Wetland geochemistry examined in international study

Flooding, sea level rise and general land use practices all have the potential to impact significantly on the worlds’ wetland environments and therefore affect water and soil quality as well as marine environments on a large scale.

Fish kills are a well documented example.

An Australian Research Council Discovery Projects scheme grant awarded to a Southern Cross University Special Research Centre, Southern Cross GeoSCience project, has funded research that aims to rethink how soil mineralogy and biogeochemistry affect wetland environments and consequently the broader environment.

The project, entitled ‘a new paradigm for the accumulation and persistence of metastable iron sulfides in sulfidic soils’, is being led by Southern Cross GeoScience Associate Professor Ed Burton who said there was still a lot to learn about the behavior of organic material and minerals in wetland soils.

“I have been studying the geochemical behaviour of iron and sulfur in acid-sulfate soil wetlands since joining Southern Cross University in 2005 and one of my initial discoveries was that the soils that underlay these wetlands often have extremely high concentrations of a group of iron sulfide minerals that have traditionally been considered quite rare,” Dr Burton said.

“My work showed that these iron sulfide minerals exert an amazingly strong influence over the composition of soil pore-water and shallow groundwater, particularly the abundance of arsenic and heavy metals. This lead me to question why normally very rare, and highly reactive, iron sulfide minerals tend to accumulate and persist in acid-sulfate soil wetlands.

“I am also looking at mineral behavior because I have observed that the natural accumulation of metastable iron sulfide can be harnessed to remediate wetland soils that are acidic or contaminated with heavy metals and conversely, since metastable iron sulfides are very reactive, that their natural accumulation may, in some cases, represent a ‘time-bomb’ that might release associated heavy metals when wetland conditions change.

“By understanding how wetlands respond to environmental conditions and by having better tools to monitor such responses, soil and water managers will be able to forecast how potential management scenarios will ultimately affect water quality and ecosystem health.

“Up to now, there has been a yawning gulf between, firstly, the molecular-level chemistry of iron sulfide minerals and, secondly, field-based observations of geochemical phenomena affecting iron sulfide occurrence. My research approach aims to bridge this gulf by connecting observations at the wetland scale with observations of molecular-scale dynamics.

“My earlier research has demonstrated that a dual approach is needed to truly understand and predict changes in wetland water-quality, and optimize land management efforts. The project will be the first in the world to systematically unravel the driving forces behind the accumulation and persistence of highly-reactive iron sulfides in wetland soils.

“This is internationally-significant because iron sulfides are ubiquitous in wetland soils, yet systematic studies into their geochemical behaviour have been largely confined to laboratory-based ‘model’ systems.”

Dr Burton was awarded a prestigious five-year Australian Research Fellowship in association with the Australian Research Council grant in recognition that this research project is of international significance and will be facilitated within a world class research environment.

The research team includes Associate Professor Ed Burton as the Chief Investigator along with Professor Richard Bush, co-director of Southern Cross GeoScience. Professor Mats Astrom from Linnaeus University in Sweden and Professor Stefan Peiffer from the University of Bayreuth in Germany are both Partner Investigators.

The scientific results will be published over the course of the five-year project in international geochemistry journals. The project aims to enable Australia and international communities to better protect their water resources for the benefit of the environment and dependant rural and regional economies.

Southern Cross University received the highest classification of a 'well above world standard' rating in the field of geochemistry in the Excellence in Research for Australia 2010 National report released this week.

Photo: Associate Professor Dr Ed Burton taking a soil sample in Tuckean swamp which is a 4000 hectare wetland that is known to strongly influence water quality in the lower Richmond River in Northern NSW.