普定冲头峰丛洼地泥沙沉积速率的^137Cs法测定

Estimating Sediment Deposition Rates by the Cs-137 Technique in Karst Depression of Chongtou,Puding County,Guizhou Province

侵蚀速率是中国西南喀斯特山地水土流失和石漠化研究的热点和难点,本文采用137Cs断代法测定了贵州普定县马官镇冲头峰丛洼地的沉积速率,据此推算了冲头小流域上世纪60年代以来的侵蚀速率。采用137Cs分布深度判别法和质量平衡理论模型两种方法计算了洼地沉积物的沉积速率,求得冲头洼地平均土壤沉积速率分别为6.39 t/a和9.53 t/a,取后者代表洼地的平均沉积速率,不计引水带入水库的泥沙和落水洞带出的泥沙,据此推断1963年以来的平均产沙模数为20.27t/km2.a,与当地径流场的实际监测结果基本吻合。

The erosion rate is a hot and difficult topic involved in the study of rocky desertification in the karst areas of South- west China. The ^137Cs dating method was used to measure the deposition rate of sediment in the Chongtou depression, Puding County, Guizhou Province. According to the result, the erosion rate has been calculated since the 1960s. The two methods （the depth distribution discrimination of ^137Cs and mass balance mode）were used to calculate the rates of sediment deposition to be 6.39t/a and 9.53 t/a, respectively. For the latter as the average deposition rate, silt water was not taken into the depression and that flew out of it through the cave, the average sediment rate is 20.27 t/km2·a. It is basically consistent with the actual monitoring results.