Laboratory Immersion Method for Accelerated Prediction of Preservative Leaching from Pressure-Treated Wood Exposed to Precipitation


  • S T Lebow USDA, Forest Service, Forest Products Laboratory
  • P K Lebow USDA, Forest Service, Forest Products Laboratory
  • K C Hirth USDA, Forest Service, Forest Products Laboratory


Wood preservative, leaching, precipitation, accelerated test methods, immersion


This paper reports on the development of accelerated laboratory methods to allow estimation of preservative leaching from pressure-treated wood exposed to precipitation. End-matched lumber specimens were pressure-treated with a boron-copper formulation and exposed to either natural weathering for one year, laboratory immersion protocols, or a laboratory simulated rainfall protocol. The rainfall run-off or immersion water was collected at intervals according to the method used and analyzed for concentrations of copper and boron. Of the laboratory methods evaluated, the simulated rainfall approach resulted in leaching patterns most similar to outdoor exposure, especially in the case of copper. However, this method is relatively complex and not ideally suited for standardized use. Although the immersion methods evaluated initially exaggerated leaching, reasonable approximations of leaching from one year of natural weathering were achieved with accelerated testing. Models were developed to relate hours of immersion to millimeters of precipitation, and used to evaluate how well the immersion methods might predict leaching from natural weathering over many years of exposure. One of the methods produced boron and copper leaching estimates that were within 15% and 7% (respectively) of losses predicted for wood exposed to 5 years of natural weathering. The results indicate that laboratory immersion methods have value in estimating long term preservative leaching from treated wood products exposed to precipitation.

Author Biographies

S T Lebow, USDA, Forest Service, Forest Products Laboratory

Research Scientist, Durability and Wood Protection Research

P K Lebow, USDA, Forest Service, Forest Products Laboratory

Research Mathematical Statistician, Economics, Statistics and Life Cycle Analysis Research

K C Hirth, USDA, Forest Service, Forest Products Laboratory

Chemist, Analytical Chemistry and Microscopy Laboratory


AWPA (2017) E11. Standard Method for Accelerated Evaluation of Preservative Leaching. Book of Standards. American Wood Protection Association, Birmingham, AL. 624p

Baines EF (2005) A review of the current status of the estimation of emissions from preserved wood and their use in the environmental risk assessment of wood preservatives under the Biocidal Products Directive. Int Res Group Wood Preservation Document No. IRG/WP 05-50224-7. Stockholm, Sweden. 13p

Bahmani M, Schmidt O, Fromm J, Melcher E (2016) Influence of wood sample size and species on the leaching of chromium and copper using different lab tests. Maderas, Cienc. tecnol. 18(2): 265-272.

Bolker, B.M. (2008). Ecological Models and Data in R. Princeton University Press. Princeton, NJ. 408pp.

BSI (1997) BS EN 84:1997. Wood preservatives. Accelerated ageing of treated wood prior to biological testing. Leaching procedure. British Standards Institute, London.

CNS (2000) Chinese National Standard CNS 6717.Qualitative Standards and Testing Methods of Wood Preservatives. Bureau of Standards, Metrology and Inspection, Ministry of Economic Affairs (MOEA), Taipei, Taiwan.

Cooper PA, MacVicar R (1995) Effect of water repellents on leaching from CCA treated wood. Int Res Group Wood Preservation Document No. Document No. IRG/WP 95-50044. Stockholm, Sweden. 6p.

JSA (2004) JIS K 1571: Wood preservatives -- Performance requirements and their test methods for determining effectiveness. Japan Standards Association, Tokyo.

Lebow ST (2014) Chapter 14. Evaluating the Leaching of Biocides from Preservative-Treated Wood Products. In: Deterioration and Protection of Sustainable Biomaterials. T. P. Schultz, B. Goodell, and D.D. Nicholas, eds. ACS Symposium Series, Volume 1158. 397p.

Lebow ST, Lebow PK, Foster, DO (2008) Estimating preservative release from treated wood exposed to precipitation. Wood and Fiber Sci. 40(4): 562-571.

Lebow ST, Foster, DO, PK Lebow (2004) Rate of CCA leaching from commercially treated decking. Forest Prod. J. 54(2): 81-88.

Lebow, ST, Lebow, PK, Hirth, KC (2017). Comparison of accelerated methods for evaluating leaching from preservative treated wood. Wood and Fiber Sci. 49(1):93-104.

Lebow ST, Williams RS, Lebow PK (2003) Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood. Environ. Sci. Technol. 37:4077-4082

Lesar, B, Krali, P, Žlindra, D, Kancilija, V, Humar, M (2008) Comparison of standard

procedures for estimation of biocides leaching from impregnated wood. Acta Silvae et Ligni 86:59-64

Mitsuhashi J, Love CS, Freitag C, Morrell JJ (2007). Migration of boron from Douglas-fir lumber subjected to simulated rainfall. Forest Prod. J. 57(12): 52–57.

Mankowski, M.E., and Manning, M.J. 2008. Depletion and Redistribution of Boron in Bundles of Commercially Treated Lumber Exposed to Artificial and Natural Rainfall. In: Proceedings IRG Annual Meeting Istanbul, Turkey. Document No. IRG 08-30474, 14 pp. The International Research Group on Wood Protection. Stockholm, Sweden.

Morrell, JJ, Chen H, Simonsen J, (2004) Migration of metals from Douglas-fir lumber treated with ACZA using Best Management Practices: Preliminary tests. Proceedings, American Wood Preserver’s Association Annual Meeting, Vancouver, B.C. 100:158-161.

Morsing, N, Lindegaard B (2004) Leaching of active components from preservative-treated timber: Stages 2 & 3: Laboratory testing and comparison with semi-field testing. Int Res Group Wood Preservation Document No. IRG/WP 04-20303. Stockholm, Sweden. 15p.

OECD (2009) OECD Guidance on the Estimation of Emissions from Wood Preservative-Treated Wood to the Environment: for Wood held in Storage after Treatment and for Wooden Commodities that are not covered and are not in Contact with Ground. Series on Testing and Assessment No. 107. OECD Environment, Health and Safety Publications. OECD Environment Directorate, Paris, France.

Pinheiro, J. C. and Bates, D. M. (2000) Mixed-Effects Models in S and S-PLUS. Springer-Verlag New York, Inc. New York, New York. 528 pp.

Pinheiro J, Bates D, DebRoy S, Sarkar D and R Core Team (2016) _nlme: Linear and Nonlinear Mixed Effects Models_. R package version 3.1-128,>.

R Core Team (2016) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. URL





Research Contributions