简介：Karstaquiferssupplyasignificantfractionoftheworld'sdrinkingwater.Thesetypesofaquifersarealsohighlysusceptibletopollutionfromthesurfacewithrechargeusuallyoccurringthroughfracturesandsolutionopeningsatthebedrocksurface.Thicknessoftheprotectivesoilcover,macroporesandopeningswithinthesoilcover,andthenatureoftheweatheredbedrocksurfaceallinfluenceinfiltration.Rechargeopeningsatthebedrocksurface,however,areoftencoveredbyunconsolidatedsediments,resultingintheinadvertentplacementoflandfills,unregulateddumpsites,tailingpiles,wastelagoonsandsepticsystemsoverrechargezones.Inthesesettingssurfacegeophysicalsurveys,calibratedbyafewsoilcores,couldbeemployedtoidentifytheserechargeopenings,andqualitativelyassesstheprotectionaffordedbythesoilcover.Inatestofthishypothesis,geophysicalmeasurementsaccuratelypredictedthethicknessofunconsolidateddepositsoverlyingkarsticdolomiteatasiteabout100kmsouthofChicago,Illinois.Zonesofelevatedelectricalconductivityandhighground-penetratingradar(GPR)attenuationwithinthesedimentscoincidedwithsubcroppingsolutionally-enlargedhydraulicallyactivebedrockfractures.Thesefracturesextendtoover12-mdepth,asshownby2-Dinvertedresistivitysectionsandsoilcoring.Anomalouselectromagnetic(EM)conductivityandGPRresponsemaybeduetohighersoilmoistureabovetheseenlargedfractures.Anepikarstalconduitat2.5-mdepthwasdirectlyidentifiedthroughaGPRsurvey.Theseresultssuggestthatsurfacegeophysicalsurveysareaviabletoolforassessingthesusceptibilityofshallowkarstaquiferstocontamination.``

简介：