Starting from the Industrial Revolution in the 18th century to date, urban areas have faced increasing environmental challenges due to the diffusion of harmful substances, resulting from vehicular traffic, the activities of different industries, waste, and building construction, etc. These pollutants are dangerous, since they pose a threat to both the environment and human health. Phytoremediation is an environmentally friendly and low-cost technique that uses plants and their associated microorganisms to clean-up contaminated sites. In this review, we explore its main applications in urban settings. Specifically, we investigate how phytoremediation works, highlighting the most effective plants for its success in a city context. Moreover, we also describe the main factors influencing its effectiveness, such as soil, climate, and pollutants. In this regard, several case studies, conducted worldwide, have reported on how phytoremediation can successfully reclaim contaminated areas, transforming them into reusable city green spaces, with reduced costs compared to traditional remediation techniques (e.g., soil replacement, soil washing, etc.). Moreover, by integrating it into urban planning, cities can address environmental pollution, while promoting biodiversity, enhancing the landscape, and increasing its social acceptance. This nature-based solution offers a practical path toward more sustainable and resilient urban environments, especially in regard to the climate change framework.

The impact of pollutants in urban wastewater on Constructed Wetlands (CWs) rhizoplane microbial communities remains quite understudied. Our study explores how civil wastewater influences the structure and ecological stability of rhizoplane microbial communities associated with three macrophytes: Nerium oleander L., Arundo donax L., and Juncus conglomeratus L. in simulated conditions as in the case of CWs. Therefore, a pot experiment was set up, using wastewater repeated exposure of the three macrophytes, to assess the microbial (bacteria and fungi) resistance and resilience by means of next-generation sequencing. The results showed that all three macrophytes contributed to pollutant removal; however, the effects on microbial communities were taxon-specific. In general, the rhizobacterial community exhibited moderate resilience and low resistance to wastewater, indicating a partial recovery post-disturbance. The fungal community showed high resistance (ResI = 0.99), in contrast with limited resilience (RI < 1), suggesting a stable but less dynamic response to the wastewater exposure. Effluent repeated addition positively influenced the relative abundance of certain bacteria taxonomical groups, specifically Firmicutes and Actinobacteria, but also of some fungal taxa. Our findings underscore the key role of microbial communities in CWs, where complementary resistance and resilience strategies contribute to system stability, plant health, and pollutant attenuation.

Soil degradation can strongly constrain plant establishment and ecosystem restoration, highlighting the need for amendments able to improve both soil functionality and plant–microbiome interactions. This study evaluated whether biochar preconditioned for six months in healthy pine forest soil could enhance the early growth of Pinus halepensis Mill. compared with untreated biochar in degraded agricultural soil. Seedlings were grown for 85 days under controlled conditions in five substrates, including pine forest soil, non-intensively cultivated agricultural soil, degraded agricultural soil, and degraded soil amended with either untreated or bioactivated biochar. Above- and below-ground plant morphological traits, soil chemistry, and rhizosphere microorganism communities were assessed. Untreated biochar markedly promoted root development, increasing absorptive fine-root length, root biomass, and stem diameter compared with degraded soil and forest-conditioned biochar. In contrast, bioactivated biochar resulted in more limited early seedling growth. Microbial community composition varied among treatments, whereas Shannon diversity did not differ significantly. Bacterial communities showed partial overlap among treatments, while fungal communities displayed clearer treatment-associated separation. Overall, forest-soil conditioning did not improve biochar effectiveness during early seedling development. Further drought and field trials are required to determine whether these contrasting growth and rhizosphere responses influence long-term establishment and restoration performance.