Comparison between daily airborne arboreal and non- arboreal pollen patterns in Mar del Plata (Argentina)

Intradiurnal variation of arboreal (AP) and non - arboreal (NAP) pollen are described using the data obtained with a Burkard trap in Mar del Plata City. The daily trend followed broadly the typical shape described for the whole pollen spectrum with high concentrations during daylight hours and low concentrations in the night. In comparison, AP maximum concentration is reached shortly afterwards its NAP counterpart, between 10 and 12:00 h, while the minimum occur at 18:00 h with a slight increase at 22:00 h. The daily mean arboreal pollen pattern is also much more irregular than that of the non - arboreal fraction of the spectrum because it is represented by a great number of pollen contributors. From a physical point of view, dispersion is a process mainly governed by mechanical forces and atmospheric stability, therefore the rhythm of daily pollen concentration should be the same for AP and NAP. Differences found could be explained based on the characteristics of the pollen source as distribution, density and height. Herbaceous vegetation has a homogeneous distribution, a more or less constant density and low height of pollen release, which are characteristics of a diffuse source. Trees often grow in groups, and its pollen is released some metres high, so they could be considered as a point source. Interaction between this characteristics and wind speed and direction, led to hourly changes in the arboreal pattern while non - arboreal pattern remains relatively invariable.