Aerobiological Data Research Articles

Spatial and temporal variations of pollen concentrations in Islamabad (Pakistan): effect of meteorological parameters and impact on human health

This study focuses on the identification and quantification of airborne pollen grains from allergenic plant species and their relationship with meteorological factors, i.e. maximum and minimum daily temperature, relative humidity, rainfall and wind speed in the city of Islamabad, Pakistan. An aerobiological data set (2010–2012), collected using rotorod samplers in five different sectors of the city, was supplied by the Pakistan Meteorological Department. Pollen of eight allergenic species was identified amongst which Broussonetia papyrifera exceeded the highest pollen level and, therefore, likely played a key role in aggravating the symptoms of pollen allergy in the city. The mean weekly pollen counts were next correlated with the weekly number of allergic patients visiting hospitals during 2010–2011. Clinical data were acquired from the Pakistan Institute of Medical Sciences. The highest number of allergic patients visiting hospital was usually observed during weeks with high pollen level. These results suggest a close relationship between the pollen concentration in the air and the allergy symptoms. Spearman’s rank correlation analysis was performed to establish the relationships between meteorological parameters and daily average pollen counts. A pollen calendar for the Islamabad city was also prepared to provide a guide for the timing and duration of season for all encountered pollen types.

Models to predict the start of the airborne pollen season.

Aerobiological data can be used as indirect but reliable measures of flowering phenology to analyze the response of plant species to ongoing climate changes. The aims of this study are to evaluate the performance of several phenological models for predicting the pollen start of season (PSS) in seven spring-flowering trees (Alnus glutinosa, Acer negundo, Carpinus betulus, Platanus occidentalis, Juglans nigra, Alnus viridis, and Castanea sativa) and in two summer-flowering herbaceous species (Artemisia vulgaris and Ambrosia artemisiifolia) by using a 26-year aerobiological data set collected in Turin (Northern Italy). Data showed a reduced interannual variability of the PSS in the summer-flowering species compared to the spring-flowering ones. Spring warming models with photoperiod limitation performed best for the greater majority of the studied species, while chilling class models were selected only for the early spring flowering species. For Ambrosia and Artemisia, spring warming models were also selected as the best models, indicating that temperature sums are positively related to flowering. However, the poor variance explained by the models suggests that further analyses have to be carried out in order to develop better models for predicting the PSS in these two species. Modeling the pollen season start on a very wide data set provided a new opportunity to highlight the limits of models in elucidating the environmental factors driving the pollen season start when some factors are always fulfilled, as chilling or photoperiod or when the variance is very poor and is not explained by the models.

Forecasting olive crop yields based on long-term aerobiological data series and bioclimatic conditions for the southern Iberian Peninsula

In the present study, bio-meteorological models for predicting olive-crop production in the southern Iberian Peninsula were developed. These covered a 16-year period: 1994-2009. The forecasting models were constructed using the partial least-squares regression method, taking the annual olive yield as the dependent variable, and both aerobiological and meteorological parameters as the independent variables. Two regression models were built for the prediction of crop production prior to the final harvest at two different times of the year: July and November. The percentage variance explained by the models was between 83% and 93%. Through these forecasting models, the main factors that influence olive-crop yield were identified. Pollen index and accumulated precipitation, especially as rain recorded during the pre-flowering months, were the most important parameters for providing an explanation of fluctuations in fruit production. The temperature recorded during the two months preceding budburst was another important variable, which showed positive effects on the final yield. The July model that provides accurate predictions of fruit production eight months prior to the final harvest is proposed as an optimal model to forecast fruit produced by olive trees in western Mediterranean areas.

Trends in atmospheric concentrations of weed pollen in the context of recent climate warming in Poznań (Western Poland)

A significant increase in summer temperatures has been observed for the period 1996–2011 in Poznań, Poland. The phenological response of four weed taxa, widely represented by anemophilous species (Artemisia spp., Rumex spp. and Poaceae and Urticaceae species) to this recent climate warming has been analysed in Poznań by examining the variations in the course of airborne pollen seasons. Pollen data were collected by 7-day Hirst-type volumetric trap. Trends in pollen seasons were determined using Mann–Kendall test and Sen’s slope estimator, whereas the relationships between meteorological and aerobiological data were established by Spearman’s rank correlation coefficient. Significant trends in pollen data were detected. The duration of pollen seasons of all analysed taxa increased (from +2.0 days/year for Urticaceae to +3.8 days/year for Rumex), which can be attributed to a delay in pollen season end dates rather than earlier start dates. In addition, the intensity of Artemisia pollen seasons significantly decreased and correlates with mean July–September daily minimum temperatures (r = −0.644, p < 0.01). In contrast, no significant correlations were found between temperature and characteristics of Rumex pollen seasons. The results of this study show that observed shifts in weed pollen seasons in Poznań, i.e. longer duration and later end dates, might be caused by the recorded increase in summer temperature. This influence was the strongest in relation to Artemisia, which is the taxon that flowers latest in the year. The general lack of significant correlations between Rumex and Urticaceae pollen seasons and spring and/or summer temperature suggests that other factors, e.g. land use practices, could also be partially responsible for the observed shifts in pollen seasons.

Variations in Quercus sp. pollen seasons (1996-2011) in Poznań, Poland, in relation to meteorological parameters.

The aim of this study is to supply detailed information about oak (Quercus sp.) pollen seasons in Poznań, Poland, based on a 16-year aerobiological data series (1996–2011). The pollen data were collected using a volumetric spore trap of the Hirst design located in Poznań city center. The limits of the pollen seasons were calculated using the 95 % method. The influence of meteorological parameters on temporal variations in airborne pollen was examined using correlation analysis. Start and end dates of oak pollen seasons in Poznań varied markedly from year-to-year (14 and 17 days, respectively). Most of the pollen grains (around 75 % of the seasonal pollen index) were recorded within the first 2 weeks of the pollen season. The tenfold variation was observed between the least and the most intensive pollen seasons. These fluctuations were significantly related to the variation in the sum of rain during the period second fortnight of March to first fortnight of April the year before pollination (r = 0.799; p < 0.001). During the analyzing period, a significant advance in oak pollen season start dates was observed (−0.55 day/year; p = 0.021), which was linked with an increase in the mean temperature during the second half of March and first half of April (+0.2 °C; p = 0.014). Daily average oak pollen counts correlated positively with mean and maximum daily temperatures, and negatively with daily rainfall and daily mean relative humidity.

Spores of lichen-forming fungi in the mycoaerosol and their relationships with climate factors

Fungal particulates are a dominant component of the bioaerosol, but aerobiological studies traditionally focused on a limited set of fungi having relevance as allergens or plant pathogens. This study first analyzes the occurrence of lichen meiospores in the mycoaerosol, quantitatively evaluating in the atmosphere of an alpine environment the occurrence of polar diblastic spores, unequivocally attributable to the lichen family Teloschistaceae. The analysis of air-samples collected one week per month for one year with a Hirst-type sampler displayed a low percentage occurrence of polar-diblastic spores (<0.1%) with respect to the whole mycoaerosol, dominated by Cladosporium. Spearman's correlation tests on aerobiological and climatic data highlighted a strong relationship between the detection of Teloschistaceae spores and rainfall events, excluding seasonal patterns or daily rhythms of dispersion. The fact that all the air-sampled spores were attributable to the species of Teloschistaceae occurring in the site, together with laboratory observations of predominant short range dispersal patterns for polar diblastic and other lichen spores, indicated that sexual reproduction is mostly involved in the local expansion of colonization, dispersal from a long distance appearing a less probable phenomenon. These findings indicated that responses of lichen communities to climate factors, usually related to physiological processes, also depend on their influence on meiospore dispersal dynamics. Spatial limitations in dispersal, however, have to be taken into account in evaluating lichen distributional shifts as indicators of environmental changes.

Combining stable isotope (δ13C) of trace gases and aerobiological data to monitor the entry and dispersion of microorganisms in caves

Altamira Cave (north of Spain) contains one of the world's most prominent Paleolithic rock art paintings, which are threatened by a massive microbial colonization of ceiling and walls. Previous studies revealed that exchange rates between the cave and the external atmosphere through the entrance door play a decisive role in the entry and transport of microorganisms (bacteria and fungi) and nutrients to the interior of the cave. A spatial-distributed sampling and measurement of carrier (CO2) and trace (CH4) gases and isotopic signal of CO2 (δ(13)C) inside the cave supports the existence of a second connection (active gas exchange processes) with the external atmosphere at or near the Well Hall, the innermost and deepest area of the cave. A parallel aerobiological study also showed that, in addition to the entrance door, there is another connection with the external atmosphere, which favors the transport and increases microorganism concentrations in the Well Hall. This double approach provides a more complete knowledge on cave ventilation and revealed the existence of unknown passageways in the cave, a fact that should be taken into account in future cave management.

Optimization of integrated pest management for powdery mildew (Unincula necator) control in a vineyard based on a combination of phenological, meteorological and aerobiological data

SUMMARYPowdery mildew is one of the most important vineyard diseases. Infection requires the interaction of a susceptible host (a vine in a phenological phase susceptible to the pathogen), a virulent pathogen (the fungusUncinula necator(Schw.) Burr) and an environment favourable for disease development (optimal meteorological conditions). The aim of the present study was the implementation of a system to predict powdery mildew infection periods in order to optimize and reduce the application of pesticide treatments in a vineyard. The study was conducted in a vineyard of the ‘Ribeiro’ Designation of Origin region located in north-western Spain from 2006 to 2011, during the Vitis vegetative period. The phenological study was conducted following the BBCH phenological scale and infection risk index (IRI) was calculated based on the maximum temperature. Aerobiological sampling was performed using a LANZONI VPPS-2000 volumetric trap. The results of the study show that the critical phenological stages for powdery mildew infection are 5 (inflorescence emergence), 6 (flowering) and 7 (development of fruit), as consequence of the high susceptibility of the vine. The IRI allows determination of the periods in which the meteorological conditions could facilitate fungal attacks during the aforementioned phenological phases. Finally, the aerobiological model helps to identify and predict the times of real infection risk among the possible periods described by the IRI with high accuracy, in order to avoid possible reappearance of infection symptoms in the vine. The combination of these three variables provides a valuable tool to establish an accurate, modern, integrated pest-management strategy in a vineyard.

Spatio-temporal investigation of flowering dates and pollen counts in the topographically complex Zugspitze area on the German–Austrian border

Flowering behavior of the major allergenic species Betula pendula Roth (silver birch), Dactylis glomerata L. (cocksfoot) and Alopecurus pratensis L. (meadow foxtail), was examined by phenological observations in 2009 along an altitudinal gradient (from 700 m up to 1,700 m a.s.l.) in the topographically complex Zugspitze area on the German–Austrian border. The results were compared with pollen counts derived from pollen traps located at different altitudes (720 m, 1,503 m, 2,650 m a.s.l.). Phenological onset dates showed a great dependence on altitude and on exposition. Altitudinal gradients of the two grass species showed a delay of between 6 and 7 days (100 m)−1 and can be interpreted as a temperature response rate varying between −9 and −10 days (1 °C)−1. For birch phenophases, the altitudinal gradients were ca. 3 days (100 m)−1, corresponding to temperature response rates of circa −7 days (1 °C)−1. Northern and western exposed birch trees at the same altitude showed large differences in flowering dates (5–7 days). A comparison of phenological and aerobiological data in the phenological survey area revealed good agreement in the start of season dates, especially at lower altitude. Therefore, it was local pollen emissions, not long- or medium-range pollen transport that accounted for the timing of the aerobiological start of the season. Pollen counts at the highest and vegetation-free site were particularly affected by medium-range transport. More pronounced responses to altitude and therefore to temperature for the analyzed grass species indicate a greater temperature sensitivity. This suggests that further temperature increase could result in a remarkably earlier grass pollen season and, in turn, lead to major consequences for human health. Particular wind patterns can contribute to high and medically relevant pollen concentrations even at high elevation sites, implying less favourable conditions for those people allergic to pollen.

Airborne pollen of allergenic herb species in Toledo (Spain)

This study analysed airborne pollen counts for allergenic herb taxa in Toledo (central Spain), a major tourist city receiving over 2 million visitors per year, located in the region of Castilla-La Mancha. The taxa selected were Chenopodiaceae-Amaranthaceae, Plantago, Poaceae and Urticaceae, all of which produce allergenic pollen giving rise to serious symptoms in pollen-allergy sufferers. Aerobiological data were recorded over a 6-year period (2005 to 2010) using the sampling and analysis procedures recommended by the Spanish Aerobiology Network. The abundance and the temporal (annual, daily and intradiurnal) distribution of these pollen types were analysed, and the influence of weather-related factors on airborne pollen counts was assessed. Pollen from herbaceous species accounted for 20.9% of total airborne pollen in Toledo, the largest contributor being Poaceae, with 8.5% of the total pollen count; this family was also the leading cause of respiratory allergies. Examination of intradiurnal variation revealed three distinct distribution patterns: (1) peak daily counts for Chenopodiaceae-Amaranthaceae and Plantago were recorded during the hottest part of the day, i.e. from 1400 to 1600 hours; (2) Urticaceae displayed two peaks (1400-1600 and 2200 hours); and (3) Poaceae counts remained fairly stable throughout the day. Two main risk periods were identified for allergies: spring, with allergies caused by Urticaceae, Plantago and Poaceae pollen, and summer, due to Chenopodiaceae-Amaranthaceae pollen.

Incidence of Echium pollen in the Middle West of Iberian Peninsula: an unusual flowering period and its significance in aerobiological studies

We analysed the occurrence of the Echium pollen in the atmosphere of Salamanca, on the basis of 8-year observation (2000–2007) with the aim to evaluate its aerobiological behaviour. Aerobiological samples were collected by the Hirst volumetric method with a 7-day Burkard spore trap. The atmospheric pollen season of Echium was observed in late spring (May and June), showing also high levels in midday hours. However, an anomalous flowering period was detected in late autumn and early winter between years 2006 and 2007 and it could be connected with high daily temperature registered in October 2006 in comparison with the 2000–2005 period and its particular increasing tendency similar to those detected in the preceding month of the late spring flowering period. Statistical analysis by means of the Spearman’s non-parametrical test and linear regression analysis reflected a positive correlation with temperature and a trend to increase in daily temperature during late October 2006 and April in 2000–2005 with similar indexes (R2 = 0.50, R2 = 0.58, respectively). In conclusion, aerobiological data could contribute to the development of further studies in order to a better understanding of different plant species phenology.

Estimation of yield ‘Loureira’ variety with an aerobiological and phenological model

The knowledge of potential grape production is of great value for harvest and post-harvest planning because it enables the winery to estimate requirements in terms of crop insurance and grape-picking workforce, to optimise post-harvest processes, and the detection of frauds as a consequence of grape introduction from outside into the denomination areas. An aerobiological and phenological study of the ‘Loureira’ grape variety was carried out at a Ribeiro Designation of Origin vineyard (Ourense, Spain) from 2004 to 2009. Aerobiological data were obtained using a Lanzoni VPPS-2000 volumetric trap placed inside the vineyard, while phenological observations were conducted on 20 selected vines, using the BBCH (Biologische Bundesanstalt, Bundessortenamt and chemical industry) standardised scale. During the grapevine cycle, the highest total fungal spore amount was recorded in 2008 (Botrytis cinerea: 40 773 spores, Uncinula necator: 4141 spores, Plasmopara viticola: 921 spores). The highest number of flowers per plant (8449) and the highest final grape production (3885 kg) was recorded in 2004, while the lowest number of flowers per plant (1645) and grape production (1178 kg) in 2008. This information along with meteorological data was used to develop a model for predicting ‘Loureira’ yield. The equation obtained accounted for 98.3% of harvest variability, thus enabling accurate prediction of grape production one month in advance.

Prediction of grape production by grapevine cultivar Godello in north-west Spain

SUMMARYAdvance knowledge of potential grape production is of great value for harvest and post-harvest planning, in that it enables the winery to estimate requirements in terms of crop insurance and grape-picking workforce, and to optimize post-harvest processes.An aerobiological and phenological study of the Godello grape variety was carried out at a vineyard belonging to the Ribeiro Designation of Origin (Ourense, Spain) from 2004 to 2009. Aerobiological data were obtained using a Lanzoni VPPS-2000 volumetric trap placed inside the vineyard, while phenological observations were conducted on 20 selected vines, using the Biologische Bundesanstalt, Bundessortenamt and chemical industry(BBCH) standardized scale. Pollen production per anther and per grapevine was studied during the flowering stage, and airborneVitispollen counts were recorded. This information was used to develop a model for predicting local grape production. The equation obtained accounted for 0·99 of harvest variability, thus enabling accurate prediction of grape production 1-month in advance.

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.

Phenological records as a complement to aerobiological data

Phenological studies in combination with aerobiological studies enable one to observe the relationship between the release of pollen and its presence in the atmosphere. To obtain a suitable comparison between the daily variation of airborne pollen concentrations and flowering, it is necessary for the level of accuracy of both sets of data to be as similar as possible. To analyse the correlation between locally observed flowering data and pollen counts in pollen traps in order to set pollen information forecasts, pollen was sampled using a Burkard volumetric pollen trap working continuously from May 1993. For the phenological study we selected the main pollen sources of the six pollen types most abundant in our area: Cupressaceae, Platanus, Quercus, Plantago, Olea, and Poaceae with a total of 35 species. We selected seven sites to register flowering or pollination, two with semi-natural vegetation, the rest being urban sites. The sites were visited weekly from March to June in 2007, and from January to June in 2008 and 2009. Pollen shedding was checked at each visit, and recorded as the percentage of flowers or microsporangia in that state. There was an association between flowering phenology and airborne pollen records for some of the pollen types (Platanus, Quercus, Olea and Plantago). Nevertheless, for the other types (Cupressaceae and Poaceae) the flowering and airborne pollen peaks did not coincide, with up to 1week difference in phase. Some arguments are put forward in explanation of this phenomenon. Phenological studies have shown that airborne pollen results from both local and distant sources, although the pollen peaks usually appear when local sources are shedding the greatest amounts of pollen. Resuspension phenomena are probably more important than long-distance transport in explaining the presence of airborne pollen outside the flowering period. This information could be used to improve pollen forecasts.

Airborne pollen of ornamental tree species in the NW of Spain

This study analyzed airborne pollen counts for the tree taxa most widely used for ornamental purposes in the northwestern Iberian Peninsula (Platanus, Cupressaceae, Olea, Myrtaceae, Cedrus, and Casuarina) at four sites (Vigo, Ourense, Santiago, and Lugo), using aerobiological data recorded over a long period (1993-2007). The abundance and the temporal and spatial distribution of these pollen types were analyzed, and the influence of weather-related factors on airborne pollen counts was assessed. Platanus (in Ourense) and Olea (in Vigo) were the taxa contributing most to pollen counts. In general terms, the results may be taken as indicators of potential risk for pollen-allergy sufferers and therefore used in planning future green areas.

Phenological trends in southern Spain: A response to climate change

The impact of climate change, and particularly of climate warming, is being tracked in many physical and biological systems. Plant phenology is seen as one of the most important bio-indicators, since trends can provide considerable temporal and spatial information regarding ongoing changes. Analyses performed at six sites in southern Spain from 1986 to the present have focused on vegetative and overall reproductive phenology in Olea europaea L., and Vitis vinifera L. and in various species of Quercus spp. and Poaceae. Early results suggest that trends in flowering patterns derived from field phenological observations were similar to trends in aerobiological data for most study species, and indicate a trend towards earlier foliation, flowering and fruit ripening. This advance is more evident in arboreal than in herbaceous species. Statistical analysis showed temperature increase was the major factor affecting earlier foliation, flowering and fruit ripening, as well as prompting delayed leaf fall. Herbaceous species were more affected than trees by changes in rainfall records.

Benford’s law applied to aerobiological data and its potential as a quality control tool

Benford’s phenomenological law gives the expected frequencies of the first significant digits of any given series of numbers. According to this law, the frequency of 1 is higher than that of 2; this in turn appears more often 3, and so on. Similarly, Benford’s law can also be applied to the first two significant digits (i.e., from 10 to 99), and so on. Here, we show that gross data sets of daily pollen counts from three aerobiological stations (located in European cities with different features regarding vegetation and climatology) fit Benford’s law for the first significant digits, but this is not always true for the data transformed by a correction factor used in aerobiological studies. That is to say, the biases introduced by rounding and lower and upper built-in limits in pollen counts are detected by Benford’s law analysis. The analysis of the first two significant digits from transformed data is better explained by a Power law than Benford’s law. We propose that Benford’s law could be used as a quality control tool for numerical aerobiological data sets.

Reproducibility between counts of airborne allergenic pollen from two cities in the East Midlands, UK

Historically in the East Midlands, UK, airborne pollen has been monitored in two cities, Derby and Leicester, situated 41 km (25 miles) apart. The aim of the present study was to compare aerobiological data from both sites to determine if a forecast based on data from one site would be sufficient for both, and to address the wider issue of reproducibility between geographically separated sites. Pollen types recorded could be split into two groups according to annual abundance, maximum daily concentration and the number of high count days. Six taxa made up the abundant group; ash, birch, grass, oak, nettle-type and yew-type, representing 90 and 88% of the total air spora for Derby and Leicester, respectively. Three consecutive years of grass and nettle pollen data are presented, supported by one year of abundant tree pollen data. There were highly significant positive correlations between the counts obtained. Line charts showing the average number of pollen grains m−3 air day−1 show similar trends, and Bland–Altman plots show little discrepancy between the amounts of pollen counted on any given day. Each day was classified according to the UK accepted threshold levels for grass. Weighted kappa statistics showed substantial or almost perfect agreement between the forecast classifications. With the caveat that this would not apply in a region with restrictions to air flow such as a mountain range or with extreme fluctuations such as a coastline site, this study suggests that data from a single site is suitable for forecasting a distance of up to 41 km.

Study of the floral phenology of Olea europaea L. in Jaén province (SE Spain) and its relation with pollen emission

Phenological and aerobiological studies provide important information regarding the reproductive biology of cultivated species such as the olive. This article presents the results of an exploratory study of the floral phenology of Olea europaea L. at different altitudes in Jaen province (SE Spain) and an analysis of the main meteorological factors affecting flowering. As well, this study aimed to detect the relationship between phenology and olive pollen emission as a means of interpreting Olea pollen curves in the city of Jaen. Phenological observations were performed on olive trees at six sites, each at different altitudes and distributed over the whole area of olive cultivation in the province. Pollen data were obtained using a Hirst-type volumetric spore trap located within the city of Jaen. Phenological and aerobiological data were recorded in 2006 and 2007. This study shows that the chronology of the start of the flowering period depends on altitude. Statistical analyses indicate that the temperature, humidity, cumulative rainfall and cumulative solar radiation are the meteorological parameters that most affect olive floral phenology. The pollen season in Jaen generally lasts from May to June, with an annual total emission of over 40,000 pollen grains, the highest annual level of olive pollen emission in the world. The airborne pollen concentrations recorded in the city of Jaen are above all influenced by the olive groves located in the Guadalquivir valley.