Microplastic pollution in compost from municipal composting facilities in Uttarakhand Himalayan region, India:...

Composting is regarded as a sustainable method for recycling organic materials in municipal solid waste; however, it could also serve as a potential pathway for microplastics (MPs) to enter the waste-to-soil cycle. This study examined the prevalence, physical characteristics, polymer composition, and ecological risks of MPs in compost sourced from composting facilities across nine different cities in the Uttarakhand Himalayan Region. Compost samples were subjected to oxidative digestion, density separation and then analyzed using stereomicroscopy and micro attenuated total reflectance-Fourier transform infrared spectroscopy (μATR-FTIR) for MPs analysis. MPs abundance varied between cities, ranging from 3,800 ± 223 to 8,800 ± 280 particles/Kg, primarily fibres, with size ranges of 1-5 mm (40.87 %), 106-500 μm (34.92 %), and 500 μm-1 mm (24.21 %), MPs colour included white (45.64 %), black (34.0 %), and other colours (20.03 %). μATR-FTIR results indicated polyethylene (21.34 %), polyacrylonitrile (17.14 %), polystyrene (15.53 %), and acrylonitrile butadiene styrene (14.36 %) as the predominant polymers. Ecological risk assessments showed pollution load index values ranged between 10 and 30, categorizing the composting facilities as moderately polluted. Due to hazardous MPs polymers, all composting facilities were classified as dangerously polluted based on the pollution hazard index. In contrast, the potential ecological risk index indicated an extremely high level, suggesting a significant potential ecological risk when such compost is used in the agroecosystem. Addressing this issue requires stricter waste segregation, reduction of plastic inputs, and improved solid waste management. Furthermore, national standards for compost quality, mandatory monitoring of MPs, and the integration of circular economy principles into policy frameworks are urgently needed to mitigate risks and protect agricultural sustainability in these areas.