Anthropogenic footprint and ecological risk assessment of organochlorine pesticides and polychlorinated biphenyls in sediments from Lake Victoria, East Africa

Abstract

Lake Victoria, the world’s second-largest freshwater lake, continues to face pressure from anthropogenic activities in its catchment area, releasing pollutants, which are ultimately trapped in the sediment core, thereby posing threats to aquatic organisms. This study quantified thirteen organochlorine pesticides (OCPs) and ten polychlorinated biphenyls (PCBs) in sediments from the Uganda, Kenya, and Tanzania sides of Lake Victoria using soxhlet method, fractionation column and GC–MS/MS analysis. Total (∑13) OCPs levels were up to 412, 148, and 522 µg kg-1 dry weight (d.w), and 12.1, 8.69 and 9.87 µg kg-1 dw for total (∑10) PCBs for sediments from Uganda, Kenya, and Tanzania, respectively. Diagnostic ratios suggested past and ongoing use of OCPs while principal component analysis confirmed that OCP profiles were mainly due to their application in controlling pests in agriculture and public health programs, and PCB congeners were largely due to volatilization, degradation of higher PCBs into lighter PCBs, improper waste disposal of old transformers, hydraulic fluids, plasticizers, and capacitors. Ecological risk assessment highlighted that the PCB levels in sediments were below threshold effect and probable effect levels, but p,p′-DDD, and lindane were likely to pose adverse effects to sediment-dwelling organisms in Lake Victoria. These results imply persistent pollutant loads in Lake Victoria, and consequently, a need for its enhanced management.