High temporal resolution of airborne Ambrosia pollen measurements above the source reveals emission characteristics

The aim of this study was to setup a field experiment that will collect suitable data for parameterizing the release of Ambrosia pollen. The study took place on the Pannonian plain during three flowering seasons: 2014, 2015 and 2016. The sampling of airborne pollen was performed using volumetric spore traps at 0.5 m and 5 m above the canopy level of a strong homogenous Ambrosia artemisiifolia L. field (10 m x 10 m) in three temporal resolutions: 1 h, 7.5 min and 1.07 min. This high temporal resolution revealed characteristics that were hitherto unknown. Pollen production per day was estimated to range from 6.38 billion to 770 billion pollen grains for the whole experimental field. Measurements of meteorological parameters included: temperature, relative humidity, solar radiation, precipitation, wind speed and wind direction. Weak correlations between pollen concentration and meteorological parameters were obtained, indicating nonlinear relationships among them. The distribution of pollen concentration with respect to meteorological parameters showed that high pollen concentrations coincide with temperature in the interval 20-24 degrees C, and that relative humidity of around 95% can delay or even switch off the emission, while the turbulent kinetic energy of a wind less than 0.1 m(2) s(-2) is sufficient for lifting the pollen into the air. The test of the new model for Ambrosia pollen emission processes showed a strong correlation between measured and modeled data when the estimated emission capacity for the field was in the range of 45-75 billion pollen grains per day.