Samantha Wolf, Mark Emerson, Derek Laskowsky Microbial Activity in Arsenic Contaminated Soil
Hypothesis • Will soil previously contaminated with CCA contain microbes that show more resilience to prolonged exposure to CCA wood than microbes in an uncontaminated soil?
Introduction • 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.
Introduction Cont. • 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.
Methods: Soil sampling and analysis • Soil samples from 3”, 6”, and 9” from CCA contaminated site.
Metal Concentrations 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
Microbial Enrichment • 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.
Colony Forming Units • Plated on agar, incubated for 24 hrs. • Counted and extrapolated to 10^4
Conclusion • 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.