Characterization of microplastics in water, sediment, and fish from Nyumba-ya-Mungu water reservoir, Tanzania

Abstract

This study characterized microplastics (MP) that were extracted from water, sediment and fish of Nyumba-ya-Mungu Water Reservoir (NWR) an important source of water and fish for human consumption in the Kilimanjaro Region, Tanzania. A cross-sectional research design was employed to study the extracted MP using microscopy and Fourier Transform Infrared (FTIR) spectroscopy. Isolated MPs were characterized by color, form, and polymer type, and their relative abundances were determined. Microplastics were detected in all water and sediment samples, while 54% of fish intestines were contained MP. Mean MP concentrations were 2.29 ± 2.55 MP L⁻¹ (water), 39.93 ± 5.49 MP kg⁻¹ (sediment), and 2.80 ± 3.14 MP per fish. Color distribution was dominated by black (65.2%), followed by white/transparent (24.7%), blue (8.6%), yellow (1.5%), pink (1.4%), brown (1.1%), and red (0.5%). Fragments were the predominant form (78.3%), followed by fibers (7.9%), filaments (7.9%), and regular shapes, e.g., spherical, and rectangular (5.9%). Polymer composition was dominated by high-density polyethylene (37.5%) and low-density polyethylene (28.6%), with lesser contributions from polypropylene (9.8%), polyester (8.1%), polystyrene (6.1%), polyvinyl chloride (5.6%), and polyethylene terephthalate (5.0%). Microplastic concentrations were significantly higher in areas with greater human activity for both water (p = 0.04) and sediment (p = 0.028). Likely sources of MP include mismanaged plastic waste, open burning, and tire wear within the catchment. These findings highlight the need for improved waste management and continued monitoring of microplastics in freshwater systems.