Assessment of Selected Heavy Metals in Sediments from Ndambuk River, Busia County, Kenya

Abstract

Anthropogenic activities have significantly contributed to soil and sediment pollution. Heavy metals are among the most common soil/sediment pollutants, owing to the fact that they easily get adsorbed on sediment surfaces and get carried from one ecosystem to another. This study examines the pollution effect of heavy metals in sediments from River Ndambuk, Busia County, Kenya. A total of eight heavy metals (Co, Cu, Fe, Cr, Ni, Cd, Pb and Zn) were examined during dry and wet seasons. The levels of Cd, Ni and Pb were above the World Health Organization (WHO) recommended limits for heavy metals in sediments. However, Pb levels were only above the WHO limit during the dry season, with the wet season registering concentrations way below WHO limits.  Co, Cu, Fe, Cr and Zn recorded concentrations below WHO limits during the dry and wet seasons. Pollution indices were used to determine the extent of sediment pollution. Geoaccumulation index, pollution load index, contamination factor and enrichment factor were calculated from the heavy metal concentrations in sediments. Fe, Cr and Zn recorded negative I geo values during both seasons, signifying no pollution by these metals. Ni recorded moderately polluted to strongly polluted status whereas Pb recorded strongly polluted status only during the dry season. Points 1 – 4 recorded lack of pollution due to anthropogenic activities, while points 5 – 7 recorded pollution due to anthropogenic activities as per the PLI values. The study recommends proper land use and dumping of wastes and controlled mining activities to keep soil pollution at bay. Pollution by heavy metals can be controlled by embracing circular economy, which advocates for the reuse and reduction of waste to a minimum. Waste reduction will go a long way in reducing water and sediment pollution as the volume of pollutants discharged into water bodies will significantly reduce. The other principles of circular economy that will aid in mitigating water and sediment pollution include: regeneration of reagents, close water loops, integration of materials and waste flows, safe disposal of harmful elements, use of benign chemicals (which are less harmful to the environment) and reduction of chemical diversity.