The scientific community highlighted the role of urban areas in global greenhouse gas emissions, estimating their contribution at up to 70% and recognised the need to apply specific monitoring/verification protocols for urban areas. Urban greenery was proved to contribute significantly to overall urban CO₂ fluxes and mixing ratios, however its role in urban C flows remains poorly constrained. Vegetation in urban areas experiences conditions different to rural areas, requiring a specific modelling/monitoring approach. Among the urban stressors, Microplastics (MP, i.e. plastic particles below 5 mm in size) are contaminants of emerging concern, exerting a further stress factor for urban ecosystems, affecting soil properties, with implications on ecosystem services and human well-being.
Currently Modena is one of the very few cities in Italy with the infrastructure for urban CO₂ emission verification, by the deployment of an eddy covariance (EC) flux tower at the top of the Unimore Geophysical Observatory, providing direct observations of CO₂ fluxes from a representative part of the urban area. Moreover Unimore has recently completed the research project MicroTRACES, achieving a first assessment of the airborne MP concentration levels and deposition rates. Results showed a high prevalence of petrochemical-based polymers, including MP from tyre abrasion and textile, with differences between traffic and background sites. Indeed, while the impact of MP on marine ecosystems is well detailed, its role in urban ecosystems is still highly uncertain, due to the very few observations of MP in urban areas, preventing a reliable estimate of its impact on the ecosystem health and, ultimately, on the exchange of CO₂ with the urban atmosphere.
The project aims to estimate the ecosystem flux of CO₂ in Modena and how it is affected by MP pollution. Project tasks include experimental monitoring of urban CO₂ fluxes from an EC tower, experimental monitoring of soil/grass respiration in representative areas of the city and under controlled MP contamination, assess the impact by MP on the soil biology quality and eventually on the ecosystem and modelling of spatially/temporally resolved ecosystem fluxes across the city. The integration of the outcomes from these tasks will lead to the very first (still preliminary) experimental partitioning of urban CO₂ emissions to combustion, human respiration and ecosystem. Moreover, we will estimate future projections of the change in CO₂ flux from urban ecosystems based on scenarios of MP pollution in Modena and use them to assess the current pathway towards carbon neutrality for Modena. Key project outputs include the collection and dissemination of a unique dataset on urban CO₂ fluxes, the engagement of students and the general public, and the advancement on the impact of MP pollution on soil quality in a pilot urban system. Finally, the project will lay the foundations for a monitoring/verification system of Modena’s CO₂ emissions.