Comparative study on leaching of CCA from treated timber: Modelling of emission data

IRG/WP 94-50027

G M F Van Eetvelde, M Stevens, L Van der Mijnsbrugge

Results of a comparative study on leaching of CCA from treated timber are reported. The study aims at investigating the applicability of prestandard leaching test methods for modelling purposes. Prestandards used are the European standard proposed by CEN/TC38/WG11 and NEN 7345 (Dutch prestandard for building materials). Parameters of study are type of fixation, wood species (pine - spruce), specimen dimensions and leaching pH. Due to the conditions of test, a higher level of metal emission is observed in the CEN procedure. Both methods show a similar time-related decrease in leaching flux, however. The CEN small wood block test using a dynamic stirring leaching system proves to be an accellerated version of the static NEN method in which pole sections are immersed in water over a long period of time. Steam fixation generally reduces the emitted quantities of chromium. When naturally fixated, the initial chromium flux exceeds the copper flux, while in accelerated (steam) fixation tests copper is leached out to a higher level. In most tests the initial arsenicum emission flux does not exceed one tenth of the respective copper flux. With regard to hazard assessment of CCA leaching from treated timber in surface waters, an emission model is worked out taking into account a number of controlable and verifiable parameters influencing the final environmental concentration. The PEC-formula used (predictable environmental concentration) is kept short and is based on time dependency of the emission data (curve fitting on experimental data) and substraction of calculated dilution factors.


Conference: 94-05-29...06-03, Nusa Dua, Bali, Indonesia

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