岩溶地下河浊度来源及对示踪试验影响的定量分析

摘要

The quantitative tracer technique is an important method for analysis of geometrical and hydraulic characteristics of karst aquifer. Turbidity is the key factor for accuracy of tracer test although its source and relationship to tracers remain unclear. Three tracer tests under different hydrodynamic conditions were conducted for typical southwest karst underground rivers. Actual measurement data on turbidity, discharge and tracer concentration were analyzed to discuss the source and the effect of turbidity on tracers. During the test, the upper and lower critical discharge was proved to be existent, which caused the gradual transition from the laminar to turbulence and the transition of the main source of turbidity from resuspended origin to allochthonous origin. The values of upper and lower critical discharge were inferred to be 0.7 and 0.4 m3/s, respectively. The result shows that there is a negative correlation between turbidity and tracer concentration when the value of turbidity is greater than 25. With the increasing turbidity, the impact on the tracer concentration becomes greater. Finally, the karst conduit parameters were estimated by the first test which was relatively insignificantly influenced by the turbidity. The results achieved by the authors provide the basis for further water resource evaluation.%定量示踪技术是分析岩溶含水层水力特征和岩溶水系统结构的重要手段，地下河浊度是制约定量示踪试验精确性的关键因素。针对西南典型岩溶地下河，以三次不同水动力条件下示踪试验为研究对象，通过对比分析浊度、流量及示踪剂浓度变化探讨浊度来源及其对示踪剂和管道参数的影响。试验过程中，确定存在上、下临界流量使水流从层流过渡为紊流状态，浊度主要来源从管道内部再悬浮颗粒过渡为外源悬浮物，计算上、下临界流量分别为0.7 m3/s和0.4 m3/s。通过浊度与示踪剂的相关关系研究浊度对示踪剂的影响，结果表明当浊度大于25时，浊度与示踪剂浓度呈负相关关系，且浊度越大，对示踪剂的影响越大。最后通过对比确定，第一次示踪试验浊度影响较小，并估算了岩溶管道参数，为进一步水资源评价提供基础。