Direct observation of nanoplastics in seawater via shrinking surface bubble deposition

Plastics production surpasses all other synthetic materials globally, with 0.4-4 million tons of them entering the oceans every year, posing serious environmental challenges. After disposal, these plastics can be fragmented by UV irradiation and mechanical means. While microplastics are detected in abundance, the morphological information on nanoplastics in our environment has never been confirmed, although they are believed to be significantly more toxic to living organisms compared to their microscopic counterparts. Here we report the direct observation of nanoplastics in ocean water around the world leveraging a unique shrinking surface bubble deposition (SSBD) technique. We identified nanoplastics with a variety of compositions, including polycaprolactam (Nylon), polystyrene (PS) and polyethylene terephthalate (PET), which are common materials for daily consumables (e.g., textiles, coffee cup lids and water bottles). They also possess diverse morphologies, such as nanoflakes, nanofibers and ball-stick nanostructures. The identification of a variety of nanoplastic particles from the water samples collected from several locations on the coastlines of the U.S., China, South Korea and deep (>300 m) in the Gulf of Mexico suggests their widespread distribution in ocean. These results should promote investigations into the environmental impact of plastic disposal.