A New Perspective of Sustainable Perception: Research on the Smellscape of Urban Block Space

Abstract

The smell of space is inseparable from the sustainable development of the living environment. The research on olfactory perception and smell landscape has a positive effect on landscape design and urban planning and contributes to the formation and design optimization of unique urban memory. This study combines urban smell tracking experiments with Internet social media data analysis to classify smells in the old city center of Guangzhou, China, and analyzes the study within the inner ring and six historic districts. Based on the research results, the smell map was drawn, and the reliability of the smell map was tested through social data and semantic analysis. The emotional score heat map of smell and emotion in six regions was constructed, highlighting the impact of smell in key neighborhoods on the environment. In the conclusion to the study, the thematic routes of green urban design are proposed: sightseeing routes, cultural routes, and food routes, as well as improvement strategies to promote the integration of smell and urban operation activities and the sustainable development of urban regional characteristics.

1. Introduction

The sense of smell is a kind of perception that cannot be ignored in the human senses. As early as the 20th century, Gibson believed in “Direct Perception Theory” where perception is a direct product of human contact with the outside world [1]. The human olfactory system, with its hundreds of different olfactory receptors, far outperforms the other senses in the number of physically different stimuli it can discriminate [2]. The “Taste–Smell System” is one of the five basic systems of human perception of the environment [3]. We live in the environmental space, we can choose not to see and touch, but we cannot stop breathing. The closest relationship with people is air and smell. Smell follows people’s breathing into their bodies, and the smell information must be received by the body and has a persistent feature. After the threshold is reached, there is an impact on how a person feels and behaves [4]. In 1985, Canadian geographer Portes formally proposed the concept of “Smellscape”, which is similar to the visual landscape, and smell should be a spatial order or spatial relationship. As a part of landscape design, smell participates in the combing of spatial order and spatial relationship. Therefore, smell landscape has important value as a research object of environmental aesthetics [5].

There is a connection between human olfactory recognition and spatial memory, and smell can help us build a cognitive map in a certain environment [6]. Pallasmaa believes that the most lasting memory of space is usually its smell, which can play an important role in capturing and long-term preservation of spatial imagery [7]. The smell landscape has always been discussed around the three relationships of “people–smell–environment”, and is closely related to traditional landscape science, olfactory psychology, and environmental science. When human physiology and psychology participate in environmental olfactory perception at the same time, human history and regional culture are also embedded in it [8]. Research in the field of soundscapes can be used for reference. A series of “events” are composed of fragments of multiple important “marks”. The same is true for smellscape. Multiple “Smellmarks” in the space form a series of “Smellevents”, which promote a stronger connection between olfactory recognition and spatial memory [9].

The smell can be used as an element of space design and urban space design, because it has the ability of space experience. It can create the atmosphere of the environment, the narrative of the environment, and even the form of the environment. Not only the visual image can become a sign of a region, but the smell can also be recognized as a characteristic of a region [10]. We can connect smell and vision with local characteristics, build blocks with local and regional characteristics, and optimize urban space and image memory [11]. The study of urban space smells adds a dimension to our understanding of urban design, enriches our sensual experience, and provides some reference strategies for green urban design and low-carbon urban planning [12].

2. The Research and Application of Smellscape

In the mid-to-late 20th century, Western scholars realized that the vision-centered theory of modern environmental perception brought a serious lack of multi-sensory experience and began to emphasize the importance of non-visual senses in environmental perception [2,4,5]. Brand marketing expert Martin Lindstrom pointed out that 75% of human emotions are generated by smell [13]. The more contact points there are between smell and consumers, the richer the experience will be and the deeper the memory will be. Olfactory perception can directly evoke emotion and memory associations.

In the relationship between smell and the environment, traditional environmental science mainly studies the detection, transmission, and control of smell [14,15], which usually does not involve the aesthetic characteristics of the environment and does not involve the literary aesthetic connotation of smell. The smell environment is often only considered as a negative issue, and investigations into it have focused almost exclusively on odor pollution. However, this study focuses more on the characteristics of smellscape and the perception of the regional environment. Norwegian odor specialist Sissel Tolaas has devoted himself to collecting different forms of odor and building a huge “smell museum”. Dedicated to embodying “smell”, Trust’s “Scent of the City” project has collected scents from cities such as Stockholm, London, and Berlin, and produced scent maps [16]. Due to the participation of people’s aesthetic activities, the smellscape is embedded with historical and cultural connotations. Unlike the air quality level, odor can be detected with equipment to analyze the chemical composition in the air. However, the smellscape itself is not easily determined quantitatively.

From ancient times to the present, garden landscapes have applications that focus on odor perception and plant configuration. In the Trianon Palaces of Versailles (France), the beauty and fragrance of flowers are used to symbolize the power of the emperor. Through the study of Jewish garden and plant literature, scholars found that the aroma of roses spread throughout Israel, becoming the most representative of the country’s scent. In the oriental classical gardens, the aroma elements are closely related to the garden design, and the “fragrant scenery” is formed through the arrangement of plants [17]. Modern architect, architectural historian, and academician of the Chinese Academy of Sciences, Mr. Liu Dunzhen pointed out in the book The Classical Gardens of Suzhou that according to the characteristics of “floral fragrance”, there are different planting forms in different spaces. The “Humble Administrator’s Garden”, which is listed in the World Cultural Register, is a typical example. In front of the “Magnolia Hall” of this garden, scented magnolias and osmanthus fragrans are grown alone. Similarly, a lot of osmanthuses are planted in the “Lingering Garden”, and smellscape is realized in the traditional garden landscape design [18]. In 1978, Chen Congzhou pointed out in the book One Chinese Garden that invisible scenery such as flowers and fragrances is the key factor that promotes the poetic painting of gardens, “there is the scenery outside the scenery” and “has an inexhaustible meaning”, opening up the aesthetic value of plant smell discussion [19].

The smell not only has research value such as perception and aesthetics values, but also has the design practice and social service value of participating in urban planning and design, reconstruction of historical blocks, and landscape design. The smell is an important factor in forming the appeal of space art, and from theory to practice it has played an important role in the design of the blind park. A park for the blind is a park that mainly serves the blind and is equipped with safe facilities that can perform tactile, auditory, and smell perception activities. For example, Seattle Aroma Garden in the United States, Bremen Botanical Garden for the Blind in Germany, Bradbury Park in Hong Kong, and Xiangmi Park in Shenzhen, have all added a large number of aromatic flowers to create a unique and comfortable space experience [20]. Scent not only affects human emotions but is also used in the design of themed gardens with healing functions, using aromatic plants to treat mental or physical diseases, such as in the European Monastery Herbal Garden, the Japanese Yamato Garden Sensory Garden, and the Russian Plant Gas Clinic [21,22,23,24].

Smell also has a temporal and spatial cognition function for human beings and has important value in urban planning and cultural tourism. The landmark smells emitted by different regions and spaces can help people locate the spatial range, evoke time and space memories and associations, evoke people’s regional cultural memories and time reveries, and contribute to the establishment of a unique image of urban cultural tourism.

Since the beginning of the 21st century, many scholars and researchers have organized “smell walk” surveys to discuss the relationship between smell and urban space in depth. British researcher Victoria Henshaw conducted a detailed study on the understanding and design of urban scent environments [25]. In the book Urban Smellscapes, she explored the sense of smell and personal characteristics surrounding buildings, streets, and surrounding activities and other external factors relationship. She conducted a smell survey on many streets and six stop points in Doncaster (England), and drew a smell map. Based on the feedback of participants, she formulated a smell model and combined the smell of places and spaces for urban design.

British sensory artist Kate Mclean created the scent system classification roulette, which used different colors to represent different smells and drew a “sensory map” of the city center and main areas [26,27]. The German scholar Rossano Schifanella focused on the data analysis of social media platforms on the Internet, and combined with field research and network data to establish a more complete urban smell classification system to map the main street smell classification, composition ratio, and pedestrian mood, to feel the smell map, and to analyze the relationship between the above elements and urban planning [28]. At present, their team has conducted smell landscape research and mapping in London, Barcelona, New York, and other cities. However, in China, the smellscape research in urban space is not adequate: the smellscape research and mapping in the central urban area of Beijing is a good case [29]. It is still necessary to further expand the smellscape research in Chinese cities, which is of great significance.

3. Research Framework and Methods

The overall framework of this study is shown in Figure 1, which is divided into four stages. The first stage is to describe the relationship between human sense of smell and environmental space, and to review the literature. The second stage is the development of smell experiments and field research activities. The third stage is comprehensive data analysis, and the presentation of smellmaps, etc. The fourth stage is to develop design strategies based on the analysis of the results, to provide strategies for green urban design themed route planning and tourism, and to promote urban vitality and image building.

This research method is based on the two mainstream method systems of current smellscape research: the subjective evaluation method and the literature survey method, combined with the Internet and the big data analysis method of computer “python” tools. The literature survey method emphasizes the construction history and humanistic connotation of the scent landscape, investigates the historical data of various disciplines related to it, and sorts out the s and images related to the scent landscape. The subjective evaluation method is mainly applied to the perception and evaluation of the already built environmental smellscape. Aiming at the content of this research, the subjective evaluation of the field perception of scent walking is used to investigate and experience the street space in the central urban area of Guangzhou (China). At the same time, combined with network data collection and analysis, the smell map is drawn by modern mapping techniques. The scientific nature of this paper is based on two methods, which are big data analysis based on computer “python” tools and field research by experimenters to achieve double demonstration and an in-depth understanding of the composition of the smellscape in the old city of Guangzhou, and to explain the application prospects of this research in urban planning and design.

3.1. Subjective Evaluation In Situ of the Smellwalk Experiment

Smellwalks are a method that requires a reorientation of the senses to temporarily emphasize the information received from the nose. In this way, smellwalking offers an active, researcher led, embodied methodology with the capacity to attend to more than vision and more than representation [30]. The purpose of the scent walk is to identify how the scent of a particular location affects the experience of the place. When beginning an olfactory walk, use “smell catching” methods and strategies such as walking slowly, breathing deeply, attending to the aromas that are encountered, and finding hidden scents by using your other senses. Throughout the smellwalk, McLean suggests the importance of being attentive to three different types of smell: curious or unexpected smells that are short-lived, such as a passerby’s perfume or tobacco smoke; episodic elements of a smellscape for specific areas of a town, such as fish from a seafood market; and ‘background’ smells that represent a constant presence in the smellscape like the dampness of the canals. These “smellnotes” can comprise information about the type of smell, its location, intensity, duration and effect, whether it is expected/unexpected, and any personal feelings it provokes [31,32].

The convergence of modern urban development makes the composition of urban smells, the degree of impact on people’s lives, and the degree to which people care about these smells. Because cities are located in different geographical locations, their climate, soil, food, and industries are different, so each city has unique odor components that can be reflected in the smell classification. Guangzhou smell research is combined with Victoria Henshaw and Kate Mclean’s smell classification, the actual situation in Guangzhou, and focus interviews of 30 Guangzhou locals to determine the smell type and evaluation system. The seafood smell with Guangzhou regional characteristics was added, and the smell classification was adjusted to 11 categories such as food, nature, domestic emissions, urban construction, animals, exhaust gas, medicine, tobacco, artificial smell, and seafood, as shown in

Table 1. Old town old street smell classification.

Class of Original Smell	Investigation and Analysis	Classification Adjustment
Food	For hot pot, beef offal, kebabs and other pungent, strong smells, dislike and like the ratio is close; for dessert, drink smell more light food, dislike and like the ratio is about 3:1.	There are two types of food: mild and stimulating.
Nature	Most of the respondents liked to think that life lacks such a smell.	Keep the original classification
Life emissions	Consistently negative comments on garbage, toilets, kitchen fumes, sewage, burning rubber, musty smell, etc.	Classify perfume and aromatherapy as artificial aroma
Urban construction	Neighboring residents believe that paint, carpentry, and construction sites have a great impact on life.	Keep the original classification
Animal	For animals such as cats, dogs, and birds, the ratio of dislike to like is 3:2.	Keep the original classification
Tail gas	Nearly 90% of respondents expressed negative emotions.	Keep the original classification
Medicine	Hospital and pharmacy smell evaluations are similar.	Keep the original classification
Tobacco	Nearly 40% expressed negative emotions about the smell of cigarettes.	Keep the original classification
Artificial aroma	Perfume, aromatherapy, and other smells are disliked and liked in a similar proportion.	Leather goods, detergents, candle incense is classified as artificial aromas
Other	Due to the influence of the commercial streets of seafood wholesale shops, respondents said that there was a smell of seafood in the streets.	Increase seafood smell according to actual research and geographical characteristics

.

In the inner ring roads of Guangzhou, the “Smellwalk” experiment and collection analysis are focused on six historical old streets to be renovated by the Guangzhou Municipal Government. They are: Beijing Road and Gaodi Street in Yuexiu District; Haizhu South-Changdi Historical and Cultural District; Yanjiang West Road District; Shuzhuyong-Haizhusi District and Haizhu Bridge South District in Haizhu District; Pantang in Liwan District Wuyue; Enning Road and Duobao Road historical and cultural districts. These six areas are located in the main central city area and are important areas visited by tourists every year. At the same time, some old residents have lived in the area for many years, which needs to be activated and used to improve quality. Based on the student union organization of Guangzhou University, 30 college students with a normal sense of smell (no respiratory disease and anosmia) and 30 teachers were openly recruited as free volunteers, aged 18 to 50, with equal numbers of men and women. The researchers and the 60 volunteers participated in the “Smellwalk” experiment and fieldwork and completed the experimental survey within one day. According to the general diffusion range of various smells in the absence of rain, wind, and obstacles, the influence radius was determined, and then the spatial distribution of various smells on the street was obtained. Based on individual sensory experience, space smells were recorded and descriptively evaluated. First, the perceived smell and location were marked on the map; second, the environmental smell was evaluated through human perception, including smell intensity, frequency, concentration, etc. Finally, personal preferences for smell and the surrounding environment were observed and recorded, and the impact of smell on life was identified through dialogue with surrounding residents.

3.2. Network Data Collection and Analysis

The research data come from the Guangzhou urban road network, some of the most visited information-sharing platforms in China, social networking sites and life consumption review websites, including Sina Weibo (Weibo.com), public reviews net (Dianping.com), Baidu Tieba (tieba.baidu.com) and map POI (Point of Interest). Map POI: Simplify the streets on the map and select key areas in the streets and points of interest related to the smell of the old city. Use Python as the scripting language to write crawler scripts based on the scrapy framework and use MySQL as the storage database to collect a total of 162,767 related comment data on Weibo and Dianping. Further filtering the data, to clarify the correlation between the smell of the block and the mood, each comment was filtered by “scented words”. Filter out those emotional words that have nothing to do with smell and filter out a total of 81,432 comment data containing “smell”, “scent”, “fragrance”, and “stink”. Based on the BosonNLP sentiment dictionary, sentiment words are mainly positive and negative words, and the sentiment analysis interface of the Baidu AI open platform was used to score the sentiment of the comment data. At the same time, the Baidu map interface was used to query the latitude and longitude location information of the smell source comment address and draw a heat map based on the sentiment score result.

4. Results

4.1. Spatial Distribution of Smell

Based on the above index system, the smell map and urban smell concentration map of the historical and cultural blocks of Guangzhou’s old city are drawn (Figure 2). There are many smell sources in the old city of Guangzhou. Various POIs have a corresponding impact on the streets of the old city, and each historical street has a rich smell. Further study of the smells on the street and the main smell categories analyzes these smells under the influence of the old city of Guangzhou’s historical and cultural street system, the formation of Guangzhou’s historical and cultural streets of the four main smell levels.

• Food: There are many old shops, all kinds of restaurants, concentrated crowds, and unique Cantonese pastry and cooking tastes.

Food is an important layer in the smell landscape system of the old city of Guangzhou. The food culture has a long history in Guangzhou, and “Cantonese cuisine” is famous all over the world. The phrase “food in Guangzhou” is well known and has been a proverb for a long time [33]. In the base of the smell map of the old city of Guangzhou, food accounts for the majority, as there are about 6539 restaurants of all kinds scattered in the streets and alleys in the old city. In the inner ring map of Guangzhou, the distribution of food is roughly east-west and along the river, which shows that there are many people in these areas and the vitality of the blocks is high. In all kinds of catering, besides stores that meet the basic needs of the people, there are also some characteristic catering blocks, such as Beijing Road, Shangxiajiu Pedestrian Street, Enning Road, Duobao Road, etc., which are people’s gathering places and areas with high vitality as well as food gathering places in the old city.

2.

Nature: It is concentrated in scenic spots and parks. The green space beside the streets of the old city is small, and the visibility of the unique river flow is low.

The distribution of natural areas is in a north-south position and some is distributed along the banks of the Pearl River. Due to urban planning, expansion, and other reasons, the green space in the old city was occupied, the original river and water corridor system was covered, the trees on both sides of the original roads were cut down, and the continuity of the green landscape of the old city was destroyed. The relationship between people, the natural environment, and smell was destroyed, and part of the green space system and the smell of the old city are superimposed to form the second level of the historical and cultural block.

3.

Medicine: All kinds of pharmacies and hospitals in the old city are evenly distributed; there are many traditional Chinese medicine health care categories, and the old-fashioned herbal tea pharmacy has a new look.

There are many medical stores, nursing homes, and community health services in the old city. Guangzhou is currently building a Guangzhou Medical Center with Yuexiu District as the core. It is also fully deploying the health industry in other districts. In addition, Guangzhou has a long history of traditional Chinese medicine and you can smell the taste of Chinese herbal medicines. Visually, you can see obvious pharmacy signs and billboards, for instance the century-old pharmacy “Caizhilin”. The unique characteristic of Guangzhou is the herbal tea with the smell of Chinese herbal medicine and a lot of tangerine peel is placed at the entrance of each pharmacy. Many old-fashioned drugstores and brands enhance sustainable development through cultural creativity. For example, the Chen Liji brand has been rejuvenated, forming a third unique layer of the old city smell background.

4.

Domestic discharge and urban construction: old city garbage, toilets, sewage, etc. need to be treated; construction sites, paint, and other smells affect the quality of streets.

The streets of the old city are narrow, and the population density is high. In the past five years, the old city has been renovated frequently and the renovation plan will continue in 2022. A total of 18 communities over 30 years old and many streets will undergo public space, road management, barrier-free facilities, aging facilities, sanitation facilities, and many other renovations. During construction, it brings new environmental pollution problems. Smells accompany breathing into the body and air pollution contributes to mortality and morbidity [34]. The smell of construction waste, sewage discharge, toilet smell, and living and living discharge formed the fourth level of the old city smell.

4.2. Smells Preferences

• Favorite smells:

The smells are classified and subdivided to screen the favorite smells in historical and cultural blocks, as some smells emitted in the city can reflect the characteristics of these blocks. According to the smell classification, these scents include the taste of food and nature, the pastry scent placed in the old store of the century-old gourmet brand, scent of the diversity of plants in the warm climate, and the rich scent of flowers, trees, and fruits. Corresponding to the relative blocks, Beijing Road Pedestrian Street, up and down the nine-step street, Enning Road and Duobao Road historical and cultural blocks, Shamian Island, Liwan Lake Park, Yuexiu Park, and other areas are suitable for walking and full of rich smells (Figure 3). They can stimulate people’s appetite and living consumption, soothe people’s emotions and regulate the microenvironment.

2.

Unpleasant smells:

Classification of smells, screening historical and cultural blocks for offensive smells, these smells spread in the city affecting the street quality of the historical and cultural blocks. These smells include sewage discharge, construction sites in urban construction, paint smells, and so on, which are all in the public spaces with high population use in the old city (Figure 3). They affect people’s feelings in these spaces and stay in communication. The respondents feel various unpleasant smells that have an adverse impact upon the quality of life that they perceive. A possible need for relocation of domiciles out of the current place of residence due to unpleasant smells would affect the perceptible specific level of grief, and the greater it is, the more attached the residents are to their current place of residence [35,36].

4.3. Emotional Analysis

The impact of smell on mood is innate [37]: different smells will make people’s nervous systems react differently [38]. Pleasant smells produce positive emotions, while unpleasant smells will make the corresponding autonomic nervous system respond to anger or disgust, that is, negative emotions [39]. In the process of using Python programs and analyzing network data, the semantic vocabulary of consumer reviews is screened, such as “scent”, “smelly”, “joy” and “like” are positive emotions; “pain”, “anger” and “disgust” are negative emotions. Then a heatmap of emotions is plotted and generated. According to the spatial information corresponding to the emotional heat map, as shown in Figure 4, the areas with high positive emotions are mainly concentrated in Beijing Road Pedestrian Street, Shameen Park, Liwan Lake Park, Enning Road, Duobao Road, and other places. At the same time, using the comment extraction service provided by Baidu AI open platform, the opinions of tourists evaluating the texts of six blocks were analyzed. The service can automatically analyze comment concerns and comments, and output comment labels and heat values. The value is between 0 and 1 and identified by color. The warmer (red) and the higher the negative sentiment is, the cooler the color (blue) will be. By superimposing the smell concentration map, it can be seen that places with high positive emotions mainly exude food, nature, and other flavors that the public likes, with good air quality, good landscape ecology, high crowd vitality, and high green space coverage in Shameen Park. The sentiment is measured through sentiment analysis, a method that uses sentiment score metrics to quantify qualitative data [40]. The data come from people’s text comments on online platforms, including words of various emotional colors and emotional tendencies, such as joy, anger, sadness, and joy, also criticism, praise, etc., through the natural semantic analysis method, and analyzing the evaluator and emotional tendencies. Using the Python program to score, the text sentiment polarity is judged as negative and negative between 0 and 0.5, and between 0.5 and 1 is judged as positive and positive. The positive and negative attributes are used to determine the emotional tendency, and people’s emotional values are connected to the space. Finally, people’s emotional values are superimposed on the smell map to visualize the relationship between spatial smell and pedestrian emotions.

4.4. Key Blocks Analysis

Since the on-site data collection is limited by factors such as time and manpower, the most famous Beijing Road pedestrian block in the old city is selected, which is the most popular and has rich smells. For selected regions, we use the smell tracking method of existing methods [41]. Two groups of people conducted smell tracking experiments to test the reliability of big data to reflect urban smells and to understand the composition of the smellscape of the old city of Guangzhou from a microscopic scale. The experimenter needs to identify the smell and find the source during the field visit, mark the approximate location on the map, and record the type of smell, the intensity of the smell, the duration of the smell, the feeling of smelling the smell, and whether the smell affects life or life smells that are lacking in smells and are eventually depicted on smellmaps.

Gaodi Street–Beijing Road plot in Yuexiu District, from Cangbian Road in the east to Guangzhou Uprising Road in the west, from the front of the Department of Finance in the north to Daxin Road in the south and Gaodi Street. The history of Beijing Road can be traced back to the Southern Han Dynasty; since the Song Dynasty, it has been rebuilt more than ten times; from the Ming and Qing Dynasties, the neighborhood expanded; in 2002, in the process of transforming Beijing Road, the northern section produced the ancient road relics of 11 stories in the five dynasties from the Tang Dynasty to the Republic of China, and the southern section produced the base of the arch north building of five stories from the Song Dynasty to the Ming and Qing Dynasties, which added a longer history and high cultural value. Today, Beijing Road is still the most prosperous commercial district. There are Taiping restaurants with a history of 135 years, which are deeply loved by the local people, time-honored brands, such as Lin Heung Tea House, Guangzhou Distillery, TaoTaoJu restaurant, Wang Laoji herbal tea, and several specialty restaurants, such as Dayang original stew, Yinji intestinal powder, Paozai cake and so on. In the original survey, the majority of respondents felt the scents were good and said they were important in their daily lives. By analyzing the big data smell map, it can be seen that there are many kinds of smells and rich levels in the Gaodijie-Beijing Road area. The field investigation found that there are many kinds of smells, mostly comfortable and pleasant, which are happily accepted by tourists and local residents.

In addition, the experimenters find that the green plants on the streets in the Gaodi Street and Beijing Road area give off a faint smell of vegetation; some perfume lavender shops exude a faint smell, but because of the wide street, the air circulation speed is fast, the smell is not rich, and in the Beijing Road Pedestrian Street area the most intense and lasting smell is the one emitted by the food along the street. At the same time, there are also some unwelcome smells in this process, such as the smell of paint and wood chips in some shops or road construction and transformation, urban life emissions, public toilets, sewers, and other smells.

According to the feelings of the comprehensive experimenters in the field investigation, the most obvious smells in the street walking were the smells of hot pot, pastry, and frying string in the street. On both sides and intersections of Huixin West Street and Pedestrian Street, the smells of pastry and frying string are the strongest, which are deeply loved by young groups. Standing on the section from Zhongshan No. 5 Road to Guangzhou South Vietnam Palace Museum, the smell of food is not strong, because nearby are the Guangdong Provincial Department of Finance, the old site of the office of the Chinese Business Daily in Guangzhou, and a small number of residential areas. Compared with the pedestrian street, the flow of people is less, so the smells are mostly temporary such as the smell of food purchased by passers-by, the smell of perfume on people, and the smell of pets. Yuexiu Academy Road west to east and Huijing New Street north to go into the Beijing Road Cultural Tourism Area because of the construction, so people can smell the paint and wood, whose flavors last for a short time, but they are not popular and people feel uncomfortable (Figure 5).

According to the key area of human perception, urban smell is analyzed hierarchically. The basic smell is a persistent, relatively stable background smell within a certain spatial range, which is not easy to change with time; examples are the smell of plants, the fragrance of food and cakes etc., short-lived smells that reflect regional characteristics and usually appear relatively fixed in a certain area, such as the smell of fresh fish, flowers, fresh meat, and medicines. Temporary smells refer to urban smells (that other people may or may not smell at other times), which are temporarily present in that venue and are noticed by accident or intention, such as perfume, metal, paint, second-hand books.

Through a comprehensive analysis of the smell landscape of Beijing Road, it is found that the important reason for the popularity of that road lies in its profound historical and cultural heritage and food culture, as a prosperous commercial distribution center located in the center of Guangzhou City. There are different types of services such as shopping malls, catering, leisure, and fast food around it so that visitors can get a brief relaxation and taste the food there. At the same time, the Beijing Road business circle is constantly advancing the transformation into the “Internet + new business” mode, letting the old and new Guangzhou people look for memories, while Chinese and foreign tourists experience the pleasures of food and clothing in Guangzhou.

5. Discussion

The study of urban smell landscape has great significance for urban space as follows. First of all, optimizing the urban smell landscape itself can improve the regional quality. Through the smell map, the high-quality smell areas in the district are connected to a network, and the street culture and tourism projects are combined to improve the quality of the street, attracting pedestrians and thereby enhancing the vitality of the street. Secondly, integrating the urban scent landscape into the urban design framework can clarify the regional characteristics, define the regional theme, and then create the themed landscape, create the themed atmosphere, and plan the themed activities. At the same time, the urban smell landscape can also be used as one of the elements of urban operation to create a beautiful smell environment, emphasize the urban personality, and strengthen the urban image.

5.1. Green Urban Design: Theme Route Planning

• Sightseeing route

There are many famous tourist spots in Guangzhou’s historical and cultural blocks, and by marking popular places on the map, such as Beijing Road Pedestrian Street, Upper and Lower Nine-Pedestrian Street, Chenjiaci Temple, Sandy Surface, Stone Room Holy Heart Cathedral, and other popular attractions, as well as referring to the smell map, appropriate sightseeing routes are created (Figure 6).

2.

Cultural route

Socio-cultural and the tourist’s experiences are important in fidelity to the visited destination, and the new habits of tourist consumption favor the rise of cultural tourism [42]. The historical and cultural blocks of the old city of Guangzhou have a long cultural history, and there is also a variety of cultural activities, such as the South Yue King Museum of the Western Han Dynasty, the ancient house of Xiguan, the Cantonese Opera Museum, the sand European architectural complex, and other public facilities. Referring to the smell map, as well as restaurants, bars, coffee shops, and other smells, this paper analyzes and summarizes the appropriate cultural routes, so that visitors can fully understand the atmosphere of the historical and cultural city of Guangzhou and feel the old and broad customs. (Figure 5). In historical and cultural blocks, culture is the driving force promoting the interaction of trialectic spaces (trialectic spaces including” spatial practice”, “representations of space”, and “representational spaces”) [43].

3.

Food route

The tradition of food is important in Guangdong in general, and particularly Guangzhou which is one of the most representative cities of the province. There are many old food restaurants in the historical blocks of the old city of Guangzhou, which is also a major destination for tourists to places such as the Guangzhou winery, Panxi winery, Beiyuan winery, Diandude, Taotaoju, Lin Heung Tea House, etc. The old food shops are marked on the map, and the smell map is used to analyze and plan the suitable route for walking. (Figure 7).

5.2. City Operation: City Vitality and Image Creation

Smell affects people’s behavior and mood at any time. Use scent as a medium to strengthen the urban smellscape, guide people’s behavior, create a unique urban perception experience, and improve the uniqueness and recognition of urban space. Attention should be paid to regional smell selection design, planning smell experience scheme design, and the planting of various aromatic plants to create specific olfactory space content and to promote the sustainable ecological cycle development of urban space [44].

• Planning of commercial space smell

According to the commercial space form and image of the city, design exclusive scents, optimize the distribution of commercial formats, stimulate taste perception, enhance consumer emotions and needs, and form a good consumption environment [45]. Olfactory marketing has been increasing its presence in commercial environments, as smell gives the space a better-perceived quality, increases the willingness of visitors to return, and promotes marketing [46]. There is an interaction between emotion and environmental smell on perceived value, purchase intention, and decision quality. Managers can increase business value by rationally deploying ambient smells and inducing consumers’ emotions [47,48,49,50].

2.

Establishment of street smell recognition system

Establish a street smell library, design an olfactory recognition system, and form an overall sensory brand. Sensory branding is a holistic way of spreading information and value, by creating brand messages that rely on all five senses, not just sight and sound, to increasing people’s strong connection to their environment [51,52]. Improve the street smell landscape and form a high-quality street with strong affinity and many crowds.

3.

Collaborative creation of art, culture performance and smell

Ambient scents evoke perceptions and memories of art, as well as the underlying interactions between different scents and artworks [53]. Use smell as design material and integrate urban culture for artistic creation. Assist art workers to integrate scent into various artistic creations and expand the field of city image promotion.

4.

Use vegetation to enhance the smell space of the block

On the one hand, vegetation has the effect of space purification for the environment. The plant configuration in South China is used to create a space atmosphere, and the space is purified according to the characteristics of the plants, which improves the air quality and the space environment in the city center. On the other hand, the smell emitted by plants can improve the social atmosphere and increase pleasant emotions. The use of the collocation application of aromatic plants enhances the perception of smellscape, while the plant density, height, location and spatial extent are directly related to the concentration and diffusion of aroma [54]. From the micro-environmental space to the urban environment, this has played an important role.

6. Conclusions

The smell research of Guangzhou’s historical and cultural blocks: summarizes the research situation of the urban smellscape at home and abroad, combined with the actual situation in Guangzhou; proposes a set of methods suitable for the classification of smells in Guangzhou historical and cultural blocks; connects block smell and emotion; organizes and analyzes with Internet data; draws a smell map; and proposes theme route planning suggestions for green urban design. It is also necessary to establish solutions for negative smells and guidance programs for positive smells, which have far-reaching significance for creating the characteristics of the central city.

There are some deficiencies and limitations in the smellscape research in Guangzhou. The research was carried out in a limited area and time, failed to cover the entire city, failed to reflect the changes of smell near and far, and failed to simulate the impact of weather conditions on the urban smellscape. This study was conducted within certain constraints, and the fieldwork was conducted without rain, wind, or obstructions. The important influence of environmental variables on smell should be considered, such as wind strength and direction, temperature, etc., which have varying degrees of influence on smell perception and have an important impact on the presence or dissipation of continuous smells in a space. As an important factor, environmental variables can be monitored in the follow-up research, and the issue of smellscape in environmental changes can be discussed in depth, so it is not examined in detail in this article. At the same time, the construction of the smell landscape is conducive to the perception of the tour experience for the blind, who are particularly sensitive to smell and hearing. The creation of smell blocks and auditory blocks with local characteristics satisfy the blind people’s understanding of the area to a certain extent, and form smell memory and hearing. Sound memory [55], adds to the memory of their lives. The characteristic ambient smell can also prompt most consumers to feel familiarity, intimacy, and authenticity in the area [56]. In the future, the smell can play an important role in the interactive experience of the digital twin city, and the smell landscape of city blocks can be experienced through VR glasses. The exploration of digital scents will be opened up, and people’s favorite scents can be continuously released according to the differences and needs of environmental space [57]. Three areas of future research have also been identified for this field: smell archives and databases; social justice within smell control; and management and research into advanced building materials [58]. Smell has space and time to connect the relationship between people and regions. It can also break through the limitations of space and time, establish emotional connections between people and regions, form a unique and profound urban memory, and promote the friendly and sustainable development of human and environmental spaces.