, while cadmium was the lowest. The Little Akaki River carried the heaviest metal burdens, linked to nearby industrial and commercial operations. Conversely, Aba Samuel reservoir exhibited lower metal levels, attributed to its recent rehabilitation and shorter sediment residence times. Risk assessment indices indicated widespread contamination predominantly driven by cadmium and lead, followed by manganese, nickel, and zinc. These metals occur at concentrations that pose potential adverse biological risks to local aquatic life, highlighting a need for systematic environmental monitoring.
Untreated urban and industrial waste releases hazardous metals into river systems, directly threatening freshwater ecosystems and wildlife. Identifying primary pollutants, such as lead and cadmium, enables environmental authorities to pinpoint industrial pollution hotspots. Understanding how recent reservoir rehabilitation lowers sediment contamination also informs municipal river restoration strategies and helps target future pollution monitoring programmes.
The abstract does not indicate a direct commercial application pathway, as it focuses on environmental diagnostic assessment. However, environmental regulators, municipal authorities, and remediation services could use the contamination data to design targeted river clean-up programmes and industrial discharge enforcement measures. Based on the findings, the work represents early-stage environmental monitoring rather than an applied commercial technology.
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Due 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. Twenty-two surface sediment samples were collected, digested using the Mehlich-3 procedure and analyzed quantitatively using inductively coupled plasma optical emission spectrometer. The 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. The 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.
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DOI: 10.1186/s40068-018-0127-8
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