柴河小流域草地土壤环境的同位素示踪研究

以滇池柴河小流域为研究区域,于2011年7月采集草地样品全样、分层样共17个,对土壤粒度、w(SOM)(SOM为有机质)、w(TN)进行测定；采用放射性核素137Cs示踪技术估算研究流域土壤侵蚀速率；同时,测定δ13C(稳定性碳同位素丰度),以研究该流域生态环境状况. 结果表明:①土壤粒度组成为粉粒(66.74%~77.55%)>黏粒(21.22%~31.29%)>砂粒(1.23%~3.33%),同一土地利用方式的土壤粒度组成差异较小,土壤适宜耕作. ②CH1、CH2、CH3采样点的w(SOM)分别为3.51%、1.72%、2.54%,w(TN)分别为0.22%、0.17%、0.18%,二者相对偏低,并且土壤剖面的w(SOM)、w(TN)均随深度增加呈降低趋势. ③CH1、CH2、CH3采样点的137Cs含量分别为586.91、279.83和217.82bq/m2,侵蚀模数分别为324.96、879.33和1066.83t/(km2·a),表明研究区整体属于轻度侵蚀且表层土壤侵蚀较为严重. ④CH1、CH2、CH3采样点的δ13C平均值分别为-18.49‰、-24.5‰和-21.74‰,表明有机质主要来源于陆源. 

Study of Grassland Soil Environment in Chaihe Watershed by Isotope Tracer

The Chaihe reservoir of Dianchi watershed was investigated. Seventeen soil samples including grassland full samples and profile samples were collected in July, 2011. The soil particle size distribution, concentrations of soil organic matter (SOM) and total nitrogen (TN) in the soil samples were measured. The 137Cs radiometric technique was applied to estimate the soil erosion rate in the study area. In addition, the abundance of carbon stable isotopes (δ13C) in soil samples was analyzed using a thermo Delta plus XL mass spectrometer (UK) to indicate the environmental conditions. The results obtained in the study were shown as:1)The decreasing order of soil particle size composition was:powder particle (66.74%~77.55%)>clay (21.22%~31.29%)>sand (1.23%~3.33%). No significant difference was found in soil granulometric composition for the same land use patterns. In the study area, the characteristics of soil are suitable for farming. 2)The average content of SOM in CH1, CH2and CH3was 3.51%, 1.72% and 2.54%, respectively, and the average content of TN was 0.22%, 0.17% and 0.18%, respectively. Both contents of SOM and TN were relatively low. Results of the investigation of the profile soil samples showed that contents of SOM and TN decreased with the sampling depths. 3)The contents of 137Cs in CH1, CH2and CH3were 586.91,9.83and 217.82bq/m2, respectively and the soil erosion modulus were 324.96,9.33and 1066.83t/(km2·a), respectively, indicating mild soil erosion. The topsoil of the sampling areas were under serious soil erosion status. 4)The average δ13C content of CH1, CH2and CH3was -18.49‰,-24.5‰ and -21.74‰, respectively. Generally, reflecting that organic matter in the study areas maybe mainly derived from a terrigenous matter.