Characterization of Antarctic soil by gamma spectrometry and enzymatic activity

Dr Adriana Montañez and Marcos Tassano, Faculty of Science

Strong winds along with the accelerating effects of thawing as a result of rising global temperatures as well as increased human activity has led to changes in soil surface in the Antarctic Peninsula. These changes need to be studied in relation to the erosion rate and to the enzymatic activity of microbial soil communities. To determine soil quality and its conservation, it is necessary to know the factors that can degrade it, such as: erosion rates (due to climatic factors, the ice-thaw cycle and human factors) together with the microbial enzymatic activity. To determine the medium-term erosion rates (from the 1960s to the present time) it is proposed to use the Cesio-137 radio-radiator (137Cs). The 137Cs is an artificial radioactive isotope by-product of the nuclear tests conducted between the years 1945-1980, which has a global distribution and can be used as soil tracer resulting in rates of erosion or sedimentation in tons of soil lost or gained by Hectare per year. The high resolution gamma spectrometry technique (with hyperpure germanium crystals) is used to determine the amount of uranium, thorium and potassium in the samples tested, permitting a general radioisotopic characterization of the surface soil. The enzymatic activity together with the microbial biomass is an integrated measure that informs about the biogeochemical processes in the soil and the cycling of the nutrients. It is proposed to study three enzymes, hydrolases, dehydrogenases and acid and alkaline phosphatases related to the cycles of C, N and P respectively. The relationship between radioisotope measurements (137Cs, uranium, thorium and potassium) and soil chemical characteristics (eg C, N and phosphorus (P)) are well studied and the results obtained show that 137Cs is an efficient tool in the evaluation of erosion on soil fertility. However, studies that relate 137Cs to biological parameters are incipient but very promising. Microbiological indicators would enable us to quickly detect erosion-related factors. The general objective of the present project is to determine soil erosion rates in the medium term using radiotracers, together with the early indicators of soil quality, microbial biomass and its enzymatic activity, which will allow us to have the necessary tools For decision-making in a strategic plan for soil conservation in the Antarctic Peninsula and especially Lake Uruguay which is the water reservoir of the Artigas Antarctic Scientific Base.