A new understanding of how charcoal formed in natural events like bushfires can minimise the effect of pollutants in soil and sediments as well as aquatic environments.
Background
When wood or grass burns with limited oxygen, charcoal is formed. All charcoal plays an important role in the global carbon cycle and the process of removing carbon dioxide from the atmosphere — carbon sequestration.
Charcoal with differing characteristics and properties is produced depending on the original plant materials, such as grass or wood, and the temperature the material was burnt at.
New study
In a new study reported in the international journal Chemosphere, CSIRO’s visiting scholar Mr Ludger Bornemann and CSIRO's Dr Rai Kookana describe the ability of different types of charcoal to absorb the group of pollutants 'aromatic hydrocarbons'.
These compounds, which include benzene and toluene, are released into the environment as a result of industrial pollution.
This study suggests positive outcomes from adding charcoal to soils which have pollutant residue problems.
The study showed that the combustion temperature was more critical to the absorption properties of the resulting charcoal than the original plant material source.
The critical temperature was within the scope of temperatures observed for wildfires (200 - 1 000 ºC).
Results
The results of this study provide a new understanding of how charcoal formed in natural events like bushfires can minimise the effect of pollutants in soil and sediments as well as aquatic environments.
This research also suggests positive outcomes from adding charcoal to soils which have pollutant residue problems, which may be particularly applicable in developing countries where charcoal from burnt materials is commonly available.
For example, it is an established practice in eastern and southern parts of China to mix firewood ashes with soils and livestock dung, followed by heating and ageing for several months, then adding this mixture directly into the field as a fertiliser.
A follow-up project in China demonstrated that the addition of charcoal to contaminated soil reduced the uptake of pesticides by the plants and the degradation of pesticides in soil.
This insight may provide a simple and cheap method of reducing the effect of residual pollutants on crops in developing countries.
Read more about Environmental biogeochemistry: protecting our land and water resources.
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