Application of a stable carbon isotope for identifying Broussonetia papyrifera pollen

The objective of this study was to investigate whether δ¹³C values can be used to identify pollen specie in the atmosphere. A Burkard 7-day recording volumetric spore trap was used to collected pollens in the atmosphere in Tainan City, Taiwan, from January 2 to December 28, 2006, and a light microscope was used to identify the pollen species and concentrations. A Burkard cyclone sampler was used to collect particulate matter and an elemental analyzer with an isotope ratio mass spectrometer was used to analyze the δ¹³C values. Our data showed that the predominate pollen specie in the atmosphere was Broussonetia papyrifera pollen and that the annual average concentration was 27 grains/m³ (pollen season, 36; nonpollen season, 9 grains/m³). The average δ¹³C value was - 26.19‰ for particulate matter in the atmosphere (pollen season, - 26.00‰; nonpollen season, - 26.28‰). No significant association was observed between δ¹³C values and Broussonetia papyrifera pollen concentrations. However, the δ¹³C value in the atmosphere was associated with the levels of Broussonetia papyrifera pollen among the samples with a diameter of particulate matter smaller than 10 μm at a level lower than 40 μg/m³. In addition, the relative contribution of Broussonetia papyrifera pollen to the carbon in the atmosphere using a two end-member mixing models was found to be associated with the Broussonetia papyrifera pollen concentration. In summary, our study suggested that δ¹³C values can be applied in the assessment of Broussonetia papyrifera pollen specie under specific conditions in the atmosphere.