Plant adaptability and heavy metals accumulation of different landscape plants in soil applied with sewage sludge

Objective  This study aimed to explore plant adaptability and heavy metals accumulation of different landscape plants and the co-planting system in sludge-amended landscape soil and provide a theoretical basis for the sewage sludge landscape utilization and the selection of landscape plants for heavy metals remediation.

Method  Landscape tree Bischofia javanica and landscape ground cover plant Dianella ensifolia,Syngonium podophyllum, and Schefflera odorata were selected as tested plants. The greenhouse pot experiment contained seven treatments, including four kinds of plant species monoculture, and co-planting of B. javanica with three kinds of landscape ground cover plant, respectively. In addition, substrate without planting was designated as control (CK). The seedlings were harvested after six months. Plant dry biomass, root activity, root antioxidative enzyme activity, root morphology, plant heavy metals accumulation, and the fraction changes of soil heavy metals were analyzed.

Result  Compared with monoculture treatment, the treatment co-planting with S. podophyllumt significantly reduced the dry biomass, root superoxidase dismutase (SOD) activity and root activity of B. javanica. In contrast, the treatment co-planting with S. odorata significantly increased the total root length, total surface area, root volume, specific root length, root peroxidase (POD) and catalase (CAT) activities of B. javanica. The treatment co-planting with B. javanica significantly increased the dry biomass, root total volume, and root CAT activity of S. podophyllum. Compared with monoculture treatment, the treatment co-planting with D. ensifolia increased the Cd accumulation ofB. javanica by 238.73%. The treatment co-planting with S. odorata increased the Cd, Cu, and Ni accumulation of B. javanica by 278.76%, 53.68%, and 71.44%, respectively. The treatment co-planting with B. javanica increased the Cd, Cu, Zn, and Ni accumulation of S. podophyllum by 161.61%, 139.77%, 78.37%, and 65.70%, respectively. Also, the exchangeable and Fe-Mn oxides fractions of Cd were significantly reduced but the residual fractions of Cd, Cu, and Ni were significantly increased by co-planting of B. javanica and S. podophyllum.

Conclusion  Compared with monoculture treatment, co-planting of B. javanica with S. odorata and co-planting of B. javanica with S. podophyllum increased the accumulation of heavy metals in sludge-amended landscape soils.