Identification of microplastics from urban informal solid waste landfill soil; MP associations with COD and chloride

Abstract

Microplastics (MPs) are an issue of prime environmental concern globally. The abundance of MP particles in the informal open solid waste landfill soil was evaluated showing 180-1120 MP particles per kg of soil. Moisture content (MC), electrical conductivity (EC) and pH of the MP-contaminated soil compared to the baseline showed 2.96% MC, 187-441 μS/cm EC and 6.94 pH. Morphology of extracted MPs in SEM showed particle fragmentation as film fragments (13.7%), fragments (56.1%), fibres (26.4%) and foam (3.8%). EDS results showed Carbon 71.8% and 24.5% oxygen with traces of Na, Al, Si and Cl-. FTIR of field obtained MPs identified were polyethylene and polypropylene. The association of MP particles with COD and chloride was discovered. MP particles of Low-density Polyethylene of size of 1 mm × 1 mm and thickness 25 μm up to 20 numbers showed no effect adding to the COD values. The COD values increased with increase in MP particle numbers. Similarly, chloride associations with MP particles showed an increase in MP particles reducing chloride values by 31% in landfill runoff water. It is interpreted that MP particle disintegration into nano-sized plastics (NPs) in the soil/runoff water can greatly increase the COD values and impair the salt mass balance.