Aerobiologia 19: 21–27, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. 21 Airborne pollen concentration in the region of Braga, Portugal, and its relationship with meteorological parameters Helena Ribeiro 1 , M´ ario Cunha 2 & Ilda Abreu 1,∗ 1 Department of Botany, Faculty of Science, University of Porto. Rua Campo Alegre, 1191 4150Porto. Portugal; 2 Section of Agrarian Sciences, Faculty of Sciences of the University of Porto (E-mail: mcunha@mail.icav.up.pt) ( ∗ Author for correspondence: E-mail: ianoronh@fc.up.pt) Received 14 January 2002; accepted 16 September 2002 Key words: aerobiology, diurnal variation, meteorological parameters, northern Portugal, pollen grains Abstract The variation in airborne pollen concentration of the Braga region (Portugal) was studied in springtime, during the flowering of Vitis vinifera. The data set was obtained for two consecutive years (1999 and 2000), using a Cour- type sampler. During this period, thirty-six taxa were observed in a total of 3,200 pollen grains m −3 of air (CPA). The main pollen types observed were Olea, Poaceae and Castanea, representing 74% of the pollen spectrum. The airborne pollen concentration (CPA) was significantly correlated with certain meteorological parameters. Pollen concentration was positively correlated with temperature and wind direction (East and Northeast) and negatively correlated with rainfall and number of rainy days. 1. Introduction The air contains an enormous number of particles of various origins, shapes and sizes found in suspen- sion, constituting atmosphere aerosol. The atmosphere concentration of different pollen types varies enorm- ously from one country to another, in regions of the same country, and even among different cities, because pollen emissions depend on vegetation and environmental conditions. Generally, meteorological factors have an important influence on this airborne concentration. Aerial transport may have an important impact on earth life, which increases with economic expansion around the world (Wilkening et al., 2000). Compared with other European countries, very few aerobiological studies have been conducted in Portugal. The important ones, in Évora, are by Pinto- da-Silva in 1950–1960, Paiva and Leitão (interrup- tedly since 1978) in Coimbra, Porto and Lisboa and Brandão and Lopes (1990, 1992, 1995). No aero- biological studies have been performed in the Braga region. The study area corresponds to the Braga district, in the Minho province situated at the Northwest corner of Portugal, 50Km North of Porto. The river Minho, which has given its name to the region, is the natural border between the provinces of Minho in Portugal and Galicia in Spain. This district has an area of 187 km 2 , being surrounded by the mountains Bom Jesus, Sameiro, Falperra and Parque Natural do Gerês. Bounded to the North by the district of Viana do Castelo, to the East by that of Vila Real, to the South by that of Oporto and to the West by the Atlantic Ocean, the Braga region has a privileged geographical situation. Portugal is part of the Atlantic European area, affected by the Gulf Stream with a cold season (Paiva and Leitão, 1989). The climate of Braga is affected by maritime influence, being described as rainy with low temperatures in winter and low humidity and high temperatures in summer. The most frequent winds are from the Northwest with an average annual mean temperature of 14 ◦ C and a mean rain- fall of 126.2 mm/year with a total maximum of 1,514.9 mm/year. Human and animal influences mostly determine Portugal’s vegetation, apart from some mountains in the North and some maritime fringe areas. The