Seasonal variation of airborne ragweed (Ambrosia artemisiifolia L.) pollen in Zagreb, Croatia

Abstract

Previous research indicated that airborne ragweed pollen concentrations may be influenced by weather-related factors. Therefore, the object of this work was to examine the variation in daily pollen concentrations during four ragweed pollen seasons (2006–2009) in the highly urban area of Zagreb. Ragweed pollen grains were collected using a Burkard volumetric sampler (N45°49′55″, E15°58′54″). Meteorological data (maximum, minimum and mean temperatures, relative humidity, wind speed, precipitation, atmospheric pressure and irradiance) were related to daily pollen counts during the ragweed pollen season. The ragweed pollen season started around late July in 2007 and 2009, while it started on 15 August in 2006, the year characterized by a cold spring. However, the start dates of the pollen seasons were not related to the accumulation of thermal units. Maximum daily concentration of 363 grains m−3 was detected on 27 August 2008. Total airborne pollen concentrations ranged from 1188 grains m−3 in 2007 to 4384 grains m−3 in the following year, whereas the duration of ragweed pollen season varied from 50 days in 2008 to 72 days in 2007. The peak of the ragweed pollen season varied from 21 days in 2007 to 36 days in 2009 for airborne pollen concentrations ≥20 grains m−3 and from 1 day in 2007 to 20 days in 2008 for airborne pollen concentrations >80 grains m−3. Airborne pollen levels were affected by weather parameters such as temperature, sunshine, relative humidity, precipitation and wind speed in some ragweed pollen seasons in Zagreb, but these responses were inconsistent over the entire investigated period. Our study showed that large year-to-year variations in atmospheric pollen concentrations in Zagreb could not be consistently related to any of the analysed weather parameters.