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Urban trees provide many benefits to citizens but also have associated disservices such as pollen allergenicity. Pollen allergies affect 40% of the European population, a problem that will be exacerbated with climate change by lengthening the pollen season. The allergenic characteristics of the urban trees and urban parks of the city of Valencia (Spain) have been studied. The Value of Potential Allergenicity (VPA) was calculated for all species. The most abundant allergenic trees with a very high VPA were the cypresses, followed by Platanus x hispanica and species of genera Morus, Acer and Fraxinus, with a high VPA. On the contrary, Citrus x aurantium, Melia azedarach, Washingtonia spp., Brachychiton spp. and Jacaranda mimosifolia were among the most abundant low allergenic trees. VPA was mapped for the city and a hot spot analysis was applied to identify areas of clustering of high and low VPA values. This geostatistical analysis provides a comprehensive representation of the VPA patterns which is very useful for urban green infrastructure planning. The Index of Urban Green Zone Allergenicity (I UGZA ) was calculated for the main parks of the city. The subtropical and tropical flora component included many entomophilous species and the lowest share of high and very high allergenic trees in comparison with the Mediterranean and Temperate components. Overall, a diversification of tree species avoiding clusters of high VPA trees, and the prioritization of species with low VPA are good strategies to minimize allergy-related impacts of urban trees on human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

This study aims to analyze the effects that snow cover may have on the survival of one-year-old seedlings from 15 different taxa in the Mediterranean high mountains (Sierra Nevada National Park, SE Spain) in order to have clearer criteria for the planning and management of restoration efforts in these environments. Additionally, the influence of variables that have been scarcely explored up to now is also revised. We use the survival rates of the seedlings observed from the ecological restoration trial as reference values. The survival data analyzed are based on six variables to evaluate their effects. The results confirm that the permanence of snow is a favorable factor for seedlings, independent of the plant community. Contrastingly, a specific type of foundation (stones and rocks) stands out for being clearly unfavorable, regardless of other variables. For both altitude and solar radiation, a worsening of the survival ratio has been observed as they increase. The species' geographic ranges are all shown to be unfavorable for taxa of a boreo-alpine distribution. Finally, the plant community does not have a significant influence on the survival of seedlings. These results provide novel indications to improve the results of the first stages of restoration work in the Mediterranean high mountains. They are also valuable for the management and cataloging of threatened flora, as well as having direct applications in recovery plans and protection lists.

Pollen grains emitted by urban vegetation are the main primary biological airborne particles (PBAPs) which alter the biological quality of urban air and have a significant impact on human health. This work analyses the interactions which exist between pollen-type PBAPs, meteorological variables, and air pollutants in the urban atmosphere so that the complex relationships and trends in future scenarios of changing environmental conditions can be assessed. For this study, the 1992-2018 pollen data series from the city of Granada (southeast Spain) was used, in which the dynamics of the total pollen as well as the 8 main pollen types (Cupressaceae, Olea, Pinus, Platanus, Poaceae, Populus, Quercus and Urticaceae) were analysed. The trend analysis showed that all except Urticaceae trended upward throughout the series. Spearman's correlations with meteorological variables showed that, in general, the most influential variables on the pollen concentrations were the daily maximum temperature, relative humidity, water vapor pressure, global radiation, and insolation, with different effects on different pollen types. Parallel analysis by neural networks (ANN) confirmed these variables as the predominant ones, especially global radiation. The correlation with atmospheric pollutants revealed that ozone was the pollutant with the highest influence, although some pollen types also showed correlation with NO 2 , SO 2 , CO and PM 10 . The Generalized Linear Models (GLM) between pollen and pollutants also indicated O 3 as the most prominent variable. These results highlight the active role that pollen-type PBAPs have on urban air quality by establishing their interactions with meteorological variables and pollutants, thereby providing information on the behaviour of pollen emissions under changing environmental conditions., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Urban green space (UGS) is an essential element in the urban environment, providing multiple ecosystem services as well as beneficial effects on physical and mental health. In a time of societal crisis these effects may be amplified, but ensuring that they are maintained requires effective planning and management - which is a complex challenge given the rapid changes in modern society and the need for continual adaptation. This study aims to identify the drivers that normally attract visitors to UGS, and to assess the effects of social isolation on the usage and perception of UGS during the COVID-19 pandemic. We conducted an online survey during the period in which restrictive measures were imposed in response to the pandemic (March-May 2020), in Croatia, Israel, Italy, Lithuania, Slovenia and Spain. Results showed that urban residents normally have a need for accessible UGS, mainly for physical exercise, relaxing and observing nature. The reduction in UGS visitation during the containment period was related to distinct changes in the motivations of those who did visit, with a relative increase in "necessary activities" such as taking the dog out, and a reduction in activities that could be considered non-essential or high-risk such as meeting people or observing nature. Behavioral changes related to proximity were also observed, with an increase in people walking to small urban gardens nearby (e.g. in Italy) or tree-lined streets (e.g. in Spain, Israel), and people traveling by car to green areas outside the city (e.g. in Lithuania). What the respondents missed the most about UGS during the pandemic was "spending time outdoors" and "meeting other people" - highlighting that during the COVID-19 isolation, UGS was important for providing places of solace and respite, and for allowing exercise and relaxation. Respondents expressed the need for urban greenery even when legally mandated access was limited - and many proposed concrete suggestions for improved urban planning that integrates green spaces of different sizes within the fabric of cities and neighborhoods, so that all residents have access to UGS., Competing Interests: The authors reported no declarations of interest., (© 2020 Elsevier GmbH. All rights reserved.)

Platanusx hispanica (London plane) is a tree species widely used in urban areas due to the diversity of ecosystem services it provides. However, its functions also have some negative effects or associated disservices, such as the emission of Biogenic Volatile Organic Compounds (BVOCs) and allergens. This work aims to analyze the effect that urban environmental conditions and air pollutants have on pollen emissions of plane tree. The study has been carried out in Granada, in the southeast of the Iberian Peninsula, a city with a Mediterranean climate and one of the most polluted in Spain. Granada is also one of the Mediterranean cities in which the increase in the percentage of the population affected by allergy to Platanus pollen in recent decades has been most significant. The 1992-2019 Platanus pollen data series has been considered to establish the main aerobiological parameters, trends and correlations with meteorological variables and particulate and gaseous atmospheric pollutants, both before and during the flowering period. The average Seasonal Pollen Integral (SPIn) of about 2700 pollen grains has shown a significant increase throughout the series. This increase in allergen emissions could be related to the increase in crown volume associated with tree growth, but also to other environmental factors. Precipitation and minimum temperatures of the winter prior to flowering were the parameters that have shown the most influence with SPIn, while O 3 and NO x are the pollutants that have the most effect on the peak value. Due to the good adaptation that London plane has to changing climatic conditions in urban environments, its hegemonic presence as an element of Urban Green infrastructure must be reviewed so that the net balance of ecosystem services is not diminished by the disservices., Competing Interests: Declaration of competing interest Paloma Cariñanos, as corresponding author and on behalf of the co-authors, declares that she has not have any conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The impact of allergens emitted by urban green spaces on health is one of the main disservices of ecosystems. The objective of this work is to establish the potential allergenic value of some tree species in urban environments, so that the allergenicity of green spaces can be estimated through application of the Index of Urban Green Zones Allergenicity (I UGZA ). Multiple types of green spaces in Mediterranean cities were selected for the estimation of I UGZ . The results show that some of the ornamental species native to the Mediterranean are among the main causative agents of allergy in the population; in particular, Oleaceae, Cupressaceae, Fagaceae, and Platanus hispanica . Variables of the strongest impact on I UGZA were the bioclimatic characteristics of the territory and design aspects, such as the density of trees and the number of species. We concluded that the methodology to assess the allergenicity associated with urban trees and urban areas presented in this work opens new perspectives in the design and planning of urban green spaces, pointing out the need to consider the potential allergenicity of a species when selecting plant material to be used in cities. Only then can urban green areas be inclusive spaces, in terms of public health., Competing Interests: The authors declare no conflict of interest.

This paper explores the dynamics of temporal evolution of the high mountain Mediterranean grasslands, (Sierra Nevada, Spain SE). The indicator used is the emission of pollen (Pollen Index, PI) with respect to two important aspects: the incidence of the snow dynamic together with other hydro-meteorological parameters, and the changes in land use, which can Influence the evolution of the grasslands throughout time. The results reveal that pollen emissions in the last 25 years have shown a slight downward trend, with large interannual fluctuations, which are a consequence of diverse environmental factors, both general and specific to the area. One of the most influential parameters on pollen concentrations is snow cover, which reinforces the importance of the presence of snow-packs as water resource outside the winter season in the High Mediterranean Mountain environments. The changes in land use experienced in the area are a driver of change, especially due to the losses experienced in the last decades in the preferred habitats for many species of grasses. It can be concluded that the vulnerability of these ecosystems will be affected by an increase in winter temperatures and/or a decrease in rainfall (climate change) and an increase in the intensity of anthropogenic activities on land use. In this context, the PI is shown as a useful indicator of global change given its sensitivity to both anthropic and hydro-meteorological changes. In addition, it has a wide range of spatial detection and discrimination capacity by altitudinal dimensions., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ethnopharmacological Relevance: The different species of the genus Datura have been used traditionally by some pre-Columbian civilizations, as well as in medieval rituals linked to magic and witchcraft in both Mexico and Europe. It is also noteworthy the use of different alkaloids obtained from the plants for medicinal purposes in the treatment of various groups of diseases, especially of the respiratory and muscularskeletal systems., Aim of the Study: A review of the ethnobotanical uses of the genus Datura in Mexico and Spain has been conducted. We focus on the medicinal and ritualistic uses included in modern ethnobotanical studies, emphasizing the historical knowledge from post-colonial American Codices and medieval European texts. Datura's current social emergency as a drug of recreation and leisure, as well as its link to crimes of sexual abuse is also considered. The work is completed with some notes about the distribution and ecology of the different species and a phytochemical and pharmacological review of Datura alkaloids, necessary to understand their arrival in Europe and the ethnobotanical uses made since then MATERIALS AND METHODS: A literature review and compilation of information on traditional medicinal uses of the genus has been carried out from the main electronic databases. Traditional volumes (codices) have also been consulted in libraries of different institutions. Consultations have been made with the National Toxicological Services of Spain and Mexico for toxicological data., Results: A total of 118 traditional uses were collected in both territories, 111 medicinal ones to be applied in 76 conditions or symptoms included in 13 pathological groups. Although there are particular medicinal uses in the two countries, we found up to 15 similar uses, of which 80% were previously mentioned in post-Colonial American codices. Applications in the treatment of asthma and rheumatism are also highlighted. Apart from medicinal uses, it is worth noting their cultural and social uses, in the case of Mexico relating to diseases such as being scared, astonishment or falling in love, and in the case of Spain, as a recreational drug and lately, for criminal purposes., Conclusions: This review highlights the variety of uses traditionally given to the different species in both territories. The fact that most of the coincident or similar uses in both countries also appear in the classical codices can be found an example of the flow, not only of the plants from America to Europe, but also of their associated information. It is also relevant that particular uses have derived in both countries, reflecting the difference in the cultural factors and traditions linked to rituals and cultural practices. Finally, the significant growth of Datura consumption in recent years as a drug of leisure and recreation, as well as in crimes of sexual submission, should be considered as research of maximum relevance in the field of forensic botany and toxicology., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Urban parks play a key role in the provision of ecosystem services, actively participating in improving the quality of life and welfare of local residents. This paper reports on the application of an index designed to quantify the allergenicity of urban parks in a number of Spanish cities. The index, which records biological and biometric parameters for the tree species growing there, classifies parks in terms of the risk they pose for allergy sufferers, graded as null, low, moderate or high. In this initial phase, the index was applied to 26 green areas in 24 Spanish cities; green areas varied in type (urban park, historical or modern garden, boulevard, square or urban forest), size 1-100 ha), geographical location, species richness, number of trees and tree density (number of trees / ha.). The data obtained were used to calculate the percentage of allergenic species in each park, which varied between 17-67%; density ranged from 100 to 300 trees/ha. The index values recorded ranged from a minimum of .07 to a maximum of .87; a significant correlation was found between index value and both number of trees and tree density. Taking an index value of .30 as the threshold considered sufficient to trigger allergy symptoms in the sensitive population, 12 of the parks studied may be regarded as unhealthy at any time of the year. Corrective measures to mitigate the impact of pollen emissions include the implementation of nature-based solutions at various levels: planning and design, handling and management, and strengthening of urban green-infrastructure elements. The index proved to be a useful tool for environmental analysis, and complies with the principles of portability and scalability central to current and horizon scientific research., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Particulate matter (PM) deposited on Platanus acerifolia tree leaves has been sampled in the urban areas of 28 European cities, over 20 countries, with the aim of testing leaf deposited particles as indicator of atmospheric PM concentration and composition. Leaves have been collected close to streets characterized by heavy traffic and within urban parks. Leaf surface density, dimensions, and elemental composition of leaf deposited particles have been compared with leaf magnetic content, and discussed in connection with air quality data. The PM quantity and size were mainly dependent on the regional background concentration of particles, while the percentage of iron-based particles emerged as a clear marker of traffic-related pollution in most of the sites. This indicates that Platanus acerifolia is highly suitable to be used in atmospheric PM monitoring studies and that morphological and elemental characteristics of leaf deposited particles, joined with the leaf magnetic content, may successfully allow urban PM source apportionment.

Pollen released by urban flora-a major contributor to airborne allergen content during the pollen season-has a considerable adverse impact on human health. Using aerobiological techniques to sample and characterize airborne biological particulate matter (BPM), we can identify the main species contributing to the pollen spectrum and chart variations in counts and overall pollen dynamics throughout the year. However, given the exponential increase in the number of pollen allergy sufferers in built-up areas, new strategies are required to improve the biological quality of urban air. This paper reports on a novel characterization of the potential allergenicity of the tree species most commonly used as ornamentals in Mediterranean cities. Values were assigned to each species based on a number of intrinsic features including pollination strategy, pollen season duration, and allergenic capacity as reported in the specialist literature. Findings were used to generate a database in which groups of conifers, broadleaves, and palm trees were assigned a value of between 0 and 36, enabling their allergenicity to be rated as nil, low, moderate, high, or very high. The case study presented here focuses on the city of Granada in southern Spain. The major airborne-pollen-producing species were identified and the allergenicity of species growing in urban green zones was estimated. Corrective measures are proposed to prevent high allergen levels and thus improve biological air quality., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)

Air quality is a major issue for humans owing to the fact that the content of particles in the atmosphere has multiple implications for life quality, ecosystem dynamics and environment. Scientists are therefore particularly interested in discovering the origin of airborne particles. A new method has been developed to model the relationship between the emission surface and the total amount of airborne particles at a given distance, employing olive pollen and olive groves as examples. A third-degree polynomial relationship between the air particles at a particular point and the distance from the source was observed, signifying that the nearest area to a point is not that which is most correlated with its air features. This work allows the origin of airborne particles to be discovered and could be implemented in different disciplines related to atmospheric aerosol, thus providing a new approach with which to discover the dynamics of airborne particles., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The Amaranthaceae family includes a number of species which, through a series of specific adaptations, thrive in salty soils, arid environments and altered human settlements. Their ability to tolerate high temperatures favours summer flowering, giving rise to the widespread involvement of Amaranthaceae pollen grains in summer allergies, both in Mediterranean Europe and in areas with arid climates. This study analysed a 21-year set of historical airborne Amaranthaceae pollen records for an area located in the southern part of the Iberian Peninsula, in order to chart species' environmental reaction to changing climate conditions which occurred in the last decades. Airborne pollen data were collected from January 1991 to December 2011 using a Hirst-type volumetric impact sampler. Results showed that Amaranthaceae pollen remained in the atmosphere for over 6 months along the year, from early spring until early autumn. The annual Pollen Index ranged from barely 200 grains to almost 2000 grains, and was strongly influenced by rainfall during the flowering period, which prompted the development of new individuals and thus an increase in pollen production. A trend was noted towards increasingly early pollen peak dates; peaks were recorded in August-September in years with summer rainfall, but as early as May-June in years when over 50% of annual rainfall was recorded in the months prior to flowering. The gradual decline in the annual Pollen Index over later years is attributable not only to growing urbanisation of the area but also to a change in rainfall distribution pattern. High maximum temperatures in spring were also directly related to the peak date and the Pollen Index. This ability to adapt to changeable and occasionally stressful and restrictive, environmental conditions places Amaranthaceae at a competitive advantage with respect to other species sharing the same ecological niche. An increased presence of Amaranthaceae is likely to have a greater impact on future scenarios for pollen allergy diseases associated with climate change., (© 2013.)

An analysis was made of solid particulate matter suspended in the air in the city of Cordoba. Particles greater than 10 micra were collected using volumetric particle samplers (Lanzoni VPPS 2000, Bologna, Italy), and analysed by means of aerobiological methods enabling identification of the source of biological particulate material (BPM). Particles smaller than 10 micra were collected using automatic high-volume air samplers. Subsequent analysis showed that traffic, and particularly diesel engine exhaust emissions, were the main source of non-biological particulate matter (nBPM). The dynamics of airborne BPM and nBPM were also studied over one year: although distribution patterns differed--BPM displaying marked seasonality and non-BPM exhibiting dependence on human activity--the curves ran parallel at certain times of the year. Statistical results point to the possible presence of plant residues on smaller particles. The occurrence of simultaneous peaks in airborne pollen-grain and PM10 counts suggests potential coadjuvant activity, which may lead to high-risk situations for people with respiratory disease.

The occurrence of symptoms in pollen allergy patients in urban areas may be affected by local environmental factors such as sources of pollution, natural and ornamental vegetation, local architecture impeding dispersion, etc. The aim of this study was to analyse the frequency of sensitization in pollen allergy patients and the relationship with antihistamine sales. For this study, a large number of clinical records, together with pharmaceutical and pollen data, were collected between 1999 and 2001 in the city of Córdoba, in the south of the Iberian Peninsula. Differences were observed in the symptoms suffered by pollen allergy patients in different areas of the city due to varying local emission of both biological and non-biological particles. Temporal distribution of symptoms over the three study years was influenced by meteorological factors, especially rainfall patterns; higher water supply to plants was associated with increased airborne pollen concentrations. Air pollution might be one of the main factors affecting the distribution of pollen allergy patients within the city. Recent years have seen a worsening of symptoms and increased sensitization to urban species such as plane-trees.

Dust-cloud episodes were detected in summer 1999 in the city of Cordoba, southwestern Spain, with a higher frequency than usual. Solid airborne particles were collected using a suction volumetric sampler and analyzed to determine both their nature and their origin. Nonbiological material was mostly identified as mineral sand and partially burned remains of hydrocarbons and stubble. Amounts were estimated in terms of the percentage of microscopic field of view covered. Biological materials, in this case pollen grains, were identified and classified as belonging to either autochthonous or remote flora; in the latter case, the possibility was examined that they might originate in North Africa. Some pollen types were also used as tracers to chart the path followed by the sand clouds within the Iberian Peninsula. Meteorological conditions on the days in which episodes occurred were analyzed. In all cases, very dry southwesterly winds were recorded, at moderate to high speeds, together with temperatures of over 35 degrees C. The increase in airborne pollen detected, together with the large amount of particles collected, could have an adverse effect on health, particularly in pollen allergy sufferers, for whom dust-clouds represent an added risk.

Plane-trees are widely grown in Spain as ornaments. This taxon releases large amounts of pollen into the air and this pollen type seems to have proved implications on pollinosis. The aim of this study was to analyse airborne Platanus pollen content in the air of C6rdoba (South-western Spain) over the last 10 years, and its distribution in different areas of the city, as well as to consider possible implications regarding pollen allergies. Results revealed that Platanus pollen concentrations have been at their highest over the last 5 years. Within the city, the lowest pollen concentrations were in Northern areas of the city. Nevertheless, concentrations high enough to be of risk are reached over the whole city. All the patients studied presented symptoms during the Platanus pollen season. We can therefore conclude that plane pollen presents a risk for the whole city although symptoms are more intense and persistent in districts with a higher number of plane-trees. Platanus allergy is a particular problem for city-dwellers, where these trees are commonly used as ornamentals.

Over 80% of weekday time is spent indoors and the air quality of this environment may affect the incidence of symptoms in allergy sufferers. However, indoor/outdoor measurements have been jointly considered only in a few studies. The objective of this paper is to analyse indoor/outdoor biological and non-biological particle content togeher with other factors affecting the severity of symptoms during working periods in an Aerobiology Lab during the most troublesome period of the year for allergy sufferers. For this purpose, indoor/ outdoor air samples were taken using standard portable particle traps at the National Coordinating Centre of the Spanish Aerobiology Network, University of Cordoba. The analysis differentiated between biological and non-biological material, and the allergy symptoms suffered by workers were quantified and correlated accordingly. An inventory of the incoming and outgoing sources of emissions was done in order to identify agravating co-factors. The results showed that since there was very little air movement between indoors and outdoors, there was a significant difference in the amount of biological material present in the two areas. The presence of some indoor source of emissions, such as the Plant Collections property of the Department, the Air Conditioned System and the volatile compounds of the copying machine was responsible of high particle content. External factors such as weather conditions or human activities contributed exacerbating symptoms. As Conclusion, the knowledge of airborne biological particle content could be a useful tool in minimising allergy symptoms when environmental conditions render them inevitable.

The aim of this study was to analyse the relationship between the distribution of hay-fever patients in the city of Córdoba, south-western Iberian Peninsula, and the specific atmospheric biological content originating from local sources. Four different districts were established in the metropolitan area of the city, according to vegetational and urbanistic characteristics. Air samples were taken in each area using portable Hirst-type samplers (Lanzoni VPPS 1000) and the spectrum of biological content was defined. Patients attending the Allergy Unit at Córdoba Teaching Hospital in 2000 with allergic rhinitis and/or asthma, and displaying a positive reaction to aeroallergen extracts, were distributed within the areas as a function of their district of residence. Aerobiological results revealed differences in pollen content between areas, in terms of both quantity and number of pollen types recorded. These differences were largely due to proximity to rural areas, prevalence of pollen from typically urban species and the possible effect of urban architecture as a barrier to the dispersal/ concentration of particles and other pollutants. Patients were not uniformly distributed within the city. The majority lived in districts in which pollen from rural species was mixed with pollen from ornamentals. Patients living in typically urban districts displayed a higher prevalence of allergy to pollen from ornamentals. It is concluded that a high degree of exposure to the same environment may influence the development of sensitisation to the particular pollen load associated with that area.

Background: Privet pollen rarely accounts for more than 1% of the annual total of daily pollen concentrations measured in a city; however in areas where these trees are widely used as ornamentals the amounts collected may be high enough to cause allergy symptoms., Methods: Air samples taken with volumetric particle samplers Lanzoni VPPS 1000 (Lanzoni s.r.l., Bologna, Italy) show that there are differences in privet pollen concentrations measured in neighbourhoods with a high incidence of privet trees and in those taken at some distance from the source of emission., Results: The results suggest that differences are due to the short dispersal range of the pollen grains once released from the plant, resulting from both the entomophilous nature of the plant and the large size of the pollen grains. Urban design, moreover, may play an important role in impeding pollen grain dispersion if the air cannot flow freely through long, narrow avenues. Another important consideration is that the last stages of the flowering period of privet overlaps with the flowering period of olive trees, the main allergen in the area. The fact that the two pollen types share common allergens means that there may be a cross-reaction between olive tree pollen and privet pollen., Conclusions: Privet pollen should be considered as a potential causative agent of local allergy problems in areas where its presence is extensive and is in combination with other allergens.

Data on predicted average and maximum airborne pollen concentrations and the dates on which these maximum values are expected are of undoubted value to allergists and allergy sufferers, as well as to agronomists. This paper reports on the development of predictive models for calculating total annual pollen output, on the basis of pollen and weather data compiled over the last 19 years (1982-2000) for Córdoba (Spain). Models were tested in order to predict the 2000 pollen season; in addition, and in view of the heavy rainfall recorded in spring 2000, the 1982-1998 data set was used to test the model for 1999. The results of the multiple regression analysis show that the variables exerting the greatest influence on the pollen index were rainfall in March and temperatures over the months prior to the flowering period. For prediction of maximum values and dates on which these values might be expected, the start of the pollen season was used as an additional independent variable. Temperature proved the best variable for this prediction. Results improved when the 5-day moving average was taken into account. Testing of the predictive model for 1999 and 2000 yielded fairly similar results. In both cases, the difference between expected and observed pollen data was no greater than 10%. However, significant differences were recorded between forecast and expected maximum and minimum values, owing to the influence of rainfall during the flowering period.

Temperature is one of the main factors affecting the flowering of Mediterranean trees. In the case of Olea europaea L., a low-temperature period prior to bud development is essential to interrupt dormancy. After that, and once a base temperature is reached, the plant accumulates heat until flowering starts. Different methods of obtaining the best-forecast model for the onset date of the O. europaea pollen season, using temperature as the predictive parameter, are proposed in this paper. An 18-year pollen and climatic data series (1982-1999) from Cordoba (Spain) was used to perform the study. First a multiple-regression analysis using 15-day average temperatures from the period prior to flowering time was tested. Second, three heat-summation methods were used, determining the the quantities heat units (HU): accumulated daily mean temperature after deducting a threshold, growing degree-days (GDD): proposed by Snyder [J Agric Meteorol 35:353-358 (1985)] as a measure of physiological time, and accumulated maximum temperature. In the first two, the optimum base temperature selected for heat accumulation was 12.5 degrees C. The multiple-regression equation for 1999 gives a 7-day delay from the observed date. The most accurate results were obtained with the GDD method, with a difference of only 4.7 days between predicted and observed dates. The average heat accumulation expressed as GDD was 209.9 degrees C days. The HU method also gives good results, with no significant statistical differences between predictions and observations.

The yearly distribution of Artemisia and Chenopodiaceae-Amaranthaceae, two of the most common types of pollen in a rural area located in the southeastern part of the Iberian peninsula, was studied over a 3-year period (1995-1997). The particular bioclimatic conditions of the area, such as its subdesert climate, extreme dryness and high mountain location (1,000 m above sea level), have led to the adaptation and abundance of these species in this area. They usually flower in the second half of the year, and are the main pollen types collected in the samples in that time period. The Artemisia pollen levels recorded are the highest in Spain, since there are several species in the area which flower at different times. Chenopodiaceae-Amaranthaceae pollen counts are also very high. The severity of both pollen types was also analyzed. The height of the sampler was taken into account because the quantities at human height can be considerably higher than those recorded at 20 m off the ground. It was concluded that both pollen types should be considered some of the main causes of allergy in this area.

Winter is not traditionally considered to be a risky season for people who suffer from pollen allergies. However, increasing numbers of people are showing symptoms in winter. This prompted our investigation into the levels of solid material in the air, and some of the meteorological phenomena that allow their accumulation. This study showed a possible relationship between the phenomenon of thermal inversion, which occurs when very low temperatures, cloudless skies and atmospheric calms coincide, and an increase in the concentration of solid material in the atmosphere. Frequently, this situation is associated with other predictable phenomena such as fog, dew and frost. This may allow a warning system to be derived for urban pollution episodes. The effect caused by parameters such as wind and rainfall was also analysed. Solid material was differentiated into non-biological material from natural and non-natural sources (e.g. soot, dust, sand, diesel exhaust particles, partially burnt residues) and biological material. The latter mainly comprises pollen grains and fungal spores. Owing to its abundance and importance as a causal agent of winter allergies, Cupressaceae pollen was considered separately.

The influence of meteorological factors on daily Urticaceae pollen counts were studied in Córdoba (southwest Spain) in 1996 and 1997. The daily Urticaceae pollen concentrations were obtained by using a Hirst-type volumetric sampler, and meteorological data were obtained from the Córdoba airport, located near the sampling site. The highest correlation between pollen concentration and meteorological parameters was obtained during non-rainy seasons. Temperature was found to be the most important meteorological parameter influencing pollen counts in spring, as temperature is the main reason for the increase of pollen concentration in the atmosphere. In autumn, humidity was another important parameter influencing pollen counts. Rain, however, did not appear to be significant. The influence of the pollen concentration of the 2 previous days and the pollen concentration of the previous day has been studied. During periods with low precipitation, the pollen concentration of the previous day was a useful predictor of Urticaceae pollen concentrations for the following day.

This study examined the effect of sampling height on the measurement of airborne particles (pollen grains) common in the sampling area in the outskirts of the city of Córdoba, Spain. The effect of certain meteorological parameters on variations in concentration at different heights were also examined. The study was carried out throughout 1991 and 1992 using two Hirst samplers placed at two different heights (1.5 and 15 m) at the Faculty of Science at the University of Córdoba. The statistical results indicated that there were significant differences in the concentrations obtained at different heights, the values at 1.5 m being generally higher with the exception of pollen belonging to the Urticaceae family. The pollen counts of this type were greater at the higher elevation, probably due to the small size of the pollen, especially in the Urtica membranacea species, and to the convective phenomena in this climatic zone in spring, the season in which this species blooms. When these height comparison studies were conducted, the importance of the effect of placing the sampler in relation to a nearby building was also observed. Higher pollen concentrations were detected when the lower sampler was located on the leeward side. The meteorological parameters studied had some influence on the vertical dispersion of the pollen, although the percentage of variation according to height was very small, probably due to the short duration of the study. However, a certain relation between the differences in concentration per height and the degree of atmospheric stability was observed.

The diurnal variation in airborne pollen concentrations in the air of Córdoba at two different heights (1.5 m and 15 m) was studied during 2 consecutive years with the help of two Hirst volumetric samplers. According to pollen percentages obtained every hour, we determined whether every taxon studied presented a morning or an afternoon pattern, and whether this model was homogeneous (with a slight difference between the time of maximum and minimum reading) or heterogeneous (with a large difference between the two readings). We observed that the taxa that had many species in the area, such as Plantago, Poaceae, and Chenopodiaceae-Amaranthaceae showed a homogeneous model, while those taxa with few species present, such as Cupressaceae and Urticaceae showed a more heterogeneous model. Furthermore, the pattern of the plants with a large presence in the study area was more heterogeneous at 1.5 m because the pollen collected at this height is released from anthers. In the sampler placed at 15 m we detected airborne pollen, found that the curves were smoother and also observed a slight time delay for the taxa that were highly present in the area of study.