Overcoming the tsunami’s harmful legacy
by Vincent Ciccarello
An Indian researcher, here to find ways to help her tsunami-ravaged neighbours, may just help Australia with a number of its own problems.
Beyond the tragic loss of life and the destruction of property and livelihoods, the catastrophic tsunami of December 2004 has also left a harmful legacy.
The seawater which inundated coastal agricultural lands up to 2km inland brought with it sea salt and, more worryingly, the mineral pyrite. When the water receded, pyrite, an iron sulphide, was exposed to air, producing sulphuric acid and destabilising heavy metals in the soil.
The resulting acid sulfate soils rendered the land unusable for farmers, further hampering their efforts to recover from the devastating tidal wave.
Motivated by the predicament of the people in her home state of Tamil Nadu, Dr Kavitha Shanmugan from India’s Annamalai University has successfully carried out innovative research in growing salt tolerant crops such as aloe and periwinkle in salinated soils.
Now, she has come to UniSA, courtesy of a Federal Government Endeavour Research Fellowship, to work with Professor Nanthi Bolan at the Centre for Environmental Risk Assessment and Remediation where researchers are looking at ways to recover acid sulfate soils in parts of drought-stricken Australia.
"Agricultural lime can go some way to recovering acid sulfate soils," Dr Shanmugan said, "but its use is limited by cost and the depth of the acid problem.
"Australia has a lot of coal combustion by-products such as bottam ash, FBA (fluidised boiler ash) and fly ash that can also be used to neutralise the acidity and make soils productive again."
With the help of Dr Ed Burton from Southern Cross University, Dr Shanmugan and her UniSA colleagues have collected acid sulphate soils from the Tuckean Swamp in NSW, and treated them with different neutralising agents including agricultural lime, hydrated lime, rock phosphate and coal combustion products at various levels.
"We are monitoring the incubated soils for pH (the level of acidity or alkalinity), electrical conductivity (a measure of salt levels) and heavy metals," Dr Shanmugan said.
"We are also trying to germinate canola in the treated soils."
The researchers hope to trial the industrial by-products in the field soon.
Prof Bolan said that while these coal combustion products with relatively high liming potential can overcome the problem of acid sulfate soils, care is needed as some of the materials themselves may contain heavy metals.
"We have to be very selective," he said.
"The materials we add should act as a sink, not a source of heavy metals. But the results so far have been promising and suggest this process has the potential to recover soils adversely affected by the drought while putting industrial by-products to good use."
Dr Shanmugan said her time at UniSA has been "a wonderful experience, both professionally and personally".
"I have had lots of opportunities to learn here, to operate equipment and to use excellent facilities we don’t have at home," she said.
"When I go back, I’m looking forward to continuing my research in enhancing the growing conditions of the tsunami affected soils and guiding my postgraduate students."