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

Abstract

Access to portable water remains a major global concern due to its dimishing supply and increasing andcompetiting
demand. Water scarcity is aggrevated by the increasing pollution from different sources. Nkenye stream in Meru
South is depended upon source of water for domestic, agriculture and agricultural processing, Nonetheless, little
attention has been accorded to ascertain the quality of its water despite of the stream being located in an urban areawith high exposure to pollutants. Pressure on Nkenye wetlands ecosystem that habour Nkenye stream has seenmajor destruction of riparian leaving just few plant communities such as Commelina banghalensis whose water
purification potential is not well known. A study was conducted to determine water quality of Nkenye stream.
Samples were collected at designated locations using ecological survey method and taken to Chuka University for
analysis. Macrophyte roots were cleaned and dried then powdered and digested using nitric acid. Sediment samples
were dried, ground to pass a 2 mm non-metal sieve.The 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 allowable concentrations
for potable water 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 townparticularly 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 is an indication that Commelina banghalensisfo can be used can be used for the removal of contaminants from water. Local authorities should provide waste management disposal systems and policies that prohibit direct discharge of untreated effluents into the stream.