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Elevational variations in atmospheric microplastics and surface-adsorbed heavy metals in roadside and non-roadside areas in Iligan City, Philippines
Summary
Researchers measured atmospheric microplastic concentrations at roadside and non-roadside sites in Iligan City, Philippines at ground and elevated heights, finding higher levels near traffic — dominated by polyethylene and polypropylene fibers — with scanning electron microscopy detecting toxic metals including lead, mercury, and nickel adsorbed onto particle surfaces, indicating vehicles as a key contamination source.
While microplastic contamination in aquatic and terrestrial systems has been widely documented, atmospheric microplastics (AMPs) remain less understood, particularly regarding their sources, vertical behavior, and associated risks. This study examined the abundance, morphology, polymer types, and surface-adsorbed metals of AMPs in Iligan City, Philippines, comparing roadside and non-roadside environments at ground and elevated heights. Suspended particles were collected using a respirable dust sampler (1.4 m³/min) and filtered through Whatman GF/C paper. Analytical techniques included microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). AMP concentrations were higher in roadside (0.09 ± 0.04 MP/m³) than in non-roadside areas (0.08 ± 0.03 MP/m³), with the highest levels in elevated roadside samples (0.11 ± 0.04 MP/m³). Although the roadside–non-roadside difference was not statistically significant (p = 0.05772), this borderline value suggests a trend of increased MPs in traffic-influenced areas. Fibers dominated in shape, with black and transparent colors most common. Identified polymers included high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). SEM-EDX detected toxic metals such as lead (Pb), mercury (Hg), and nickel (Ni), particularly in elevated roadside samples, indicating contributions from vehicular emissions and resuspended urban dust. This study highlights the vertical and spatial variability of AMPs and their role as carriers of heavy metals, offering important insights into their environmental behavior and potential health implications in urban Southeast Asian settings.