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Exposure to pressure treated lumber increases heavy metal tolerant microbes in soil

Page history last edited by Ian Balcom (Dr B.) 8 years, 6 months ago

S. Wolf, M. Emerson, D. Laskwosky, and I. Balcom. Lyndon State College, Lydonville, Vermont. 2012

 

Abstract:

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? What is the prevalence of microbes in each soil?

Our project focuses on a) the amount of copper and arsenic found in soil that has been exposed to Chromated Copper Arsenate (CCA) pressure treated wood, and b) the presence and activity of microbes in four soil samples: one control soil, one CCA soil, and one control and one CCA that have been inoculated with PT wood chips containing CCA.

 

Background:Introduction:

For more intro material:

http://onlinelibrary.wiley.com/doi/10.1016/S0168-6496(03)00232-0/full

See: http://www.ccaresearch.org/Pre-Conference/pdf/stilwell.pdf

http://ccaresearch.org/Pre-Conference/document/Fl_Env_Cent_Treated_Wood_Proceedings2.pdf

http://scholar.google.com/scholar?q=cca+wood+and+soil&hl=en&btnG=Search&as_sdt=1%2C46&as_sdtp=on

 

 

The purpose of CCA is to prevent rot and damage to lumber from termites, effectively a pesticide, besides strengthening the lumber. The EPA has deemed that CCA is too toxic for use on lumber intended for homes and play grounds. CCA PT wood came into use in the 1940s, and was widely used in the 1970s for residence purposes. By Dec. 2003, manufacturers were prohibited from applying CCA to lumber intended for homes or playgrounds (http://www.epa.gov/oppad001/reregistration/cca/)

The site selected is a rental residence once belonged to a local handyman. Within the door yard was a small pile of Pressure Treated lumber, the pile consist of scrap pieces of Chromated Copper Arsenate and Alkaline Copper Quaternary treated lumber. The lumber of main interest is that treated with Arsenic.


There are no records indicating when the previous owner began stock piling this debris, but has been there since September of 2009. The pile is located adjacent to the driveway and shares the same grade as the driveway. The pile is scattered amongst a patch of what appears to be berry bushes, the bushes themselves don’t appear to be producing fruit.

 

 

Methods:

 

Soil sampling and analysis:

The soil samples where extracted during winter, predetermined the sample depths to be 3, 6, and 9 inches, speculating that the aArsenic mMetal wouldn’t be much deeper. During the sampleingsampling process, discovered that the frost in that area wasn’t any deeper than three inches, partly due to contaminated site was mostly buried under a snow bank. Used a power auger to break through the initial frost line and then hand dug with small spade to remaining depths.

GPS reading for the selected site was N 44, 39.738 and W 71, 56.199 and an elevation of 1533 feet above sea level.

Microbial enrichment cultures:

On 2.17.12, we began incubating soil samples of sand, loam, and gravel in a broth. There are 3 control units, and 3 units to be inoculated with PT wood. The loamy soil was sampled from a site that had been exposed to CCA wood. Samples from this site were taken at 3 inch, 6 inch, and 9 inch depths, and sent for analysis to UVM's soil lab (figure 1).


One control flask with uncontaminated top soil, one control flask with CCA contaminated soil, one flask with uncontaminated top soil inoculated with a 2.2 g piece of CCA wood, and one flask of CCA contaminated soil inoculated with a 2.2 g piece of CCA wood. Incubation of these specimens began on Mar. 1 at 2 pm. After one day of incubation, samples were plated for a colony count. Concentration was far too high to count colonies. We diluted samples 4 times at a concentration of .5 ml and plated them again, and let them incubate at 30°C for 24 hours. Results were easier to count. See figure 2 below.


Results and Data:

Samples from this site were taken at 3 inch, 6 inch, and 9 inch depths, and sent for analysis to UVM's soil lab (figure 1).

 

Figure . Soil heavy metal analysis results.

 

Figure 1

Arsenic was found in the 3 inch depth sample at 63.5 ppm. In average soil, arsenic is present at 3-4ppm (excluding sites near arsenic rich mineral deposits) (http://www.eco-usa.net/toxics/chemicals/arsenic.shtml).

Method: We have one control flask with uncontaminated top soil, one control flask with CCA contaminated soil, one flask with uncontaminated top soil inoculated with a 2.2 g piece of CCA wood, and one flask of CCA contaminated soil inoculated with a 2.2 g piece of CCA wood. Incubation of these specimens began on Mar. 1 at 2 pm. After one day of incubation, samples were plated for a colony count. Concentration was far too high to count colonies. We diluted samples 4 times at a concentration of .5 ml and plated them again, and let them incubate at 30°C for 24 hours. Results were easier to count. See figure 2 below.



 

 

 

 

 

 

 

 

 

Figure . Counts of colony forming units (CFU) per plate based on 4 x 10 fold serial dilution.

figure 2

As an interesting side note, a new bacteria was discovered within the last year. Bacteria were discovered that are able to use arsenic in place of phosphorus in their DNA. The bacteria were discovered by Felisa Wolfe-Simon through a study done on Mono Lake in California. The lake has extremely high levels of arsenic and not many organisms are able to live in the lake. This is a small breakthrough in the science world. Prior to this discovery our rules for the basic needs of life forms remained the same for many years. All life forms need elements like carbon, oxygen, nitrogen and phosphorus. The phosphorus is used in the DNA of the living being. It acts as the structure or the back bone of the DNA. Prior to this discovery we believed that all living things required phosphorus for their DNA. We now know that there are living things, bacteria in this case that are able to use arsenic instead of phosphorus in their DNA. This is possible because arsenic is similar to phosphorus on a molecular level. They can be mistaken for each other in some chemical processes; this is why arsenic is toxic to most living things. Due to the fact that it is similar and not identical when the swap does take place it leads to problems in the living being. In light of this, the fact that something is able to survive off of arsenic is quite extraordinary.

http://scienceblogs.com/pharyngula/2010/12/its_not_an_arsenic-based_life.php

http://www.nature.com/news/2010/101202/full/news.2010.645.html

The microbe, named strain GFAJ-1, is a salt-loving member of the Halomonadaceae family of proteobacteria that came from the sediments of toxic Mono Lake in eastern California. This old alkaline lake is known for its being hyper-salty and naturally high in arsenic http://www.livescience.com/9046-microbe-eats-arsenic.html

 

 

 

microbes.pptx

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