典型石漠化地区土壤地下漏失研究

Soil erosion and rocky desertification issues are most critical ecological disasters in China, research and monitoring carrying on both of which is the main content of ecological civilization construction at the same time. Karts rocky desertification area in southwest China covers global largest and occupies highest concentration of fragile ecological karst area. This project intends to study water and soil loss process and mechanism in southwest Chinese karst area. Aim to explore relationship between surface and underground water loss and soil erosion and environmental factors through geomorphology, karstology, sedimentology, soil and water conservation and sediment dynamics, field monitoring, sampling and laboratory analysis, plus sediment's determination, to require groundwater soil erosion data and monitoring records in southwest karst area. The monitoring indicator systems of karst underground soil erosion and leakage model have been established,which can calculate the amount of underground water loss and define surface - underground soil erosion contribution. The study has an important scientific significance to understand soil and water loss dual structure problems in karst area, and to scientifically evaluate soil erosion hazards. This provides ecological recovery, comprehensive control of soil and water conservation, soil and water resources allocation project and drought relief measure for karst rocky desertification area.

水土流失和石漠化问题是中国重大生态灾害之一，对其进行研究与监测也是喀斯特区生态文明建设的主要内容。西南喀斯特石漠化区是世界面积最大、最集中的喀斯特生态脆弱环境区。本项目以西南典型的喀斯特山区花江为研究对象，以减少水土地下流失量为目的，开展土壤地下漏失发生的过程及形成机理研究。从地貌学、岩溶学、沉积学、水土保持学以及泥沙动力学等多学科联合攻关，通过野外监测采样和实验分析，结合洞穴沉积物年代测定，探索喀斯特区水土地下流失形成的时空规律，获取典型石漠化区地下水土运移和流失量的数据以及监测记录，揭示喀斯特地面-地下水土运移过程、形成机制和途径；建立喀斯特地下水土流失监测指标体系和土壤地下漏失模型，求出土壤地下流水量。这对于认识喀斯特区水土流失二元结构问题，科学评价水土地下流失的危害，具有重要的科学意义，为喀斯特石漠化地区的生态防治和水土保持综合治理提供科学依据。

喀斯特关键带岩溶节理裂隙是水土漏失地下的主要场所。碳酸盐岩面受风化作用损伤产生节理裂隙，含有CO2的酸性水沿碳酸盐岩节理裂隙界面对其进行溶蚀作用，形成漏斗、洞穴、洼地等地貌形态。岩-水-气相互作用迫使节理裂隙通道不断拓宽，水土沿这些通道网格漏失地下。氯化钠示踪剂揭示水土漏失地下的暗箱管道，通过磁化率监测水土流失情况，与土壤的磁化率本底值比对计算出土壤流失量，得出土壤年侵蚀模数。地质雷达技术能有效地探测浅层喀斯特节理裂隙的发育情况，对雷达图象研究可准确定位地下断层裂隙深度、发育方向以及空间布局。采取地下洞穴土壤剖面土样，用放射性碳十四（14C）测年方法，获得了洞穴土壤剖面沉积时间序列，剖面三个土壤层次分界线的碳十四年龄为1.25±0.1cal ka BP、11.95±0.5cal ka BP和18.39±0.6cal ka BP，最底层地质年代为晚更新世地层。地下泥土粒度分析显示为流水携带沉积物。据监测情况，筛选出岩性、节理裂隙密度、断层、坡长、岩溶面积比重、坡度、峰谷密度、地形起伏度等13项因子作为地下土壤漏失指标，建立地下泥土漏失模型。计算结果与实测数据比较接近。该模型指标比较合理，数据易于获取，可操作性强，数据可信。