Arsenic speciation in Soils and Sediment Myron Georgiadis Florida International University TAG Meeting February 11, 2004

Backgrounds Leaching occurs from CCA-Treated Wood into soil and sediments Traditional methods for arsenic analysis in soil - Digestion Develop an extraction method for Arsenic in soils and sediments while preserving their chemical species.

Method Development Reference Soil PACS2 PACS2 – Marine Sediment Reference Material from National Research Council Canada Extraction Solution: pH, Buffer Capacity, Chemical Interactions PACS2 was extracted with a phosphate buffer. Analyzed by HPLC-HG-AFS.

Arsenic Concentration vs Time - Conversion of As(III) to As(V). - Readsorption back into soil.

Methodology Conversion of arsenic species –Reactions involving metals Use of EDTA for other metals Use of Hydroxylamine Adsorption of Arsenic –Potential of Iron and Manganese –The use of Chelating Agents for Arsenic Sodium diethyldithiocarbamate trihydrate (NaDDC) Ammonium pyrrolidine dithiocarbamate (APDC)

Extraction with EDTA

Uncoated Sand 12 Hour Extraction Good recoveries for both As(III) spiked and As(V) spiked uncoated sand was achieved indicating NaDDC helps preserve As(III) species and minimizes re-adsorption.

Naturally Coated Sand + Peat 12 Hour Extraction Good Recoveries were again observed with the use of NaDDC with naturally coated sand containing peat spiked with As(III) or As(V).

Deck Soil 12 Hour Extraction 12 Good recoveries for both As(III) spiked and As(V) spiked deck soil was achieved indicating that NaDDC helps preserve As(III) species and minimizes re-adsorption.

CCA-Treated Wood Deck Experiment 13

Time Period: 12 Months Above is a depth profile of the arsenic speciation found from the surface of the soil to a depth of 11 inches of soil underneath a CCA-Treated Wood Deck.