Download Microbial Activity in Arsenic Contaminated Soil

Samantha Wolf, Mark Emerson, Derek Laskowsky

Will soil previously contaminated with CCA
contain microbes that show more resilience
to prolonged exposure to CCA wood than
microbes in an uncontaminated soil?


The purpose of CCA is to prevent rot and
damage to lumber from termites, effectively
acting as a pesticide, in addition to
strengthening the lumber.
During the 1940’s the lumber industry began
its large-scale treatment of lumber with
chromated copper arsenate (CCA) for
preservation.


The complications brought on by the CCA
treated lumber is the leaching of chromated
copper arsenate into the surrounding soil.
The focus of this study is to determine if CCA
exposed microbes are resilient to the CCA,
compared to non-CCA exposed microbes.

Soil samples from 3”, 6”, and 9” from CCA
contaminated site.
Sample at 3”:
 Arsenic at 63.5 ppm
 cadmium at 2.2 ppm
 chromium at 31 ppm
 copper at 44 ppm
Average concentrations:
 Arsenic 6.5 ppm
 cadmium at 0.1 -1.0
ppm
 chromium at 70 ppm
 copper at 20 ppm
Brain-heart nutrient
broth in shaker
incubator for 1 week.
 Control, CCA Soil,
Control soil with 2.2g
CCA wood, CCA Soil
with 2.2g CCA wood.

Plated on agar,
incubated for 24 hrs.
 Counted and
extrapolated to 10^4

Colony count per sample
400000
350000
Bacteria Colonies
300000
250000
200000
150000
100000
50000
Results
0
All results are per .5ml


The CFU count was highest in the CCA soil
sample inoculated with the CCA wood chip.
The microbes in the soil must be conditioned
to presence of arsenic.
Arsenic loving microbes.