Online supporting information for Manuscript titled, “Quantities of Arsenic Treated Wood in Hurricane Katrina Demolition Debris” by Dubey, B., Solo-Gabriele, H., and Townsend, T. Calculation of Arsenic concentration in treated wood sample from the XRF As counts: Weathered and un-weathered wood samples were used in this study by Block et al (in-review). Sawdust was collected using a drill and was placed in a plastic bag, mixed thoroughly, and analyzed in triplicate through the sample bag using XRF. The plastic bag was necessary to minimize cross-contamination of samples. The presence of the plastic bag did not affect the results. A pre-weighed aliquot of sawdust (1g) was then digested using Method 3050B (US EPA, 2003) and subsequently analyzed by atomic absorption (AA) with flame atomization (Perkin Elmer Instruments AAnalyst 800) using Method 7000A (US EPA, 2003). The detection limit of the atomic absorption analysis was 0.1 mg/kg for arsenic in wood. The results for the XRF and AA were correlated (R 2 = 0.97). Conversion equations using data for the entire concentration range evaluated were created to estimate AA results from XRF readings through linear regression (AA=0.26(XRF) 1.12 ). Please see Block et al. (in press) for more details. Calculation for Soil Concentration Increase in the Upper 1inch of Mississippi and Louisiana State Volume of disaster debris = 94 million yd 3 = 71.4 million m 3 Volume of C&D debris = 50% of disaster debris = 35.7 million m 3 Volume of wood waste = 33% of C&D debris = 11.8 million m 3 Weight of wood waste (assuming a density of 512 kg/m 3 ) = 6.04 x 10 9 kg Percent CCA-treated wood in wood waste = 23.1% (data from present study) Weight of CCA-treated wood in the demolition debris = 1.4 x 10 9 kg Overall geometric mean As concentration from this study = 1240 mg/kg (The geometric mean was computed by multiplying the measured values for each sample and then taking the nth root where “n” is the number of samples). Weight of Arsenic from treated wood in demolition debris = (Weight of CCA-treated wood) x (Average As concentration) = 1736 metric tons. Land Area of the two states = 247,192 square kilometers, = 2.5 X 10 11 m 2 Porosity of Soil = 0.37 (corresponds to a medium sand; Davis and Cornwell 1998)