Progress 07/01/04 to 06/30/09
Outputs
OUTPUTS: All proposed work on this project is being completed and published. An additional study of samples treated with two organic biocides with and without co-added antioxidant and metal complexing compounds was established and, after one year of outdoor exposure at two sites, depletion samples were pulled and analyzed. Both additives, alone or combined, reduced depletion of both organic biocides. Additional studies to better understand this effect are planned. Stakes treated with two different formulations of copper/organic systems, installed previously using CSREES funding and exposed outdoors for nine and 14 years, were re-inspected and the long-term efficacy versus the initial laboratory efficacy data compared. It appears that investigators need to understand the limitations and advantages of the particular laboratory screening tests to optimize the data obtained while minimizing the test's drawbacks. A review article was published on recent developments in wood preservation. PARTICIPANTS: Co-authors of publications based on this project are D. Nicholas, Professor, Forest Products Department, MSU; and Dr. C. McIntyre, Consultant, Mississippi. TARGET AUDIENCES: This work has provided both fundamential and applied knowledge to industrial personnel and government/academic scientists. PROJECT MODIFICATIONS: As all objectives of this project will be completed soon, an additional study will be initiated employing two organic biocides and non-biocidal additives to determine if an antioxidant and/or metal complexing agent will reduce biodegradation of the organic biocides in outdoor exposure.
Impacts
Concerns over leaching of heavy metals and the disposal of lumber treated with metallic systems has resulted in three European countries recently requiring wood to be treated with totally organic preservatives. Some restrictions on metallic treated wood has already been eneacted in a few locations in the U.S., and many professionals expect this trend to accelerate with totally-organic systems required for residential applications in the future. However, several problems exist with employing organic biocides to preserve wood, including the biodegradation of the organic biocides over the long service life expected fromt reated wood. This research will help develop additives that may reduce biodegradation of organic biocides, and generate data of copper depletion and migration in wood.
Publications
- Schultz, T., and D. Nicholas. 2008. Long-term ground-contact efficacy studies of two synergistic biocide mixtures that laboratorydecay studies suggested may be promising wood preservative systems. Forest Products Journal 58(5):73-76.
- Schultz, T., D. Nicholas and C. McIntyre. 2008. Recent patents and developments in biocidal wood protection systems for exterior applications. Recent Patents on Materials Science 1:128-134.
- Schultz, T. and D. Nicholas. 2008. Long-term outdoor efficacy trials of wood treated with organic biocides and co-added non-biocidal additives. Proceedings, 104th Annual Meeting of the American Wood Protection Association, pp. 96-102.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: All proposed work on this project has been completed and published. An additional study was started where southern yellow pine sapwood samples were treated with two organic biocides, with and without a co-added antioxidant, BHT, and a metal complexing agent, resin acids. These samples were installed in early 2007 at Saucier, MS, and Hilo, HI. Samples will shortly be pulled to determine if the non-biocidal additives reduce depletion of the organic biocides. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: As all objectives of this project has been completed, an additional study was initiated employing two organic biocides and non-biocidal additives to determine if an antioxidant and/or metal complexing agent will reduce biodegradation of the organic biocides in outdoor exposure.
Impacts
Concerns over leaching of heavy metals and the disposal of lumber treated with metallic systems has resulted in three European countries recently requiring wood to be treated with totally organic preservatives. Some restrictions on use of metallic treated wood has already been enacted in a few locations in the U.S., and most professionals expect this trend to accelerate with totally-organic systems required for residential applications in the future. However, several problems exist with employing organic biocides to preserve wood, including the biodegradation of the organic biocides over the long service life expected from treated wood. Indeed, we have recently observed a rapid drop in efficacy with several organic biocides that have been exposed outdoors for five or more years. This research will help to develop additives to reduce the biodegradation of organic biocides and to generate data on copper depletion and migration in wood.
Publications
- Schultz, T.P. and D.D. Nicholas. 2007. Totally organic wood preservative systems for exterior residential applications. In: Wood Protection 2006, Forest Products Society, Madison, WI, pgs: 289-294.
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Progress 01/01/06 to 12/31/06
Outputs
Stakes were treated with the copper-rich wood preservative alkaline copper quat (ACQ), which is currently the major wood preservative in the U.S. After treatment these samples were bagged for various times, then dried, and the distribution among the latewood and earlywood in the stake end and center determined. It was found that this copper-rich system takes much longer to fix than chromated copper arsenate, which explains the relatively higher leaching of copper from wood treated with the new systems versus CCA. The study on the effect of the antioxidant butylated hydroxytoluene, BHT, on biocide depletion was completed. In ground contact after 54 months of exterior exposure in two locations with high or severe deterioration, it was found that BHT had a significant protective effect on reducing depletion of the organic biocide chlorothalonil. Additional samples were treated with two promising organic biocides, with and without non-biocidal BHT and/or a metal complexing
compound co-added, and will be installed shortly in two locations.
Impacts
Concerns over leaching of heavy metals and the disposal of lumber treated with metallic systems has resulted in three European countries recently requiring wood to be treated with totally organic preservatives. Restrictions of lumber treated with copper-rich systems is expected to occur shortly in North America; indeed, this has already occurred in a few U.S. localities with this trend expected to accelerate. Several problems exist with employing organic biocides for the long service life expected from treated wood, including biodegradation of the biocide. This research will help to statistically determine the many soil characteristics which can affect leaching of heavy metals in lumber placed in different soils, the effect of copper migration and subsequent leaching from wood treated with the new copper-rich preservatives, and may develop methods to reduce biodegradation of organic biocides.
Publications
- Schultz, T., D. Nicholas, G. Kirker, M. Prewitt, and S. Diehl. 2006. Effect of the antioxidant BHT on reducing depletion of chlorothalonil in treated wood after 54 months of ground-contact exposure. International Biodeterioration and Biodegradation 57:45-50.
- Kelly, A.M., W.E. Holmes, T.P. Schultz. 2006. An environmentally benign method for reducing off-flavor terpenoids in aquaculture: Initial laboratory studies. North American Journal of Aquaculture 68:249-252.
- Li, G., D.D. Nicholas, T.P. Schultz. 2006. Effect of wood decay on the proportional limit of thin wood samples stressed in the bending mode. The International Research Group on Wood Protection, IRG/WP 06-20334. 10 pp.
- Li, G., D. Nicholas and T. Schultz. 2006. Effect of delayed drying time on copper distribution in the annual rings of ACQ-treated southern yellow pine research stakes. Forest Products Journal 56(3):29-31.
- Lebow, P. R. Ziobro, L. Sites, T. Schultz, D. Pettry, D. Nicholas, S. Lebow, P. Kamdem, R. Fox, and D. Crawford. 2006. Statistical analysis of influence of soil source on leaching of arsenic and copper from CCA-C treated wood. Wood and Fiber Science 38:439-449.
- Tilly, B. K., K.A. Brasher, D.D. Nicholas, L. Sites, I.A. Munn, T.P. Schultz. 2005. Wood preservation in Mississippi. Tree Talk 27(4):28, 30-32.
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Progress 01/01/05 to 12/31/05
Outputs
Small southern yellow pine stakes, cut from defect-free sapwood, had been earlier treated with CCA-type C and leached using an accelerated laboratory method for 12 weeks in five soils obtained from different locations and deionized water. The loss of Cu and As was measured using x-ray fluorescence. The results have been fully statistically analyzed in the past year. The levels of As and Cu leached were highly correlated to the initial metal retention. The particular soil which the samples were exposed to also was a significant factor in the amount of Cu and As leached. Average Cu loss was approximately equal to or greater than the loss for specimens exposed to soil. For specimens leached in water, however, As loss was about twice that of Cu loss. Generally, more Cu leached from specimens in soil contact compared to specimens in water, suggesting that leaching studies of the new copper-rich systems should employ soil-based methods for realistic depletion measurements.
The amount of As and Cu leached was influenced by the chemical and physical properties of the various soils. While the limited number of soils examined and the wide variation possible in soil chemical and physical properties make it difficult to statistically identify the most important soil properties associated with leaching, models associating the extent of As and Cu leached were developed that explained over 80% of the variation in extent of leaching for both of these heavy metals.
Impacts
Concerns over the leaching of heavy metals from wood treated with the older CCA and the new copper-rich preservative systems are well known and have impacted the use of metallic wood preservatives in the U.S. and Europe. This research will help develop an accelerated standard laboratory method for soil-contact leaching of metals from wood products treated with metallic systems so that any possible concerns can be quickly identified.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Three replicate stakes from each treatment and research plot of the chlorothalonil/antioxidant (BHT) study were pulled after 54 months of ground-contact exposure at the Saucier, MS, and Dorman Lake, MS test sites. From each stake three samples were cut: 1) near the stake bottom; 2) at the ground-line down two inches; and 3) several inches above the ground line. Each sub-sample was cut, chopped, and then ground. The original cut-off sample which served as the unexposed control was also chopped/ground. The samples were then extracted with toluene to remove the chlorothalonil and/or BHT, with these components analyzed by gas chromatography. For samples from the two sections in ground-contact and treated at the two highest chlorothalonil levels, the presence of the antioxidant BHT greatly reduced biocide depletion. The lessened depletion was likely due to reduced biodegradation, as we previously hypothesized. However, at the lower biocide treatment level, or in stake
sections obtained from above-ground, the protective effect of the BHT was less apparent. When no BHT was present, the least biocide depletion occurred above-ground, with no difference in depletion in the other two ground-contact stake sections. The extent of BHT depletion after 54 months was approximately 30-50%, but an oxidized product of BHT was observed by GC/MS which would still have antioxidant properties; other BHT byproducts are likely also present. Based on this depletion data and the 67 months average decay and termite ratings, a manuscript is being prepared. Results from soil leaching of the stakelets from the earlier CCA-leaching round-robin study were sent to Dr. P. Lebow, USDA-Forest Products Laboratory, for a full statistical study of the copper and arsenic leached. The initial copper and arsenic retention in a particular stakelet was shown to be strongly dependent on the particular lumber piece from which the stakelet was cut. Furthermore, the initial copper and arsenic
retentions were found to highly influence the amount of metal leached, with higher metallic retentions leaching the most. Consequently, the original lumber pieces from which the samples were cut was found to significantly impact the amount of copper and arsenic leached in laboratory studies. Further studies to determine which soil factors influence the amount of copper and arsenic leached are underway. A preliminary manuscript has been roughed out.
Impacts
Over $5 billion worth of treated wood which helps to prevent decay and termite degradation of residential structures is used in residential construction annually. However, not using treated lumber where appropriate and/or poor design and construction practices is common in the U.S.; thus, fungal decay and termite degradation costs U.S. homeowners over $5 billion annually. Up to the end of 2003, over 95% of treated lumber used for residential construction was CCA treated. However, arsenic leaching from CCA-treated wood led to the voluntary withdrawal of CCA-treated lumber for residential applications at the end of 2003, with the new systems approved for residential applications being copper-rich. Unfortunately, these systems leach relatively high levels of copper; thus, they can negatively impact aquatic ecosystems. This is one of the major reasons why these copper-rich systems are currently restricted in three European countries, with restrictions in North America
likely at some future point. If the factors which cause leaching can be fully understood, then it may be possible to design more realistic leaching experiments and subsequently test modified formulations designed to minimize copper leaching.
Publications
- No publications reported this period
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