粤北石漠化地区土壤侵蚀的137Cs法研究

据2005年10月的野外调查及对TM卫星影像解译分析结果,研究了粤北不同程度的石漠化地区、不同利用类型土地的¹³⁷Cs区域分布以及土壤侵蚀速率特征。结果表明:粤北石漠化地区土壤¹³⁷Cs活度的平均值为(6.54±0.57) Bq·kg^-1,土壤中¹³⁷Cs水平随石漠化程度增加有先降低然后升高的趋势,表明在重度石漠化阶段,过高的基岩裸露率导致其周围土壤对¹³⁷Cs的集中吸附,¹³⁷Cs在某些沉积小环境内逐渐富集。研究区¹³⁷Cs背景值为(1 433.60±131.40) Bq·m^-2,低于北半球的平均值,¹³⁷Cs剖面分布基本符合指数分布,最高值出现在2~4 cm深度范围内。在轻度、中度石漠化地区,非耕作土壤侵蚀速率的平均值分别为1 369.0、1 833.5 t·km^-2·a^-1;耕作土壤侵蚀速率远高于非耕作土壤,坡度对土壤侵蚀影响非常明显。

Study of Soil Erosion Using 137Cs Method in Rocky Desertification Region of Northern Guangdong

Soil erosion is a main factor determining the ceasium-137 (¹³⁷Cs) content and its redistribution in soil. Based on the field investigation in October, 2005 and the interpretation and analysis of TM images, this paper discussed the distribution of ¹³⁷Cs in karst mountainous region in northern Guangdong, the soil erosion rate and erosion characters in rocky desertification land of different degrees. The ¹³⁷Cs activity in soils in rocky desertification region of northern Guangdong averages (6.54±0.57) Bq·kg^-1, and the ¹³⁷Cs level in soils tends to decrease at first and then increase with the increase of the degree of rocky desertification, which shows that in severe rocky desertification stage, the soil particles around the bare rock adsorb the ¹³⁷Cs collectively and the ¹³⁷Cs is gradually enriched in depressions. The ¹³⁷Cs reference inventory in the study region is (1 433.60±131.40) Bq·m^-2, which is lower than the mean value of northern hemisphere. The ¹³⁷Cs distribution in soil profile roughly conforms to an exponential distribution pattern, and the highest point appears in the range of 2-4 cm deep. The mean erosion rates of non-cultivated soil at slight and moderate rocky desertification land are 1 369.0 and 1 833.5 t·km^-2·a^-1 respectively. The erosion rate of cultivated soil is much higher than that of non-cultivated soil, and is much affected by slope.