Aeropalynological assessment of Beja (South Portugal)

Abstract

Introduction: The city of Beja in the Baixo Alentejo, Southern Portugal has not been previously aerobiologically studied. Aim: To study and characterise the airborne pollen concentration in Beja for a period of two years. Material and methods: The atmosphere of Beja was studied aerobiologically from January 2003 to January 2005, using a Hirst volumetric sporetrap placed 13 m above ground level. Results: Sixty -two pollen types were identified, 22 of which were present for at least 50 days, in at least one of the years. The mean annual pollen concentration was 135 pollen grains/m3 for 2003 and 85 pollen grains /m3 for 2004. Most of the pollen (76%) was from four types – in decreasing order: Poaceae, Quercus spp., Olea europaea, and Cupressaceae. May was the month with the highest mean pollen concentration, with mean values of 1069 pollen grains /m3 in 2003 and 466 pollen grains /m3 in 2004, and a daily pollen peak of 2485 pollen grains /m3 for Poaceae in 2003, and 1198 pollen grains /m3 for Olea europaea in 2004. The ornamental flora of the city was recorded, and a total of 6633 ornamental trees belonging to 58 species were identified. Conclusions: This first aerobiological assessment of Beja allowed the draft of a preliminary pollen calendar. The differences between the two years were mainly due to the Poaceae pollen type, which had a threefold higher value in 2003, compared to 2004, probably due to the more intense April rains in 2003 that favoured the growth and pollen production of grasses and other herbaecea. In 2003, there was also a statistically significant correlation between the number of ornamental trees and their respective airborne pollen in the air of the city. Key -words: