Spatial distribution of microplastics in soil with context to human activities: a case study from the urban center

Abstract

Plastic pollution is an emerging issue faced worldwide owing to rapid urbanization and extensive use of plastic products. The objective of this study was to determine and highlight the spatial distribution of microplastics (MPs) in the top soils of different land use types of an urbanized city, i.e., Lahore, Pakistan, influenced by different human activities. Soil samples (n = 40) were collected from eight different land use groups including agricultural areas, drains, dumping sites, industrial areas, lawns, parks, roadsides, and wastelands to represent the influence of corresponding human actions. After cleaning the samples through wet peroxide digestion and density separation, MPs were identified under a stereomicroscope. The range of MPs in top soils within Lahore district varied from 1750 to 12,200 MPs/kg with an average of 4483 ± 2315 MPs/kg. The highest concentration of MPs was present in the parks while the lowest numbers of MPs were enumerated in soil from dumping sites. About 99% of the identified MPs particles were fibers, sheets, and fragments in shape while foams and beads accounted for the rest. Moreover, among the size ranges, the large size MPs (300-5000 μm) were found in the majority (41.16%) followed by the fine size MPs (50-150 μm; 30.67%) and medium size MPs (150-300 μm; 28.17%). The current level of MPs pollution attracts the attention of researchers for a more comprehensive investigation in the future. It also incites the policy-makers to implement the regulations to prevent plastic pollution and its environmental implications.

Keywords: Human activities; Land use; Microplastics; Plastic pollution; Top soil.