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Science & Arts Media
jca-media at starclass.com.au
Tue Apr 6 18:20:30 EST 2004
CERAR Media Release 04/03
April 7, 2004
TAKING THE RISK OUT OF TOXIC CLEAN-UPS
Across Australia stand warehouses filled with drums of contaminated soil - yesterday's headaches dug up, carted away and threatening to become a new toxic curse tomorrow.
A call for a fresh approach to the challenge of cleaning up the nation's estimated 100,000 contaminated sites has come from a group of leading environmental scientists.
"We simply cannot go on forever shifting our pollution problems in the vain hope they will go away," warns Professor Ravi Naidu, director of the Centre for Environmental Risk Assessment and Remediation (CERAR) at the University of South Australia.
"It's too risky, too expensive and too impermanent as a solution."
Instead, Professor Naidu and his team at CERAR say, the first step is to properly assess the risk at a contaminated site - and then decide whether to remediate it on the spot, dig it up or even leave it completely alone.
"Every contaminated site is different, not only in the hazardous chemicals it contains and how they interact, but in the question of whether they can reach humans through water, the food chain or as airborne dust and soil, and cause poisoning.
"Every site differs in its soil and groundwater conditions, in its acidity or alkalinity, in its soil microbes - all of which determine the extent to which toxic substances are mobilised and find their way back into our environment and into us."
Differing microbial conditions for instance, can decide whether the toxins break down into harmless substances - or turn into forms more highly poisonous and available to be taken up by humans, plants and animals.
"Environmental risk assessment examines all these factors in detail and helps you to decide the most sensible action to take with a contaminated site.
"Sometimes it can actually increase the hazard if you decide to dig the contamination up and move it elsewhere, and the best policy may be to leave it where it is, remediate it or to seal it.
"This is the cost effective, green solution to the problem - but it is not yet one that is widely understood in the Australian community."
When a contaminated site is revealed - often as a result of new real estate development on the urban fringe or inner-city re-development - social pressure is often intense to remove it elsewhere regardless of the danger this holds, the cost of removal and storage, or the risk to future generations.
Prof. Naidu says the key to making toxic sites safe is to reduce the bioavailability of the chemicals they contain.
"We can do this either by immobilizing the contaminants chemically, by removing them selectively or by using bacteria to break them down. This can all take place on the spot, avoiding the necessity to dig and dump large amounts of contaminated soil."
Prof. Naidu says that CERAR is modifying a naturally-occurring mineral product so it can mop up various kinds of pollution and bind them, to prevent them from reaching people.
In another project the team is experimenting with an advanced electrical technique for selectively removing pollutants from the soil.
"CERAR was set up especially to assess the risk of toxins being unlocked, mobilised and getting into the population," Professor Naidu says.
"These approaches are both safer and cheaper in the long run than the present 'dig and dump' practice, which merely transfers the problem elsewhere, where it will probably recur in a few decades' time."
Professor Ravi Naidu, CERAR, University of SA,
phone 08 8302 5041, 0407 720 257
ravi.naidu at unisa.edu.au
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