Beryllium-7 atmospheric deposition and soil inventory on the northern Loess Plateau of China

Beryllium-7 is a potentially powerful tracer of soil erosion, but information on 7Be atmospheric deposition and associated soil inventories on the Loess Plateau of China is not readily available. In the study reported in this paper, we measured the 7Be inventories in undisturbed soil at different sampling times on the northern Loess Plateau of China for three years, between 2010 and 2012, and estimated the 7Be deposition fluxes and the daily 7Be inventories in undisturbed soil. The annual 7Be deposition fluxes during this period varied between 1303 ± 119 and 2222 ± 147 Bq m−2, with a mean of 1759 ± 416 Bq m−2. There is a marked seasonality for the 7Be deposition fluxes with the maximum in summer, approximately 50% to the annual deposition flux, and the minimum in winter, approximately 5% to the annual deposition flux. Precipitation amounts can explain more than 70% of the variation in 7Be deposition flux. 7Be deposition in the form of dustfall, dew and frost make a significant contribution to the 7Be deposition flux in the study region. The daily 7Be inventories in undisturbed soil varied markedly through time and ranged between 89.2 and 941.8 Bq m−2 with a mean of 392 ± 210 Bq m−2. They demonstrated a unimodal distribution over the year, with the highest values in August or September and the lowest in late winter or early spring.