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SEM images of PM2.5
(a) SEM results of blank filter (magnified by 3000 times); (b) SEM results of SM sample (magnified by 3000 times), (c) SEM results of SM sample (magnified by 10 000 times); (d) SEM results of WM sample (magnified by 3000 times). a: flocculent particles; b: spherical particles; c: deformation of spherical particles; d: irregularly shaped agglomerate particles; e: elongated particles; f: spongy spherical particles
