Effects of acute gamma irradiation on chemical, physical and biological properties of soils

The use of gamma (gamma-) irradiation as a method for soil sterilisation for laboratory experiments has been recommended over other sterilisation techniques. We reviewed literature dating back over 50 years to investigate the chemical and biological effects on gamma-irradiated soils and to determine its practicality for sterilising soils which will subsequently be used for experimental purposes. Typically, gamma-irradiation at 10 kGy will eliminate actinomycetes, fungi and invertebrates in most soils. The majority of soil bacteria are eliminated by 20 kGy, however, a dose higher than 70 kGy may be required to kill certain radio-resistant bacteria. We recommend prior to experimentation that the radiosensitivity of soils are determined so as to ensure the desired chemical and biological effects are achieved. gamma-Irradiation may not be an appropriate method for all experiments as it can influence soil chemical properties, in particular soil nitrate and ammonium levels. Where chemical stability is required we recommend sterilising soils air-dry rather than moist. (C) 2003 Elsevier B.V. All rights reserved.