Environmental sustainability and resilience in a polluted ecosystem via phytoremediation of heavy metals and plant physiological adaptations

Natural Ecosystems are being degraded significantly due to increasing industrial pollution. Marble pollution is one of them. It was hypothesized that such a polluted ecosystem host unique set of plant species growing and tolerating the level of the pollution they dwell in. These can be used as phytoremediators successively, once the level of their tolerance is determined for environmental sustainability and resilience. The current research work was aimed to assess the phytoremediation ability of the selected resistant plant species by studying their physiological adaptations in the Marble Waste Polluted Ecosystem (MWPE) of northern Pakistan. Quantitative Ecological Techniques (QET) were adopted to sample the vegetation of polluted zones, initially. Indicator species were identified using Indicator Species and Total Importance Value, Indices. Topmost indicator plants were further evaluated for environmental sustainability and resilience based on indicator species analysis and a higher importance value index in the region for their phytoremediation abilities using Biological Concentration Factor (BCF), Translocation Factor (TF) and Bioaccumulation coefficient (BAC) analyses using atomic absorption spectrophotometric techniques. Physiological responses i.e., Proline accumulation and chlorophyll contents (a, b and carotenoids) for each indicator plant species were recorded and examined using standard experimental protocols. Atomic absorption spectrophotometry was also used to assess heavy metals concentration. All the collected data were analyzed through Structural Equation Modeling, Mixed effect modeling and Regression analysis using R software. Preliminary results showed that out of 220 species, 19 indicator plants, i.e., Adiantum capillus-veneris, Ailanthus altissima, Albizia lebbeck, Calotropis procera, Cynodon dactylon, Datura innoxia, Debregeasia salicifolia, Desmostachya bipinnata, Dodonaea viscosa, Erigeron bonariensis, Ficus carica, Morus alba, Morus nigra, Parthenium hysterophorus, Persicaria glabra, Ricinus communis, Setaria viridis, Tamarix aphylla and Withania somnifera were the significant phytoextractor and phyto-stabilizer of potential toxic elements (Cr, Ni, Cu, Mn, Zn, Fe, Co, Cd, Ca and Mg) based on bioaccumulation coefficient, translocation and biological concentration factors. These indicators increase the accumulation of proline osmolyte and decrease chlorophyll-a, chlorophyll-b and total carotenoids as a defense or survival mechanism against pollution. These results were reconfirmed through Structural Equation Modeling, Mixed Effect Modeling and Bivariate Regression. It was concluded that the indicator plants have a significant role in the cleaning of ornamental rocks pollution and hence in the environmental sustainability and resilience. It is recommended that these indicator plants can be grown to remediate the heavy metals or PTEs released from the MWPE and their vicinities for better environmental management and pollution control in the subtropical regions of the world.