No abstract

To improve the current understanding of the ammonia distribution in the major urban area of Chile, measurements of atmospheric NH 3 were collected in Santiago during three sampling periods (25 April to 27 May, 11 to 26 June and 27 June to 31 July 2008). Additionally, air quality and meteorological data as well as NH 4 + , NO 3 -, SO 4 = and Ca +2 concentrations in fine particles were collected during the same period. NH 3 concentrations for the different sites in the three sampling periods varied from 7.7 ± 2.0 µg/m 3 to 19.8 ± 2.1 µg/m 3 . The results of one-way ANOVA and cluster analysis suggest that were no significant differences between the three sampling periods, but significant differences in NH 3 concentrations were detected between the sampling sites. Furthermore, two clusters were found with a pronounced difference between sampling sites located in the eastern part of the city and those located in the western part of the city. The results suggest that the distribution of ammonia in the western part of the city is due to the emissions of ammonia by agricultural areas, wetlands and the large sewage treatment plants, while in the eastern part of the city, ammonia emissions are governed by vehicular emissions. Fine particles (PM 2.5 ) chemical speciation showed NH 4 + /SO 4 = and NO 3 -/SO 4 = molar-equivalents ratios of 5.7 ± 0.3 and 1.8 ± 0.1, respectively. The results show that during the sampling period, complete neutralisation of H 2 SO 4 and HNO 3 occurred in the presence of excess of NH 4 + and NH 3 . Therefore, the atmosphere of Santiago can be considered to be ammonia-rich in the gas phase. Abundant NH 3 was present to neutralise the acid components, such as H 2 SO 4 and HNO 3 , and to form fine particulate ammonium salts, such as (NH 4 ) 2 SO 4 , NH 4 NO 3 and others. Relatively high humidity and low temperatures in the cold season support the formation of particulate ammonium nitrate.

Pollen is one of the primary causes of allergic rhinoconjunctivitis in urban centers. In the present study, the concentrations of 39 different pollens in the Santiago de Chile metropolitan area over the period 2009–2013 are characterized. The pollen was monitored daily using Burkard volumetric equipment. The contribution of each type of pollen and the corresponding time trends are evaluated. The concentrations of the pollens are compared with the established threshold levels for the protection of human health. The results show that the total amount of pollen grains originating from trees, grasses, weeds and indeterminate sources throughout the period of the study was 258,496 grains m-3, with an annual average of 51,699 ± 3,906 grains m-3 year-1. The primary source of pollen is Platanus orientalis, which produces 61.8% of the analyzed pollen. Grass pollen is the third primary component of the analyzed pollen, with a contribution of 5.82%. Among the weeds, the presence of Urticacea (3.74%) is remarkable. The pollination pattern of the trees is monophasic, and the grasses have a biphasic pattern. The trends indicate that the total pollen and tree pollen do not present a time trend that is statistically significant throughout the period of the study, whereas the grass pollen and weed pollen concentrations in the environment present a statistically significant decreasing trend. The cause of this decrease is unclear. The pollen load has doubled over the past decade. When the observed concentrations of the pollens were compared with the corresponding threshold levels, the results indicated that over the period of the study, the pollen concentrations were at moderate, high and very high levels for an average of 293 days per year. Systematic counts of the pollen grains are an essential method for diagnosing and treating patients with pollinosis and for developing forestation and urban planning strategies.