Risk assessment of microplastics contamination in soil and leachate from different ages of landfill

Landfills were used for the disposal of waste materials, but they could contribute to microplastic (MP) pollution. MPs waste had been released in landfills into the surrounding environment, contaminating soil and leachate collection pond. Although there were many reports that MPs could generate in leachate and soil samples from the landfill, it exists many blanks for the evolution of physical and chemical characteristics of MPs with different landfill age. In order to address the question of changing in the abundances and characteristics of MPs in different ages of landfill as potential sources of contamination and the efficacy of existing landfill treatment processes, one landfill location site from The Waste Management Center of Nonthaburi Provincial Administrative Organization was chosen for this research study. A total of 3 closed municipal solid waste landfills (The 1st landfill D closed Year 2006, the 2nd landfill G closed Year 2008 and the 3rd landfill F closed Year 2009) and water & leachates (leachate B, leachate D, leachate collection pond, influent and effluent) were chosen as research sampling points. The maximum and minimum size of MPs had been defined between 16 - 5,000 µm. Six main different types of plastics (PP, PA, PE, PS, Acrylate, EPDM) were identified in the soil samples with calculated concentration ranging from 30.57 piece/kg. to 17,412.42 piece/kg. In total landfill D was the highest concentration 21,952 piece/kg and the lowest was landfill G 15,408 piece/kg. The size between 16-100 µm. and between 1,000-5,000 µm was the highest and lowest calculated concentration ranging of all landfills. Six main different types of plastics (PP, ABS, PE, PTF, PA, Acrylate) were identified in the leachate collection pond and leachate samples with calculated concentration ranging from 0.69 piece/L to 229.80 piece/L. In total, leachate D was the highest volume 283.14 piece/L, and the lowest volume was effluent 10.80 piece/Liter. The size between 16-100 µm. was the highest calculated concentration ranging and size between 300 – 5000 µm were not found of all leachate collection pond and leachates. The contamination status of soils in landfills based on contamination factor value were very high contamination of all landfills (landfill D 121.96, landfill F 119.47, landfill G 85.60). Leachate B and D were considerable contamination. Leachate collection pond, effluent and influent were low and moderate contamination respectively. Potential ecological risk of soil in landfill D and landfill F were very high risk (landfill D 907.05, landfill F 936.44) and landfill G was intermediate risk respectively. Leachate B was very high risk (29,664.13). Intermediate risk was observed in leachate D. Leachate collection pond, influent and effluent were low risk category. The results of our study provide preliminary evidence and validate that landfill was a potential source of MPs.