DETERMINATION OF ARSENIC IN SOIL UNDER A DECK BUILT OF CCA PRESSURE TREATED WOOD IN WEST GEORGIA

Arsenic has had a long history of usage in the United States. Based on USGS data an estimated 420,000 tons of arsenic has been used in pressure treated wood since 1960. During this time another 350,000 tons of arsenic were used in agricultural chemicals. A voluntary agreement between the EPA and the manufacture's of pressure treated wood removed arsenic in pressure treated wood for residential usage in 2004. A potential health problem is the long term fate of arsenic used in pressure treated wood. Pressure treated wood contains inorganic arsenic that protects it from decay and insects. The most common treatment is with chromated-copper-arsenate or CCA. One cubic foot of CCA wood contains 1.15 oz of arsenic. Such wood in an outdoor environment may resist termites and decay for 20-60 years. However, our research shows in the warm humid southeastern United States that CCA wood in contact with the ground may after ten years disintegrate. Burning pressure treated wood releases arsenic into the smoke and ashes. Of interest to environmental geology is the very long-term environmental behavior of arsenic from this pressure treated wood (Bleiwas, 2000; EPA, 2002; Hollabaugh 2004).

Wood treated with CCA can have arsenic concentrations ranging from 0.1% to 1.8%. To determine if there was evidence that arsenic could leach from pressure treated wood, soil was tested at 94 sites around the perimeter of a deck at Cobb Hall on the campus of University of West Georgia. The deck was built with pressure treated wood that contains the preservative CCA. Samples were taken from 21 sites around the perimeter of the deck and also in four directions at 7' intervals radiating away from the deck. A series of background samples were also collected at a site not in immediate proximity of the deck and were compared with all the samples. Soil samples were dried to exclude water content in the soil from calculations. Samples were then analyzed by ICP to determine arsenic concentrations. An average concentration of 48 ppm of arsenic was found in the soil, with a maximum concentration of 338 ppm arsenic. Arsenic concentrations were found to be highest directly around the perimeter of the deck, and decreased with distance away from the site. From data analysis, it was determined that arsenic is in fact being leached from the pressure treated wood into the soil surrounding the deck.