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: 0 PLOT DATE: 12/10/03 DRAWN BY: ED

LEGENDSoil mineral with positively charged surface sites

Reaction/process

As(III)

As(V)

Arsenite

Arsenate

As(V)

+ (H2AsO4)- + (H2PO4)-

(H2AsO4)-

As(V)

GROUNDWATER REDUCTION

IRON MINERALDISSOLUTION

As(III)

ARSENIC VREDUCTION

FeAsS + 4O2 SO42- + 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)

+ (H2AsO4)- + (H2PO4)-

(H2AsO4)-

As(V)

GROUNDWATER REDUCTION

IRON MINERALDISSOLUTION

As(III)

ARSENIC VREDUCTION

FeAsS + 4O2 SO42- + As + Fe

GROUNDWATER OXIDATION

DISPLACEMENT BY OTHER ANIONS

LEGENDSoil mineral with positively charged surface sites

Reaction/process

As(III)

As(V)

Arsenite

Arsenate

MAJOR ARSENIC MOBILIZATION PROCESSES

+

MAJOR ARSENICIMMOBILIZATION PROCESSES

GROUNDWATER OXIDATION AND RESORPTION

PRECIPITATION

2As(III) + 3S As2S3(Orpiment)

As(III) + S AsS (Realgar)

As(V)(H2AsO4)-

+As(V)(H2AsO4)-

+ As(V)(H2AsO4)-+

Iron Oxides

Arsenic detections in GW, not associated w/metals

Arsenic detections in GW, not associated w/indicators

Arsenic detections in GWTracks Iron

Arsenic detections in GW,not associated w/metals

DRAFT=

Arsenic detections in GWnot associated w/indicators

DRAFT

Arsenic detections in GWTracks 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?).