7Be: A geochemical tracer for seasonal erosion of surface soil in watershed of lake hongfeng,Guizhou,China
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7Be penetrative depth in undisturbed surface soil is within 4 mm. 7 Be activity shows exponential decrease with soil depth, which is expressed as a diffusion process. 7Be penetrative depth in undisturbed surface soil is apparently deeper in the fall (0.22-0.37 g cm-2) than in the spring (0.11-0.28 g cm-2) at the same site; Whereas, 7 Be apparent activity at the top of surface soil is higher in the spring (0.3-2.2 Bq g-1) than in the fall (0.2-0.5 Bq g1) at the same site. The 7Be inventory (189-544 Bq m-2) changes with both locations and seasons. Although the 7Be flux to the earth's surface increases with amount of precipitation, its maximum inventory in the soil profiles decreases to 30%-40% after the rainy period. Calculated by the diffusion equation, the erosion and accumulation rates of soil particles are agreeable with the observation in situ., which shows that the rates in fall are 1.5 times those in spring. The eroded soil particles almost all have been removed on the tablelands rather than transported into the drainage system. This indicates that the soil erosion process in the karst region is only partial transportation within a short distance. 1996 SCIENCE PRESS,.
