Abundance and Distribution of Microplastics in Fish and Sediments from Coastal River Watersheds of Dar es Salaam, Tanzania

Abstract

Different reports indicate that microplastics have been environmental pollutants which are engulfed by aquatic organisms also are carriers of other toxic chemicals. This study aimed to characterize and determine the spatial distribution of microplastics in sediments and fish in Dar es Salaam. The study had to indicate the extent of plastic pollutants in the urban watersheds. Fish and sediment samples were collected from river watersheds and ponds. Gastrointestinal parts were digested using 10% KOH and incubated at 65 oC for 24 hours while sediment samples were extracted using the floatation method in 4 M NaOH and 3 M NaI solutions. The identity of microplastics was determined by an attenuated Fourier transform infrared spectrophotometer. The concentrations of microplastics were 94 ± 24 particles/kg for fish samples from River Msimbazi watershed ponds and 46 ± 16 particles/kg for fish samples from River Mzinga watershed ponds. The concentrations of microplastics in sediments were: 64 ± 35 particles/m2 for the River Mzinga watersheds and 25 ± 18 particles/m2 for River Msimbazi watersheds. The microplastics observed were polypropylene, polyethene, polyurethane, polyamide, polyvinyl chloride, polyethene terephthalate, and polytetrafluoroethylene. The microplastics were in the form of fragments, sponges, and fibres. The results confirmed that fish living in river watershed ponds in Dar es Salaam were exposed to microplastics and that sediments had microplastics. Further studies need to be performed to find out micro-pollutants adsorbed by microplastics in the river watersheds.