Comparative assessment of an analytical framework for atmospheric suspended microplastics: Filter suitability,...

Monitoring atmospheric suspended microplastics (ASMPs) is essential for understanding their sources, transport, and fate, yet the lack of standardized analytical methods limits data comparability. This study comparatively assessed key components of an analytical framework for ASMPs, focusing on filter suitability, pretreatment, and analysis-area effects. Five filter types were evaluated under laboratory and field conditions. Quartz, cellulose nitrate, and glass fiber filters exhibited negative peaks in specific FTIR wavenumber ranges, reducing spectral match quality and detection performance. Among the tested filters and under the conditions evaluated in this study, stainless steel (SS) filters showed the most consistent analytical performance. Direct partial analysis of 47 mm filters tended to overestimate ASMP abundance, whereas direct whole-filter analysis was excessively time-consuming. To address this limitation, a digestion-and-rinsing method was applied to concentrate particles collected on 47 mm filters onto 13 mm SS filters for whole-filter analysis. This method achieved recovery rates exceeding 80% across all tested polymer types and particle sizes under controlled laboratory tests. When applied to field samples collected at a single coastal site under relatively stable atmospheric conditions, concentrated whole-filter analysis of 13 mm filters produced abundance and size distributions comparable to those obtained by direct whole-filter analysis of 47 mm filters, while substantially reducing total analysis time. Within the scope of conditions evaluated in this study, the results suggest that the combined use of SS filters, digestion-and-rinsing pretreatment, and the concentrated whole-filter approach may provide a useful methodological basis for future efforts toward improving consistency and standardization in ASMP analysis.