Characterization of Airborne Microplastics in Coastal Environment

Abstract

Airborne microplastics (AMPs) are an emerging class of atmospheric pollutants, yet their occurrence, drivers, and health implications remain poorly constrained, particularly in coastal environments where terrestrial, marine, and atmospheric processes converge. This study provides a comparative assessment of AMPs in two contrasting coastal cities, Portsmouth (United Kingdom) and Lagos (Nigeria), with emphasis on their physicochemical properties, spatiotemporal variability, meteorological influences, and potential human exposure. A total of 96 air samples were collected across the UK (n = 64) and Nigeria (n = 32). Following quality assurance screening and selection of representative duplicate pairs, 48 samples (UK = 32; Nigeria = 16) were subjected to Micro-Raman spectroscopy and SEM-EDX analysis, generating 96 individual analytical measurements. A defined subsection of each filter corresponding to 2.7411% of the total filter area was systematically analysed. This proportion was not arbitrarily selected but was determined by the analytical grid adopted for Raman characterisation, which balanced particle recovery, spatial representativeness, and instrument time requirements. The same analytical area was applied consistently to all samples to ensure methodological comparability across sites, seasons, and particle fractionsAcross the four Portsmouth sampling sites, seasonal mean PM₁₀ concentrations ranged from 46.0 ± 19.6 particles/m³ in autumn to 70.0 ± 16.5 particles/m³ in summer, with intermediate concentrations observed in winter (47.0 ± 20.8 particles/m³) and spring (48.1 ± 7.2 particles/m³). For TSP, mean concentrations ranged from 27.2 ± 8.7 particles/m³ in autumn to 57.4 ± 16.1 particles/m³ in summer, with winter and spring concentrations of 51.2
± 23.0 and 40.8 ± 6.3 particles/m³, respectively. In Lagos, mean PM₁₀ concentrations were higher during the dry season (54.3 ± 32.7 particles/m³) than the wet season (32.4 ± 22.2 particles/m³). A similar pattern was observed for TSP, with concentrations of 29.3 ± 29.2 particles/m³ and 19.8 ± 18.5 particles/m³ during the dry and wet seasons, respectively. Fibres dominated (>70%), with polymethyl methacrylate (PMMA) as the leading polymer. Inhalable fractions (<10 µm) comprised up to 36% of the total, suggesting potential respiratory deposition. Spatial heterogeneity was marked: in Portsmouth, industrial and coastal sites recorded the highest abundances, while in Lagos, residential, industrial, and coastal sites were dominant hotspots. Seasonal peaks were observed in Portsmouth during summer and winter, and in Lagos during the dry season, consistent with site-specific meteorological patterns and emission sources. Although body weight normalised inhalation exposure estimates were low (<0.3 particles/kg/day), the comparative burden indicators showed spatial and seasonal variation in airborne microplastic occurrence, with higher relative values observed in some Lagos samples. These findings provide one of the first comparative datasets from temperate and tropical coastal cities, demonstrating that airborne microplastics are present within inhalable particle fractions and are influenced by anthropogenic activity, local environmental conditions, and coastal meteorology. The results support the need for further standardised monitoring and exposure focused research on airborne microplastics in coastal urban environments.

Date of Award	18 Jun 2026
Original language	English
Awarding Institution	University of Portsmouth
Supervisor	James Darling (Supervisor), Olusegun Fawole (Supervisor) & Fay Couceiro (Supervisor)