Assessment of Physicochemical Characteristics, Polymer Identification and Total Coliform Counts in Selected Rivers in Ado-Ekiti, Nigeria

Abstract

Microplastics are any synthetic solid particles or polymeric materials with equivalent spherical diameter ranging from 1 µm to 5 mm. The presence of microplastics in water bodies is a global menace for humans and aquatic animals, its fragments act as surfaces for the attachment of microorganisms, toxins, antibiotics and as vectors for pollutants in the environment. This study investigated the physicochemical characteristics, polymer identification of microplastics and total coliform counts in selected rivers (Ureje, Emirin, Ogbese, Odo-ayo and Elemi) in Ado-Ekiti, Nigeria. Water samples were collected biweekly over a period of 24 months (from January, 2023 to December, 2024) from the rivers using composite sampling method. The physicochemical characteristics of the water samples, microplastics concentrations and the total coliform counts in the water samples were determined using standard methods. Polymer identification was done using fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The result of the physicochemical parameters showed that the mean value of pH ranged from 9.55 - 9.87, electrical conductivity (EC) ranged from 196.67 µs/cm - 416.81 µs/cm, the total dissolved solid (TDS) ranged from 130.00 ppm – 213.00 ppm, DO ranged from 6.95 mg/L -9.62 mg/L, the biological oxygen demand (BOD) ranged from 1.95 mg/L - 3.09 mg/L and turbidity ranged from 9.47 NTU to 13.71 NTU. River Emirin had the highest concentration of microplastics with the mean value of 6.15 particles/L while water samples from Odo-Ayo river had the least value of 4.69 particles/L. FTIR spectra showed that polyethylene, polypropylene and polyethylene terephthalate (PET) were the most commonly detected microplastics in the water samples. SEM-EDX also showed that carbon and nitrogen were the predominant elements in the morphology of the extracted microplastics from the water samples.  The water samples from the rivers had high mean total coliform counts ranging from 3.80×102 CFU/100mL to 4.40 ×102 CFU/100mL.The results obtained from this study revealed that the water samples from the rivers contain different types of microplastics and are of poor microbial qualities. Therefore, there should be public awareness on good methods of plastics wastes management and water from the rivers must be adequately treated before use.