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

2. 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

3. 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

4. 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

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

6. Shredding Wood
Untreated wood mulch
Treated wood mulch

7. 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

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

9. 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

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

11. Metal Analysis: Mulch LeachatepH
Acidification
Digestion (EPA 7060a) AA

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

13. 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

14. 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)

15. 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 95 % confident level.

16. Arsenic in the leachate vs. Initial arsenic contents in mulch

17. Correlation

18. 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

19. 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

20. Thank you
Also of note are possible human health exposures