Microplastic accumulation in water from protected areas in Western Forest Complex of Thailand

Microplastics (MPs) are emerging as ubiquitous environmental pollutants worldwide. However, no research has been conducted in freshwater ecosystems within Thai protected areas (PAs), where biodiversity and natural resources are safeguarded for human well-being. The aim of this study was to explore the occurrence and abundance of potential MPs in the water of freshwater ecosystems in Thai PAs and to examine factors affecting their presence in the Western Forest Complex in Thailand (WEFCOM). Seventy water samples were collected from eight PAs in WEFCOM using a 20 μm plankton net. The water samples underwent digestion, density separation, and filtration. Potential MPs were visually identified under a stereomicroscope, and their chemical composition was further characterized using FTIR. The results revealed a 98.57 % potential MP prevalence in the water samples, with an average abundance of 0.30 ± 0.32 item·L^-1. The quantities of potential MPs among PAs were significantly different (H = 17.88, p = 0.01). Fibers (68.93 %) were the most frequently identified potential MPs, with the dominant colors being blue (22.40 %) and black (20.03 %), mostly small-sized MPs (0.05-0.5 mm; 41.80 %). The major chemical plastic types included low-density polyethylene, polyethylene, polyethylene terephthalate, polypropylene, polyethylene/polypropylene copolymer, polyester, and natural fibers. The abundance of potential MPs varied significantly among PAs, shapes, colors, and sizes (p < 0.01). Furthermore, potential MP abundance correlated with the number of tourists (p < 0.05). Proximity to open waste dumping (p < 0.01) and lower elevation (p < 0.05) tended to accumulate more potential MPs. This research suggests potential sources of microplastics in Thai PAs from wastewater effluent, human activities, and recreational activities, highlighting the urgent need for research to develop appropriate waste management technologies in Thai PAs and to raise awareness among local people and tourists about microplastic pollution.