Urban airborne pollen in a semiarid environment

The present investigation was conducted to determine the pollen types and their quantities in the atmosphere of Obregn City (a semiarid region) and establish the relationship with meteorological parameters in 2008 and 2011. A bimodal pattern with peaks in dry warm (spring) and late rainy (autumn) seasons was observed. The highest monthly pollen indexes were observed in October 2008 and September 2011. Precipitation in 2008 was 2.6 times higher than in 2011, beginning in June in both years, and ending in November (2008) and September (2011). Main pollen types were Poaceae, Chenopodiaceae/Amaranthaceae, Asteraceae and Parkinsonia (the latter was dominant in the dry warm season). Statistical correlations (Spearman's rank-order correlation p < 0.05) with meteorological parameters were performed. In both sampling years, relative humidity caused adverse effects on the atmospheric pollen content, while temperature, solar radiation and wind speed in the dry season were associated with increased pollen indexes. Compared to other studies of semiarid areas, the pollen index at Obregn is low, which is attributed to a relatively high humidity and to the large area of grain crops surrounding the city.