Influence of Watershed Land Use on Contamination of the Sediments of Lake Victoria, Africa: A Case Study of Pesticides, Alkylphenols, and Antimicrobial Agents

High Resolution Image Download MS PowerPoint Slide Freshwater lakes are vulnerable to land-use changes that promote the input and accumulation of organic pollutants in sediments, posing risks to aquatic ecosystems. This study assessed the relationship between watershed land use and the occurrence of selected pesticides, antimicrobial agents, and alkylphenols in surface sediments of Lake Victoria in Africa. Surface sediment samples ( n = 38) were collected in September 2019 across the Uganda, Kenya, and Tanzania sides of the lake. The samples were extracted using ultrasound-assisted extraction (UAE) and analyzed by gas chromatography–mass spectrometry (GC–MS). 16 out of 23 target compounds were detected, with pesticides showing low concentrations (<LOD to 0.662 μg/kg dry weight (d.w.)). Endrin-ketone and β-hexachlorocyclohexane (β-HCH) were the most frequently detected pesticides (frequency of appearance (FoA) at 42.1 and 28.9%, respectively). In contrast, alkylphenols and antimicrobial agents were ubiquitous, with 4-phenylphenol exhibiting the highest level (1,571.5 μg/kg d.w.). Spatially, elevated contaminant loads along the northern and northeastern shores of the lake coincided with catchments dominated by croplands and built-up areas, indicating the influence of agricultural runoff, urban wastewater, and riverine inputs on sediment contamination. Ecological risk assessment identified five priority compounds with risk scores >1 (4- tert -octylphenol, 2-phenylphenol, 4-phenylphenol, β-HCH, and 4- n -octylphenol) that pose potential aquatic ecotoxic risks to aquatic organisms. This study demonstrates that activities related to agriculture, industrialization, and urban development are the main drivers of sediment contamination in the lake, highlighting the need for targeted catchment management and monitoring.