Biomonitoring and bioremediating potential of commonly grown tree species against trace elements with seasonal and...

Heavy metals-mediated environmental pollution and global warming are two emerging threats to plant and human health worldwide. Several anthropogenic and natural activities with a preference for industrialization and heavy transportation have accelerated heavy metals and CO₂ emissions into aerial and soil environments. For a few decades, woody trees have been considered an effective bioaccumulator or bioindicator tool for pollution assessment processes of air-born pollutants. The present study aimed to reveal the carbon sequestration and phytoremediation potential of commonly grown tree species at industrial and residential sites of Multan City, Pakistan, during the summer (2022) and winter seasons (2023). For this purpose, Cd, Cr, Cu, Fe, Pb, Mn, and Zn were assessed from bark and leaves samples of S.cuminii, F.religiosa, C.fistula, C. erectus, and M. azedarach for phytoremediation assessment and above- and below-ground biomass, width, height, and chlorophyll contents were used to access the carbon sequestration potential. Results showed that the phytoremediation potential of tree species based on heavy metal accumulation and translocation (BAF, CBCI, MAI) followed the overall trend S.cuminii > F.religiosa > C.fistula > C. erectus > M. azedarach, while the carbon sequestration trend based on biomass production (AGB, BGB, TB) and chlorophyll pigments (Chla, Chlb, TChl, and carotenoids) followed by the overall trend S.cuminii > F.religiosa > C.erectus > M.azedarach > C.fistua. PCA analysis, mental and Pearson correlation, and PLS-SEM analysis emphasized our conclusion where F. religiosa and S. cumini showed a significantly positive correlation with carbon sequestrant (CS) and heavy metal deposition in leaf and bark samples with preference at industrial sites and summer season. In conclusion, BCF for all tree species was more than 1, which emphasized their phytoremediation potential against heavy metals and should be preferred for biomonitoring and bioremediation, but F. religiosa and S. cumini were more viable options for carbon sequestration and phytoremediation, each with unique strengths for different contexts. Finally, tree species selection should account for factors like local climate, soil conditions, land use objectives, and desired ecosystem services.