Quantifying the co-benefits of urban parks (heat mitigation, air pollution, and thermal comfort)

Urbanisation has led to numerous challenges for human sustenance, which have been aggravated by progressive climate change. Green Infrastructure (GI), which involves working with nature has gained increasing recognition as a multifunctional approach to address urban heat island challenges, including heat mitigation, thermal comfort enhancement, and air pollution reduction. However, it is crucial to establish the multi-benefits of GI in the early stages of the design process to effectively evaluate their impact. Whilst there are scientific studies showing the singular benefit of GI (e.g., heatwave reduction), studies have rarely quantified their multi-benefits. As a result, GI is often undervalued, constituting a barrier to its implementation. This study aims to evaluate the co-benefits of urban parks for reducing the harmful effects of urban heating, improving thermal comfort, and reducing air pollution using mobile monitoring measurements. To achieve this, a comprehensive monitoring campaign was conducted, collecting data inside an urban park and surrounding area to find out the extent of co-benefits provided by urban parks.

The data for this study was collected via mobile monitoring along a fixed route during summer. Meteorological parameters and air pollutant levels were measured using a set of different sensors. The study's findings reveal significant benefits provided by the urban park environment. The mean air temperature during morning runs recorded 18.2°C within the park, compared to 19.6°C in the surrounding built-up area, demonstrating a 1.4°C (7.1%) reduction. In the afternoon, the average temperature within the park was 24.6°C, contrasting with 27.0°C in the built-up area, highlighting a 2.4°C (8.9%) decrease. These results underscore the park’s role in mitigating urban heat, especially during the hotter parts of the day. Furthermore, the park environment exhibited lower average particulate matter (PM) levels than the built-up area. PM₁₀ and PM₁ levels decreased by 1 µg/m³ (8%) and 0.2 µg/m³ (9.7%) respectively during morning runs, while the afternoon runs showed a 0.6 µg/m³ (13.3%) reduction in average PM_2.5 values within the park. Additionally, CO₂ levels were reduced by 22 ppm (4.5%) during morning and afternoon runs in the park compared to the built-up area.

These findings demonstrate the substantial reduction in air temperature and pollutants, such as CO₂ and PM, with increasing distance from the built-up area towards the park. Understanding the interactions within and around urban parks regarding temperature, air pollution gradients, and thermal comfort compared to surrounding built environments is paramount. These insights can inform urban planning and design strategies to create healthier and more sustainable cities, thereby addressing contemporary urban challenges and fostering the well-being of urban populations.