Contribution of fungal spores to particulate matter in a tropical rainforest

The polyols arabitol and mannitol, recently proposed as source tracers for fungal spores, were used in this study to estimate fungal contributions to atmospheric aerosol. Airborne particulate matter (PM_2.5 and PM₁₀) was collected at Jianfengling Mountain, a tropical rainforest on Hainan Island situated off the south China coast, during spring and analyzed for arabitol and mannitol by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The average concentrations of arabitol and mannitol exhibited high values with averages of 7.0 and 16.0  ng m ^{− 3} respectively in PM_2.5 and 44.0 and 71.0 ng m ^{− 3} in PM₁₀. The two tracers correlated well with each other, especially in the coarse mode aerosol (PM_{2.5 − 10}), indicating they were mainly associated with coarse aerosol particles and had common sources. Arabitol and mannitol in PM₁₀ showed significant positive correlations with relative humidity, as well as positive correlations with average temperature, suggesting a wet emissions mechanism of biogenic aerosol in the form of fungal spores. We made estimations of the contribution of fungal spores to ambient PM mass and to organic carbon, based on the observed ambient concentrations of these two tracers. The relative contributions of fungal spores to the PM₁₀ mass were estimated to range from 1.6 to 18.2%, with a rather high mean value of 7.9%, and the contribution of fungal spores to organic carbon in PM₁₀ ranged from 4.64 to 26.1%, with a mean value of 12.1%, implying that biological processes are important sources of atmospheric aerosol.