Comparative assessment of erosion and deposition rates on cultivated land in the Transylvanian Plain of Romania using 137Cs and 210Pbex

Soil erosion and sedimentation are natural landscape forming processes. However, they can be accelerated by human activities and therefore increase negative impacts on agricultural production as well as disturbing watershed management. Romania currently faces major environmental challenges and pressure on soil and water resources due to unsustainable farming practices and inappropriate tillage practices. The present work represents the first attempt to test the combined use of radionuclide approaches (i.e. 137Cs and 210Pbex) to quantify soil erosion changes in cultivated Transylvanian fields (Romania) at different temporal scales. Fourteen soil cores were collected along two transects in a cultivated field and two reference sites were selected to establish the mean reference inventories for both 137Cs and 210Pbex. A value of 5460 ± 880 Bq m−2 (n = 10; CV = 16%) was determined for the 137Cs mean reference inventory for both sites, given as areal activity ± standard deviation, at 2σ confidence interval. As regarding 210Pbex reference inventory, its value (9640 Bq m−2) is only given by the areal activity of one soil core from the second site. The high erosion rates obtained with the 210Pbex approach are an effect of the up and down ploughing practices which took place at the time of the local agricultural cooperative starting in the late 1950s. The middle-term redistribution rates provided by the 137Cs technique highlighted preponderant deposition processes in the field investigated, reflecting the changes in the cultivation system with ploughing across the slope at the beginning of 1990s.

► It is the first combined use of 137Cs and 210Pbex for soil erosion changes in Romania. ► The high erosion rates obtained with 210Pbex are caused by the up and down ploughing. ► The 137Cs technique highlighted the change in the cultivation system in the last 20 years.