Studying and designing urban soils to optimize their ecosystem services in 'Smart Cities'

The increasing rate of urbanization, coupled with population growth and the progressive loss of natural spaces, represents a complex global challenge. Addressing this issue requires innovative strategies such as the Smart Cities management model, which aims to optimize resource management to ensure economic sustainability, energy self-sufficiency, and improved quality of life for citizens. Responding to these challenges also requires land management practices prioritising soil conservation and restoration—an essential and non-renewable resource vital for collective well-being. In this context, ‘constructed soils’—anthropogenic soils created by combining organic and mineral materials—are a key tool for achieving the United Nations' Sustainable Development Goals. This is particularly true when they are partially or entirely derived from recycled materials, integrating into a circular economy model that valorizes urban waste once appropriately treated. Such practices not only promote more efficient urban management but also reduce disposal costs and significantly contribute to the conservation of natural resources. This thesis explores the use of alternative materials in the creation of constructed soils, focusing on two main research areas. The first area examines urban desealing, analyzing the use of removed asphalt as a component of soil substrates. This approach aims to promote desealing and reduce the costs associated with it, the largest of which is the cost of landfill disposal. The reclaimed asphalt has been mixed with excavation soil and domestic compost, proving to be neither hazardous in terms of pollutant release nor inhibitory to plant growth. The second area focuses on mitigating soil compaction in urban green spaces caused by excessive pedestrian traffic. Specifically, the resistance of soils amended with organic waste materials—including chipped cork and various types of compost, derived from domestic and green waste—was assessed. In both research areas, to evaluate the effectiveness of the interventions several parameters were considered, including physical, chemical, and biological analyses of the substrates, physiological measurements of plants, and microbial assessments to explore the treatments’ effects on soil biotic communities. The results showed that using asphalt within the matrix of a constructed soil does not compromise soil health, at least in the short term examined. Additionally, the use of cork and compost effectively mitigated the adverse effects of soil compaction, improved soil microbiological quality, and supported healthy plant growth. The practical implications of this research are significant, offering insights for the development of more sustainable and resilient urban green spaces, thereby contributing to the achievement of the United Nations' Sustainable Development Goals. However, further studies are necessary to investigate the long-term effects of these practices, with particular attention to microbial dynamics and the overall sustainability of treated urban soils.