典型喀斯特坡地137Cs的分布与相关影响因子研究

通过野外考察和大量的137Cs取样分析,对喀斯特坡地土壤137Cs分布及相关影响因子进行了初步研究.结果表明,喀斯特区域137Cs剖面分布特征与非喀斯特区域相似,林地土壤剖面137Cs呈现指数分布模式,耕地剖面的137Cs呈均匀分布模式;喀斯特区域落水洞洞口45 cm以上土层中的137Cs比活度变幅为1.7~3.3 Bq/kg,137Cs分布较深,表明洞口现存土壤多由侵蚀物质堆积形成;2个石缝中的土壤样品137Cs比活度分别为16.8 Bq/kg和37.6 Bq/kg,远远高于临近土体,表明裸岩是影响喀斯特区域137Cs地表空间运移的一个重要因素;随坡面海拔升高,137Cs的面积活度表现出波动振荡趋势,空间异质性明显,林地和农耕地坡面137Cs面积活度变幅分别为299.4~1 592.6 Bq/m2和115.8~1 478.6 Bq/m2;林地坡面137Cs面积活度与坡度和海拔高度呈极显著正相关,农耕地坡面137Cs面积活度和坡度呈不明显的负相关,与海拔高度呈显著负相关.地形地貌和人为干扰强度是影响坡面137Cs空间分布规律的主要因素.

Distribution of 137Cs and Relative Influencing Factors on Typical Karst Sloping Land

Based on the field survey and the analysis of a large number of soil samples, the distribution of ¹³⁷Cs and its influencing factors were studied using ¹³⁷Cs tracer technology on typical karst sloping land. The results indicate that the distribution of ¹³⁷Cs in soil profile in karst areas show the similar characteristics as that in non-karst areas, fitted an exponential pattern in forest soils and a uniform pattern in cultivated soils. In the sinkhole points in karst areas, ¹³⁷Cs exists in deep soil layers and its specific activity vary from 1.7 to 3.3 Bq/kg in soil layers above 45cm, suggesting the existing soil around karst sinkhole is mainly formed by the accumulation of erosion materials. The ¹³⁷Cs specific activity in the soil from two rock cracks are 16.8 Bq/kg and 37.6 Bq/kg respectively, which are much higher than that in the soil around the rock, this phenomenon indicates that bare rock is an important influencing factor for ¹³⁷Cs spatial movement. With the increment of altitude, the ¹³⁷Cs area activity exhibits an irregular fluctuation and evident spatial heterogeneity. On the forest land, the ¹³⁷Cs area activities which range from 299.4 to 1 592.6 Bq/m² are highly positively correlated with the slope gradient and positively correlated with the altitude; while on the cultivated land, the ¹³⁷Cs area activities which range from 115.8 to 1 478.6 Bq/m² are negatively correlated with the slope gradient but negatively correlated with the altitude. Topography, geomorphology and human disturbance intensity are the key factors influencing ¹³⁷Cs spatial distribution.