Assessing the Seasonal Changes on Physicochemical Parameters and Major Nutrient Levels in Water and Sediments from Sulal River, Bureti Sub County, Kericho County, Kenya

Abstract

Sulal River is a victim of nutrient pollution as it crosses different small-scale tea farms in Bureti Sub County, Kericho County. A study was conducted to evaluate different physicochemical parameters and major chemical fertilizer’s nutrients levels in water and sediments from Sulal River. In order to understand the degree of pollution in the river due to inflow of agricultural chemical fertilizer residue levels from its catchment, the samples were collected in the dry (February 2019) and wet seasons (November 2019). The ten chosen sampling sites stretched a length of 12 Km. Samples were analyzed for pH, dissolved oxygen (DO), total dissolved solids (TDS), electrical conductivity (EC), sediment and water content (WC), nitrate-nitrogen (NO3-N), phosphorous (PO3-P) and potassium (K) using standard methods. Results were analyzed using IBM SPSS 20. The average results during dry and wet seasons in water samples for pH were 6.72±0.05 and 6.38±0.21, DO 6.78±0.59 and 9.58±0.64 mg/L, EC 174±5.02 and 205±20.14 µS /cm, TDS 92±4.59 and 120.70±19.57 mg/L, NO3-N 0.58±0.21 and 1.19±0.22 mg/L, PO3-P 0.00±0.00 and 0.13±0.84 mg/L and K 0.26±0.08 and 0.84±0.19 mg/L respectively. The average results during dry and wet seasons in sediment samples for pH were 6.62±0.20 and 6.75±0.17, EC, 67±6.66 and 52±10.19 µS /cm, WC 16.96±3.95 and 129.84±5.00%, NO3-N 0.70±0.35 and 0.42±0.23 mg/kg, PO3-P 0.49±0.25 and 1.14±0.40 mg/kg and K 1.53±0.45 and 2.86±0.31 mg/kg respectively. The levels of P in water during wet season and in sediments samples in both seasons were however, above the WHO (0.025 mg/L) and KEBS (0.030 mg/L) recommended limit for drinking and domestic use and WASREB (0.005 mg/L) level for the likelihood of eutrophication. Availability of excess phosphorus can accelerate eutrophication. The diversity of cancers has also been associated with drinking water containing phosphorous levels. The water from Sulal River may be used for irrigation purposes but not for drinking and domestic purposes. Significant seasonal variations were observed in all parameters analyzed except NO3-N in sediments. This indicates that rainfall had a great effect on some soil physicochemical properties.