Clean Up Australia Day Sunday 2nd March is approaching fast so it is an opportune time to describe how plants can help clean up contaminated soil and water.
Phytoremediation from the Ancient Greek phyto, meaning "plant", and Latin remedium, meaning "restoring balance", describes the many processes by which plants can be used to reduce pollutant concentrations in contaminated soils, water, or air.
Plants can take up, store, transform and degrade pollutants including metals, pesticides, macro-nutrients, solvents, crude oil and even explosives.
It is a slow and complex process but it can be a cost effective and environmentally friendly alternative to more radical options such as excavating contaminated soil and disposing of it elsewhere.
Arsenic contamination is a serious global issue. Overtime, sunflowers (Helianthus annuus) can help reduce arsenic contamination by absorbing it and concentrating it in their tissues.
Some contaminants can be inactivated or degraded by the plant’s metabolism. It has been reported that Bull Rushes (Typha sp.) can effectively remove TNT from contaminated water in this manner.
Sometimes it is not the plants themselves but the organisms that live in and on their roots, and in the surrounding soil which remove the contaminants. Microbial processes can lead to nitrogenous pollutants from fertilisers and other sources, being converted to nitrogen gas and released to the atmosphere.
Plants which have taken up contaminants need to be harvested and disposed of appropriately to avoid re-contamination.
Phytoremediation is used in the Sensory Garden, the Biodiversity Garden and the Oasis Valley, where carefully selected species of wetland plants help keep the water bodies clean. On a larger scale, Egret Park Wetland (an artificial wetland) uses wetland plants as one of the major methods of cleansing polluted urban stormwater runoff from the Keswick Estate before the water is allowed to reach the Macquarie River.
Team up with the plants on Clean Up Australia Day and make a positive difference.
By Ian McAlister and Karen Hagan