Emerging organic pollutants in sediments from Lake Victoria: Spatial patterns, sources and ecological risks

This study presents the first evaluation of contaminants of emerging concern (CECs) in sediments from the Uganda, Kenya and Tanzania sides of Lake Victoria. We applied wide-scope target screening via ultra-high performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-QTOF-MS) to 38 surface sediment samples collected in September 2019 (wet season) and detected 136 out of more than 2400 targeted compounds. These included pharmaceuticals, industrial chemicals, plant protection products (PPPs), hormones, artificial sweeteners, drugs of abuse, and naturally occurring substances. The CECs concentrations (μg/kg dry weight, d.w) were up to 2103.5 for pharmaceuticals, 506.8 for PPPs, 880.1 for hormones, 843.0 for artificial sweeteners, and 218.9 for drugs of abuse and 1306.0 for naturally occurring substances, with the highest loads of pollutants at the northern and northeastern shores of the lake attributable to majorly urban and riverine inputs. Kruskal-Wallis tests revealed no significant differences across the Uganda, Kenya, and Tanzania sides of the lake, underscoring trans-boundary pollution. Ecological-risk assessment (risk quotient, RQ) indicated that 46 % of detected compounds pose high risk (RQ > 1: FoE >1 %) to sediment-dwelling organisms, with pharmaceuticals, PPPs, and industrial chemicals showing the greatest threat. Seven (7) out of these were prioritized for future monitoring based on their risk scores being >1 due to their potential eco-toxicity. The occurrence of carbamazepine and its TP(10,11-dihydro-10,11-dihydroxy-Carbamazepine), Ibuprofen TP(2-hydroxy-ibuprofen), 17-beta estradiol, Bis-(2-ethylhexyl)-Phthalate (DEHP), and simazine in the sediments is of concern, especially since they are listed among dangerous chemicals in the environment. These findings highlight the need for coordinated regional monitoring, enhanced wastewater treatment, and sediment-targeted risk management to protect Lake Victoria's ecological integrity.