The 7Be content in runoff and sediment from different runoff plots under single rainfall event was analyzed.The result showed that 7Be concentration in runoff was relatively less than that in sediment and the average value was 0.92 Bq/L.However

the total loss of 7Be from runoff plots was great because much more runoff discharge was lost from runoff plots.It was estimated that 11%～33% of total loss 7Be in the whole cultivated plot ran off with runoff

and this had a great effect on the result of tracing soil erosion.The 7Be content in sediment was more than that in surface soil

especially in the weed and bush plot.At last

it was discovered that the grain size of sediment did not obviously influence the 7Be content in sediment

and surface erosion played an important role in the 7Be content of sediment.