Seasonal variation of selected water quality parameters and speciation of copper in Ruiru river, Kenya.

Abstract

Since civilization, human activrtres have contributed to pollution of the environment. Examples of such activities are urbanization, industrialization and agriculture which lead to introduction of heavy metals and other vices into water sources. Due to the toxic nature of metals, serious environmental implications have resulted. Some water quality parameters assessment was carried out on River Ruiru in Thika district in order to establish its pollution status. Water samples were collected at various points along the river from the Thika road bridge upstream, after everyone kilometer, to Kwamaiko. However, whenever there was a coffee processing factory. Sampling was done just before and after the river flows past the factory. Sampling was carried out thrice; during the short rains, the long rains and the dry season. The levels of selected heavy metals (Pb, Cu, Fe and Zn) in the river was determined using Flame Atomic Absorption Spectrophotometry (FAAS) and by Differential Pulse Anodic Stripping Voltammetry (DPASV) at a glassy carbon electrode. Nitrate, chloride, phosphates, electrical conductivity, total dissolved solids (TDS) and the pH were determined using standard analytical methods. Speciation studies were then carried out using copper and selected ligands using a computer program, SPECIES. The levels of TDS, conductivity, pH, chlorides, nitrates, phosphates, copper, iron, lead were found to range between 23.06 - 41.74 ppm, 30.62- 78.83 J.lSem -\ ,8.12 -9.65, 0.5 -14.67 ppm, 196.5 - 281.4 ppm, 1.97 -3.10 ppm, 2.14- 4.55 ppm, 5.31- 10.26 ppm and 0.01 - 0.90 ppm respectively. The levels were above WHO limit for aquatic ecosystems. Statistical analysis using ANOV A (single factor) showed that, there was a significant difference between the seasons but not the sapling points. Speciation studies showed the presence of free metal (Cu2l at the given pH. Since speciation depends on the pH there is need to monitor the pH to prevent changes in the speciation. From the results obtained, it implies that agriculture, industrialization and urbanization contribute to environmental pollution.