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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。
According to the field survey in October 2005 and interpretation of TM satellite images, the distribution of 137Cs and the characteristics of soil erosion rate in different levels of rocky desertification areas and different types of land use in northern Guangdong were studied. The results showed that the average 137Cs activity in the rocky desertification area of northern Guangdong was (6.54 ± 0.57) Bq · kg-1. The 137Cs level in the soil decreased firstly and then increased with the increase of rock desertification degree. In the stage of rocky desertification, the excessively high bedrock exposed rate led to the concentrated adsorption of 137Cs in the surrounding soil, and the 137Cs was gradually enriched in some sedimentary environments. The background value of 137Cs in the study area was (1 433.60 ± 131.40) Bq · m-2, which was lower than the average value in the northern hemisphere. The distribution of 137Cs basically accorded with the exponential distribution and the highest value appeared in the depth of 24 cm. In mild and medium rocky desertification areas, the average values of non-tillage soil erosion rates were 1 369.0 and 1833.5 t · km-2.a-1, respectively. The tillage erosion rates were much higher than those of non-tillage soils. The effects of erosion are obvious.