Year “7” and Year “8” Studies Focusing on Mulch

Mulch – Buffer Materials

• Early research has shown that mulches made from recycled dimensional wood can be contaminated with CCA (Townsend et al. 2003).

• Follow-up study -> Year 7 – South Florida Year 8 – Rest of Florida

Mulch made from C&D Wood

Mulch Analysis Methods

Sample

Visual Inspection

Size Distribution

Ash for total Metals

SPLP Analysis

Mulch Ashing Results

All 6 samples contained plywoodindicating that they contained recycled dimensional wood.

Ashed Samples: 20

Colored: 14

Not Positive for Arsenic: 8

Positive for Arsenic: 6

Positive for Arsenic: 1

Not Positive for Arsenic: 5

Not Colored: 6

Concentration Range of Arsenic Samples

Ashing Test

13

1 2 2 20

2

4

6

8

10

12

14

0 - 10 10 - 50 50 - 100 100 - 150 150 - 200

Arsenic mg/kg

Nu

mb

er o

f S

amp

les

Ashed Mulch

R2 = 0.88

0

100

200

300

400

500

0 50 100 150 200 250

Arsenic (mg/kg)

Ch

rom

ium

(m

g/k

g)

Arsenic vs. Chromium

Mulch SPLP Results

All 8 samples contained plywood indicating that they contained recycled dimensional wood.

SPLP Samples: 32

Not Colored: 15

Colored: 17

Not Positive for Arsenic: 10

Positive for Arsenic: 5

Not Positive for Arsenic: 9

Positive for Arsenic: 8

Concentration Range of Arsenic Samples

SPLP Test

20

3 36

0

5

10

15

20

0 - 12 12 - 50 50 - 100 100 - 150

Arsenic ug/L

Nu

mb

er o

f S

amp

les

SPLP Analysis

R2 = 0.83

0

20

40

60

80

100

120

0 50 100 150 200

Arsenic (ug/L)

Ch

rom

ium

(u

g/L

)Arsenic vs. Chromium

Conclusion

Engineered wood was found in 28% of consumer mulches

Arsenic was found in 35% consumer mulches

SPLP tested showed that arsenic leached from 37 % of consumer mulches 26% of these samples leached over 50 μg/L

Mulch Leaching StudyEffect of Iron Oxides on Leaching of CCA