ARSENIC DETECTIONS IN GROUNDWATER AT C&D FACILITIES FDEP CCA TAG GW Subcommittee Steve Clarke, Chair - WM

Arsenic in Florida

How Does Arsenic Get in C&D Groundwater Naturally Occurring? Releases from CCA Wood? Release from Pesticides? Mobilization of Naturally Occurring Minerals? Other?

REVISION: 0PLOT DATE: 12/10/03DRAWN BY: ED LEGEND Soil mineral with positively charged surface sites Reaction/process As(III) As(V) Arsenite Arsenate As(V) + (H 2 AsO 4 ) - + (H 2 PO 4 ) - (H 2 AsO 4 ) - As(V) GROUNDWATER REDUCTION IRON MINERAL DISSOLUTION As(III) ARSENIC V REDUCTION FeAsS + 4O 2 SO As + Fe GROUNDWATER OXIDATION DISPLACEMENT BY OTHER ANIONS MOBILIZATION PROCESSES + Oxygen removed by decay  Low DO Water  Fe, As FeAsS in dredge sediments  deposit on banks, oxidize  As Pesticides: As adsorbs to clays  Fertilizers: P replaces As  As EXAMPLES:

As(V) + (H 2 AsO 4 ) - + (H 2 PO 4 ) - (H 2 AsO 4 ) - As(V) GROUNDWATER REDUCTION IRON MINERAL DISSOLUTION As(III) ARSENIC V REDUCTION FeAsS + 4O 2 SO As + Fe GROUNDWATER OXIDATION DISPLACEMENT BY OTHER ANIONS LEGEND Soil mineral with positively charged surface sites Reaction/process As(III) As(V) Arsenite Arsenate MAJOR ARSENIC MOBILIZATION PROCESSES + MAJOR ARSENIC IMMOBILIZATION PROCESSES GROUNDWATER OXIDATION AND RESORPTION PRECIPITATION 2As(III) + 3S As 2 S 3 (Orpiment) As(III) + SAsS (Realgar) As(V)(H 2 AsO 4 ) Iron Oxides

Arsenic detections in GW, not associated w/metals

Arsenic detections in GW, not associated w/indicators

Arsenic detections in GW Tracks Iron

Arsenic detections in GW, not associated w/metals DRAFT=

Arsenic detections in GW not associated w/indicators DRAFT

Arsenic detections in GW Tracks Iron DRAFT

Iron detections in GW

Fe/As Detections  Turbidity

Arsenic detections in GW

Questions to the TAG How do we show that Arsenic is from –A release due to CCA Wood? –Mobilization of Naturally Occurring Minerals? –A Naturally Occurring/Other Source Other?

Moving Forward Reevaluate As against select indicators –iron, sulfate, TDS, chlorides, turbidity, D.O., others?); Categorize the types of detections; and Consider next steps –Confirming the source (sampling); and –Evaluating the significance/extent (e.g. modeling?).