ASSESSMENT OF HEAVY METALS CONTAMINANTS IN NKENYE STREAM IN MERU SOUTH, KENYA

Abstract

Access to portable water remains major global concern due to increased rate of water pollution contributed for by human pressure such as accelerated urbanization, high population, industrialization and intense agricultural activities that destroys riparian zones thus exposing the rivers and streams to toxic and pathogenic pollutants released from untreated organic and inorganic waste. Exposure of river and stream used for drinking water to pollution is detrimental to aquatic plants, human consumers and animals inhabiting water bodies. Nkenye stream in Meru South is depended upon for the use of its water in supplying fish ponds constructed along it, supplying water used for irrigation and provision of water for domestic use to the neighboring homestead. Nonetheless, little attention has been accorded to ascertain the quality of its water despite of the stream being located in an urban area with high exposure to pollutants. Pressure on Nkenye wetlands ecosystem that habour Nkenye stream has seen major destruction of riparian leaving just few plant communities such as Commelina banghalensis whose water purification potential is not well known. Based on the above fact a study was conducted to determine water quality of Nkenye stream based on the presence of heavy metals. Samples were collected at designated locations using ecological survey method and taken to Chuka University for evaluation. Macrophyte roots were cleaned and dried then powdered and digested using nitric acid. The sediment samples were dried, ground to pas a 2 mm non-metal sieve, digested samples were diluted and analyzed using atomic absorption spectrometry model PG990 at Chuka University. The concentration of anions was determined by ion chromatography at Chuka University Chemistry laboratory. The results obtained from the field and laboratory were analyzed by General linear model (GLM) on Statistical analysis system (SAS) version 9.4 and significance means separated by Least significance difference (LSD) [alpha = 0.05]. The results showed that Nkenye stream is polluted with iron, copper and lead. However, the concentration of iron and copper were within the set standards by the World Health Organization while lead was slightly higher by 0.02 ppm. The results obtained were analyzed by General linear model (GLM) on Statistical analysis system (SAS) version 9.4 and significance means separated by Least significance difference (LSD) [alpha = 0.05]. The metals contaminants observed in the Nkenye stream water, sediments and root samples may be associated with discharge of wastes from Chuka town particularly wastes from car wash, garages and from farms that surround the stream and the wetland. Considerable amount of lead, copper and iron was observed in the root samples of Commelina banghalensis. This shows that the plant can be utilized in the removal of the above cations in the Nkenye stream. Considerable amount of chemical was observed in the root samples of Commelina banghalensis this shows that the plant can be utilized in removal of chemicals in the stream. Local authorities should provide waste management disposal systems and policies that prohibit direct discharge of untreated effluents into the stream.