| Popis: |
This study investigates the heavy metals (HMs) and other constituents in Lake Tana around the Gulf of Bahir Dar City. The water sample was collected from areas receiving drainage water and a reference sample was collected from areas away from the urban impact, both during dry and wet seasons. Pollution sources and levels were determined using pollution indices and GIS spatial analyses. All in situ parameters were in the recommended range of the USEPA aquatic and WHO drinking water guidelines. The level of dissolved P was recorded between 0.03 and 0.9 mg/l and the level of N-NO3 ranged from 0.05 to 1.01 mg/l indicating that the limits were above USEPA aquatic criteria. The HMs varied from 0.08 to 2.85 mg/l for Cu, 0.10 to 1.60 mg/l for Fe, 0.04 to 0.22 mg/l for Cr, and Mn was below detection. Cr and Fe were above the aquatic and drinking water guideline limit. Spatially, pollution was more significant in areas receiving drainage. Also, except Cu and Fe, other parameters were higher in the rainy season indicating storm runoff pollution. The overall pollution indices of water quality status, such as water quality index 63, heavy metal pollution index 3.1, and nutrient pollution index 4.7, indicated the quality level of water to be alarming. Therefore, comprehensive regulatory and waste management practices are needed. HIGHLIGHTS This research is a first study evaluating the heavy metals (HMs) in Lake Tana.; Both HMs (Cr and Fe) and nutrients (N and P) exceeded the aquatic limit.; GIS spatial analysis shows that concentration is at a high level in urban drainage discharge area.; HMs and nutrients are at high levels in the rainy season.; The calculated pollution indices such as WQI, HPI, and NPI indicated the water quality of the lake to be alarming.; |
