Risk assessment and influence of microplastics on mangrove forest soil: Sandwip Island, Chittagong, Bangladesh

Microplastics (MPs) originating from diverse sources considerably contribute to pollution, posing a considerable environmental hazard by invading natural ecosystems, both terrestrial and aquatic, hence undermining soil quality and overall ecosystem health. Despite the detrimental impacts of MPs on ecosystems, there is a lack of research concerning soil MPs in mangrove forests, particularly on Sandwip Island. This study aimed to examine the abundance, characterization, potential dangers, and effects of MPs on soil physicochemical properties. Twenty soil samples have been extracted from the mangrove forest of Sandwip Island, located on the eastern coast of the Bay of Bengal, for the examination of MPs. The abundance of MPs ranges from 610 to 2300 items/kg (mean 1455 ± 845 items/kg). Different forms of MPs have been identified based on their shapes, including fibers (21%), lines (26%), films (17%), and foam (36%). Among the investigated samples, MPs were predominantly white and transparent and ranged in size from 0.5 to 5 mm. By using ATR-FTIR, four polymers were determined, including polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyamide (PA), among which PE is predominant, accounting for 46%. The presence of MPs was found to be positively correlated with soil pH, organic carbon, phosphorus (P), and bulk density, and negatively correlated with electrical conductivity (EC), nitrogen (N), potassium (K), sulfur (S), and porosity. Pollution indices (PRI, Igeo, PHI, and PLI) depict an assortment of pollution levels. According to the polymeric hazard index (PHI) and geo-accumulation index (Igeo), the area was identified as hazard grades III and II. However, the pollution load index (PLI) and ecological risk index (PRI) implied pollution and risk level I, respectively. This research provides new insights into the assessment of MP pollution in mangrove soil, highlighting the importance of eco-environmental safety and evaluating susceptibility; policymakers can use these findings to establish effective management and conservation strategies for mangrove ecosystems.