Site and Seasonal Variation of Selected Physicochemical Parameters and Levels of Heavy Metals within the Aquatic Ecosystem in South Nyanza Sugarcane Zone

Abstract

Sugarcane fanning has been the main anthropogenic activity done on a large scale in South Nyanza region of Western Kenya since 1979. Use of high rate 0t nitrogenous fertilizers has been in practice since the establishment of the sugar factory in this area. Studies have shown that use of fertilizers has had adverse impact on the quality of aquatic ecosystems. However, it remains unknown if the aquatic ecosystem within South Nyanza sugarcane zone has been similarly affected. It was therefore important to carry out a monitoring study to establish the sustainability of aquatic systems within this zone. Physicochemical parameters such as temperature, pH, turbidity, conductivity, biological oxygen demand, and organic carbon content, Fe, Zn, Cu, Cr, Pb and Cd were determined in two days of different seasons using standard procedures. The experiment was laid down in a two factor completely randomized" design format with site as the main treatment and season as a sub factor. Analysis of variance and student t-tests were used to determine the differences between trends within seasons and among sites at 95% significant levels. The results indicated a significant reduction in pH of soils and aquatic systems within South Nyanza sugarcane fields as compared to different control sites. Other physicochemical parameters recorded a significant (Ps).05) increase in their levels with some of them such as biological oxygen demand, turbidity and electrical conductivity being above recommended international aquatic systems levels. Reduction in soil pH levels has been documented to have direct effect on the increase of other physicochemical parameters such as heavy metals mobility in aquatic ecosystems. It was therefore concluded that sugarcane farming is affecting the quality of aquatic ecosystem within South Nyanza sugarcane zone and urgent measures such as correction of soil pH was needed to avoid the problem escalating beyond manageable levels.