The occurrence of microplastics in the surface water of several urban lakes in the Megacity of Jakarta

Abstract Microplastic pollution in the marine and freshwater environment has been a global concern. The pollution in densely populated urban areas may be more severe than in any other environment, especially in areas lacking plastic waste management. Urban lakes in the Megacity of Jakarta, the capital city of Indonesia, and neighboring areas, which is the most populated city in the world, have been severely polluted by plastic waste. The urban lakes studied were located downstream of watershed areas of major rivers that outflow into Jakarta Bay, the Java Sea, and finally the ocean. To our knowledge, no studies have been reported on microplastic pollution in urban lakes in the Megacity of Jakarta. This study investigated the first occurrence of microplastics in the surface water of six urban lakes in the Megacity of Jakarta. Grab water samples were collected in either inlet or outlet areas of lakes. The water samples were pretreated and sieved to separate the microplastics. The quantification and the identification of microplastics were made using a Stereo Microscope. The most downstream urban lakes in the densely populated area close to Jakarta Bay, which is the final disposal of plastic wastes from the river canal and runoff from the surrounding area, had more microplastics than the urban lakes in the area with less population and further from the Bay. The most abundant microplastics found in the lake’s surface water was about 30,000 particles/m 3 , whereas 300 - 500 µm and the foam were the dominant size and type of microplastics discovered. The concern is that the smallest size of particles of microplastics found in the lake’s water could potentially contaminate aquatic biota, especially fish, not only in the lakes but also in Jakarta Bay, where fishing activities are substantial.