Nuclear techniques to measure soil erosion


Every year 75 billion tonnes of fertile soil are lost to erosion. It is expensive and labour-intensive to monitor this invaluable resource using conventional methods, which is why the Joint FAO/ International Atomic Energy Agency (IAEA) Programme on Nuclear Techniques in Food and Agriculture has been looking into other options. Recently published by FAO and the IAEA, Use of 137Cs for soil erosion assessment describes a promising technique that uses traces of nuclear activity to measure soil loss.

Measurable amounts of the radionuclide 137Cs were released into the atmosphere during nuclear weapons testing in the 1950s and 1960s as well as more recently during accidents in Chernobyl and Fukushima. When 137Cs comes into contact with soil, it sticks to the soil particles and tends not to wash away or be taken up by plants. This means that changes in 137Cs inventories are good indicators of erosion.

Scientists analyse the 137Cs content using a method known as gamma spectroscopy, which determines levels of radioactivity. Providing that undisturbed reference sites are available, the technique can provide useful information on erosion rates and soil/sediment dynamics and redistribution. This publication sets out the practical steps involved in data collection as well as data processing and interpretation.

With a dedicated research programme launched in the 1990s, the joint FAO/IAEA division has become the international reference regarding 137Cs use to measure soil erosion.