DELINEATIONOFHAZARDOUSAREASANDADDITIONAL SAMPLINGSTRATEGYINPRESENCEOFA LOCATION·SPECIFICTHRESHOLD

Thispaperpresentsamethodologytoaccountfor multiplesourcesof uncertainty (measurementandinterpolationerrorsfor pollutantconcentrations, spatiallyvariableregulatorythresholds)inthemappingoftheprobabilityofcon­ tamination.Theapproach,whichinvolveskrigingofsoftindicatordataandprop­ agationofuncertainty by Latin-HypercubeSampling (LHS) ofccdfs, is applied toa 216 km 2 airborneCd-contaminatedareain Belgium.Theaim is topredict theprobabilityofexceedingaregulatorysanitationthreshold(ST) for vegetable gardenswhichdependsonbothsoilorganicmatter(OM)andclaycontent.Avali­ dationstudyshowsthattheccdfsprovideaccuratemodelsoftheuncertaintyabout soilproperties.ThecoefficientofvariationoftheccdfofthedifferenceD=ST-(Cd) isproposedasacriteriontodecidewhereadditionalsamplesshouldbecollected. Inthecasestudy,thiscriterionallowsonetoidentifymostlylocationsthatwere wrongly declared safe, while large predictionerrors were detected by sampling locationswherethevarianceoftheCdccdfishigh.