Microbial diversity and cover plants in de-sealed urban soil as strategies for mitigating anthropogenic volatile organic compounds

Urbanization exacerbates soil degradation, compromising global soil health and biodiversity. To reduce this, strategies for soil de-sealing and bioremediation are necessary. In a mesocosm experiment using a de-sealed soil from an urban site as substrate, an inoculum of arbuscular mycorrhizal fungi (AMF) and two cover plants, Cynara cardunculus L. and Trifolium repens L., were utilized to assess their effects on volatile organic compound (VOC) emissions and soil microbial community dynamics. The soil status was investigated employing soil VOC and metabarcoding analyses. Our results showed that the soil VOC emission was mainly composed by anthropogenic derived VOCs, especially arene and furan classes. These two classes were shown to be less concentrated in C. cardunculus soils, with and without AM fungal inoculation, suggesting a positive impact of these conditions on soil health restoration. Additionally, AM fungal inoculation of C. cardunculus resulted in increased bacterial alpha diversity, with enhanced Proteobacteria/Acidobacteria, Cyanobacteria/Chloroflexi, and Fungi/Bacteria ratios, suggesting an improvement in soil quality conditions. In our experimental conditions, order Chloroflexales and specific bacterial genera, including Ralstonia, Delftia, Ramlibacter, were identified as contributors to VOC degradation, highlighting their adaptability in contaminated environments. Overall, this study provided evidence on the importance of integrating AM fungal inoculation and specific flowerbed/ornamental plants in urban soil management after de-sealing processes.