Occurrence and polymer characterization of microplastics in surface waters of tributaries draining into Winam Gulf, Lake Victoria, Kenya

Pudens Busolo Shivachi; Grace Lagat; Samuel Lutta; Martin Wetungu

doi:10.51867/ajernet.7.3.4

Auteurs

Pudens Busolo Shivachi University of Eldoret, Kenya https://orcid.org/0009-0006-4981-3469
Grace Lagat University of Eldoret, Kenya https://orcid.org/0000-0003-4897-3509
Samuel Lutta University of Eldoret, Kenya https://orcid.org/0009-0006-9956-9441
Martin Wetungu University of Eldoret, Kenya https://orcid.org/0009-0005-4625-4676

DOI :

https://doi.org/10.51867/ajernet.7.3.4

Mots-clés :

Freshwater Pollution, FTIR Spectroscopy, Lake Victoria, Microplastics, Polypropylene, Winam Gulf

Résumé

Microplastics (MPs) are increasingly recognized as persistent contaminants in freshwater systems, yet data on tributary inputs to Lake Victoria, Africa's largest freshwater lake, remain scarce. This study assessed the occurrence and polymer composition of MPs in surface waters and sediments of three tributaries—Kisat, Nyando, and Sondu—draining into Winam Gulf, western Kenya. Water (5 L per station) and sediment samples were collected from upper and lower reaches of each river (n=1 per station), processed by ZnCl₂ density separation (1.6 g/cm³), and examined under a stereo microscope before polymer identification by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy. MPs were detected in surface water at three of six stations, with concentrations ranging from 0 to 4 particles per sample (0–0.8 particles/L). Lower Kisat recorded the highest abundance (4 particles), followed by upper Kisat (3) and lower Nyando (2); no MPs were detected in river Sondu or in any sediment sample. Three polymer types were identified—polypropylene (PP, 44.4%), ethylene-propylene-diene terpolymer (EPDM, 33.3%), and low-density polyethylene (LDPE, 22.2%)—all as irregular fragments. A one-way ANOVA (F = 5.21, p = 0.041) suggested significant inter-river variation; however, this result is exploratory given the limited sample size (n=6 stations). The absence of MPs in sediment is attributed to the low density of recovered polymers relative to water, favouring surface transport. These findings provide the first polymer-resolved baseline for these tributaries and identify the urbanized Kisat catchment as a priority for targeted pollution mitigation in the Lake Victoria basin.

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Références

Andrady, A. L. (2011). Microplastics in the marine environment. Marine Pollution Bulletin, 62(8), 1596-1605. https://doi.org/10.1016/j.marpolbul.2011.05.030

Dris, R., Gasperi, J., Saad, M., Mirande, C., & Tassin, B. (2015). Synthetic fibers in atmospheric fallout: A source of microplastics in the environment? Marine Pollution Bulletin, 104(1-2), 290-293.

https://doi.org/10.1016/j.marpolbul.2016.01.006

Egessa, R., Nankabirwa, A., & Ocaya, H. (2020). Microplastic pollution in surface water and sediments of Lake Victoria. Environmental Pollution, 257, 113442. https://doi.org/10.1016/j.envpol.2019.113442

GESAMP. (2015). Sources, fate and effects of microplastics in the marine environment: A global assessment (Rep. No. 90). IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection.

Hidalgo-Ruz, V., Gutow, L., Thompson, R. C., & Thiel, M. (2012). Microplastics in the marine environment: A review of the methods used for identification and quantification. Environmental Science & Technology, 46(6), 3060-3075. https://doi.org/10.1021/es2031505

Kole, P. J., Löhr, A. J., Van Belleghem, F. G., & Ragas, A. M. (2017). Wear and tear of tyres: A stealthy source of microplastics in the environment. International Journal of Environmental Research and Public Health, 14(10), 1265. https://doi.org/10.3390/ijerph14101265

Kosore, C., Ojwang, L., Maghanga, J., Ngisiag'e, N., Kamau, J., Magori, C., & Omondi, R. (2018). Occurrence and ingestion of microplastics by zooplankton in Kenya's Lake Victoria. African Journal of Aquatic Science, 43(3), 1-9. https://doi.org/10.2989/1814232X.2018.1492969

Lake Victoria Basin Commission (LVBC). (2016). The state of the Lake Victoria Basin 2016: Resources and environmental stress. LVBC.

Lebreton, L. C. M., van der Zwet, J., Damsteeg, J. W., Slat, B., Andrady, A., & Reisser, J. (2017). River plastic emissions to the world's oceans. Nature Communications, 8, 15611. https://doi.org/10.1038/ncomms15611

Li, J., Liu, H., & Chen, J. P. (2018). Microplastics in freshwater systems: A review on occurrence, environmental effects, and methods for microplastics detection. Water Research, 137, 362-374.

https://doi.org/10.1016/j.watres.2017.12.056

Masura, J., Baker, J., Foster, G., & Arthur, C. (2015). Laboratory methods for the analysis of microplastics in the marine environment: Recommendations for quantifying synthetic particles in waters and sediments (NOAA Technical Memorandum NOS-OR&R-48).

Ojwang, W. O., Kaufmann, R. S., Asila, A. A., & Getabu, A. (2017). Pollution in Lake Victoria: Impacts and management strategies. Lakes & Reservoirs: Research and Management, 22(1), 1-12. https://doi.org/10.1111/lre.12168

Rochman, C. M., Hoh, E., Kurobe, T., & Teh, S. J. (2013). Ingested plastic transfers hazardous chemicals to fish and induces hepatic stress. Scientific Reports, 3, 3263. https://doi.org/10.1038/srep03263

Shim, W. J., Hong, S. H., & Eo, S. (2017). Identification methods in microplastic analysis: A review. Analytical Methods, 9(9), 1384-1391. https://doi.org/10.1039/C6AY02558G

Teuten, E. L., Saquing, J. M., Knappe, D. R., Barlaz, M. A., Jonsson, S., Björn, A., ... Takada, H. (2009). Transport and release of chemicals from plastics to the environment and to wildlife. Philosophical Transactions of the Royal Society B, 364(1526), 2027-2045. https://doi.org/10.1098/rstb.2008.0284

Thompson, R. C., Olsen, Y., Mitchell, R. P., Davis, A., Rowland, S. J., John, A. W. G., ... Russell, A. E. (2004). Lost at sea: Where is all the plastic? Science, 304(5672), 838. https://doi.org/10.1126/science.1094559

Wright, S. L., & Kelly, F. J. (2017). Plastic and human health: A micro issue? Environmental Science & Technology, 51(12), 6634-6647. https://doi.org/10.1021/acs.est.7b00423

Wright, S. L., Thompson, R. C., & Galloway, T. S. (2013). The physical impacts of microplastics on marine organisms: A review. Environmental Pollution, 178, 483-492. https://doi.org/10.1016/j.envpol.2013.02.031