The Study On Critical Basic Questions Of Using Beryllium-7 To Trace Soil Erosion

Radionuclides tracing technique displays marked characteristics and advantages in soil erosion research. It was necessary to develop applying scope of the nuclides tracing technique with the research improvment, and to promote accuracy of tracing result, besides, it provides effective technical support for further understanding the soil erosion processes and establwashing soil erosion predict model.Atmospheric radionuclide ~7Be that has continuous deposition and short half-life was used as a soil erosion tracer to trace event rainfall or short period (a rainy season) soil erosion. At present, when ~7Be was used as a tracer to study soil erosion rule, we all think that ~7Be has the similar deposition - soil adsorption - migration process with 137Cs, 210Pbex. But in the worldwide, there are almost no concern on the critical basic questions that ~7Be adsorbed by the soil particle, intercepted and adsorbed by the vegetation in the depositional process, and ~7Be content in runoff and sediment.Combined methods of sampling and experimenting in field with detecting in the laboratory, we studied on the critical basic questions of the atmospheric radionuclides ~7Be tracing soil erosion, and drawn the main conclusions as follow:1. Measured the ~7Be depositional characteristic, analyzed the relationship between ~7Be depositional fluxes and rainfall, and discussed superficially ~7Be dry depositional fluxs on the Loess Plateau.The ~7Be concentration in the rainwater was from 0.2Bq/L to 2.6 Bq/L and the mean was 0.88 Bq/L by analyzing many rainfall events. There was no significant correlation between ~7Be concentration in the rainwater and the rainfall; however, in one rainfall event, the correlation between the rainfall and the ~7Be wet depositional fluxes was more significant, and correlation coefficient was 0.69. ~7Be concentration in the rainwater has less effect to the wet depositional fluxes, and the main impact factor was the precipitation. ~7Be fallout has the obvious seasonal change, the depositional fluxes was much more during the rainy season, and less during the spring and winter. The monthly accumulative rainfall and ~7Be depositional fluxes have significantly correlation, and the correlation coefficient was 0.97. The preliminary analysis indicated that the monthly ~7Be dry depositional fluxes was from 32 Bq/m2 to 48 Bq/m~2, the percentage was from 14% to 75% of the whole monthly deposition.