Sources and distribution of atmospheric microplastics in Northwest China river valleys via land use

Suspended atmospheric microplastics (SAMPs) present a direct inhalation risk in arid regions, however, their pollution patterns and emission drivers in the river valleys of Northwest China poorly understood and require urgent investigation. This study quantifies SAMPs across eight land use types in Lanzhou during autumn 2024. Key results demonstrate: (1) Mean SAMPs abundance reached 4.5 n/m³, peaking in residential areas (9.68 n/m³); (2) SAMPs of 25-50 μm dominated (48.21 %), primarily as fragments (71.18 %); (3) Polymer analysis revealed 15 distinct types, among which acrylate copolymer (21.43 %), polyethylene (18.75 %), and polyester (10.71 %) exhibited variability dependent on land use; (4) Ecological risk assessment indicated generally low risk levels (RI<150), driven mainly by polymer toxicity characteristics rather than absolute abundance; (5) Trajectory modeling identified dual sources: local emissions and long-range transport via northwestern air masses. These findings establish an active sampling and LDIR analytical baseline for autumn SAMPs in Lanzhou, underscoring the urgent need for enhanced regional particulate monitoring and source control in arid environments.