Researchers study floodwaters

Southern Cross University researcher Damien Maher tests flood water samples in the laboratory.

AS floodwaters flow out to sea, scientists are testing the waters to understand what drives the de-oxygenation of estuary and river systems.

Southern Cross University researchers are investigating the true impact of the carbon cycle, which follows major flooding leading to fish kills and greenhouse gas emissions from estuaries.

Focussing their wok mainly on the Richmond River, the research group aims to find out how great the carbon dioxide concentrations are in floodwaters.

Damien Maher, a post doctoral fellow and Dr Isaac Santos, a senior lecturer, from SCU's Centre for Coastal Biogeochemistry Research, are undertaking the study.

"The run off from these flood events delivers a lot of nutrients from the catchment to the estuary and we know the potential for a fish kill is high. We're wondering how these events influence greenhouse gas emissions from estuaries," Mr Maher said.

"We want to understand how much carbon delivered to the estuary is released to the atmosphere and how much is buried and sequestered for long term storage."

"Like many estuaries the Richmond River catchment has significant areas of acid sulphate soils.

"Our preliminary findings indicate that the carbon dioxide concentrations in these waters are among the highest ever measured."

One hypothesis is that water draining from acid sulphate soils drives the de-oxygenation of estuarine water and an associated release of carbon dioxide, anecdotally leading to fish kills.

 Radon concentrations - a naturally occuring gas that alerts researchers to groundwater - are also being measured. 

"Radon is a good groundwater tracer because it is naturally high in groundwater while being low in surface water," says Dr Isaac Santos, who recently brought radon technology to Australia.

"By monitoring concentrations of radon along the estuary we will be able to determine the role of groundwater in estuarine de-oxygenation and greenhouse gas emissions.

This research is funded by grants by the Hermon Slade Foundation and the Australian Research Council.