THE SUITABILITY OF 239 +240PU ISOTOPES AS SOIL EROSION TRACERS IN THE NORTHERN HARDWOOD FORESTS

Accelerated soil erosion is one of the greatest threats to soil health and function, therefore, understanding the impact of deforestation on erosional processes is crucial for sustainable soil management. This study investigates the suitability of ^239+240Pu as erosion tracers in a Northern Hardwood Forest under the influence of lateral podzolization (a sub-surficial process characterized by the lateral downslope movement of water, Fe, Al, and organic matter). This study occurred in watersheds 3 (control) and 5 (deforested) of the Hubbard Brook Experimental Forest and samples were collected across different hillslope positions. Preliminary results illustrate a typical exponential decrease of ^239+240Pu with depth and a decrease of total inventory between watersheds on the backslope from 110.6 ± 26.9 Bq/m² (control) to 63.2 ± 19.4 Bq/m² (deforested) which indicates erosion. However, the ^239+240Pu inventory in the control watershed does not exponentially decrease with depth nor decrease in total inventory, rather an increase of ^239+240Pu is seen at all depths. The total inventory in this toe slope position is 177.8 ± 39.4 Bq/m² which is indicative of the mobilization of ^239+240Pu through lateral podzolization. Additionally, preliminary results of total organic carbon and d¹³C qualitatively indicate soil disturbance in the deforested watershed with a weak negative correlation of R² = 0.37, while a strong negative correlation of R² = 0.69 confirms the validity of our reference site. Based on these preliminary data, we hypothesize that ^239+240Pu results from studies on hillslopes influenced by lateral podzolization may represent both ^239+240Pu transported through erosional processes and sub-surficial transport by lateral podzolization. We expect this comparative approach to produce insights into soil erosion and ^239+240Pu mobility on hillslopes in the Northern Hardwood Forests.