Phytoedaphic Interactions and Distribution of Heavy Metals and Microplastics in the Vicinity of an Open Dump

Abstract

Open dumping is a global issue exacerbated by the increasing accumulation of waste and inadequate waste management practices. Lebanon, notorious for its large-scale waste mismanagement, is home to one of the largest open dumps, the Saida open dump. This site has a unique history, which contributes to the environmental quality and contamination levels of surrounding soil and vegetation. This study aims to investigate the relationship between heavy metals and microplastics in the soil and changes in plant community diversity at varying depths and distances in and from the open dump. While the interactions and distribution of heavy metals in soils and plants near open dumps have been extensively studied globally, research on microplastics in this context is less prevalent. A total of 8 soil samples were collected within the open dump, in addition to 12 soil and 16 plant samples from the vicinity of the open dump in a spatial gradient. The soil was found to be alkaline with a pH range of 7-8 and exhibited varying levels of contamination. Significant pollution by nickel and lead was observed, with higher concentrations detected greater soil depths and farther from the open dump. Microplastic analysis revealed a similar distribution pattern in both gradients, predominantly composed of fibers and fragments. The open dump exhibited little impact in terms of heavy metal and microplastic contamination on its vicinity. The selected plant species, Dittrichia viscosa, Phragmites australis, and Ricinus communis, demonstrated acceptable levels of heavy metal accumulation and resilience in contaminated soils. Higher species diversity was noted in older, more stabilized areas. Several measures are recommended for further research, including the assessment of heavy metal and microplastic levels in sediments and waterbodies near the open dump, as well as longitudinal monitoring of plant-soil interactions.