The impact of pollution on the ecology of the Nairobi-Athi River system in Kenya

Abstract

The pollution of the Nairobi-Athi River System is assessed by heavy metal analysis of the river water, industrial effluents, the invertebrate community and the riverine vegetation between Nongara upstream (UP) and 14 falls. heavy metal analysis of heavy sewage showed the elements Pb(3-88)ng/ml, cu (19-88)ng/ml, Oln(93-1350)ng/ml, cr (12 -330)ng/rd and Fe (190-857)ng/ml. Most invertebrate faxa were found to disappear beyond Kijabe Street (St.8). Only Oligochetes and Chironomides and the 'Sewage fungus' complex sphaerotilus natans are found below this point. A first recovery of the invertebrates fauna was noticed at the Nairobi falls (st.19), 20 km. beyond the city centre, where Trichoptera, simuliidae, tubificidae, and Chrinomidae were found. The riverine vegetation colonizing the banks was progressively further apart from the Channel. At sts. 15 and 16(Mathare junction and Njiru) the part of the bank that was proximal to the water was almost devoid of vegetation. Edges of the leaves touching the water were corroded and damaged