Critical review on microplastics in landfill leachate

Abstract

Microplastic (MP) pollution has emerged as a critical environmental concern. Landfills, as significant repositories of plastic waste, represent a potential source of MPs. Furthermore, landfill leachate (LL) has been identified as an important pathway for the release of these stored MPs into the environment. MPs found in LL originate from various sources, including discarded plastics, synthetic fabrics and industrial waste. This review systematically analysed the various studies conducted on MPs in LL. Study revealed that the three most populous countries themselves were the top three countries in terms of number of publications in the area, in the order China > India > United States. Polyethylene (PE) was the most dominant type of polymer in LL, followed by polypropylene. Fibre was the most prominent shape of MPs in leachate. The colours of MPs identified in LL included black, blue, white, green and transparent. The size of MPs sampled from leachate ranged from 0.03 to 5 mm. Comparison across studies was difficult due to differences in size classifications and extraction methodologies. Micro-Fourier transform infrared spectroscopy (FTIR) and Raman techniques are the most effective methods for characterizing the MPs for polymer type, although for particles of size >1 mm, FTIR with attenuated total reflectance is widely used. With PE as the most abundant polymer type in leachate, there is a need to investigate the role of high-density PE membranes used as landfill liners in contributing MPs to LL. This is to ensure that a system introduced to protect the environment is not contributing to its degradation.