The effect of sampling height on grass pollen concentrations in different urban environments in the Helsinki Metropolitan Area, Finland

Abstract

Introduction It is important to study potential differences in pollen concentrations between sampling heights because of diverse outdoor and indoor activity of humans (exposure) at different height levels in urban environments. Previous studies have investigated the effect of height on pollen concentrations based on just one or a few sampling points. We studied the effect of sampling height on grass pollen concentrations in several urban environments with different levels of urbanity. Methods This study was conducted in the Helsinki Metropolitan Area, Finland, in 2013 during the pollen season of grasses. Pollen grains were monitored in eight different points in the morning and afternoon. Rotorod-type samplers were attached on sampling poles at the heights of 1.5 meters and 4 meters. Results Grass pollen concentrations were on average higher at the height of 1.5 meters (Helsinki mean 5.24 grains / m 3 ; Espoo mean 75.71 grains / m 3) compared to the height of 4 meters (Helsinki mean 3.84 grains / m 3 ; Espoo mean 37.42 grains / m 3) with a difference of 1.40 grains / m 3 (95% CI-0.21 to 3.01) in Helsinki, and 38.29 grains / m 3 (7.52 to 69.07) in Espoo, although not always statistically significant. This was detected both in the morning and in the afternoon. However, in the most urban sites the levels were lower at 1.5 meters compared to 4 meters, whereas in the least urban sites the concentrations were higher at 1.5 meters.

Atmospheric transport reveals grass pollen dispersion distances

“…This is further corroborated by a study where it was demonstrated that there is no significant difference in Poaceae pollen concentrations between sampling at ground level in contrast to altitude of 16 m (Fernández-Rodríguez et al, 2014b). Due to this and the special circumstances a lower sampling height is fully justified as stated by Hugg et al (2020). The Corine Land Cover 2018 classifies the Lakeside area as a mix between non-irrigated arable land, pastures and complex cultivation patterns, with the surroundings (< 2 km) being mainly comprised of well-maintained grass areas, lakes, agricultural fields, and pastures.…”

“…The height of the pollen sampler has been shown to play a role in the interpretation of the collected pollen analysis and results (Rojo et al, 2019). The reasoning is that sampling should be done elevated from the terrain, with a typical recommendation of about 10 m, while lower elevations can be justified based on the circumstance (Hugg et al, 2020). In our particular case the local circumstance is a flat area with much less atmospheric turbulence compared to an urban area.…”

Type and size of pollen collected by Tetragonula laeviceps at various altitudes

“…The studies were conducted outside Indonesia (Azmi et al 2015;Bisui et al 2019). Studies on pollen diversity collected by honey bees at different altitudes have been done outside Banyumas District, Central Java, Indonesia (Jayuli et al 2018;Pratama et al 2018;Hugg et al 2020). There was no study about pollen diversity collected by T. laeviceps from different altitudes in the Banyumas District, especially on pollen type and size.…”

“…Determining the potential and cultivation efforts of T. laeviceps bees is necessary to investigate the types of pollen collected by stingless bees at various altitudes (Hugg et al 2020). It is also essential to measure its diameter to determine the source of feed that supports productivity (Abbas and Sucianto 2020).…”