Microplastics in Leachate Draining from Selected Landfill Sites in Sri Lanka

Abstract

Microplastics in leachate are a global concern due to their pervasiveness and potential risks to biota. Secondary microplastics are formed through physical, chemical, or biological processes that break down plastic waste deposited in landfills. Despite reports of microplastics in leachate and sediment worldwide, there has been no investigation of their presence and characteristics in Sri Lanka. This study aimed to address the research gap by assessing the abundance of microplastics in leachate and sediment at ten dumpsites in Sri Lanka: Karadiyana, Muthurajawela, Rathnapura, Balangoda, Gohagoda, Rathgama, Niyagama, Kurunegala, Matara, and Ja-ela. Density separation and wet peroxide digestion was performed to extract microplastics from sediment and leachate samples. The extracted microplastics were separated into three size categories (2-5 mm, 1-2 mm, and 0.5-1 mm) and chemical characterization was performed using FTIR spectroscopy. The microplastics were further characterized according to their shape and color. The results showed that the abundance of microplastics in leachate ranged from 0.52 to 5.95 mg/L while in sediment, it varied from 61.00 to 1173.40 mg/kg. The highest microplastic abundances were found in Balangoda leachate (5.95 mg/L) and Ja-ela sediment (1173.40 mg/kg). The mean microplastic abundance in leachate and sediment was 2.06±1.96 mg/L and 363.36±353.33 mg/kg, respectively. Polyethylene was the most abundant polymer type in both leachate (54.72%) and sediment (63.7%). Fragment shapes were commonly present in the microplastics, and more than 50% of the microplastics found in the leachate and sediments were in 1-2 mm size range. White-colored microplastics were prominent in both sediments and leachate. The study highlights the potential risks of microplastic exposure to the general population in Sri Lanka, as the surrounding waters of the dumpsites are used as public water supplies.