Investigating soil clues to water browning at Balder

Investigating soil clues to water browning at Balder

Iron leaking from forest soil is thought to be a factor in the increasing brown coloration of nearby waters called browning. It has consequences ranging from their use as drinking water to the sight of water living organisms in a darker surrounding. A recent experiment at beamline Balder aims to contribute clues to a better understanding of the iron leaching process.

Iron bound to organic material may leak more readily from forest soil. Researchers from Lund University Department of Biology are using beamline Balder to investigate how these iron-organic-material-complexes varies with age of and depth in soil from spruce forests. This type of forest is thought to have a higher amount of iron leaking as compared to other forest types.

Modern forestry has led to the increase of spruce forests and browning has increased in the northern parts of the world for the last 40 years, says doctoral student Martin Škerlep.

Browning is not necessarily bad, continues Škerlep, but it changes the ecological function of the waters as the darker water has effects for photosynthesis and the sight of the organisms living in the water. Surface waters are also often used for drinking water production and browning makes the cleaning process more complicated. Also, the water might need additives like chlorine, which could have health effects. Therefore, it’s crucial to understand more about the process underlying browning.

The researchers are using a method called X-ray Absorption Spectroscopy with which they shine X-ray light on the sample and in principle study how much of the X-rays are absorbed by the sample depending on the X-ray energy. This way it’s possible to see the chemical state of iron and conclude to what other elements the iron in the soil is bound.

The researchers hypothesize that older forests leak more iron because they have had more time to build up the form of iron bound to organic components that could readily leak into the nearby waters. Also, the pH of the soil, which typically is lower for older forests, could affect the mobility of iron.

This type of experiment is also a good confirmation of the capabilities of the Balder beamline where one of the main application areas are environmental research, says beamline scientist Kajsa Sigfridsson Clauss.