Introduction

        Lumber treated with chromium, copper, and arsenic (CCA) lasts longer because it protects against termite attacks and normal ageing of the lumber.  Because of these protections, fewer trees need to be cut from the forests.  However, this treatment may have a bad influence on our environment.  It is known that chromium, copper and arsenic concentrations in CCA treated lumber are leached by rainwater and deposited in soils.   Previous studies by some researchers have indicated the concentrations of these elements in soils below decks made of CCA treated lumber may vary with the age of the deck.                                                                                            

          My hypothesis is the soils below house decks with CCA treated lumber in my neighborhood will have higher concentrations of chromium, copper and arsenic than background values. I also think these elevated concentrations of elements in the soils will vary with the age of the deck. I also think some of the element concentrations may be higher than those approved by EPA in residential soils. 

 

 

                                                   Procedure

 

          I located houses in my neighborhood with decks of different ages made from CCA treated lumber and collected soil samples below each deck. I collected six samples from 5 different houses. At one house, one sample was collected below a deck and another collected under a handicapped deck-ramp.  Each deck in this study ranged from 1 to19 years old.   Each sample was collected from the surface to1 inch below the surface with a garden hoe and placed in labeled sandwich bags. A soil sample representing the control or background from each house property was collected the same way. The control sample was collected about 30 feet from each deck location.  All samples were dried and crushed lightly in a mortar and pestle and each placed in a small bottle.

        The soil below each deck and control samples were taken to the lab. Each sample was passed through a stainless steel sieve and the soil size less than 63-mesh was saved for analyses.  A portion of each sample was weighed to approximately 2.000 grams on a Sartorus Analytical Balance and placed in labeled plastic centrifuge tubes.  Twenty milliliters of 1 N nitric acid was added to each bottle and placed in a large centrifuge for 4 minutes.  The liquid portion from each sample was saved in separate labeled bottles for ICP analysis. The chromium, copper, and arsenic concentrations from each sample were determined with the use of a Varian 150 AX Inductively Coupled Plasma Spectrophotometer (ICP).

           Each sample location site was plotted on a map using ARCView.  The map is shown below.

 

 

 A data table was prepared using Microsoft Front-page and the concentrations of each element in the soils under each deck and control samples were placed in the table.  Included in the table was the elevated concentration value of each element in the soils under each deck.  Each of these elevated values was obtained from subtracting the concentration of each element in the appropriate control sample from that in the sample under each deck. The age of each deck was also included on this table.   Information from the data table was used to prepare graphs for each element relating the elevated concentration of each element in the soils under each deck with the age of the deck.

 

 

                                                      Results

        The information from the Data Table is located below.

 

Sample and Control* (Background) Numbers

Concentrations of Elements in Soils in ppm

Elevated Concentrations of Elements in the Soils in ppm

Age of Deck (Years)

As

Cr

Cu

As

Cr

Cu

 

2

63

56

96

52

46

66

19

2c*

11

10

30

3a

25

35

57

13

28

36

15

3c*

12

7

21

1

30

25

66

26

13

32

12

1c*

4

12

34

5

24

17

30

20

7

13

4

5c*

4

10

17

4

13

9

26

7

2

7

2

4c*

6

7

19

3b

12

8

28

0

1

7

1

3c*

12

7

21

 

  The element graphs from the Table above are shown below.

  Elevated Concentrations (PPM) of the Elements ( Sample Values Minus

     Control Values) in the Soils in Relationship to the Age of the Decks

                                   

 

The results from the table and graphs indicate the elevated concentrations of chromium, copper and arsenic in the soils below each deck increase with the age of the deck.  This trend is consistent except for two examples. The concentration of arsenic is higher in the soil associated with the12 year-old deck compared to the15 year-old deck. Also, the concentration of copper is equal in the 2 and 1 year-old decks. I am not sure why these are not consistent with the other values.  The increased trend of concentrations of the elements in the soils with age of the deck agrees with another study.  Published data by the Environmental Protection Agency (EPA) shows acceptable limits of arsenic concentrations in residential soils to be between 10 to 22 ppm.   This suggests that 2 to 4 of the soil samples in this study have concentrations above acceptable EPA levels.  All of the concentrations of chromium and copper in the samples were well below the acceptable levels established by the EPA.

 

                                                   Conclusions

           The results of this research agree with my hypothesis.  It is not known how long leaching of these elements into the soils will continue and how high the concentrations of these elements in the soils can reach.  Some CCA treated decks are over 30 years old.  If I repeated this project, I would include more CCA treated decks and decks that are older than in this study for better results.  I would also analyze samples below CCA treated lumber in daycare centers and school playgrounds.

 

                              Acknowledgements

              I wish to thank the Chemistry Department and the Geography, Geology and Planning Department for the use of their equipment and facilities.  I wish to thank my father, Dr. Erwin J. Mantei who acted as a mentor for my project and helped me to prepare my study map.  He helped and supervised me while using chemical reagents and the Inductively Coupled Plasma Spectrophotometer.  He also helped edit this project report.  I also wish to give special thanks to my teachers at St. Agnes Elementary for their help and encouragement, especially Miss Lynn Vogel and Miss Edna Payton.