Application of a stable carbon isotope for identifying Broussonetia papyrifera pollen.

The objective of this study was to investigate whether δC 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 δC 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/m (pollen season, 36; nonpollen season, 9 grains/m). The average δC value was - 26.19‰ for particulate matter in the atmosphere (pollen season, - 26.00‰; nonpollen season, - 26.28‰). No significant association was observed between δC values and Broussonetia papyrifera pollen concentrations. However, the δC 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/m. 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 δC values can be applied in the assessment of Broussonetia papyrifera pollen specie under specific conditions in the atmosphere.