摘要:The Ordovician karst groundwater in the Qiligou basin is an important water supply source. This groundwa-ter has been seriously contaminated in recent years by CCl4 from a pesticide plant located in the recharge area. The highest concentration of CCl4 in the groundwater is 3909.2 μg/L. Large scale tracer experiments were carried out to study the conveying conduits for CCl4 in the basin on May 1-6,2005. Nontoxic,edible glucose was used as a tracer and it was detected by spectrophotometric techniques. Well X-61,located near the pesticide plant in the southern recharge area of the basin,was employed for injecting the tracer. Ten wells widely located in the groundwater runoff area were used as observing and sampling wells. The results show that the migration of the pollutants is controlled by the water hydrodynamic field and by the development of karst conduits. The tracer did not enter the up-drainage wells,X-49 and X-47,near the injection point because the water levels at these wells are higher than at the injection point. The adjacent well X-62 is close to the injection site,but the tracer reached the well after eleven hours. Wells X-43,X-59,X-58,YY-1 and X-57,located in the syncline axis runoff area,are respectively 2.5,3.5,4.33,4.38 and 5.44 kilometers from the in-jection site. The time for initial appearance of tracer was 4,4,2,6 and 4 hours,respectively. The maximum runoff ve-locity (well X-58) is over two kilometers per hour,indicating that the karst conduits are well developed along the syn-cline basin axis. These conduits are the main conveying conduits for groundwater and CCl4. Closer wells were not nec-essarily the first to receive tracer. This shows the inhomogeneity in karst development which causes complex runoff,and pollutant migration,patterns.