Are the birch trees in Southern England a source of Betula pollen for North London?

Aerobiological modelling II: A review of long-range transport models

The long-range atmospheric transport models of pollen and fungal spores require four modules for their development: (i) Meteorological module: which contain the meteorological model, and it can be coupled to transport model with the same output configuration (spatio-temporal resolution), or uncoupled does not necessarily have the same output parameters. (ii) Emission module: settles the mass fluxes of bioaerosol, it can be done with a complex parameterization integrating phenological models and meteorological factors or by a simple emission factor. (iii) Sources of emission module, specifically refers to forestry/agronomy maps or, in the case of herbs and fungi, to potential geographical areas of emission. Obtaining the highest possible resolution in these maps allows establishing greater reliability in the modelling. (iv) Atmospheric transport module, with its respective established output parameters. The review and subsequent analysis presented in this article, were performed on published electronic scientific articles from 1998 to 2016. Of a total of 101 models applied found in 64 articles, 33 % performed forward modelling (using 15 different models) and 67 % made backward modelling (with three different models). The 88 % of the cases were applied to pollen (13 taxa) and 12 % to fungal spores (3 taxa). Regarding the emission module, 22 % used parametrization (four different parameters) and 10 % emission factors. The most used transport model was HYSPLIT (59 %: 56 % backward and 3 % forward) following by SILAM 10 % (all forward). Main conclusions were that the models of long-range transport of pollen and fungal spores had high technical-scientific requirements to development and that the major limitations were the establishment of the flow and the source of the emission.

Potential contribution of distant sources to airborne Betula pollen levels in Northeastern Iberian Peninsula

Betula (birch) pollen is one of the most important causes of respiratory allergy in Northern and Central Europe. While birch trees are abundant in Central, Northern, and Eastern Europe, they are scarce in the Mediterranean territories, especially in the Iberian Peninsula (IP), where they grow only in the northern regions and as ornamental trees in urban areas. However, the airborne birch pollen patterns in Catalonia (Northeastern IP) show abrupt high concentrations in areas with usually low local influence. The intensity of the derived health problems can be increased by outbreaks due to long-range pollen transport. The present work evaluates the different potential contributions to Catalonia from the main source regions: Pyrenees, Cantabria, and the forests of France and Central Europe. To this end, we computed the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) back trajectories of air masses associated with the main Betula pollen peaks occurring simultaneously over different Catalan monitoring stations, and we studied their provenance over a 15-year period. The Vielha aerobiological station on the northern slopes of the Central Pyrenees was used to identify the dates of the pollen season in the Pyrenean region. In order to better understand the role of the Pyrenees, which is the nearest of the four birch forested regions, we classified the pollen peaks in the other Catalan stations into three groups based on the relationship between the peak and the pollen season in the Pyrenees. Our analysis of back-trajectory residence time, combined with the associated pollen concentration, reveals that two principal routes other than the Pyrenean forest sustain the northerly fluxes that enter Catalonia and carry significant concentrations of Betula pollen. This study has also allowed quantifying the differentiated contributions of the potential source regions. In addition, the Weather Research Forecast (WRF) mesoscale model has been used to study three specific episodes. Both models, HYSPLIT and WRF, complement each other and have allowed for better understanding of the main mechanisms governing the entry of birch pollen to the region.

Atmospheric transport reveals grass pollen dispersion distances

Identifying the origin of bioaerosols is of central importance in many biological disciplines, such as human health, agriculture, forestry, aerobiology and conservation. Modelling sources, transportation pathways and sinks can reveal how bioaerosols vary in the atmosphere and their environmental impact. Grass pollen are particularly important due to their widely distributed source areas, relatively high abundance in the atmosphere and high allergenicity. Currently, studies are uncertain regarding sampler representability between distance and sources for grass pollen. Using generalized linear modelling, this study aimed to analyse this relationship further by answering the question of distance-to-source area contribution. Grass pollen concentrations were compared between urban and rural locations, located 6.4 km apart, during two years in Worcestershire, UK. We isolated and refined vegetation areas at 100 m × 100 m using the 2017 CEH Crop Map and conducted atmospheric modelling using HYSPLIT to identify which source areas could contribute pollen. Pollen concentrations were then modelled with source areas and meteorology using generalized linear mixed-models with three temporal variables as random variation. We found that the Seasonal Pollen Integral for grass pollen varied between both years and location, with the urban location having higher levels. Day of year showed higher temporal variation than the diurnal or annual variables. For the urban location, grass source areas within 30 km had positive significant effects in predicting grass pollen concentrations, while source areas within 2-10 km were important for the rural one. The source area differential was likely influenced by an urban-rural gradient that caused differences in the source area contribution. Temperature had positive highly significant effects on both locations while precipitation affected only the rural location. Combining atmospheric modelling, vegetation source maps and generalized linear modelling was found to be a highly accurate tool to identify transportation pathways of bioaerosols in landscape environments.

Understanding hourly patterns of Olea pollen concentrations as tool for the environmental impact assessment

Bioinformatics clustering application for mining of a large set of olive pollen aerobiological data to describe the daily distribution of Olea pollen concentration. The study was performed with hourly pollen concentrations measured during 8 years (2011-2018) in Extremadura (Spain). Olea pollen season by quartiles of the pollen integral in preseason (Q1: 0%-25%), in-season (Q2 and Q3: 25%-75%) and postseason (Q4: 75%-100%). Days with pollen concentrations above 100 grains/m³ were clustered according to the daily distribution of the concentrations. The factors affecting the prevalence of the different clusters were analyzed: distance to olive groves and the moment during the pollen season and the meteorology. During the season, the highest hourly concentrations during the day where between 12:00 and 14:00, while during the preseason the highest hourly concentrations were detected in the afternoon and evening hours. In the postseason the pollen concentrations were more homogeneously distributed during 9-16 h. The representation shows a well-defined hourly pattern during the season, but a more heterogeneous distribution during the preseason and postseason. The cluster dendrogram shows that all the days could be clustered in 6 groups: most of the clusters shows the daily peaks between 11:00 and 15:00 with a smooth curve (Cluster 1 and 3) or with a strong peak (2 and 5). Days included in cluster 9 shows an earlier peak in the morning (before 9:00). On the other hand, cluster 6 shows a peak in the afternoon, after 15:00. Hourly concentrations show a sharper pattern during the season, with the peak during the hours close to the emission. Out of the season, when pollen is expected to come from farther distances, the hourly peak is located later from the emission time of the trees. Significant factors for predicting the hourly pattern were wind speed and direction and the distance to the olive groves.

Inventory of the Recommendations for Patients with Pollen Allergies and Evaluation of Their Scientific Relevance

Pollens are responsible for allergic rhinitis, conjunctivitis, and asthma. The incidence of these diseases, which have adversely impacted the social and professional lives of people who are allergic to pollen, has tripled in the past 25 years. Official institutes, health care institutions, public interest groups, and mainstream news media provide people who are allergic to pollen with advice aimed at reducing their symptoms. The aim of this work was to provide an inventory of the prevention guidelines in the world and to evaluate their scientific relevance. A PubMed search was carried out using specific keywords. The scientific relevance of the recommendations was evaluated based on the publications disproving or confirming their merit. The guidelines issued by 12 countries in Europe, North America, and Australia were inventoried. The recommendations for avoidance were most often based on scientific data regarding their impact on pollen exposures, but they have not been clinically validated. Several studies provided additional details, however, that allowed the guidelines to be further substantiated. These guidelines have been adopted in numerous industrialized countries in the world, and they generally appear to be of relevance.

Exposure to pollen allergens in allergic rhinitis expressed by diurnal variation of airborne tree pollen in urban and rural area

Exposure to airborne pollen allergens results in allergic symptoms in subjects who are sensitized. The paper presents diurnal variation in the counts of airborne allergenic pollen of selected trees (Betula L., Alnus Mill., Corylus L., Fagus L. and Ulmus L.) in two localities differing in the degree of urbanization: the city of Szczecin (urban) and the village of Gudowo, West Pomerania in northwest Poland (rural) in the years 2012–2014. The measurements were made by the volumetric method using a Burkardtype sampler operating in a continuous mode. The greatest similarities in the beginning of the main pollen season between the two sites studied were observed for birch and elm trees, while in the length of the main pollen season, for birch and alder trees. Pollen counts of alder and hazel reached higher levels in the rural area, while the levels of ash tree pollen counts were higher in the urban area. The level of birch tree pollen counts was similar in the two sites studied. For the majority of taxons observed in the urban and rural areas the dynamics of hourly changes in tree pollen counts were similar. The pollination peak was noted in the daytime, usually in the afternoon. For ash and elm trees increased pollen counts were observed at nighttime, while the birch tree pollen counts were at a high level for most of the 24 h cycle. The knowledge of seasonal and diurnal variations in tree pollen counts is crucial for prevention in patients with allergic rhinitis, sensitized to tree pollen allergens.

Wind dynamics' influence on south Spain airborne olive-pollen during African intrusions

Given its proximity to northern Africa, southern Spain is regularly affected by high-altitude African intrusions. This determines a well-defined wind dynamics at surface levels. Although this weather event-mainly recorded in spring and summer-coincides with the flowering season of many wind pollinated species, its potential influence on long term airborne pollen transport has been not investigated in detail. We analyse their influence on olive pollen transport at surface level in south Spain. Daily and bi-hourly olive pollen data from 2010 to 2015, recorded at two sites 150km apart, Málaga (coast) and Córdoba (inland), were analysed together with 1) air masses at 300m above ground level (m.a.g.l.), 2) surface wind direction and 3) surface wind speed over the same period. Air masses at 3000m.a.g.l. were used to identify the periods under the influence of African intrusions. The combined analysis has enabled the identification of different pollen patterns and source contributions. In Málaga, hourly pollen peaks were recorded during the early morning coinciding with the arrival of north-westerly winds (developing sea-land breezes), with a minimal impact of local pollen sources; in Córdoba, by contrast, pollen concentrations reflected the joint contribution of local and long term sources, being the maximum concentrations associated with the arrival of southerly air masses in the afternoon. These results help to understand the potential distant sources and back-trajectories of olive pollen detected. In our case pollen from sources located at the west-northwest areas in the case of Malaga, and from the south in Cordoba. These results reinforce the idea that combined studies between synoptic meteorological and aerobiological data together with different atmospheric height air masses data, offer us a better explanation and understanding of the behaviour and the potential sources of recorded airborne data in a given place.

Large-Scale Atmospheric Dispersal Simulations Identify Likely Airborne Incursion Routes of Wheat Stem Rust Into Ethiopia

In recent years, severe wheat stem rust epidemics hit Ethiopia, sub-Saharan Africa's largest wheat-producing country. These were caused by race TKTTF (Digalu race) of the pathogen Puccinia graminis f. sp. tritici, which, in Ethiopia, was first detected at the beginning of August 2012. We use the incursion of this new pathogen race as a case study to determine likely airborne origins of fungal spores on regional and continental scales by means of a Lagrangian particle dispersion model (LPDM). Two different techniques, LPDM simulations forward and backward in time, are compared. The effects of release altitudes in time-backward simulations and P. graminis f. sp. tritici urediniospore viability functions in time-forward simulations are analyzed. Results suggest Yemen as the most likely origin but, also, point to other possible sources in the Middle East and the East African Rift Valley. This is plausible in light of available field surveys and phylogenetic data on TKTTF isolates from Ethiopia and other countries. Independent of the case involving TKTTF, we assess long-term dispersal trends (>10 years) to obtain quantitative estimates of the risk of exotic P. graminis f. sp. tritici spore transport (of any race) into Ethiopia for different 'what-if' scenarios of disease outbreaks in potential source countries in different months of the wheat season.

Aerobiology in the International Journal of Biometeorology, 1957-2017

Aerobiology and biometeorology are related fields. Here we provide a broad review of aerobiology articles published in the International Journal of Biometeorology (IJB) over the past 60 years. We consider how the quantity of such work has varied over this period as well as which regions and countries have been the focus of such work, and where there is a relative paucity. We then focus on a number of highlights and themes in this research, including aerobiology and climate change and aerobiological modelling and forecasting. While much of the article focusses on airborne pollen research, we also discuss the extent to which other airborne organic particles such as fungal spores and bacteria have been the focus of research published in IJB. Also considered are knowledge gaps and research needs and priorities with respect to the field of aerobiology. While the IJB has been one of the main platforms for presenting aerobiological research over recent decades, the article highlights the need for the field of aerobiology to embrace new sampling technologies such as spectral analysis and next-generation sequencing to identify and quantify airborne biological particles.

Biometeorology for cities

Improvements in global sustainability, health, and equity will largely be determined by the extent to which cities are able to become more efficient, hospitable, and productive places. The development and evolution of urban areas has a significant impact on local and regional weather and climate, which subsequently affect people and other organisms that live in and near cities. Biometeorologists, researchers who study the impact of weather and climate on living creatures, are well positioned to help evaluate and anticipate the consequences of urbanization on the biosphere. Motivated by the 60th anniversary of the International Society of Biometeorology, we reviewed articles published in the Society's International Journal of Biometeorology over the period 1974-2017 to understand if and how biometeorologists have directed attention to urban areas. We found that interest in urban areas has rapidly accelerated; urban-oriented articles accounted for more than 20% of all articles published in the journal in the most recent decade. Urban-focused articles in the journal span five themes: measuring urban climate, theoretical foundations and models, human thermal comfort, human morbidity and mortality, and ecosystem impacts. Within these themes, articles published in the journal represent a sizeable share of the total academic literature. More explicit attention from urban biometeorologists publishing in the journal to low- and middle-income countries, indoor environments, animals, and the impacts of climate change on human health would help ensure that the distinctive perspectives of biometeorology reach the places, people, and processes that are the foci of global sustainability, health, and equity goals.

Are the Pyrenees a barrier for the transport of birch (Betula) pollen from Central Europe to the Iberian Peninsula?

This work provides a first assessment of the possible barrier effect of the Pyrenees on the atmospheric transport of airborne pollen from Europe to the North of the Iberian Peninsula. Aerobiological data recorded in three Spanish stations located at the eastern, central and western base of the Pyrenees in the period 2004-2014 have been used to identify the possible long range transport episodes of Betula pollen. The atmospheric transport routes and the origin regions have been established by means of trajectory analysis and a source receptor model. Betula pollen outbreaks were associated with the meteorological scenario characterized by the presence of a high-pressure system overm over Morocco and Southern Iberian Peninsula. France and Central Europe have been identified as the probable source areas of Betula pollen that arrives to Northern Spain. However, the specific source areas are mainly determined by the particular prevailing atmospheric circulation of each location. Finally, the Weather Research and Forecasting model highlighted the effect of the orography on the atmospheric transport patterns, showing paths through the western and easternmost lowlands for Vitoria-Gasteiz and Bellaterra respectively, and the direct impact of air flows over Vielha through the Garona valley.

Airborne Quercus pollen in SW Spain: Identifying favourable conditions for atmospheric transport and potential source areas

The pollen grains of Quercus spp. (oak trees) are allergenic. This study investigates airborne Quercus pollen in SW Spain with the aim identifying favourable conditions for atmospheric transport and potential sources areas. Two types of Quercus distribution maps were produced. Airborne Quercus pollen concentrations were measured at three sites located in the Extremadura region (SW Spain) for 3 consecutive years. The seasonal occurrence of Quercus pollen in the air was investigated, as well as days with pollen concentrations ≥80Pm(-3). The distance that Quercus pollen can be transported in appreciable numbers was calculated using clusters of back trajectories representing the air mass movement above the source areas (oak woodlands), and by using a state-of-the-art dispersion model. The two main potential sources of Quercus airborne pollen captured in SW Spain are Q. ilex subsp. ballota and Q. suber. The minimum distances between aerobiological stations and Quercus woodlands have been estimated as: 40km (Plasencia), 66km (Don Benito), 62km (Zafra) from the context of this study. Daily mean Quercus pollen concentration can exceed 1,700Pm(-3), levels reached not less than 24 days in a single year. High Quercus pollen concentration were mostly associated with moderate wind speed events (6-10ms(-1)), whereas that a high wind speed (16-20ms(-1)) seems to be associated with low concentrations.

Spatiotemporal models for predicting high pollen concentration level of Corylus, Alnus, and Betula

Corylus, Alnus, and Betula trees are among the most important sources of allergic pollen in the temperate zone of the Northern Hemisphere and have a large impact on the quality of life and productivity of allergy sufferers. Therefore, it is important to predict high pollen concentrations, both in time and space. The aim of this study was to create and evaluate spatiotemporal models for predicting high Corylus, Alnus, and Betula pollen concentration levels, based on gridded meteorological data. Aerobiological monitoring was carried out in 11 cities in Poland and gathered, depending on the site, between 2 and 16 years of measurements. According to the first allergy symptoms during exposure, a high pollen count level was established for each taxon. An optimizing probability threshold technique was used for mitigation of the problem of imbalance in the pollen concentration levels. For each taxon, the model was built using a random forest method. The study revealed the possibility of moderately reliable prediction of Corylus and highly reliable prediction of Alnus and Betula high pollen concentration levels, using preprocessed gridded meteorological data. Cumulative growing degree days and potential evaporation proved to be two of the most important predictor variables in the models. The final models predicted not only for single locations but also for continuous areas. Furthermore, the proposed modeling framework could be used to predict high pollen concentrations of Corylus, Alnus, Betula, and other taxa, and in other countries.

Potential sources of airborne Alternaria spp. spores in South-west Spain

Fungi belonging to the genus of Alternaria are recognised as being significant plant pathogens, and Alternaria allergens are one of the most important causes of respiratory allergic diseases in Europe. This study aims to provide a detailed and original analysis of Alternaria transport dynamics in Badajoz, SW Spain. This was achieved by examining daily mean and hourly observations of airborne Alternaria spores recorded during days with high airborne concentrations of Alternaria spores (>100 s m(-3)) from 2009 to 2011, as well as four inventory maps of major Alternaria habitats, the overall synoptic weather situation and analysis of air mass transport using Hybrid Single Particle Lagrangian Integrated Trajectory model and geographic information systems. Land use calculated within a radius of 100 km from Badajoz shows that crops and grasslands are potentially the most important local sources of airborne Alternaria spores recorded at the site. The results of back trajectory analysis show that, during the examined four episodes, the two main directions where Alternaria source areas were located were: (1) SW-W; and (2) NW-NE. Regional scale and long distance transport could therefore supplement the airborne catch recorded at Badajoz with Alternaria conidia originating from sources such as crops and orchards situated in other parts of the Iberian Peninsula.

Is long range transport of pollen in the NW Mediterranean basin influenced by Northern Hemisphere teleconnection patterns?

Climatic oscillations triggered by the atmospheric modes of the Northern Hemisphere teleconnection patterns have an important influence on the atmospheric circulation at synoptic scale in Western Mediterranean Basin. Simultaneously, this climate variability could affect a variety of ecological processes. This work provides a first assessment of the effect of North Atlantic Oscillation (NAO), Arctic Oscillation (AO) and Western Mediterranean Oscillation (WeMO) on the atmospheric long-range pollen transport episodes in the North-Eastern Iberian Peninsula for the period 1994-2011. Alnus, Ambrosia, Betula, Corylus and Fagus have been selected as allergenic pollen taxa with potential long-range transport associated to the Northern Hemisphere teleconnection patterns in the Western Mediterranean Basin. The results showed an increase of long range pollen transport episodes of: (1) Alnus, Corylus and Fagus from Western and Central Europe during the negative phase of annual NAO and AO; (2) Ambrosia, Betula and Fagus from Europe during the negative phase of winter WeMO; (3) Corylus and Fagus from Mediterranean area during the positive phase of the annual AO; and (4) Ambrosia from France and Northern Europe during the positive phase of winter WeMO. Conversely, the positive phase of annual NAO and AO are linked with the regional transport of Alnus, Betula and Corylus from Western Iberian Peninsula. The positive phase of annual WeMO was also positively correlated with regional transport of Corylus from this area.

Improvement in the accuracy of back trajectories using WRF to identify pollen sources in southern Iberian Peninsula

Airborne pollen transport at micro-, meso-gamma and meso-beta scales must be studied by atmospheric models, having special relevance in complex terrain. In these cases, the accuracy of these models is mainly determined by the spatial resolution of the underlying meteorological dataset. This work examines how meteorological datasets determine the results obtained from atmospheric transport models used to describe pollen transport in the atmosphere. We investigate the effect of the spatial resolution when computing backward trajectories with the HYSPLIT model. We have used meteorological datasets from the WRF model with 27, 9 and 3 km resolutions and from the GDAS files with 1° resolution. This work allows characterizing atmospheric transport of Olea pollen in a region with complex flows. The results show that the complex terrain affects the trajectories and this effect varies with the different meteorological datasets. Overall, the change from GDAS to WRF-ARW inputs improves the analyses with the HYSPLIT model, thereby increasing the understanding the pollen episode. The results indicate that a spatial resolution of at least 9 km is needed to simulate atmospheric flows that are considerable affected by the relief of the landscape. The results suggest that the appropriate meteorological files should be considered when atmospheric models are used to characterize the atmospheric transport of pollen on micro-, meso-gamma and meso-beta scales. Furthermore, at these scales, the results are believed to be generally applicable for related areas such as the description of atmospheric transport of radionuclides or in the definition of nuclear-radioactivity emergency preparedness.

Identification of potential sources of airborne Olea pollen in the Southwest Iberian Peninsula

This study aims to determine the potential origin of Olea pollen recorded in Badajoz in the Southwest of the Iberian Peninsula during 2009-2011. This was achieved using a combination of daily average and diurnal (hourly) airborne Olea pollen counts recorded at Badajoz (south-western Spain) and Évora (south-eastern Portugal), an inventory of olive groves in the studied area and air mass trajectory calculations computed using the HYSPLIT model. Examining olive pollen episodes at Badajoz that had distinctly different diurnal cycles in olive pollen in relation to the mean, allowed us to identify three different scenarios where olive pollen can be transported to the city from either distant or nearby sources during conditions with slow air mass movements. Back trajectory analysis showed that olive pollen can be transported to Badajoz from the West on prevailing winds, either directly or on slow moving air masses, and from high densities of olive groves situated to the Southeast (e.g. Andalucía). Regional scale transport of olive pollen can result in increased nighttime concentrations of this important aeroallergen. This could be particularly important in Mediterranean countries where people can be outdoors during this time due to climate and lifestyle. Such studies that examine sources and the atmospheric transport of pollen are valuable for allergy sufferers and health care professionals because the information can be incorporated into forecasts, the outputs of which are used for avoiding exposure to aeroallergens and planning medication. The results of studies of this nature can also be used for examining gene flow in this important agricultural crop.

Pollen season and climate: is the timing of birch pollen release in the UK approaching its limit?

In light of heightened interest in the response of pollen phenology to temperature, we investigated recent changes to the onset of Betula (birch) pollen seasons in central and southern England, including a test of predicted advancement of the Betula pollen season for London. We calculated onset of birch pollen seasons using daily airborne pollen data obtained at London, Plymouth and Worcester, determined trends in the start of the pollen season and compared timing of the birch pollen season with observed temperature patterns for the period 1995-2010. We found no overall change in the onset of birch pollen in the study period although there was evidence that the response to temperature was nonlinear and that a lower asymptotic start of the pollen season may exist. The start of the birch pollen season was strongly correlated with March mean temperature. These results reinforce previous findings showing that the timing of the birch pollen season in the UK is particularly sensitive to spring temperatures. The climate relationship shown here persists over both longer decadal-scale trends and shorter, seasonal trends as well as during periods of 'sign-switching' when cooler spring temperatures result in later start dates. These attributes, combined with the wide geographical coverage of airborne pollen monitoring sites, some with records extending back several decades, provide a powerful tool for the detection of climate change impacts, although local site factors and the requirement for winter chilling may be confounding factors.

A numerical model of birch pollen emission and dispersion in the atmosphere. Model evaluation and sensitivity analysis

An evaluation of performance of the System for Integrated modeLling of Atmospheric coMposition (SILAM) in application to birch pollen dispersion is presented. The system is described in a companion paper whereas the current study evaluates the model sensitivity to details of the pollen emission module parameterisation and to the meteorological input data. The most important parameters are highlighted. The reference year considered for the analysis is 2006. It is shown that the model is capable of predicting about two-thirds of allergenic alerts, with the odds ratio exceeding 12 for the best setup. Several other statistics corroborate with these estimations. Low-pollen concentration days are also predicted correctly in more than two-thirds of cases. The model experiences certain difficulties only with intermediate pollen concentrations. It is demonstrated that the most important input parameter is the near-surface temperature, the bias of which can easily jeopardise the results. The model sensitivity to random fluctuations of temperature is much lower. Other parameters important at various stages of pollen development, release, and dispersion are precipitation and ambient humidity, as well as wind direction.

A numerical model of birch pollen emission and dispersion in the atmosphere. Description of the emission module

A birch pollen emission model is described and its main features are discussed. The development of the model is based on a double-threshold temperature sum model that describes the propagation of the flowering season and naturally links to the thermal time models to predict the onset and duration of flowering. For the flowering season, the emission model considers ambient humidity and precipitation rate, both of which suppress the pollen release, as well as wind speed and turbulence intensity, which promote it. These dependencies are qualitatively evaluated using the aerobiological observations. Reflecting the probabilistic character of the flowering of an individual tree in a population, the model introduces relaxation functions at the start and end of the season. The physical basis of the suggested birch pollen emission model is compared with another comprehensive emission module reported in literature. The emission model has been implemented in the SILAM dispersion modelling system, the results of which are evaluated in a companion paper.

The occurrence of Ambrosia pollen in Rzeszów, Kraków and Poznań, Poland: investigation of trends and possible transport of Ambrosia pollen from Ukraine

Previous studies have shown that ragweed pollen arrives in Poland from sources in the south, in Slovakia, the Czech Republic, Hungary and Austria. It is likely that ragweed pollen also arrives from sources in the southeast (e.g. Ukraine). This hypothesis was investigated using 13 years of pollen data and back-trajectory analysis. Ambrosia pollen data were collected at three sites in Poland, Rzeszów, Kraków and Poznań. The amount of ragweed pollen recorded at Rzeszów was significantly higher than in Poznań and Kraków. This can be related to either a higher abundance of local populations of Ambrosia in south-east Poland or the proximity of Rzeszów to foreign sources of ragweed pollen. The combined results of pollen measurements and air mass trajectory calculations identified plumes of Ambrosia pollen that were recorded at Rzeszów, Kraków and Poznań on 4 and 5 September 1999 and 3 September 2002. These plumes arrived at the pollen-monitoring sites from an easterly direction, indicating sources of Ambrosia pollen in eastern Poland or Ukraine. This identifies Ukraine as a possible new source of ragweed pollen for Poland and therefore an important source area of Ambrosia pollen on the European Continent.

Source areas and long-range transport of pollen from continental land to Tenerife (Canary Islands)

The Canary Islands, due to their geographical position, constitute an adequate site for the study of long-range pollen transport from the surrounding land masses. In this study, we analyzed airborne pollen counts at two sites: Santa Cruz de Tenerife (SCO), at sea level corresponding to the marine boundary layer (MBL), and Izaña at 2,367 m.a.s.l. corresponding to the free troposphere (FT), for the years 2006 and 2007. We used three approaches to describe pollen transport: (1) a classification of provenances with an ANOVA test to describe pollen count differences between sectors; (2) a study of special events of high pollen concentrations, taking into consideration the corresponding meteorological synoptic pattern responsible for transport and back trajectories; and (3) a source-receptor model applied to a selection of the pollen taxa to show pollen source areas. Our results indicate several extra-regional pollen transport episodes to Tenerife. The main provenances were: (1) the Mediterranean region, especially the southern Iberian Peninsula and Morocco, through the trade winds in the MBL. These episodes were characterized by the presence of pollen from trees (Casuarina, Olea, Quercus perennial and deciduous types) mixed with pollen from herbs (Artemisia, Chenopodiaceae/Amaranthaceae and Poaceae wild type). (2) The Saharan sector, through transport at the MBL level carrying pollen principally from herbs (Chenopodiaceae-Amaranthaceae, Cyperaceae and Poaceae wild type) and, in one case, Casuarina pollen, uplifted to the free troposphere. And (3) the Sahel, characterized by low pollen concentrations of Arecaceae, Chenopodiaceae-Amaranthaceae, Cyperaceae and Poaceae wild type in sporadic episodes. This research shows that sporadic events of long-range pollen transport need to be taken into consideration in Tenerife as possible responsible agents in respiratory allergy episodes. In particular, it is estimated that 89-97% of annual counts of the highly allergenous Olea originates from extra-regional sources in southern Iberia and northern Africa.

Projections of the effects of climate change on allergic asthma: the contribution of aerobiology

Climate change is unequivocal and represents a possible threat for patients affected by allergic conditions. It has already had an impact on living organisms, including plants and fungi with current scenarios projecting further effects by the end of the century. Over the last three decades, studies have shown changes in production, dispersion and allergen content of pollen and spores, which may be region- and species-specific. In addition, these changes may have been influenced by urban air pollutants interacting directly with pollen. Data suggest an increasing effect of aeroallergens on allergic patients over this period, which may also imply a greater likelihood of the development of an allergic respiratory disease in sensitized subjects and exacerbation of symptomatic patients. There are a number of limitations that make predictions uncertain, and further and specifically designed studies are needed to clarify current effects and future scenarios. We recommend: More stress on pollen/spore exposure in the diagnosis and treatment guidelines of respiratory and allergic diseases; collection of aerobiological data in a structured way at the European level; creation, promotion and support of multidisciplinary research teams in this area; lobbying the European Union and other funders to finance this research.

The Pannonian plain as a source of Ambrosia pollen in the Balkans

This study aims to find likely sources of Ambrosia pollen recorded during 2007 at five pollen-monitoring sites in central Europe: Novi Sad, Ruma, Negotin and Nis (Serbia) and Skopje (Macedonia). Ambrosia plants start flowering early in the morning and so Ambrosia pollen grains recorded during the day are likely to be from a local source. Conversely, Ambrosia pollen grains recorded at night or very early in the morning may have arrived via long-range transport. Ambrosia pollen counts were analysed in an attempt to find possible sources of the pollen and to identify Ambrosia pollen episodes suitable for further investigation using back-trajectory analysis. Diurnal variations and the magnitude of Ambrosia pollen counts during the 2007 Ambrosia pollen season showed that Novi Sad and Ruma (Pannonian Plain) and to a lesser degree Negotin (Balkans) were located near to sources of Ambrosia pollen. Mean bi-hourly Ambrosia pollen concentrations peaked during the middle of the day, and concentrations at these sites were notably higher than at Nis and Skopje. Three episodes were selected for further analysis using back-trajectory analysis. Back-trajectories showed that air masses brought Ambrosia pollen from the north to Nis and, on one occasion, to Skopje (Balkans) during the night and early morning after passing to the east of Novi Sad and Ruma during the previous day. The results of this study identified the southern part of the Pannonian Plain around Novi Sad and Ruma as being a potential source region for Ambrosia pollen recorded at Nis and Skopje in the Balkans.