Investigating the amounts and distribution of microplastics in the surface soil around the landfill site of Tabriz city in 1401-1402

Abstract

Abstract Background: With the ever-increasing population and mismanagement of plastic waste, the world, including Iran, is witnessing a rise in waste quantities, particularly plastic waste. This is emerging as a significant threat to the environment. Landfilling remains a widely used method of waste disposal globally. However, no comprehensive study has yet been conducted in Tabriz to assess soil pollution from macro-, meso-, and microplastics around landfill areas. Therefore, given the importance of health and environmental considerations, this study aims to investigate the distribution of microplastics in the surface soil surrounding the landfill in Tabriz City. Methodology: This study was conducted in three stages. In the first stage, both quantitative and qualitative data on municipal solid waste generation in Tabriz were collected based on reports from the Waste Management Organization of the Municipality of Tabriz, along with field observations at the landfill site in northwestern Iran. In the second stage, the distribution of macro, meso, and microplastics in the soil around the landfill in Tabriz City was investigated. To determine their quantities, surface soil samples around the landfill were collected. For sampling from the landfill site, a composite sampling method was used. Samples were taken from the soil to a depth of 20 cm using a metal template with dimensions of 0.5m x 0.5m. The weight of each composite sample is about 2 kg. Sampling was conducted at regular intervals in the direction of the prevailing wind, against the prevailing wind, and in two directions perpendicular to the prevailing wind. A total of 22 samples were analyzed. To identify and assess microplastics, five main steps were taken: 1.Primary screening (for macro- and mesoplastics), 2. Separation based on density (using ZnCl2), 3. Acid digestion, 4. Screening and filtration, 5. Visual sorting. In the third stage of this study, the Raman spectroscopy method was used to determine the characteristics of microplastics in terms of the type of constituent polymers, and the SEM method was used in terms of the surface morphology of microplastics. Results: Findings revealed that although per capita waste generation in Tabriz has decreased in recent years, the current system for managing and landfilling plastic waste remains inadequate. The mean abundance of macro, meso, and microplastics from the surface to a depth of 20 cm in the soil of the landfill site is 2.95±12.62, 1.24±4.79, and 470±188 Item/ kg(dw) was obtained. The statistical results also showed that the prevailing wind in the region did not have a significant effect on the dispersion and distribution of microplastics. The most abundant microplastics in the soil of the studied area belonged to pieces and film-shaped particles, respectively, and the most abundant color was white. Five types of polymers were identified in the soil around the landfill site, the highest and lowest frequencies of which were PS and PA with 40 and 5%, respectively. Conclusion: Despite the decrease in total waste, the percentage of plastic waste entering Tabriz's waste landfill has been increasing in recent years (1384-1402). Key contributors to soil plastic pollution include excessive plastic consumption (especially single-use plastics), rapid lifestyle changes, improper burial practices, and neglect of the waste management hierarchy. Therefore, promoting sustainable lifestyles, minimizing the production and use of plastic, especially packaging materials, and rigorously implementing the waste management hierarchy (avoidance, reduction, segregation, recycling, processing, and proper disposal) are strongly recommended to mitigate environmental impacts, particularly on soil and water resources. Keywords: plastic, microplastic, soil, landfill, waste.