Effects Of Visibility On Green Space Recovery And Residents’ Perception And Preference

In the context of rapid urban development and fast-paced work life,modern urban residents are facing huge physical and psychological pressure.The natural environment has been proven to promote human physical and psychological health,and urban green space,as an important natural resource in the city,can play a restorative role to help people relieve stress and relax.However,the prevalence of air pollution in cities not only damages human health through pollutants,but also causes a decrease in visibility that directly affects people’s visual perception,thus damaging the experience of using the green space environment,yet this effect has not been taken seriously.Therefore,using visibility as an entry point to study the impact of air pollution on the restorative effect of green space and exploring its influence mechanism can help to design and build a better quality restorative environment to meet the demand of residents for recreation and relaxation.Based on the Stress Reduction Theory(STR)of the restorative environment theory,this study classify the green space into three types according to the vegetation structure: open space,semi-open and semi-closed space,and closed space,and also sets a grey space as a control,and then selects three representative air quality levels according to the air quality index levels: excellent level(AQI=50),light pollution level(AQI=150),and moderate pollution level(AQI=200),and combine their corresponding visibility levels(visibility high,visibility medium,visibility low)with the four space types.The photo elicitation was used to compare the physiological(electrodermal,EEG α wave / EEG β wave)and psychological(Profile Of Mood States)restorative effect obtained by the participants after viewing different green spaces at different visibility levels,and to explore the mechanism of the effect of visibility on the green spaces restoration in conjunction with the perception and preference dimensions of the environment.The following findings were obtained.(1)Visibility and green space type can affect green space recovery.When the visibility is low,the difference in recovery among green spaces is the greatest,and the overall trend shows the best recovery of physical and psychological indicators in semi-open and semi-closed spaces and the worst recovery in gray spaces.The recovery level of physiological indicators was the lowest at visibility medium(i.e.,AQI=150),and the recovery level of psychological indicators decreased with decreasing visibility.Therefore,areas with poor air visibility should choose to create more semi-open and semi-closed spaces,and try to increase green facilities in hard spaces.(2)Changes in visibility affect human perceptions in the environment.When visibility decreases,the intensity of participants’ perceptions of the eight Perceived Sensory Dimensions(PSDs)generally decreases,and the perceptions of negative properties increase.The decrease in visibility resulted in a significant decrease in the perceived intensity of Serene,Nature,Prospect,Refuge,and Culture,and a significant increase in the perceived intensity of Unpleasantness,Scariness,Uncleanness,Dimness,and Humdrum were significantly stronger.Green space types had an effect on participants’ perceptions of visibility and pollution levels.When visibility levels are the same,people perceive lower visibility and pollution in gray spaces lacking natural elements and open spaces with less vegetation,while reduced visibility in semi-open and semi-closed spaces and closed space with richer vagetation are more likely to be attributed to fog and other weather causes,and less likely to notice a decrease in air quality.However,the closed space is still considered dangerous because it is too secluded.In order to increase the safety of visitors,it is necessary to design the closed space to avoid a strong sense of seclusion and a lack of management of vegetation.(3)The deterioration of visibility significantly reduced participants’ preference and weakened willingness of activities in the space.The negative effect of visibility on physical and psychological activities was greater,and participants were more willing to engage in psychological activities in semi-open and semi-closed spaces with good visibility and least willing to engage in physical activities.And the better the participants evaluated the visibility of the scene and the lower the perceived pollution level,the higher the preference scores.Therefore,it is necessary to create a space for psychological activities in the green environment.(4)The strength of perceived dimensions and preference in different green space types have a significant correlation with the recovery on psychological indicators,and the spaces with higher the eight Perceived Sensory Dimensions,lower negative perceptions and higher preference have better psychological recovery.At the same time,due to the different vegetation characteristics of green space,the participants believed that the air quality in the environment with richer vegetation was better,the preference was higher and the recovery was better under the same visibility.Visibility changes have an impact on the perceived intensity of the perception and on preferences,thus influencing the recovery of green spaces.The above findings demonstrate that reduced visibility due to air pollution affects individuals’ perceptions and preferences for green spaces and negatively affects their restorative effect.At the same time,the vegetation structure characteristics of green space will affect people’s judgment on air quality.Therefore,visibility,an important visual factor,should be taken into account in the construction of restorative environments,and green space should be selected in areas with severe air pollution in a targeted manner,so as to bring into play more effectively the positive benefits of urban green space in terms of stress relief and relaxation,and to seek the optimal solution for the creation of green space in the context of air pollution.