Foliar Heavy Metal Concentrations of 19 Tree Species Grown on a Phytocapped Landfill Site

Abstract

An alternative landfill capping technique ‘Phytocapping’ (establishing plants on the waste directly, or on a layer of soil placed over the waste) was trailed at Rockhampton, Australia, as it is eco-friendly, less expensive and socially acceptable. In this capping trees are used as ‘Bio-pumps and Screen’ and soil cover as a ‘Storage’. They together minimise water percolation into buried waste leading to reduced leachate production. Twenty one tree species were grown on two soil depths and monitored for their growth and their ability to restrict water infiltration through the buried waste. A very common question raised by most scientist and engineers is the heavy metal uptake by the tree species and its impact on flora and fauna. Hence to determine the heavy metal concentration in trees species and its cycle within the phytocapping system, foliar and foliar litter heavy metal concentrations were measured in all the tree species grown on the phytocapped landfill site. Results from this analysis suggest that heavy metal composition of the leaves show no real elevated concentrations except in Glochidion lobocarpum which showed high levels of cobalt and Acacia harpophylla and Hibiscus tiliaceus which showed higher levels of arsenic cadmium respectively.