CLUSTER COMPOSITION OF POLLEN PARTICLES OF ANEMOPHILIC PLANTS ENTERING ATMOSPHERE

A study is made on pollen emission into atmosphere of 21 species of anemophilous plants ( Betula divaricata Ledeb., Betula costata Trautv., Betula davurica Pall., Betula fruticosa Pall., Ulmus japonica (Rehd.)Sarg., Salix acutifolia Willd., Salix cinerea L., Salix purpurea L., Salix rosmarinifolia L., Alnus glutinosa (L.) Gaertn., Poa alpina L., Arrhenatherum elatius (L.) J. Presl & C. Presl, Briza maxima L., Deschampsia cespitosa (L.) P. Beauv., Urtica urens L., Carex altaica (Gorodkov) V.I. Krecz., Carex pallescens L., Carex flacca Schreb., Carex vesicaria L., Carex diluta M. Bieb., Plantago lanceolata L.), exposed by the Central Siberian Botanical Garden, SB RAS. These plants are widely spread over the territory of the Russian Federation and produce great amounts of allergenic pollen. The proportion of clusters of two or more pollen grains from the total number of pollen particles entering the atmosphere during the flowering periods of these plant species is estimated. It was shown that such clusters in significant quantities were formed in all series of experiments. At the same time, the proportion of pollen grains in their composition could reach 95% of the total number of pollen grains entering the atmosphere.

Estimation of Chilling and Heat Accumulation Periods Based on the Timing of Olive Pollination

Research Highlights: This paper compares the thermal requirements in three different olive-growing areas in the Mediterranean region (Toledo, central Spain; Lecce, southeastern Italy; Chaal, central Tunisia). A statistical method using a partial least square regression for daily temperatures has been applied to study the chilling and heat requirements over a continuous period. Background and Objectives: The olive is one of the main causes of pollen allergy for the population of Mediterranean cities. The physiological processes of the reproductive cycle that governs pollen emission are associated with temperature, and thermal requirements strongly regulate the different phases of the plant’s life cycle. However, the point when several specific processes occur—Such as the phases within the dormancy period—Is unclear, and the transition between endodormancy and ecodormancy is not easily distinguishable from an empirical point of view. This work focuses on defining the thermal accumulation periods related to the temperature balance needed to meet the chilling and heat requirements for the metabolic activation and budbreak in olive trees. Results and Conclusions: Thermal accumulation patterns in olive trees are strongly associated with the bioclimatic conditions of olive-growing areas, and the olive flowering start dates showed significant differences between the three studied stations. Our results show that the chilling requirements were fulfilled between late autumn and early winter, although the chilling accumulation period was more evident in the coldest and most continental bioclimatic areas (central Spain). The heat accumulation period (forcing period) was clearly defined and showed a close relationship with the timing of olive flowering. Heat requirements were therefore used to generate accurate forecasting models to predict the beginning of the olive bloom and subsequent olive pollen emission. A forecasting model considering both the chilling and heat requirements was generated in Toledo, where the estimated days displayed an error of 2.0 ± 1.8 days from the observed dates. For Lecce, the error was 2.7 ± 2.5 days and for Chaal, 4.2 ± 2.4 days.

Modelling and inference of maize pollen emission rate with a Lagrangian dispersal model using Monte Carlo method

This work explores the uncertainty of the inferred maize pollen emission rate using measurements and simulations of pollen dispersion at Grignon in France. Measurements were obtained via deposition of pollen on the ground in a canopy gap; simulations were conducted using the two-dimensional Lagrangian Stochastic Mechanistic mOdel for Pollen dispersion and deposition (SMOP). First, a quantitative evaluation of the model's performance was conducted using a global sensitivity analysis to analyse the convergence behaviour of the results and scatter diagrams. Then, a qualitative study was conducted to infer the pollen emission rate and calibrate the methodology against experimental data for several sets of variable values. The analysis showed that predicted and observed values were in good agreement and the calculated statistical indices were mostly within the range of acceptable model performance. Furthermore, it was revealed that the mean settling velocity and vertical leaf area index are the main variables affecting pollen deposition in the canopy gap. Finally, an estimated pollen emission rate was obtained according to a restricted setting, where the model studied includes no deposition on leaves, no resuspension and with horizontal pollen fluctuations either taken into account or not. The estimated pollen emission rate obtained was nearly identical to the measured quantity. In conclusion, the findings of the current study show that the described methodology could be an interesting approach for accurate prediction of maize pollen deposition and emission rates and may be appropriate for other pollen types.

Timely information on birch and grass pollen levels in Belgium

<p>Air pollution has tremendous effects on mortality and the quality of life. Air pollution is not restricted to anthropogenic contaminants only, since also natural sources (soils, lakes, marshes, vegetation, volcanoes, etc) may emit substantial amounts of unhealthy pollutants (VOCs, SO<sub>X</sub>, NO<sub>X</sub>, aerosols, etc). Releases of biogenic aerosols such as pollen affect the public health badly, putting additional distress on people already suffering from cardiovascular and respiratory diseases. In Belgium, ~10% of the people is estimated to suffer from allergies due to pollen released by the birch family trees and ~15% due to pollen emitted by grasses. In some European countries the prevalence is up to 40%.</p><p>To date, the only available airborne pollen level data in Belgium are retrieved by Sciensano at five stations that monitor off-line daily concentrations of grass and birch pollen among other species. Patients suffering from rhinitis have therefore no access to detailed real-time spatial information and warnings on forthcoming exposures.</p><p>Chemistry Transport Models (CTM) can both quantify as well as forecast the spatial and temporal distribution of airborne birch and grass pollen concentrations if accurate and updated maps of birch and grass pollen emission sources are available, and if the large inter-seasonal variability in emissions is considered.</p><p>Here we show the results of the modelled spatio-temporal distributions of grass and birch pollen over Brussels and other locations in Belgium using the CTM SILAM. This CTM is driven by ERA5 meteorological reanalysis data from ECMWF, an updated MACC-III birch tree fraction map, based on local information, and a grass pollen emission map showing the spatial distribution of the potential pollen sources. Pollen release is based on the temperature degree days approach. Inter-seasonal variability in birch pollen release was taken into account by using spaceborne MODIS vegetation activity (Gross Primary Productivity, GPP). For grass pollen this approach does not fit, therefore we use average temperature and precipitation of the previous year in a first approach.</p><p>SILAM modelled and observed time series of daily birch pollen levels of 50 birch pollen seasons at multiple sites in Belgium correlate well for the period 2008-2018 with an increased R² of up to ~50% compared to the reference run. What is more, SILAM is able to capture the allergy thresholds of 50 and 80 pollen grains m<sup>-</sup>³ exposure from the observations for birch trees. Grass pollen simulations are in progress.</p>

Ash pollen allergy and aerobiology

Background Allergy to ash pollen is common in some parts of Europe. Sensitization is overlooked if Oleaceae pollen allergens are not included in screening tests. Methods Between 1983 and 2007, sensitization to aeroallergens was systematically investigated using serological methods in 15-year-old school children (Immuno-CAP [carrier polymer] test). Samples from 1986 and 2006 were also tested using the immuno-solid-phase allergen chip (ISAC) assay. School children with sensitizations in 1986 were retested in 2010. Airborne pollen concentrations were determined by the Swiss pollen measuring network. Results Sensitization (>0.7 kU/l) to ash pollen (Fraxinus americana t15)—16.3% (102/627)—was more frequent than to birch pollen (Betula verrucosa t3): 15.3% (96/627). ISAC assays performed in children in 1986 and 2006 revealed higher molecular seroprevalence for nOle e 1 (15%; 15/100) compared to rBet v 1 (12%; 12/100). Followed-up subjects (age, 39) showed an increase in sensitizations to ash pollen. IgE levels to pollen from indigenous ash (Fraxinus excelsior t25) were higher than to pollen from American ash (Fraxinus americana t15). Low ash pollen emission levels were recorded at all measuring sites in Switzerland every 2–4 years. The infection of ashes by Chalara fraxinea resulted in increased emission of ash pollen. Conclusion Symptoms in individuals sensitized to ash pollen vary according to the pollen count and may be masked by pollen from other trees that flower at the same time of year. Sensitization to ash/Ole e 1 can be higher than to birch/Bet v 1. The determination of IgE to common ash (Fraxinus excelsior) is more sensitive than to American ash (Fraxinus americana). Ash dieback due to Chalara appears to increase pollen emission. Allergies to ash pollen can be significantly underestimated due to a failure to (correctly) identify them; they can also be masked by other pollen families (birch). Harmful organisms such as Chalara can intensify pollen emissions at least temporarily.

CLUSTER COMPOSITION OF POLLEN PARTICLES OF ATMOSPHERE UPON BLOOMING OF ANEMOPHILOUS PLANTS

A study is made on pollen emission into atmosphere of 12 species of anemophilous plants (Betula fusca Pall. ex Georgi, Betula pubescens Ehrh., Ulmus pumila L., Corylus americana Marsh., Corylus avellana L., Stipa pennata L., Poa nemoralis L., Achnatherum splendens (Trin.) Nevski, Panicum virgatum L., Lolium perenne L., Avena sativa L., Setaria maximowiczii Tzvelev & Prob.), exposed by the Central Siberian Botanical Garden, SB RAS. These plants are widely spread over the territory of the Russian Federation and produce great amounts of allergenic pollen. Estimated is the share of clusters of two and more pollen grains in the total number of pollen particles, entering the atmosphere upon blooming of plants of a given species. It is shown that although the anemophilous plants display morphological properties, that prevent the formation of clusters, substantial number of such clusters is recorded in all experimental series. In this case, the share of pollen grains could exceed 50% of the total number of pollen grains, entering the atmosphere.