Comparative Characterization of Atmospheric Bioaerosols in the Yangtze River Delta and the Tibetan Plateau

Bioaerosols are an important component of atmospheric particulate matter and include a wide range of biological materials such as bacteria, fungal spores, pollen, and biological fragments, originating from sources including vegetation, soil, water surfaces, and human activities. They play a key role in air quality, climate processes, and ecosystem functioning. While bioaerosol sources and properties are expected to differ markedly between polluted urban regions and remote background environments, direct comparative observational evidence remains limited.In this study, we present a comparative characterization of bioaerosols under contrasting atmospheric conditions in eastern China and the Tibetan Plateau (TP), using real-time measurements from a Wideband Integrated Bioaerosol Sensor (WIBS). Field observations were conducted at an urban site in the Yangtze River Delta (YRD), strongly influenced by anthropogenic emissions, and at a high-altitude background site on the TP, representing a minimally disturbed environment. Particle-resolved fluorescence signals, optical size, and number concentrations were analyzed to examine regional differences in bioaerosol abundance and properties. In addition, unsupervised clustering methods were applied to classify bioaerosol particles based on their optical and fluorescence characteristics.Clear contrasts in bioaerosol behavior were observed between the two regions. The YRD site exhibited substantially higher bioaerosol concentrations and pronounced diurnal variability, closely associated with pollution periods and urban atmospheric dynamics. In contrast, bioaerosols observed on the TP were characterized by lower concentrations and distinct size distributions, reflecting cleaner background conditions. Clustering results further indicate differences in dominant bioaerosol types: bioaerosols in the YRD were largely associated with anthropogenic-influenced biological particles, whereas the TP showed fluorescence types more closely linked to natural sources such as vegetation and long-range atmospheric transport.Overall, this study demonstrates how environmental context strongly influences bioaerosol abundance, composition, and temporal behavior. By combining real-time fluorescence measurements with data-driven classification, this work provides a coherent framework for comparing bioaerosols across contrasting atmospheric environments and contributes to a broader understanding of bioaerosol variability within the Earth system.