SPATIAL AND TEMPORAL VARIATIONS IN PHYSICO-CHEMICAL

Abstract

Increased human activities have led to water pollution, especially metals and nutrients. Therefore, prudent management of aquatic environments require information on their quality status that can be estimated by monitoring water to determine extent of pollution. This study examined the spatial and temporal variations of heavy metals and nutrients in water, soil and sediments which were sampled along four sites (S1, S2, S3 and S4) as Kapsabet River flows from upstream to down stream for both dry and wet season. The parameters analyzed were: temperature, pH, chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS) and total suspended solids (TSS) while phosphates and nitrates were the nutrients analyzed. Heavy metals analyzed included Pb, Cu, Fe and Zn using atomic absorption spectroscopy (AAS). TSS and TDS were determined by gravimetric method, COD titrimetrically, BOD by incubation, phosphates and nitrates by colorimetric method. Data was analyzed statistically using SPSS computer package. All parameters analyzed increased downstream, except Cu, with maximum mean values recorded in wet season. Their spatial and temporal values were: in water, pH (7.2 -10.3), TSS (110 -1301 mg/L), TDS (868 - 2990 mg/L), COD (6.0 – 67 mg/L), BOD (3.0 - 33.7 mg/L) PO43- (0.2 - 2.1 mg/L) and NO3- (0.6 - 4.5 mg/L), in soil and sediments, PO43- mean values were: 0.5-1.8 mg/L and 0.7 – 2 mg/L, respectively, while NO3- in soil and sediments were: 5-5.2 mg/L and 8-8.0 mg/L, respectively. For heavy metal, Fe had high concentration with mean values in water, soil and sediment being, 0.19 – 12.02 g/g, 1.15 – 38.78 g/g and 0.12 – 69.89 g/g, respectively, while Cu had the least concentration with mean values being, 0.017 - 0.174 g/g, 0.008- 0.424 g/g and 0.08 - 3.056 g/g in water, soil and sediments, respectively. There was significant (p < 0.05) spatial and temporal distribution of metals along the river profile. In both water and sediments, S3 and S4 contained significantly (p < 0.05) the highest concentrations of Pb, Fe and Zn associated with anthropogenic pollution. Based on the results obtained Kapsabet river water is not safe for drinking and other domestic uses and therefore, it is recommended that a for nutrient reduction strategy be undertaken, for example, construction of buffer zone.