Historical application of metal-based pesticides has resulted in a large number of ex-horticultural sites in New Zealand showing higher than normal concentrations of metals such as; lead (Pb), copper (Cu), and arsenic (As), as reported by Gaw et al. (2003). Heavy metals accumulate in the soil and are considered the most widely occurring contaminants world wide (Li et al. 2004). Metals are capable of causing significant damage to the environment and human health as a result of their potential to bioaccumulate and their ability to remobilize under changing land use regimes.

Soils were sampled from an ex-orchard site located in the Waikato Region of New Zealand. This site is currently undergoing remediation treatments including; phytoremediation, chemical immobilization and bio-augmentation. Diffusive gradients in thin-film (DGT) were used to quantify metal fluxes from solid phase to solution for the main metals of concern (Cd, Cu, As, Pb, Zn). Deployment of DGT gels was carried out using intact soil cores collected from different treatment plots within the site and placed in leaching columns. Data will be presented on temporal metal re-supply over the project period under three different remedial treatments as compared to an untreated control soil.

Once the mechanisms governing the re-supply of heavy metals and their consequent phytoavailability of heavy metals is better understood there are implications for optimizing remedial options in the future and protecting against offsite effects.