Konstantinos Koronios

Lazaros Ntasis

Panagiotis Dimitropoulos

Anna Gerke

Unlocking the black box of sponsorship in participant-based sport

Keywords: Sport Sponsorship, Participant-based sport, Martial Arts

teaching and research institutions in France or abroad, or from public or private research centers.

Introduction

The ability of organizations to influence consumers becomes increasingly important [START_REF] Marin | The Role of Identification in Consumers' Evaluations of Brand Extensions[END_REF]. Organizations need to consider more compelling procedures of advertisement, for example, events sponsoring. Sponsorship is a strategy of nontraditional or below-the-line communication that has created a lot of consideration among scholars [START_REF] Meenaghan | Measuring sponsorship performance: challenge and direction[END_REF] and can be characterized as "a money or in-kind fee paid to a property [a property rights holder] regularly in games, arts, entertainment, or causes) as a tradeoff admittance to the exploitable business capability of that property" [START_REF] Walliser | An international review of sponsorship research: extension and update[END_REF].

Sponsorship-based marketing, while useful in building awareness and improving brand image, holds more prominent potential than traditional advertising methods since it correlates with an individual's passion [START_REF] Meenaghan | Measuring sponsorship performance: challenge and direction[END_REF]. Sponsoring takes various forms relying upon the sponsored "object" [START_REF] Cornwell | Less "Sponsorship As Advertising" and more sponsorship-linked marketing as authentic engagement[END_REF]. Examples include (1) stadiums/equipment/things, namely the Allianz Arena Stadium in Munich, (2) activities/events/programming, for example, the Paris Marathon, with sponsors, such as, Schneider Electrics, (3) groups/individuals, for example, footballer's Cristiano Ronaldo sponsoring by Nike, and (4) organizations/leagues, for example, the Euroleague Basketball Championship sponsoring by Turkish Airlines.

Regardless of the Covid-19 health emergency and the subsequent mass retractions or delays of sports events worldwide, overall sport sponsorship spending in 2020 was $28.92 billion, while it is estimated to reach $89 billion before the end of 2024 [START_REF] Gough | Top eSports Countries by Active Player Count 2019[END_REF].

Nonetheless, these numbers do not recount the entire story on the significance of sponsoring in the present marketing and communications scene. It is not the supreme spending on sponsorship that is so significant yet rather how support has been instrumental in changing how brands connect with audiences. One characteristic among numerous others of contemporary sport is its capacity to motivate people passionately and engage them emotionally, which has made sport a valuable tool for consumer-driven marketing. In sport sponsorship, the sponsoring brand associates with the sport property and can convey messages to consumers in a less commercial way. Organizations invest resources in sport sponsorship expecting that the positive attitude that fans have toward their preferred sport entity (e.g., team) will be transferred to their brand through sponsor-sponsee relationship [START_REF] Madrigal | Social identity effects in a belief-attitude-intentions hierarchy: Implications for corporate sponsorship[END_REF].

Target audiences from the sponsor's viewpoint include current and expected customers, workforce and communities. From the sport property point of view, fans, supporters, and participants could be objective target audiences. Nonetheless, most sponsorship research has been oriented toward understanding sport viewers as consumers of sponsoring brands. Sport participants, for example, are under-researched and the capability of sponsorship to impact such "internal" audiences is simply starting to be acknowledged [START_REF] Cornwell | Less "Sponsorship As Advertising" and more sponsorship-linked marketing as authentic engagement[END_REF].

The present work recommends that a more profound connection among brands and their audiences can be achieved in sponsorship when advertising-driven correspondence is not the sole goal. Regardless, sponsorship research which remains a field dominated by marketing and research that investigates internal audiences is restricted in amount [START_REF] Khan | A model of sponsorship effects on the sponsor's employees[END_REF]. Some experimental commitments have zeroed in on the internal audiences of organizations occupied with sponsorships [START_REF] Edwards | The Olympic effect: Employee reactions to their employer's sponsorship of a high-profile global sporting event[END_REF]), yet so far barely any empirical study has explored internal audiences (such as sport participants) as potential vehicles in the sport sponsorship setting. One expected field for sport sponsorship that seems to be developing overall is the section of participant-driven sport, which may speak to a bigger portion of the sport business than viewer-driven sports [START_REF] Kim | The role of gratitude in sponsorship: the case of participant sports[END_REF].

One renowned participant-based sport is Taekwondo, the Korean martial art that has been an Olympic event since the year 1988. The practice of Taekwondo has spread worldwide and is right now a popular sport reaching about 70 million practitioners in 204 nations, while the number of children who join Taekwondo training is increasing each year, with 380,000 applying for the Taekwondo belt test on a yearly basis [START_REF] Lee | Ambush Marketing in Sport Taekwondo and How to Prevent It". I do Movement for Culture[END_REF]. Taekwondo competitions have likewise expanded in number and size as of late. These events draw in contenders and fans from around the globe and have local and worldwide sponsorships. Associations and organizations that make products associated with Taekwondo practice and competition (for instance, the Taekwondo industry) are similarly keen on supporting Taekwondo events. Multinational companies, for example, Adidas, which makes Taekwondo uniforms and attire, frequently support Taekwondo competitions and events that draw a huge number of contenders [START_REF] Lee | Ambush Marketing in Sport Taekwondo and How to Prevent It". I do Movement for Culture[END_REF].

The enhanced development of participants and Taekwondo events has attracted corporate sponsors. Organizations see opportunities for lifestyle marketing, and regular participants in grassroots and specialty sport events are more passionate about the promotion of their sport than the average sport consumer [START_REF] Miloch | Consumer awareness of sponsorship at grassroots sport events[END_REF]. provide interesting opportunities for corporate social responsibility initiatives, given that associations that run participant sports are frequently not-for-profits as well as depend on corporate funding to provide projects and opportunities to general society [START_REF] Kim | The role of gratitude in sponsorship: the case of participant sports[END_REF]. Hence, albeit grassroots and niche sport events do not get the same mainstream (media) exposure as major spectator-based sports, they actually proivde an alluring vehicle to sponsors to draw in explicit objective target sectors.

Notwithstanding the development of participant-driven sport sponsorship, there is as yet a general deficiency of analyzing sponsorship in participant sport settings. A large part of the present sponsorship research is led through the viewpoint of sport fans and spectators [START_REF] Herrmann | I support your team, support me in turn!": The driving role of consumers' affiliation with the sponsored entity in explaining behavioral effects of sport sponsorship leveraging activities[END_REF]; nonetheless, as [START_REF] Eddy | Sponsorship antecedents and outcomes in participant sport settings[END_REF] noted, there is a demand to comprehend sport participants' reaction to sponsors as well.

Various contrasts exist between the variables that anticipate why individuals take an interest in sport as participants versus as viewers [START_REF] Rapun-Garate | Determinants of sports participation and attendance: differences and similarities[END_REF]. In accordance with the developing need to explore the effectiveness of sponsorship using a theoretical framework and because of the above inadequacies, the aim of the current research is to create a model of consumer-buyer attitude relating to the sponsorship of participant-driven sport. To be more explicit, the purpose of this study was to introduce an integrated conceptual model for sport sponsorship assessment in the participant sport setting, by analyzing the effect of sponsorship on participants' attitudes and intentions toward sponsors. The suggested model draws on a comprehensive review of the literature related to sport participants, athletes, team brands, and sponsorship of sports.

While past examinations have focused separately on the antecedents affecting sponsorship awareness or the connection between sponsorship and purchase purposes [START_REF] Biscaia | A model bridging team brand experience and sponsorship brand experience[END_REF], to date, no thorough system has been created linking these points of view to the participant sport setting, to provide a thorough comprehension of the elements impacting sponsorship's effectiveness.

The proposed model is comprised of ten (10) variables that, when taken as a whole, offer a thorough knowledge of how to strengthen the relationships between the antecedents and outcomes of sport sponsorship in participant-based sports. The essential components of this concept include individuals' awareness and attitudes toward official sponsors, as well as their influence on the purchase and word-of-mouth intents of participants with regard to sponsoring businesses. The main components of this model include participants' awareness of and attitudes toward official sponsors, as well as their effect on participants' purchase and word of mouth intentions regarding sponsoring firms. This research also explored the role of significant antecedents, for example, participants' involvement with sport, their beliefs about sponsorship, their satisfaction from the sport event, sponsoring firms' degree of sincerity, the frequency of visiting the sport event's site and social media accounts and the sponsoring companies' image.

The previously mentioned antecedents play a key role in upgrading sponsorship effectiveness, which is reflected through a continuum of responses that regularly begins with sponsorship awareness and ultimately leads to increments in participants' purchase and word of mouth intentions for sponsors' products.

Theoretical Background

Sponsorship is the endorsement of a specific event to help corporate goals by improving corporate image, expanding attention to brands, or straightforwardly stimulating sales of products and services, that can be personal or joint; the occasion can be a one-time affair or a continuing series of activities [START_REF] Kang | The Effects of Sports Sponsorship Recognition on Corporate Image, Purchasing Intention and Brand Identification[END_REF]. The impact of sports is expanding through different channels and media because of the expansion of the sports population and the advancement of the media. Sports sponsorship is an advertising medium for consumers who are exposed to a flood of data and sports sponsorship is more centered around the target group than traditional cluttered advertising media, empowering effective communication in the communication cycle, and intensifying the perception of the message.

Sports sponsorship is an exchange between a sponsor and sport sponsee/sponsored sport association, event, athlete etc. (Koronios et al., 2020b). Sponsors are linked to sport events that receive economic, material, and human assistance from sponsors. Sport sponsorship is the most widespread sponsorship type, regularly receiving 70% of the complete yearly overall sponsorship expenditure (IEG, 2017). Corporate marketing, communications, public relations, and/or promotional purposes have been referred to as main sport sponsorship aims [START_REF] Greenhalgh | What's in it for me? An investigation of North American professional niche sport sponsorship objectives[END_REF]. Overarching corporate goals are met by using the sport sponsorship relationship as a vehicle. Increase public awareness, enhance corporate image and alter public perception, build business/trade goodwill, enhance employee relations/motivation and increase sales/market share are just a few of the sponsorship objectives that were identified by the majority of sport sponsorship research. This happens because via sponsorship, companies can feel a sense of intimacy and homogeneity and can create a new corporate image. Furthermore, the firm's brand value can be boosted through established corporate image and brand awareness, proficient access to target groups, supported positive ties with customers and expanded customers reliability to expand deals. Past examinations express that another reason behind the fast development of sports sponsorships as marketing instruments is that sports sponsorships are generally compelling, while traditional marketing techniques are less powerful [START_REF] Kang | The Effects of Sports Sponsorship Recognition on Corporate Image, Purchasing Intention and Brand Identification[END_REF]. As sports sponsorships emerge as new marketing vehicles, there is a growing scientific interest in sports and academia research.

Up until today, sport sponsorship research has commonly been engaged with the emotive and attitudinal results of spectators. Constructs generally distinguished as (attitudinal) indicators of sponsor results (the most well-known of which being buying goals) are sponsorship awareness [START_REF] Hickman | The impact of fan identification, purchase intentions, and sponsorship awareness on sponsors' share of wallet[END_REF], sponsor image and engagement [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF], and sponsor generosity [START_REF] Dees | Measuring the effectiveness of sponsorship of an elite intercollegiate football program[END_REF]. These kinds of variables, especially awareness [START_REF] Eagleman | Sponsorship awareness, attitudes, and purchase intentions of road race series participants[END_REF], have also started to show up in investigations of sport participants. It is essential to take note of the fact that there is some proof to propose that, in all probability, there are differences between how participants and spectators process sponsorship.

According to Andreani et al. (2014) and [START_REF] Madrigal | Social identity effects in a belief-attitude-intentions hierarchy: Implications for corporate sponsorship[END_REF], regardless of the environment, the theoretical frameworks used to investigate the attitudinal impacts of sponsorship are largely modifications of the theory of reasoned action, which was first suggested by Ajzen and Fishbein in the 1980s. The theory of reasoned action (often referred to as the belief-attitude-intention chain), states that an individual's personal beliefs about an item or entity impact their attitudes toward that item or entity, which in turn influences their future intentions toward that item or entity. In addition to the cognition-affect-conation chain (or possible combinations of any of the above), other hierarchy of effects models, have been used to explain the effects of sponsorships on consumers [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF], but these adaptations are typically grounded in the theory of reasoned action. The present study, proposes a research framework, based on two focal components: (a) the antecedents of sport sponsorship awareness (for example, participants' degree of involvement with sport, their beliefs about sponsorship, the sponsor's image, participants' satisfaction with the sport event, participants' frequency of social media and website usage, sponsors' anticipated degree of sincerity, which as a result impact the intermediate factor (i.e. attitude toward sponsors), which thus impact the (b) desired results for the sponsor (i.e. purchase and word of mouth intentions regarding their products/services). A review of the specific constructs included in the model follows below.

Sport Involvement

Involvement theory exhibits that an individual's association with an object of interest is a determinant of how the individual's assumptions are shaped, and the object is assessed. Views and assumptions for objects of interest can be influenced by the level of inclusion with the object [START_REF] Kim | The Effect of Sport Involvement on Support for Mega Sport Events: Why Does It Matter[END_REF]. As indicated by [START_REF] Zaichkowsky | Measuring the involvement construct[END_REF], engagement is "an individual's apparent importance of the object dependent on intrinsic requirements, qualities, and interest" (p. 342). The degree of engagement is revealed by personal identification towards the object of interest. Moreover, the degree of engagement influences a series of attitudinal choices and can act as a significant mediator that clarifies the connections between the factors inside the attitudinal choices of people [START_REF] Kim | The Effect of Sport Involvement on Support for Mega Sport Events: Why Does It Matter[END_REF]. Involvement can be alluded to as the level of responsibility with respect to an object, action, or experience, perceived individual significance, and degree of psychological association [START_REF] Funk | The psychological continuum model: A conceptual framework for understanding an individual's psychological connection to sport[END_REF]. Along these lines, a martial art like Taekwondo can be the object of inclusion in sport participant context and can be utilized as an antecedent to awareness of as well as attitude toward sponsors.

Sport involvement can be viewed as the evaluation of how much sport activity is at the focal point of an individual's life, involving watching and taking part in different sport occasions.

Thusly, sport engagement can influence the intrinsic assumption development and assessment cycle of the occasion's results (for example, financial, social, environmental) among participants with various degrees of engagement. Concurrently, other past explorations have concentrated on the role of inclusion as a mediator in relation to indicators and result factors. Notwithstanding, a couple of studies have investigated the impacts of participants' sport association on their behaviors and buying purposes [START_REF] Dees | Measuring the effectiveness of sponsorship of an elite intercollegiate football program[END_REF].

Sponsors' Sincerity

In spite of the expanded acknowledgment of sponsorship, there is still worry about purchaser skepticism toward sponsorship and the apparent sincerity of the sponsor [START_REF] Tyler | Schadenfreude, rivalry antecedents, and the role of perceived sincerity in sponsorship of sport rivalries[END_REF]. Sport members may respond adversely in perceiving that a sponsor is excessively motivated by commercial contemplations (for instance, anti-social intentions) rather than the pro-social motives of supporting the sport itself [START_REF] Speed | Determinants of sports sponsorship response[END_REF]. [START_REF] Speed | Determinants of sports sponsorship response[END_REF] emphasized the role of perceived sinceritydescribed as pro-social parts of the sponsorship contrasted with commercial inspirationsin upgrading sponsor interest, positivity, and utilization of the sponsor's item. People who see a sponsor as genuine appear to like the sponsorship, especially when those people are exceptionally included or related to the sponsored occasion [START_REF] Gwinner | A model of fan identification: Antecedents and sponsorship outcomes[END_REF].

Sponsors of one's preferred sport event may be criticized less severely and perceived as motivated more by pro-social purposes. As such, emotionally connected sport participants could see the sponsorship support of a sport event as an earnest acknowledgment of the significance of the sport. Sponsoring informing that stresses pro-social contention components may advance this impression of sponsor sincerity. The purpose of an influence heuristic is for individuals to utilize their emotions to advise their resulting decisions. Taking into account that a sport participant holds a positive feeling (for example, bliss, joy) about the occasion, it should promote good decisions of correlated data, for instance, a related sponsorship. Whilst truthfulness has been discovered to be a significant indicator of more elevated level sponsorship impacts [START_REF] Olson | Are rival team fans a curse for home team sponsors? The moderating effects of fit, oppositional loyalty, and league sponsoring[END_REF], no past examination has endeavored to incorporate this factor into a comprehensive sponsorship structure, as an important precursor of sport sponsorship adequacy in the participant sport setting.

Beliefs about Sponsorship

Participants' impression of a signal will be fundamental in accomplishing the ideal sponsorship impacts. Keeping in view the grounded connection among beliefs and attitudes (Ajzen and Fishbein, 1980), an individual's views about sponsorship may influence their behavior towards the sponsoring organization. To be more explicit, Ajzen and Fishbein (1980) suggest that the development of views, behavior, and conduct ought to be particular. This multidimensional structure views belief as a predecessor and attitude as an outcome of mentality, shaping a cognition-fondness-conation relationship. Individuals may have various purposes behind the development of a similar behavior towards a specific object. An individual can imagine how business sponsorship can be valuable in the advancement of sport. For this situation, the individual's viewpoint could shape their demeanor (likely to be favorable) towards sports sponsorship. On the other hand, in the event that someone else believes that sponsorship uses are a waste, at that point the behavior towards sponsorship could be negative (Koronios et al., 2020).

For instance, a Taekwondo athlete may shape a negative attitude towards a sponsor since it makes Taekwondo more commercialized. Another participant may likewise have a similar negative attitude towards the sponsor due to the sponsor logo interruptions throughout in the competition because of an absence of fit between the sport and the sponsor. Belief can therefore explain attitude. Deeply embedded general beliefs and attitudes apply more noteworthy impact (than low-embedded behaviors) on explicit assessments of circumstances [START_REF] Prislin | When it is embedded, it is potent: Effects of general attitude embeddedness on formation of specific attitudes and behavioral intentions[END_REF]. Accordingly, participants' overall viewpoints and behaviors towards an activity can prompt positive behaviors towards an association's inclusion with a particular action. Likewise, a participant's overall viewpoints and behavior towards sponsorship and the impact on their behavior towards sponsors requires examination.

Sponsor Image

A brand speaks to a "repository of implications filled by a blend of marketers' aims, consumers' interpretations, and various sociocultural networks' affiliations" (Parmentier, 2011, p. 219). Information processing theories structure the reasons for branding research. For instance, [START_REF] Keller | Strategic brand management process[END_REF] fundamental work of customer-driven brand value model depended on the cooperative organization memory model, which introduce that consumers' different dynamic generally relies upon their insight into the brand and the views they connect with the brand. One attitudinal factor which can be utilized as it related to other precursor variables in order to yield more significant discoveries, is sponsor image [START_REF] Crompton | Conceptualization and alternate operationalizations of the measurement of sponsorship effectiveness in sport[END_REF][START_REF] Kim | Factors influencing sponsorship effectiveness: A meta-analytic review and research synthesis[END_REF]. Sponsor image is characterized as a good demeanor toward the sponsor and its products [START_REF] Meenaghan | Measuring sponsorship performance: challenge and direction[END_REF]. In this research, sponsor image is being operationalized as a proportion of positive conclusions about the sponsoring brand, for example, liking or connection [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF][START_REF] Bennett | Analysing the effects of advertising type and antecedents on attitude towards advertising in sport[END_REF][START_REF] Dees | Measuring the effectiveness of sponsorship of an elite intercollegiate football program[END_REF].

The measure of information previously held by consumers about the sponsor will influence how a sponsoring organization will initially be comprehended and therefore stored in memory by consumers. Participating in sponsorship can have a particularly incredible beneficial outcome on the sponsor's image if customers accept that the sponsorship is profiting the sport association. This cycle, regularly alluded to as image transfer [START_REF] Gwinner | A model of fan identification: Antecedents and sponsorship outcomes[END_REF], happens when the image of the sport property is moved to the sponsor [START_REF] Koo | Effect of perceived sport event and sponsor image fit on consumers' cognition, affect, and behavioral intentions[END_REF]. Impression of brand image has been found to emphatically affect both behavior toward brand and purchase purposes of a sponsor's items. In this way, the sponsor's image assumes a significant part in participants' assessments of sponsorships, as anticipated image can impact purchase choices [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF]. To be more precise, studies on the mental processing by purchasers of a sponsor's relationship with a property shows that individuals are bound to accurately recognize sponsoring brands that have an unmistakable image and are natural to them. People distinguish brands with unmistakable images more regularly than lessimage conspicuous sponsors of sporting events on the grounds that these brands are all the more intellectually open in the minds of consumers, and they can all the more productively learn about the brand's sponsorship activities [START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF].

Social Media & Website Use

For quite a long time, contemporary sponsorship has not been connected distinctly with the presentation of the sponsor's logos Nowadays it resembles 360-degree communication, covering various marketing and communication activities, for example, creating brand image and brand awareness, reliability, corporate social obligation, product and service advancement, deals support or caring about relationships with stakeholders. As of late, there has been significant expansion in the quantity of communication and limited time activities, which has permitted sponsors to contact their stakeholders and more significantly, their supporters in a considerably more successful way. While conventional media remains the essential value driver for sponsors, when all media platforms are taken into consideration, social media accounts for 5-20% of absolute value created for sponsors [START_REF] Hurst | The rising importance of social media for football clubs[END_REF]. For instance, according to Nielsen-Sports' information, one soccer match between FC Barcelona and Real Madrid in December of 2016 created US$42.5 million in media worth for sponsors, of which social media contributed 12% or around US$5.1 million [START_REF] Hurst | The rising importance of social media for football clubs[END_REF].

Since it has reclassified buyer-brand association, social media is viewed as a significant customer activation vehicle by organizations across the globe. Social media has as of late become a powerful device that can be used by marketers for tapping shared interests of their customers and stimulating commitment in order to bring about positive attitudinal and social results, particularly in the sponsorship area (Koronios et al., 2020). This is on the grounds that social media is populous with sports supporters, and acts as an extraordinary source of conversations identified with sport and sport-wise issues, which occasionally spill over to discussions about related brands [START_REF] Cleland | Racism, football fans, and online message boards: How social media has added a new dimension to racist discourse in English football[END_REF]. Although there is academic focus on consumer commitment on online platforms, there are insufficient investigations on the utilization of social media by sport members, and on how social media can act as an instrument for accomplishing sponsorship targets [START_REF] Abeza | Social media scholarship in sport management research: A critical review[END_REF]. This examination looked to analyze the connection between sponsor awareness, behaviors, and buying purposes dependent on the sport participant's recurrence of visiting a sporting event's social media, a determinant not previously analyzed in participant-driven sport sponsorship research.

Satisfaction from event

Satisfaction begins from the psychological condition and anticipated worth of individuals toward the events and objects that they cooperate with during the engagement cycle. Fulfilment has become the essential pointer for corporate marketing and sales and has gained a noticeable situation at the core of marketing hypothesis and practice over recent years [START_REF] Kim | Factors influencing sponsorship effectiveness: A meta-analytic review and research synthesis[END_REF].

The generic framework of consumer satisfaction has been broadly brought into the sport marketing field. There are numerous parts of sport viewer fulfillment that sport associations ought to consider, including how to fulfill viewers and the results of viewer fulfillment.

Notwithstanding, past examinations on sponsorship chiefly centered around viewers; then again, there is scant experimental proof with respect to the participants' fulfillment from the occasion and its impact on sponsorship.

Sport participants' general satisfaction with the sport event includes their own success for competition, the presence of headlines, the lead trainer, the team management, the arena or field where the games are taking place, and explicit kinds of communication with the team.

Powerful management of the range and variety of the components of the sports item will be incorporated into the participants' general fulfillment with the occasion [START_REF] Tsuji | Consumer satisfaction with an action sports event[END_REF].

Generally, fulfillment is conceptualized by sport participants' overall or aggregate fulfillment with their total experience of the support to the sport event. The sport participants' general fulfillment with the occasion can be theoretically proposed as a precursor of awareness and behavior toward the occasion's sponsors. To be more explicit, a participant's general satisfaction from an event will prompt the advancement of trust between the participant and the sponsor and this ultimately prompts the improvement of a long-term responsibility between the two [START_REF] Tsuji | Consumer satisfaction with an action sports event[END_REF].

Awareness of Sponsors

Sponsorship is viewed as a productive instrument for expanding client awareness of a brand [START_REF] Speed | Determinants of sports sponsorship response[END_REF]. Brand awareness gives consumers suggestions or signs that promptly help them to remember certain brands, which is significant in light of the fact that this includes reviewing explicit brand names and product data from a client's long-term memory [START_REF] Keller | Strategic brand management process[END_REF]. As information on a brand expands, the apparent useful and enthusiastic risks of selecting the brand decline. In other words, brand awareness influences cognitive and emotional states, and such states decide the strength of the consumer-brand relation [START_REF] Koo | Effect of perceived sport event and sponsor image fit on consumers' cognition, affect, and behavioral intentions[END_REF].

Sponsorship awareness has been characterized as a cognitive capacity through which simple openness to stimuli (for example, sponsor enactment) can create an affiliation structure among brand and event [START_REF] Hickman | The impact of fan identification, purchase intentions, and sponsorship awareness on sponsors' share of wallet[END_REF]. Regularly, awareness is estimated by testing purchasers' capacity to review sponsoring organizations (independent) or perceive sponsors of the occasion (aided) from a list of organizations [START_REF] Bennett | Analysing the effects of advertising type and antecedents on attitude towards advertising in sport[END_REF]. Even more explicitly, brand review is the consumers' capacity to recall the brand name with no notice of product category or different brands, while brand acknowledgment is the capacity to recollect past openness to a brand when given top notch brands as a prompt [START_REF] Biscaia | A model bridging team brand experience and sponsorship brand experience[END_REF]. In this sense, sponsorship awareness in professional sports can be characterized as supporters' knowledge of the team sponsors, being communicated through the proper review and acknowledgment. [START_REF] Madrigal | Social identity effects in a belief-attitude-intentions hierarchy: Implications for corporate sponsorship[END_REF] proposed that awareness is the underlying phase of a continuum of people's reactions that can prompt their purchase and word of mouth intentions. Previous exploration for the most part shows that attention to the sponsorship is a significant determinant to more elevated-level attitudinal and conduct reactions to sponsorship, however it ought to be referenced that outcomes are to some degree mixed [START_REF] Bennett | Analysing the effects of advertising type and antecedents on attitude towards advertising in sport[END_REF][START_REF] Eagleman | Sponsorship awareness, attitudes, and purchase intentions of road race series participants[END_REF].

Attitude towards sponsor

An attitude is a positive or negative assessment of an item (for example, individuals, occasions, activities, and ideas), going from very negative to incredibly positive (Koronios et al., 2020b). Such assessments are constructed by the emotional and cognitive decisions of the object (Bagozzi and Bumkrant, 1985). The affective determinant of a behavior incorporates a good or negative emotional reaction to the item and the cognitive factor of a behavior includes convictions about the attributes of the item. As a general rule, affective and cognitive assessments of an item structure is the evaluator's general good or negative behavior towards the item. Appropriately, audience behaviors towards a sponsor could be characterized as the general positive or negative behavior towards the organization that is shaped by the audience's affective (for example, emotional reactions to the sponsor) or cognitive (for example, viewpoints about the organization's attributes) assessments of the sponsoring companies.

The improvement of a great behavior toward a sponsor is an urgent component of sponsorship adequacy [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF] on the grounds that ideal perspectives toward sponsors are required to prompt positive social goals. Companies participating in sponsorship activities are hoping to see sport consumers experiencing similar good emotions when seeing a sponsorship brand as to those experienced toward their team, and also hope that sport consumers will in general have beneficial behaviors toward the sponsor on the off chance that they accept that the sponsorship is essential to the sport [START_REF] Madrigal | Social identity effects in a belief-attitude-intentions hierarchy: Implications for corporate sponsorship[END_REF][START_REF] Cornwell | Sponsorship-linked marketing: The role of articulation in memory[END_REF]. Accordingly, sponsorship activity can alter participants' reactions to a particular association, resulting in the improvement of beneficial behaviors toward the sponsor, which would, in turn, prompt expanded purchaser eagerness to purchase the sponsor's items.

Purchase Intentions

Purchase intention has been viewed as one of the most famous determinants of both advertising and sponsorship viability [START_REF] Crompton | Conceptualization and alternate operationalizations of the measurement of sponsorship effectiveness in sport[END_REF]. There have been different examinations endeavoring to disclose consumers' aims to carry on in specific manners in advertising or sponsorship, for example, buying purposes [START_REF] Biscaia | A model bridging team brand experience and sponsorship brand experience[END_REF][START_REF] Dees | Measuring the effectiveness of sponsorship of an elite intercollegiate football program[END_REF] and beneficial word-of-mouth purposes [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF]. As behavior is a component of people's convictions about a product (for example, sponsored organization) and social expectations are emphatically affected by behavior, if participants evidence beneficial behaviors toward the sponsorship organizations, they will show much stronger buying purposes concerning their products. Buying purposes can be characterized as an individual's conscious plan in making an effort to buy a brand. From a sponsor's viewpoint, the buying purposes of a consumer is a critical indicator of sponsorship adequacy given its normal effect on future deals [START_REF] Choi | An investigation of sponsorship implications within a state sports festival: the case of the Florida Sunshine State Games[END_REF]. Supporters will in general hope that sponsoring organizations sponsoring their preferred teams are allies [START_REF] Madrigal | Social identity effects in a belief-attitude-intentions hierarchy: Implications for corporate sponsorship[END_REF], creating beneficial behaviors around them. This beneficial demeanor may even grow through the improvement of buying purposes to the sponsor's product.

In view of this assumption, it is normal that behavior toward the sponsoring organization will assume a mediating role between awareness of sponsoring organizations and the purchase purpose of the sponsoring organization's products.

Word of Mouth Intentions

Word of mouth (WOM) is an incredible and distinctive type of communication on account of the individual sentiments and experiences it inspires. Also, past examination proposes that people will spread positive or negative information when they experience extraordinary positives or negatives. Commonly, people disperse this data in a vis-à-vis communication as well as utilizing social media (e.g., Twitter, Facebook, and Instagram). Social media can be a ground-breaking technique in informal conduct in light of the fact that an individual can share and examine a single thought with numerous others and consequently spread messages rapidly and broadly. Sport supporters frequently utilize social media for dispersing current data about their preferred teams, sports, players just as sponsors do [START_REF] Ahn | Effects of perceived interactivity and web organization on user attitudes[END_REF]. Analysts have suggested WOM as a significant result in sponsorship research [START_REF] Gwinner | A model of fan identification: Antecedents and sponsorship outcomes[END_REF].

Word of Mouth is affected by the attitude towards the brand [START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF]. [START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF] discovered that there was a consensus on a connection between attitude towards the brand and the expectation of spreading positive word of mouth. A few researches including authoritative reputation, corporate social responsibilities of NBA teams and online contexts [START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF] have shown that behavior towards the brand was a significant indicator of individual's aims to enjoy positive Word of Mouth. Previous examination [START_REF] Biscaia | A model bridging team brand experience and sponsorship brand experience[END_REF][START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF] likewise showed that behavior towards the sponsor impacted the goal to take part in beneficial Word of mouth about the sponsor brand.

Hypotheses Development

According to the previous literature review, the proposed model (Figure 1

Methodology

The survey questions were designed based on methods employed by previous sponsorship researchers (e.g., [START_REF] Biscaia | A model bridging team brand experience and sponsorship brand experience[END_REF][START_REF] Eagleman | Sponsorship awareness, attitudes, and purchase intentions of road race series participants[END_REF][START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF]. Mediator scales were used in order to define the measurement under each variable sub-dimension. Content validity analysis took place by using a group of experts as well as a field test. The instrument was edited based on the group of experts' feedbacks. If items were identified as valid by experts at a percentage of 75%, they were kept. The questionnaire was translated from English into Greek after a back-translation procedure with the assistance of a board of specialists.

Sample and data Collection

A quantitative methodology was utilized for the scopes of this study and questionnaires handdelivered to the sampled taekwondo athletes who had participated in 2019-2020 tournaments.

Convenience sampling was employed for the scope of the research and athletes from three national events were approached. Data were collected at different intervals during the award ceremonies by a team consisting of eight researchers. Taekwondo athletes were randomly approached while they were waiting for the award ceremony to commence, and they were asked to respond to a survey. Respondents were told that their responses would remain anonymous, that there were no correct or incorrect responses and that they should be as truthful as possible when answering questions. These procedures minimized method bias which has been discovered to affect outcomes in behavioral research (Koronios et al., 2020a). During the three tournaments 1,500 taekwondo athletes were approached for the aim of the research and asked to complete the questionnaire. Five-point Likert scales were used to evaluate fundamental variables. The data analyses were based in the 1,056 returned questionnaires (70.40% response rate) that were fully completed and analyzed by means of Statistical Package for Social Science (SPSS) and SPSS Amos as well.

Construct validity of questionnaire

Exploratory factor analysis (EFA), reliability analysis and anti-image correlation were performed to investigate the factorial structure of each scale. One EFA's characteristic is that the observed variables are first with a mean of zero and standard deviation of 1.

Data is suitable for factor analysis when Kaiser-Meyer-Olkin's (KMO) and the Bartlett Sphericity Test are acceptable. The KMO index ranges from 0 to 1, with values above 0.70 being considered satisfactory for factor analysis [START_REF] Delen | Measuring firm performance using financial ratios: A decision tree approach[END_REF]. Additionally, Bartlett sphericity test should be significant at 5% significance level [START_REF] Delen | Measuring firm performance using financial ratios: A decision tree approach[END_REF]. Moreover, rotation of axes was performed using Varimax method based on correlation between the variables. The criteria that were used to choose the number of factors and the items corresponding to each factor: eigenvalues should be related to eigenvalues>1 for each factor and the factor loading of each item in the corresponding factor should be over 0.6. Also, the values above 0.7 are considered acceptable by Cronbach α coefficient. Furthermore, validation analysis was performed using confirmatory factor analysis (CFA). CFA is a special statistical method of structural data processing that is used to understand whether an instrument has the same factor structure across different groups. Furthermore, determine the Goodness of Fit Index -GFI between factorially structured model. It is an important tool in the second stage of an investigation and has been used in our research to the proposed exploratory model. The rejection or acceptance of a model is based on two types of control. Firstly, the global fit indices and secondly the magnitude of the variance explained by the resulting factors. The general indicators of good adaptation studied were: the index x2, Root Mean Square Error (RMSE) and Comparative Fit Index (CFI). Accepted results are: x2 (x2df) degrees of freedom with ratio <2.0, RMSEA <0.1 and CFI> 0.90 [START_REF] Lomax | A beginner's guide to structural equation modeling[END_REF] an acceptable adaptation is shown.

Results

Sample descriptive statistics

In total, of 1,056 participants the study, 862 were males (81.63%) and 194 were females (18.37%). Most of the participants workout from three to five times per week (n=888, 84.09%). Most (n=980, 92.8%) of the participants usually workout over 60 minutes per time and most of them started taekwondo after the age of 5 years old (n= 868, 82.19%). 90.9% of participants (n=960) usually train in sport clubs while only 9.1% of them train(n=96) outdoors.

Results regarding the taekwondo experience showed that 38.9% of participants (n=398) have participated in 11-30 professional events and 3.3% (n=34) of them have taken part in more than 100 events. Finally, 7.67% (n=81) of participants have participated in a European championship, while most of them (n=975) have participated in one at least national championship.

Tool validation and reliability

Explanatory factor analysis showed that five questions of Sport Involvement Scale (Table A) have factor loadings varied from 0.581 to 0.708, which is accepted for our sample size (Hair et al., 2006). Moreover, EFA analysis showed that three questions of Sincerity Scale (Table B) have a factor explanation of 13.96% of the data's variability. The factor loadings varied from 0.611 to 0.842, which is accepted for our sample size. As far as the social media and website use scale is concerned, seven questions (presented in Table C) created the factor. The factor explains 8.09% of the data's variability, while the factor loadings were between 0.425 to 0.942.

The analysis regarding Beliefs About Sponsorship Scale (Table D) showed that three questions create one factor which explains 6.1% of the data's variability, while the factor loadings varied from 0.828 to 0.607. Moreover, six items of the Satisfaction Scale (Table E) create one factor, which explains 6.9% of the data's variability and the factor loadings were greater than 0.501.

Additionally, the EFA analysis showed that four questions of Sponsor Image Scale (Table F) create one factor. The factor explains 9.19% of the data's variance. The factor loadings varied from 0.581 to 0.693 which is accepted for our sample size. Additionally, Awareness of Sponsor scales (Table G) create one factor, with factor's loadings varying from 0.592 to 0.831 and the eigenvalue being 2.12 with 12.5% explain power of data's variance. In the Attitude toward sponsor scale (Table H) loading factors are over 0.815 with eigenvalue 1.453 and variance 9.575%. As for Purchase intention scale, three questions (Table I) create the factor. The factor explains 4.86% of the data's variability, while the factor loadings were between 0.724 to 0.793 respectively. Finally, the analysis regarding Word-of-Mouth scale (Table J) showed that three questions create one factor. The final factor explains the 3.921 with eigenvalue 1.358 and factors loading from 0.431 to 0.761. The reliability analysis showed that all scales had a reliability coefficient over 0.7. The confirmatory factor analysis (CFA) showed that the proposed model for the structure of the tool was satisfactory (Normed χ 2 <1, RMSEA<0.1 and CFI>0.9). The results indicate that the proposed scales had a satisfactory validity and reliability indexes.

SEM results

Structural equation model (SEM) analysis was used to investigate the hypothesis H1-H9. Results are presented in Table K with direct affect and affected based on the mediators. The results of the final model investigate that (1) sport involvement influences sponsor awareness but not purchase intention directly (support hypothesis H1), (2) sponsor sincerity influences sponsor awareness through the mediating role of attitude toward sponsor, while directly influences purchase and word of mouth intentions (support hypothesis H2), (3) social media & web use influences sponsor awareness (support hypothesis H4), (4) beliefs about sponsorship influence sponsor awareness through the mediating role of attitude toward sponsor (support hypothesis H4), (5) satisfaction influences awareness of sponsors, purchase and word of mouth intentions (support hypothesis H5), ( 6) sponsor image influences awareness of sponsors (support hypothesis H6), ( 7) awareness of sponsors affect attitude toward sponsors (support hypothesis H7), (8) attitude toward sponsor affects participants' purchase intentions (support hypothesis H8), and (9) participants' attitude toward sponsors affect their word of mouth intentions (support hypothesis H9).

The investigated model is presented in (Table K) and results pointed out that awareness of sponsors is significantly affected by sport involvement; b=0. 218, p<.001; sincerity b=0.194, p<.001; social media & web use b=0.267, p<.001; beliefs about sponsorship b=0.176, p<.001; satisfaction b=0.154, p<.001 and sponsor image b=0.334, p<0.001. Furthermore, awareness of sponsors significantly affects attitude toward sponsor b=0.177, p<.001. Additionally, results showed up that attitude toward sponsor significantly affects participants' purchase intention; b=0.295, p<.001 as well as their word-of-mouth intentions; b=0.139, p<.001. Finally, factors with a significant direct effect on purchase intentions are sincerity b=0.112, p<.001 and satisfaction b=0.267, p<.001. On the other hand, word of mouth intentions are directly affected by sport involvement b=0.443, p<.001, sincerity b=0.038, p<.001 and satisfaction b=0.063, p<.001. The criteria of best-fitting are confirmed, based on the results (normed χ 2 =12.8, CFI=0.938, RMSEA=0.042).

Discussion and Implications

Sports sponsorship is becoming more and more significant as shown by both the money spent on it and the quantity of sports events sponsored and it has started to contend with other marketing communication procedures. Organizations are profoundly intrigued by sports sponsorships since they are powerful in improving buyers' behavior towards sponsors, and as a consequence, significantly affect their buying and word of mouth purposes with respect to sponsoring organizations' products and services. Likewise, sport sponsorships are likely to convey the message planned by the organization to the target group successfully, and the beneficial and positive feeling can be transferred to the brand in order to impact brand awareness, and to normally prompt the product buying purpose. The discoveries of this examination propose that sports sponsorship can prompt brand awareness and can lastingly affect product purchase and word of mouth goals, influencing consumers' brand devotion in the long run. The reason for this examination was to inspect sport sponsorship viability in internal crowds, and all the more explicitly in participant-driven sports. Participant-driven sport may speak to a bigger portion of the sport business than viewer-based sports [START_REF] Kim | The role of gratitude in sponsorship: the case of participant sports[END_REF].

The respondents of this examination were Taekwondo athletes who took part in a sport event of a national scale.

Commonly, the respondents in the investigation showed a serious level of awareness with sponsoring organizations, they exhibited beneficial behaviors with respect to the sponsors and displayed positive sponsor-based attitudinal aims. These discoveries were like those from viewer-based sports contexts, however the mean scores on the determinants in this examination, just as the consequences for attitudinal aims, were more noteworthy than those in past viewerdriven investigations [START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF]. The expanded size of the relations/impacts in this examination could likewise be due to the distinction in setting between a participant-driven and viewer-driven sport event. Sport participants may not see sponsorship in more modest, participant-driven sport events as being economically determined as organizations with profoundly obvious viewer sports.

As indicated by [START_REF] Choi | An investigation of sponsorship implications within a state sports festival: the case of the Florida Sunshine State Games[END_REF], despite the fact that supporters put resources into regional participant-driven sport events on the assumption that they will receive positive returns, participants do not seem to see sponsorship of these occasions as advertising, as proven by verification of the second hypotheses. Participants anticipate that sponsors have sincere motives when sponsoring the event, instead of strictly targeting economic objectives. All things considered, sponsors seem, by all accounts, to be seen as attempting to help the occasion and be socially capable in the community. . Although causal inferences are beyond the scope of this study, events such as those under investigation here may provide unique opportunities for sponsors to generate perceived goodwill in the community, and consequently improve their corporate image via the support of non-professional/amateur sport events.

It is imperative to remember that participants were being asked about sponsors and their underlying involvement in this new sport event. This is a significant perspective of this investigation, as the vast majority of past explorations here has been performed utilizing established occasions [START_REF] Eagleman | Sponsorship awareness, attitudes, and purchase intentions of road race series participants[END_REF][START_REF] Kim | The role of gratitude in sponsorship: the case of participant sports[END_REF], where it has been accepted that the participants, over a long period of time, have built up some extent of attention to occasions' sponsoring organizations. This should make the positive perceptions/goals in this investigation all the more reassuring, since attention to sponsors would probably not have been created before the cooperation related to the occasion, and accordingly would not have been driving perceptions.

One more significant highlight to underline is that the demographic profile of the sample in this examination was fundamentally the same as past exploration on participant-driven sport sponsorship, and all the more explicitly in martial arts. People taking part in these kinds of occasions will in general be dominatingly white, young adults (ages 18-35), single and profoundly educated [START_REF] Kim | Structural relationship between market demand and member commitment associated with the marketing of martial arts programs[END_REF]. Specifically, individuals that are all the more exceptionally educated appear to be overrepresented in the sport of Taekwondo [START_REF] Kim | Taekwondo participation as serious leisure for life satisfaction and health[END_REF]. Thus, the findings of this study may be somewhat generalizable not only to other small, regional race events, but also to larger scale events. Given that this demographic profile additionally speaks to a desired group of consumers across numerous product classifications, partnering with participant-driven occasions ought to be considerably more alluring to sponsors.

Hypothetically, the discoveries from this examination would recommend that awareness with sponsoring organizations just as behavior toward them should keep on being examined in sponsorship studies, particularly in participant-driven settings. Despite the fact that these determinants have appeared in past literature, the connection between attitudinal goals and awareness of sponsors with behavior toward sponsoring organizations as an incomplete partial mediator does not seem to have been tried.

The discoveries here back up this recommendationparticipants who had a beneficial attitude toward sponsors were bound to buy (supporting H8) or suggest those sponsors' products (supporting H9). Also, an important portion of this relationship was clarified by the way that sponsoring organizations' anticipated level of truthfulness improved participants' awareness of sponsors (supporting H2). This impact is not out of the ordinary since the individuals who have a more positive impression of sponsors will in general have more positive attitude purposes toward those sponsors' products [START_REF] Alexandris | Segmenting soccer spectators by attachment levels: a psychographic profile based on team self-expression and involvement[END_REF][START_REF] Choi | An investigation of sponsorship implications within a state sports festival: the case of the Florida Sunshine State Games[END_REF][START_REF] Dees | Measuring the effectiveness of sponsorship of an elite intercollegiate football program[END_REF]. Likewise, since individuals generally prefer it when sponsors seem to have unselfish inspirations to help the sport association, it appears to be sensible that the participants would have more beneficial goals toward sponsoring organizations. Subsequently, sponsoring organizations' sincerity seems to assume an important part in behavior development for brands, which can be translated into purchases. It ought to be noted that participants' evaluation of sincerity was for the most part beneficial in this investigation, maybe due again to the fact that the martial art event was a niche in the market.. Future exploration should test this relationship in other, maybe more commercial, contexts to guarantee that the relationships discovered here still hold when impressions of sincerity of the sponsors are more shifted. It is significant to underline that the participants not only responded emphatically toward the sponsors on the whole but in addition, the participants' capacity to perceive real, explicit sponsors was consistent. The findings in this study generally mirrored recognition rates of participants in comparable settings but were quite poor compared to larger scale spectator-based events [START_REF] Koronios | Sport sponsorship: The impact of sponsor image on purchase intention of fans[END_REF]. Furthermore, a portion of the dummy sponsors (foils) were perceived substantially more frequently in this investigation than in the vast majority of the past explorations. In this manner, some of the occasions' sponsors might not have benefited from the positive results that were noticed, on the grounds that numerous participants just did not understand that they were true sponsors. One clarification for the conflicting acknowledgment rates could be the wide variety in enactment systems. Past discoveries propose that more compelling activations appear to emphatically impact acknowledgment rates [START_REF] Eagleman | Sponsorship awareness, attitudes, and purchase intentions of road race series participants[END_REF][START_REF] Miloch | Consumer awareness of sponsorship at grassroots sport events[END_REF].

Limitations and further research

Despite the fact that the current examination had a beneficial outcome in assigning the significant sponsorship factors form the standpoint of the participants, the outcomes should be seen with consideration, as sponsorship actually is a demanding and equivalently minimally apprehended field. To begin with, the aftereffects of the examination were set up upon one participant sport and one tournament. To be more precise, the occasion used here was a public Taekwondo event. To have the option to sum up the results through various sponsorship settings, more examination utilizing various types of occasions, for instance, other martial arts, and at divergent levels, for instance, provincial and transnational, ought to be completed.

Secondly the recommendations for this current examination almost certainly apply to firms and sport entities that have the same features as the ones explored here. Considering that the present study focuses on Greek Taekwondo participants, the result speculation may have been affected. Subsequently, the outcomes could be seen as interesting to the Greek marketplace. Finally, since this investigation is only a snapshot in time of a new sport event, we cannot measure how insights may change, or whether the participants' attitudinal purposes will transform into a different future attitude.

  ) shows the suggested interactions by the mediation effect of Sponsor Awareness and Attitude Toward Sponsor to participants' purchase and word of mouth intentions. All the hypothesized variables are displayed in the above-mentioned model, which critically investigates the following hypotheses, for the first time in participant-based sport sponsorship: H1: Sport involvement positively influences Sponsor Awareness H2: Sponsor's sincerity positively influences Sponsor Awareness H3: Social media & website use positively influences Sponsor Awareness H4: Beliefs about sponsorship positively influence Sponsor Awareness H5: Satisfaction with event positively influences Sponsor Awareness H6: Sponsor's Image positively influences Sponsor Awareness H7: Awareness of sponsors positively influences Attitude Toward Sponsors H8: Attitude toward sponsor positively influences Purchase Intentions H9: Attitude toward sponsor positively influences Word of Mouth Intentions


Marie Choël

Anastasia Ivanovsky

Antoine Roose

Mona Hamzé

Anne-Marie Blanchenet

Nicolas Visez
email: nicolas.visez@univ-lille.fr

Quantitative Assessment of Coagulation of Atmospheric Particles onto Airborne Birch Pollen Grains

Keywords: Environmental pollution, particulate matter, atmospheric pollen sampling, pollen allergy

ABSTRACT

The coagulation of airborne particles on the surface of allergenic pollen grains is poorly described in the literature. However, particles deposited on the surface of pollen grains could have an effect on allergy and its symptoms. Observations of pollen surface alterations reported in the literature are either qualitative or are tainted by sampling artifacts that overestimate surface particulate pollution. Birch pollen grains (BPGs) were sampled in the atmosphere during pollination to quantitatively assess the extent of particulate deposition on allergenic pollen surfaces. Airborne PGs were collected with a cascade impactor ensuring no sampling artefact unlike pollen samplers usually used in this type of study. Counting, sizing and elemental analysis of particles adhering on pollen surfaces were performed by SEM/EDX. 68% of PGs did not carry any particle on their visible surface while the remaining 32% had between 1 to 16 particles on their surface. On average, polluted BPGs carried 2 ± 1 particles, representing an average surface coverage of 0.95%. We hypothesized that the main coagulation process was particle deposition by gravitational settling. Collision velocity calculations indicate that coagulation due to gravitational settling is prevalent under typical pollination atmospheric conditions. However, the effects of electric charges carried by pollen are largely unknown and may significantly alter coagulation rates. The presence of particle-polluted allergenic pollens appears to be common in the urban atmosphere, even under low air pollution conditions. The impact of chemical pollution of BPGs due to the presence of particulate matter (including soot particles) remains relatively unknown, both on the allergy and on the reproductive capacity of the tree.

1.INTRODUCTION

Birch pollen grains (BPGs) cause allergic reactions in more than 100 million people worldwide [START_REF] Lavaud | Allergie au pollen de bouleau[END_REF]). An increasing trend in atmospheric BPG concentrations has been observed in several countries in relation to the relentless rise of carbon dioxide and the effects of climate change [START_REF] Besancenot | Pollen et changement climatique. Bouleau et graminées en France métropolitaine[END_REF][START_REF] Darbah | Effects of Decadal Exposure to Interacting Elevated CO2 and/or O3 on Paper Birch (Betula papyrifera) Reproduction[END_REF][START_REF] Frei | The Effects of Climate Change in Switzerland 1969-1996 on Airborne Pollen Quantities from Hazel, Birch and Grass[END_REF][START_REF] Hoebeke | Thirty-Four Years of Pollen Monitoring: An Evaluation of the Temporal Variation of Pollen Seasons in Belgium[END_REF][START_REF] Ziska | Temperature-Related Changes in Airborne Allergenic Pollen Abundance and Seasonality Across the Northern Hemisphere: A Retrospective Data Analysis[END_REF]. In addition, air pollution can aggravate allergy symptoms [START_REF] Robichaud | A Case Study of Birch Pollen and the Synergy with Environmental Factors: Relation to Asthma in Montreal, Canada[END_REF][START_REF] Schiavoni | The Dangerous Liaison Between Pollens and Pollution in Respiratory Allergy[END_REF].

The allergic patient indeed never breathes BPGs alone; airborne BPGs are suspended in the urban atmosphere consisting of gaseous pollutants (NO2, O3, Volatile Organic Compounds), coarse, fine and ultrafine particles and other bioaerosols (spores and other potentially allergenic pollens). Taken separately, each of the constituents of the urban atmosphere can have aggravating effects on allergy but physical-chemical interactions also exist between gaseous and particulate atmospheric compounds.

Alterations of BPGs due to atmospheric biochemical reactions with ozone or nitrogen dioxide have been highlighted [START_REF] Sénéchal | A Review of the Effects of Major Atmospheric Pollutants on Pollen Grains, Pollen Content and Allergenicity[END_REF]. Gaseous air pollutants modify the lipid and protein fraction of BPGs [START_REF] Farah | Organic and Aqueous Extraction of Lipids from Birch Pollen Grains Exposed to Gaseous Pollutants[END_REF][START_REF] Pereira | The Strong and the Stronger: The Effects of Increasing Ozone and Nitrogen Dioxide Concentrations in Pollen of Different Forest Species[END_REF]Visez et al., 2020). Not only pollen grains (PGs) can be modified by air pollution, but there are clear qualitative evidences that allergenic PGs can also act as carriers of pollutants, both adsorbed gases and coagulated particles [START_REF] Okuyama | Adsorption of Air Pollutants on the Grain Surface of Japanese Cedar Pollen[END_REF][START_REF] Zhu | Uptake of Ozone and Modification of Lipids in Betula Pendula Pollen[END_REF].

Particulate pollution of the surface of allergenic PGs is, unlike pollen-gas interactions, poorly assessed in the literature [START_REF] Visez | Atmospheric Particulate Matter Adhesion onto Pollen: A Review[END_REF]. Most of the observations of particles on the surface of PGs are qualitative reports that do not estimate the extent of the pollution of the surface of PGs by extrapollinic atmospheric particles. The available quantitative studies report particularly high pollution of PG surfaces. For instance, [START_REF] Ribeiro | Characterisation of Particulate Matter on Airborne Pollen Grains[END_REF] reported an average number of particles adhering to the pollen surface of 16 ± 12 (average ± standard deviation), 39 ± 32 and 4 ± 4 particles per PG for Acer, Pinus and Platanus pollen, respectively [START_REF] Ribeiro | Characterisation of Particulate Matter on Airborne Pollen Grains[END_REF]. This study was conducted using a Hirst volumetric spore trap which is the most common method of sampling pollen on a moving slide, originally developed to count ambient pollen [START_REF] Mullins | Sampling Pollens[END_REF]. However, the use of a Hirst-type pollen sampler induces a sampling artifact with a significant overestimation of particle adhesion on PGs [START_REF] Choël | Evaluation of Hirst-Type Sampler and PM10 Impactor for Investigating Adhesion of Atmospheric Particles Onto Allergenic Pollen Grains[END_REF]. In addition, to our knowledge, there are no quantitative data on the specific pollution of the surface of BPGs by atmospheric particulate matter (APM); only one study reported a high degree of particle agglomeration onto BPGs collected from two highly polluted urban areas [START_REF] Behrendt | Allergens and Pollutants in the Air-A Complex Interaction[END_REF].

Being able to sample windborne PGs while preserving their initial state is crucial to study how PM alters the physical, chemical and biological properties of PGs. PM pollution of PGs can only be adequately assessed if particle size-selective classification is employed when sampling airborne pollen. In such way, PGs can be efficiently trapped in a specific sampling stage (for coarse particles) different from smaller ambient particles [START_REF] Levetin | Methods for Aeroallergen Sampling[END_REF]. Moreover, the sampling efficiency of airborne PGs is improved by the use of low nozzle velocity devices, such as impactors, compared to active sampling pollen trap, such as Hirst-type samplers [START_REF] Choël | Evaluation of Hirst-Type Sampler and PM10 Impactor for Investigating Adhesion of Atmospheric Particles Onto Allergenic Pollen Grains[END_REF][START_REF] Ribeiro | Characterisation of Particulate Matter on Airborne Pollen Grains[END_REF][START_REF] Wittmaack | An Overview on Bioaerosols Viewed by Scanning Electron Microscopy[END_REF]. In addition, the sampling duration should be short enough (~a few hours) to avoid the pile-up of particles, especially in highly polluted environments [START_REF] Wittmaack | An Overview on Bioaerosols Viewed by Scanning Electron Microscopy[END_REF]. The objective of this work is to document and reliably assess the size range, particle types and frequency of occurrence of particles adhered to airborne BPGs sampled under fairly clean air conditions. Sampling of airborne PGs was carried out for the first time in the literature with a cascade impactor ensuring collection of PGs without piling up of fine particles on their surface in the collector during sampling (i.e., free from sampling artifact).

2.MATERIALS AND METHODS

Pollen sampling was carried out daily from 30 March to 7 April 2017 (start and end time: 10:00 am) on the roof of a building of Lille University campus (Lat. 50° 36' 29″ N, Long. 3° 8' 25″ E, Altitude 20 m a.s.l.) (Supplementary Figure S0) when weekly cumulative birch pollen concentrations peaked at 3022 grains•m -3 according to the French monitoring network (RNSA) in Lille metropolitan area (Figure 1). On 30 and 31 March 2017, daily birch pollen concentrations peaked at 986 and 1236 BPGs per m 3 , respectively. Meteorological parameters were recorded by a weather station (Davis Vantage Pro) installed at the sampling site (Supplementary Figure S1). No rain event occurred during the study period. Birch dehiscence was triggered by a temperature rise to 16°C combined with a drop of relative humidity on 30 March. The weekly average temperature, relative humidity, and wind speed were 11.9 ± 2.2 °C, 76.7 ± 5.1 % RH, 1.4 ± 0.5 m•s -1 , respectively. Ambient PM10 and PM2.5 concentrations were 26.3 ± 8.3 µg•m -3 and 19.3 ± 8.2 µg•m -3 , respectively at the closest air quality monitoring station located 4 km away from the pollen sampling site (public data provided by ATMO Hauts-de-France). During the study period, PM10 concentrations never exceeded the WHO recommended threshold value, i.e. 50 µg•m -3 (24-hour mean). In contrast, PM2.5 concentrations were over the WHO guideline of 25 µg•m -3 (24-hour mean) on 3 and 4 April 2017 (Figure 1). Airborne PGs were trapped on the first stage PM>10 µm of a 3-stage cascade impactor (PM10 impactor, Dekati Ltd.), i.e. impaction stage with particle size cut-off diameter of 10 µm at 50% collection efficiency valid for spherical particles with a mass density of 1 g•cm -3 . The impactor was mounted on the top of a 4-meter-high mast (Supplementary Figure S2). Airborne PGs were impacted directly on a conductive carbon tape for electron microscopic examination. Bounce-off and re-entrainment of deposited PGs from the impaction surfaces can be minimized by using adhesive collection substrates [START_REF] Wittmaack | An Overview on Bioaerosols Viewed by Scanning Electron Microscopy[END_REF].

A number of 236 PGs were observed directly on the collection substrate without metal coating using a low-vacuum SEM (JEOL JSM 7800F LV) operated at a working pressure of 100 Pa in the specimen chamber. Visual detection of BPGs was carried out by low magnification SEM inspection of the whole area of daily collection substrates (circular surface with a diameter of 25 mm) (Figure 2). As the impaction surface was static in the case of our PM10 impactor, large particles might pile up on top of pollen grains during sampling. The probability of having a particle pile-up increases with the sampling duration. A typical view of the substrate loading in the case of our daily sampling is presented in Figure 2. As can be seen, after 24-hour sampling on PM>10 impaction stage, the particulate load on the collection substrate was low, with BPGs well-separated from the other collected particles, ensuring a minimized sampling artifact [START_REF] Choël | Evaluation of Hirst-Type Sampler and PM10 Impactor for Investigating Adhesion of Atmospheric Particles Onto Allergenic Pollen Grains[END_REF].

BPGs were detected by using backscattered electron (BSE) imaging. Because BSE yield depends on the atomic number of the atoms causing the backscattering, BSE images are sensitive to the elemental make-up of particles. BPGs are predominantly made up of light elements such as the carbon substrate. As a result, BPGs and the substrate appear with similar grey levels. To confirm the presence of a BPG and to examine particulate adhesion, each BPG was magnified and secondary electron (SE) images sensitive to topography were taken. Counting and sizing of particles adhering to pollen surfaces were determined from BSE images using FIJI/ImageJ software. Xray elemental analysis of particles attached to PGs was carried out with an energydispersive X-ray (EDX) detector (SDD 80 mm 2 , Oxford Instruments Inc.) at an accelerating voltage of 15 kV. Note that BPGs appear deflated as a result of shrinkage due to low-vacuum which enables EDX analysis of micrometer-sized particles down to 0.2 µm [START_REF] Choël | Development of Time-Resolved Description of Aerosol Properties at the Particle Scale During an Episode of Industrial Pollution Plume[END_REF].

3.RESULTS

A total of 236 BPGs were individually imaged by low-vacuum SEM/EDX and a total of 205 particles were observed on birch pollen surfaces. 68% of PGs did not carry any particle on their visible surface. The remaining 32% of PGs had between 1 and 16 particles adhered to their surface. On average, polluted PGs had 2 ± 1 particles on their surface. Sampling artifact was assessed to 2.2 ± 2.4 particles per PG with a conventional Hirst-type sampler under similar PM10 and PM2.5 concentrations [START_REF] Choël | Evaluation of Hirst-Type Sampler and PM10 Impactor for Investigating Adhesion of Atmospheric Particles Onto Allergenic Pollen Grains[END_REF]. The low number of particles observed on birch pollen (2 ± 1 particles per BPG) confirms the need to use an impactor because the sampling artifact of an HTS is of the same order of magnitude.

Particles deposited on BPGs had an average diameter of 1.5 ± 2.0 µm (average ± standard deviation) and ranged in size from 0.2 to 11.8 µm. Polluted PGs had particles covering an average of 0.95% of their surface. Particles lying on the substrate had an average diameter of 5.6 ± 4.0 µm with sizes varying between 0.3 and 21.9 µm (total number of particles observed on the substrate=309). Both the average diameter and the size range were larger on the collection substrate compared to PG surface, indicating a good size differentiation between PGs and fine particles in suspension using PM>10 impaction sampling device. Two other types of PGs, namely willow (Salix L.) and hornbeam (Carpinus betulus), were also observed with particles adhering on their surface (Supplementary figures S3 and S4). The nature of particles adhered to BPGs were as follow (Figure 3 and Figure 4): soil dust (calcite, quartz, orthoclase (potassium feldspath), plagioclase, olivine, clay minerals (illite, smectite, mica)), sea-salts, metal-rich (Fe-rich, Cu-rich, Ni-rich, Znrich, Ba-rich) particles, small and large soot aggregates consisting of clusters of nanospheres with a diameter of 40 to 90 nm.

4.DISCUSSION

Our atmospheric samples collected under conditions of moderate particulate air pollution reveals that pollution of the surface of pollen grains (PGs) by atmospheric particles is a common phenomenon: out of a total of 236 birch pollen grains (BPGs) examined, 32% of BPGs carried an average of 2 ± 1 particles (205 particles deposited on 75 BPGs). On a global average during our sampling, BPGs carried 0.86 particles (205 particles observed particles for 236 BPGs). The fraction of the pollen surface covered by particles is however very low, less than 1%, which contrasts with the higher fractions previously reported in the literature [START_REF] Behrendt | Allergens and Pollutants in the Air-A Complex Interaction[END_REF][START_REF] Ribeiro | Characterisation of Particulate Matter on Airborne Pollen Grains[END_REF]. For example, the area covered by particles on pine and maple pollen collected from the atmosphere with a Hirst trap was 5.7% and 7.5%, respectively [START_REF] Ribeiro | Characterisation of Particulate Matter on Airborne Pollen Grains[END_REF]. A very high degree of agglomeration was also observed for BPG collected with a high volume sampler in highly polluted urban areas [START_REF] Behrendt | Allergens and Pollutants in the Air-A Complex Interaction[END_REF]. We assume that the high degrees of agglomeration presented in these previous works may be subject to a sampling artefact involving an overestimation of the number of particles per PG. Hirst-type samplers are not suitable for the assessment of particulate pollution on the surface of PGs due to a too high impaction velocity which does not allow the discrimination of pollen and PM10 during sampling [START_REF] Choël | Evaluation of Hirst-Type Sampler and PM10 Impactor for Investigating Adhesion of Atmospheric Particles Onto Allergenic Pollen Grains[END_REF]. The use of a PM10 impactor avoids this sampling artefact and explains, at least in part, the lower particulate pollution rate obtained in this study (Choël et al., 2020). Another explanation is that the air quality was relatively good in our study (PM10 = 26.3 ± 8.3 µg•m -3 ), which reduces the probability of coagulation of atmospheric particles on the surface of PGs. One of the limitations of our study is the low number of PGs observed. Manual grain-by-grain observation by electron microscopy is indeed time-consuming and unsuitable for samples of several thousand grains but it is the only way to reliably assess the presence of particles on PGs. In addition, some particles are difficult to identify, in particular due to the presence of sub-pollen particles on the surface of BPGs [START_REF] Ruggiero | Systematic and Morphologic Survey of Orbicules in Allergenic Angiosperms[END_REF], 2020). It should also be remembered that SEM analysis only allows to observe the visible pollen surface; particles stuck to the pollen surface on the side of the collection substrate (hidden surface) are obviously not observable. The pollution rate of BPGs obtained in our sampling can be explained by several mechanisms of APM deposition (Figure 5) without the possibility to assign their respective relative contributions: dry and wet deposition on catkins before pollination (a), coagulation in the atmosphere (b), contact after deposition on a surface polluted by particles followed by resuspension of the PG (c). Particulate pollution on catkins and resuspension of PGs need to be specifically studied as these mechanisms are poorly documented [START_REF] Visez | Atmospheric Particulate Matter Adhesion onto Pollen: A Review[END_REF].

On the other hand, it is possible to estimate by calculation the contribution of coagulation of particles with PGs in the atmosphere (Figure 5 (b)) ; particles coagulation is described by the rate of collision (particles.s -1 ) between two populations of particles at concentrations and (equation 1, Table ) [START_REF] Seinfeld | Atmospheric Chemistry and Physics: From Air Pollution to Climate Change[END_REF]. Equations 1 to 4 (Table ) describe respectively Brownian coagulation, gravitational coagulation and coagulation in turbulent flow [START_REF] García-Nieto | Study of the Evolution of Aerosol Emissions from Coal-Fired Power Plants Due to Coagulation, Condensation, and Gravitational Settling and Health Impact[END_REF][START_REF] Seinfeld | Atmospheric Chemistry and Physics: From Air Pollution to Climate Change[END_REF]). The coagulation rates could also be influenced by the electrical charges of particles [START_REF] Harrison | Ion-Aerosol-Cloud Processes in the Lower Atmosphere[END_REF] ; however, the lack of data on the distribution of electrical charges in our sampling conditions does not allow to estimate this specific contribution (enhancement, no effect or reduction) on the deposition rates of APM on BPGs.

Table 1. Equations for the rate of collision between particles 1 and 2 (eq. 1) and coagulation rate coefficients for Brownian coagulation (eq. 2), gravitational coagulation (eq. 3) and coagulation in turbulent flow (eq. 4) [START_REF] García-Nieto | Study of the Evolution of Aerosol Emissions from Coal-Fired Power Plants Due to Coagulation, Condensation, and Gravitational Settling and Health Impact[END_REF][START_REF] Seinfeld | Atmospheric Chemistry and Physics: From Air Pollution to Climate Change[END_REF].

Equation 1 Calculations of for the three types of coagulation described in Table were performed for a particle deposition on BPG (21 µm in diameter) from a monomodal population of 2 µm diameter particles at a concentration of 5 particules•cm -3 , considering a terminal settling velocity of 100 cm•h -1 for particles (1.2 cm•s -1 for BPG) and no rebounds after collision. This computational estimate shows that is of the same order of magnitude for gravitational coagulation ( ≈ 4.8×10 -12 m 6 •s -1 ) as for turbulence ( ≈ 1.6×10 -12 m 6 •s -1 ) while related to Brownian motion is largely negligible ( ≈ 2×10 -15 m 6 •s -1 ). Equation 3 tends to predict very high coagulation with the finer particles, as the difference in settling velocity is greater and the concentrations of the fine particles are several thousands to tens of thousands of particles per cm 3 . However, the efficiency of collision E12, which depends on the size of the particles involved, decreases sharply as the diameter of particle 2 tends towards zero [START_REF] Seinfeld | Atmospheric Chemistry and Physics: From Air Pollution to Climate Change[END_REF]. This prediction is consistent with our observations where relatively few very fine particles (< 500 nm) were detected on the surface of BPGs.

Rate

Under typical pollination weather conditions (absence of turbulence, calm weather and low wind), and without taking into account electrostatic interactions between particles, the main coagulation process would be the deposition of particles by gravitational settling. By assuming a concentration of 2-µm-sized particles N2 in the order of 5 particles.cm -3 and a gravitational settling time of one hour (drop of 43 m), we calculate 0.09 particles deposited per PG ( =2.4×10 -5 particles•s -1 ). For pollen transported over long distances, while some PGs have been observed at considerable altitudes of 2 km (Damialis et al., 2017), it is conceivable that gravitational settling alone explains the levels of particulate contamination of PGs observed in our samples (on average 0.86 particles per BPG). If the hypothesis of coagulation primarily by gravitational settling is correct, then the presence of particles on the surface of BPGs could be a marker of atmospheric transport of pollen over long distances.

Our coagulation calculations shed interesting light on the hypothesis of increased COVID-19 propagation by virus transport on the surface of PGs [START_REF] Damialis | Higher Airborne Pollen Concentrations Correlated with Increased SARS-COV-2 Infection Rates, as Evidenced from 31 Countries Across the Globe[END_REF][START_REF] Dbouk | On Pollen and Airborne Virus Transmission[END_REF]. The thousands of droplets emitted by exhalation, and potentially infected by a virus, are in the micrometre to 100 µm range, with a maximum around 50 to 150 µm [START_REF] Xie | Exhaled Droplets Due to Talking and Coughing[END_REF]. Our estimates show that the encounter between a PG and a coarse particle of about 100 µm will be very unlikely for contact times of a few minutes. For fine particles (2 µm) exhaled at a concentration of 150,000 particles•m -3 in contact with a high concentration of BPGs

(1,000 BPGs•m -3 ), the calculated deposition rate of 2-µm-sized particles on pollen is 0.06 particles per day [START_REF] Shao | Risk assessment of airborne transmission of COVID-19 by asymptomatic individuals under different practical settings[END_REF]. In light of these estimates of the coagulation rate and the low number of particles observed on the surface of pollen in our atmospheric samples, the transport by a PG of a virus expectorated by a human being is most likely a rare event. If pollen is involved in the aggravation of COVID infection [START_REF] Gilles | Environmental Factors: A "Missing Link[END_REF][START_REF] Khaiwal | Does Airborne Pollen Influence COVID-19 Outbreak? Sustainable Cities and Society[END_REF], we suggest that co-exposure to expectorated droplets and PGs is more likely involved than virus adhesion to the pollen surface. More precise modelling work is needed; our estimates by calculating the coagulation rate of particles on pollen are only intended to give orders of magnitude of the coagulation phenomena involved.

The observation of several PGs with soot suggests that combustion-emitted particles may have a particular affinity with pollen. It has been suggested that electrostatic interactions may promote affinity between combustion particles and bioaerosols [START_REF] Roos | Atmospheric Charged Aerosol and Electric Field Observations in Western France[END_REF]. However, the number of BPGs with soot is too small to provide a reliable estimate of occurrence of soot sticking on BPGs in the urban atmosphere. Furthermore, the sampling was conducted on the roof of a building (20 m high); sampling at 1.5 m above the ground could promote soot-pollen coagulation because, on the one hand, airborne particle concentrations can be as high as 10 6 to 10 7 particles per cm 3 [START_REF] Seinfeld | Atmospheric Chemistry and Physics: From Air Pollution to Climate Change[END_REF] and, on the other hand, pollen concentrations can be higher [START_REF] Charalampopoulos | Spatiotemporal Assessment of Airborne Pollen in the Urban Environment: The Pollenscape of Thessaloniki as a Case Study[END_REF]. Further sampling, especially at street level, is therefore necessary to better assess the fraction of PGs polluted by soot, especially as a large body of literature highlights the aggravating effects on allergy of co-exposure to pollen and soot [START_REF] Chen | Artemisia Pollen Extracts Exposed to Diesel Exhaust Enhance Airway Inflammation and Immunological Imbalance in Asthmatic Mice Model[END_REF][START_REF] Nel | Enhancement of Allergic Inflammation by the Interaction Between Diesel Exhaust Particles and the Immune System[END_REF][START_REF] Shiraiwa | Hazardous Components and Health Effects of Atmospheric Aerosol Particles: Reactive Oxygen Species, Soot, Polycyclic Aromatic Compounds and Allergenic Proteins[END_REF]. Unlike nasal co-deposition (Figure 5), the pollen and soot (or pollen and particles) mixture resulting from atmospheric coagulation may have time (up to several days) to undergo atmospheric aging.

Chemical reactivity at the particle-pollen contact surface cannot be excluded. Very little information is available on this multiphase pollen chemistry; for example, it has been shown that in the presence of moisture, allergens can diffuse from the PG to soot particles deposited on its surface [START_REF] Knox | Major Grass Pollen Allergen Lol p 1 Binds to Diesel Exhaust Particles: Implications for Asthma and Air Pollution[END_REF][START_REF] Ormstad | Airborne House Dust Particles and Diesel Exhaust Particles as Allergen Carriers[END_REF].

Birch pollen is never breathed alone; each inhalation introduces gaseous pollutants, particles, other allergenic pollens, and other bioaerosols (viruses, bacteria, fungus spores or other non-allergenic pollens) into the respiratory system. A central question will be whether the level of particle deposition observed in this study on airborne BPGs (0.86 particles per PG) is significant in comparison with the effects of coexposure to pollen and APM during breathing (Figure 5d). First, it should be noted that the effects of these two mechanisms are cumulative; co-deposition also occurs on PGs that have already been subjected to coagulation of atmospheric particles. In addition, and as previously mentioned, atmospheric aging involving at least biochemical reactivity and diffusion of allergens may occur after coagulation during atmospheric transport of BPGs. Our study alone cannot determine the potential impacts of pollen surface particle pollution on allergy. However, our atmospheric observations allow to determine, for the first time without sampling artifacts, the particle pollution state of the surface of inhaled pollen, which may prompt future in vitro studies on the effects of the particle-pollen cocktail to use realistic particle contamination of the pollen surfaces (on the order of 1%).

Finally, it should be mentioned that, beyond the health effects, the adhesion of particles to the pollen surface could influence the reproductive capacity of pollen.

Some studies show a negative effect of metallic nanoparticles (Pd, Fe, ZnO) and carbon particles (fullerene, graphene) on pollen reproductive capacity [START_REF] Aoyagi | Fullerene Fine Particles Adhere to Pollen Grains and Affect Their Autofluorescence and Germination[END_REF][START_REF] Carniel | Graphene Oxide Impairs the Pollen Performance of Nicotiana Tabacum and Corylus Avellana Suggesting Potential Negative Effects on the Sexual Reproduction of Seed Plants[END_REF][START_REF] Gupta | Silver Nanoparticles (AgNPs) Induced Impairment of in vitro Pollen Performance of Peltophorum pterocarpum[END_REF][START_REF] Speranza | Pd-Nanoparticles Cause Increased Toxicity to Kiwifruit Pollen Compared to Soluble Pd (ii)[END_REF][START_REF] Speranza | In-Vitro Toxicity of Silver Nanoparticles to Kiwifruit Pollen Exhibits Peculiar Traits Beyond the Cause of Silver Ion Release[END_REF][START_REF] Yoshihara | ZnO Nanoparticles Effect on Pollen Grain Germination and Pollen Tube Elongation[END_REF]. However, these studies use particularly high particle-topollen ratios and chemical compositions that are not very representative of real atmospheric particles. It was also shown that APM does not interfere with the germination of Cichorium intybus pollen along roadsides [START_REF] Jaconis | Does Particulate Matter Along Roadsides Interfere with Plant Reproduction? A Comparison of Effects of Different Road Types on Cichorium intybus Pollen Deposition and Germination[END_REF].

Moreover, if the hypothesis of greater pollution of the pollen surface by particles during long-distance transport is correct, it appears that the reduction of germination by particle adhesion is probably insignificant because the probability of reproduction between two trees located at a long distance is itself particularly low, if not zero [START_REF] Proctor | The Natural History of Pollination (Updated, Subsequent)[END_REF].

5.CONCLUSION

An average pollen surface contamination of 2 ± 1 particles per BPG was obtained for 38% of BPGs sampled under moderate air pollution conditions (average PM10 = 26.3 µg•m -3 ). This value was not known in the literature because previous estimates were possibly subject to sampling artifacts. Determination of this particulate contamination level is important for future studies on germination or allergy as it provides an estimate of a realistic dose-response effect of APM coagulated on pollen surface.

BPGs are small (21 µm in diameter) and larger pollens could have higher APM deposition rates. Gravitational settling is indeed suspected be the predominant mechanism of coagulation in the atmosphere. Very little is known about pollen pollution by APM on the plant, about electrostatic interactions between particles and also about pollen resuspension after deposition on a surface. APM coagulation on PGs could be particularly enhanced during specific atmospheric events, such as thunderstorms, which can, for example, alter the electrical charges of APM and PGs, increase turbulence conditions, and generate large amplitude vertical transport of PGs.

In our current atmosphere, on a PG surface of only 1,400 µm², traces of particulate pollution were found on one out of three PGs. The types of particles deposited on the PGs reflect the influence of human activities intensively emitting particles: desertification, urban sprawl, forest fires (accentuated by climate change), intensive combustion of fossil fuels and excessive industrialization.

Figure 1 .

 1 Figure 1. Daily concentrations of birch pollen grains in Lille metropolitan area (green bars) and ambient PM10 and PM2.5 mass concentrations during pollen sampling (respectively black and red

Figure 2 .

 2 Figure 2. Example of SEM image of birch pollen grains (circled) and atmospheric particulate matter deposited on PM>10 µm impaction stage. The pollen grain on the bottom left carries atmospheric particles.

Figure 3 .

 3 Figure 3. SEM images of polluted birch pollen grains carrying: (a) 1 µm-sized calcium silicate particle; (b) aluminosilicate particles; (c) a large soil dust particle (plagioclase Al-Si-Ca-Fe-rich); (d) a large phyllosilicate particle, (e) one supermicron and a dozen submicron dolomite particles; (f) a spherical coal fly ash particle (O-Al-Si-rich diam 3.5 µm), a calcite particle (up) and a gypsum particle (down).

Figure 4 .

 4 Figure 4. SEM images of polluted birch pollen grains: (a) covered with a large chain-like soot aggregate of nanospheres (diameter 40-50 nm); (b-c) carrying a micrometer-sized chain-like soot aggregate of nanospheres (diameter 80-90 nm); (d) with a soot aggregate (area equivalent diameter 1.1 µm) and recrystallized sea-salts.

Figure 5 .

 5 Figure 5. Proposed mechanisms for coagulation of atmospheric particles on the surface of pollen grains. The yellow balls represent birch pollen grains. The black pictograms symbolize atmospheric particles.

Acknowledgments

MC and NV thank Université de Lille, Centre National de la Recherche Scientifique (CNRS) and Institut de Recherches Pluridisciplinaires en Sciences de l'Environnement (IREPSE Fed 4129) for financial support. The CaPPA project (Chemical and Physical Properties of the Atmosphere) is funded by the French National Research Agency (ANR) through the PIA (Programme d'Investissement d'Avenir) under contract ANR-11-LABX-005-01. This work is a contribution to the CPER research project CLIMIBIO. The authors thank the French Ministère de l'Enseignement Supérieur et de la Recherche, the Hauts-de-France Region and the European Funds for Regional Economic Development for their financial support to this project.