Arsenic Leaching out from CCA Contaminated Mulch Tomoyuki Shibata, M.S. University of Miami October 22, 2004 TAG Meeting

Background Deck Study Arsenic can be leached out from CCA-treated wood deck by rainfall Chemistry Colorant contains iron oxides Iron oxides combine with arsenic

Hypotheses Objectives CCA-contaminated mulch can be another source of soil contamination Iron oxides in the colorant can delay the rate of arsenic leaching out Objectives To monitor leachate through CCA-contaminated mulch by rainfall To evaluate how much red-dyed mulch delays the rate of arsenic leaching out

Materials and Methods Handmade Mulch Monitoring 100 % treated wood mulch 5 % treated wood mulch All untreated wood mulch (Colored & non-colored) Monitoring Since Jan 04 Rainfall & Leachate Total 6 observation boxes, a pair (non-colored and colored) of three different % of treated wood

Collecting Recycled C&D Wood Sorting into treated and untreated wood

Shredding Wood Untreated wood mulch Treated wood mulch

Initial Arsenic Contents Ashed mulches Acid Digestion EPA 3050b Initial arsenic contents 2,300 mg/kg in 100 % treated wood mulch 1 mg/kg in 100 % untreated wood mulch

Coloring Mulch Red dye manufactured by Becker Underwood and followed their instruction of coloring

Making Observation Box 100% treated 95% untreated & 5 % treated 2 pairs (colored and non-colored) 3 different concentrations (all untreated wood mulch, 5 % treated wood mulch, and all treated wood mulch) 100 % untreated Red-dyed mulch Non-dyed mulch

Sampling Have monitored everyday for the first 10 leachate samples Collect leachate sample once a week

Metal Analysis: Mulch Leachate pH Acidification Digestion (EPA 7060a) AA

Arsenic from 100 % treated wood mulch 23,000 ug/L 15,000 ug/L Non-colored treated wood mulch Colored treated mulch

Arsenic from 5% treated wood mulch Colored mixed wood mulch 2,200 ug/L 1,500 ug/L Non-colored mixed wood mulch Colored mixed wood mulch

Arsenic in Leachate from CCA Contaminated Mulch Treated wood mulch (100%) Mixed wood mulch (5% treated) 50 ug/L for Arsenic (U.S.EPA: Drinking water standard, FL criteria for surface water quality classification)

Average Arsenic Concentrations in ½ year 100 % treated wood mulch 8000 ug/L from non-colored 5200 ug/L from red-colored 5 % treated wood mulch 580 ug/L from non-colored 400 ug/L from red-colored All untreated wood mulch 4 ug/L from non-colored 2 ug/L from red-colored Some detectable levels of arsenic were observed from 100% untreated wood mulch but those arsenic concentrations levels were less than 0.05% of the arsenic concentration in the leachate from 100 % treated wood mulch. The mean arsenic concentrations from the mix wood mulch containing 5 % of treated wood were 7 ~ 8 % of the arsenic concentrations in the leachate from 100 % treated wood mulch. The mean arsenic concentrations in the leachate from red dyed mulches were significantly smaller than the concentration from non-dyed mulches at three different % of treated wood @ 95 % confident level.

Arsenic in the leachate vs. Initial arsenic contents in mulch

Correlation

Results: Mass Balance 5 % Treated Treated mulch Non color Dyed   Non color Dyed Initial As (mg) 93 1900 Leachate out (mg) 13 10 220 150 Leaching (%) 14 11 12 8 About 13 % of arsenic was leached out from non-colored mulch while 10 % was leached out from colored mulch

Conclusion 5 % CCA contaminated mulch Released arsenic 400~ 600 ug/L (average) Released 11 ~ 14 % of initial arsenic contents Colorant can delay the rate of arsenic leaching out from the contaminated mulch About 20 ~ 30 % Significantly different at 95 % confidence

Thank you Also of note are possible human health exposures