Ecosystem Services Provided by an Urban Green Space in Timișoara (Romania): Linking Urban Vegetation with Air Quality and Heat Risk

This study was conducted in a temperate-continental city of Europe (Timișoara, Romania) and aimed to investigate the contribution of urban vegetation in maintaining air quality and mitigating the heat in the analyzed city. It was studied The Central Park „Anton von Scudier” located in the downtown of Timișoara City (45°45′05″N, 21°13′16″E) for the following air parameters: fine particulate matter PM2.5 (aerodynamic diameter < 2.5 μm), fine particulate matter PM10 (aerodynamic diameter < 10 μm), AQI (Air Quality Index) (resulted from PM2.5 and PM10), particles number, air temperature, air relative humidity, TVOC (total volatile organic compounds), HCHO (formaldehyde). Nine sample points of air monitoring were established: seven inside the green space and two outside it. The air monitoring was done in the late August, in four consecutive working days (Monday-Thursday), within 12:00-14:00 a.m. The air measurements were made using a portable device for outdoor air monitoring (Temtop LKC-1000 Series Air Quality Monitor). The results of this study show that urban vegetation remains a reliable factor in reducing PM2.5 and PM10 in cities air and in keeping the AQI within the limits corresponding to good air quality, but also that air relative humidity counteracts the contribution of vegetation in achieving this goal. Thus, the study highlights the importance of air humidity in enhancing the values of PM2.5, PM10, AQI, and in exceeding their admissible or recommended limits for air quality. There was not confirmed by this study the effect of wet deposition of the airborne particles as effect of precipitations. Inside the park, the HCHO concentration increased by up to 4-5 times compared to the outside, and this increase was not caused by vehicle traffic, but rather by the photochemical reactions generating HCHO. Regarding the cooling effect on air temperature, the studied green space did not exhibit this effect, as the air temperature inside it increased by up to 1-6°C compared to the outside, which means it did not achieved its goal of providing climatic comfort to citizens during the summer and serving as a cooling spot in the city. Our results contrast the general perception and conviction that urban parks and green spaces are cooler islands within the cities and draw attention to the fact that having a green space in a city does not necessarily mean achieving environmental goals, such as reducing the heat risk of cities. In this study, based on the results, we consider that the main limitations in achieving these objectives were the park’s small size (88 hectares) and its morphology and architecture resulting from the integration of the species that compose it. It follows from these data that it is not enough that an urban green space to be established, but its design must be combined with urban morphology strategies if the heat mitigation effect is to be achieved and the cooling benefits are to be maximized in cities. Therefore, in the urban planning, the environmental strategies should comprise not only aesthetic criteria, but also scientific criteria in order to reach the final goal of the urban green spaces in the cities: a sustainable, healthy, and comfortable environment.