Extraction and characterization of microplastics in Landfill-Mined-Soil-like-Fractions: A novel methodology

Abstract

Utilization of Landfill-mined-soil-like-fractions (LFMSF), a major constituent of landfill mined residues and resembles organic soil, is essential for landfill mining activity to be a sustainable practice. In this context, the potential utilization schemes of LFMSF such as compost, buffering material, landfill biocover, road subbase, and structural fill material were explored by earlier researchers. However, as the LFMSF originates from unscientifically created landfills/dumpsites (UCLDs) and/or engineered landfills (ELFs) that contain microplastics (MPs), there exists a school of thought that its utilization might contaminate the geoenvironment in the long run. Hence, it becomes mandatory to investigate their presence in LFMSF which unfortunately has not been attempted. In this context, to estimate the presence of MPs in LFMSF, it would be prudent to adopt the methodologies applied for their extraction and characterization in the organic-rich solid matrices (ORSMs). However, limitations associated with the existing protocols of (i) organic matter removal and (ii) ultrasonication in their extraction and characterization call for developing appropriate methodologies. Keeping this in view, a novel methodology for extraction and characterization of MPs in ORSMs by incorporating modifications to the existing protocols was developed and the details are presented. Further, the efficacy of the proposed methodology when employed for extracting MPs from the standard ORSMs and LFMSF has been verified. Subsequently, this methodology was adopted to estimate the concentration of MPs present in the LFMSF samples obtained from four different UCLDs/ELF. It was observed that the concentration of MPs in LFMSF samples varies between 23361.11 ± 1927.77 and 42066.67 ± 1713.02 particles/kg. Moreover, light-density polymer (i.e., polyethylene and polypropylene) based MPs amount to ≈50 % of their total concentration. In authors’ opinion, the proposed methodology should be applied to (i) extract and characterize the MPs present in other ORSMs and (ii) develop protocols/guidelines for utilizing LFMSF for different sustainable development applications.