I found an interesting article on the Science Daily website today when I was looking for something to write about in the Geosmin. It is about how some soils can limit the function of landmine detectors used to find mines in the tropics because of ferrimagnetic minerals.
In more than 90 countries around the world we can find landmines in the ground. Most of these 90 countries are located in the tropics and the soil in the tropics are often intensively weathered. Tropical weathering occurs under high temperature and rainfall throughout the year.
To find these landmines the most common technique is using metal detectors. The tropical soils have certain properties that can limit the performance of metal detectors due to soil magnetic susceptibility. It has become a problem in the search of landmines, when mines with less metal (the “minimum-metal mines”) are getting more and more used. A minimum metal mine is a mine that is designed to use the minimum amount of metal in its construction. Some designs contain almost no metal at all. Typically this is achieved by using a plastic, wooden or glass body holding the explosive charge.
The soil has some magnetic properties that are caused by ferrimagnetic minerals, such as magnetite and maghemite. These minerals in the soil can cause negative effects as they can reduce the detector sensitivity or also cause false alarms. The detectors have become better and better through out the years with our new technology, but now the geoscientific research of the soil has also been taken into account. The detectors can now be invented for their location. The knowledge of soil magnetic properties can be counted in and adapted to meet the local conditions.
In Germany, an analyze of over 500 soil samples were made to classify their impact on landmine detection. The study showed that more than one-third of the measured soil samples can generate severe limitations when using metal detectors.
The significance of the study is highlighted by a statement of a scientist named Holger Preetz: “We are very lucky that such a large number of soil samples were available from the soil archive. This allowed us to investigate the impact of weathering and rock type on soil susceptibility simultaneously. We found a clear indication for a strong influence of soil development on the occurrence of high susceptibilities. Based on these results we are able to provide a classification scheme for the prediction of detector performance. This is of great interest for the de-mining community. During the planning phase of a de-mining mission the classification of magnetic soil properties can be done by using easily available geoscientific information.”