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Degradation of Carbon-Based Preservatives by Black-stain Fungi
2010 - IRG/WP 10-30533
Some black-stain fungi are known to exhibit resistance to carbon-based preservatives. However, the cause of this resistance is unclear. The fungi may have mechanisms to tolerate these chemicals, or they may be able to degrade and detoxify them. Fungi capable of degrading carbon-based preservatives are of interest for possible bioremediation of carbon-based preservative-treated wood at the end of its service. Moreover, such fungi could potentially facilitate the colonization of carbon-based preservative treated wood by decay fungi. Two strains of Aureobasidium pullulans and two strains of Epicoccum purpurascens were evaluated for their ability to degrade three commonly used carbon-based preservatives: propiconazole, tebuconazole, and DDAC. At low and medium concentrations propiconazole and tebuconazole were found to be vulnerable to degradation by one of the Epicoccum purpurascens isolates. Where biocides are needed to control the growth of black-stain fungi on wood, a combination of biocides with different chemistries should be used to minimize the risk posed by resistant strains.
R Stirling, P I Morris


Performance of Coatings on Wood Treated with Carbon-Based Preservatives
2013 - IRG/WP 13-40638
Wood treated with carbon-based preservatives is often used in applications where coatings are required, yet few studies have examined the effect of such treatment on coating performance. Users need to be confident that coatings on carbon-based preservative-treated wood will perform as well as or better than those on untreated wood. The present study examines the performance of three coatings on untreated wood and wood treated with three carbon-based preservative formulations after two years of exposure at two test sites. Samples treated with carbon-based preservatives were on average more resistant to black stain than those that were untreated. Coating and substrate degradation was generally similar, or slightly less intense, on wood treated with carbon-based preservatives than on untreated wood.
R Stirling, P I Morris


Respiration methods used to follow the decay of wood and the toximetric evaluation of wood preservatives
1975 - IRG/WP 249
When wood is attacked and decayed by fungi, wood substance and oxygen (02) are consumed, while carbon dioxide (CO2), water and heat are liberated. Early in the 1960's workers from England, Canada and Sweden began studying CO2 evolution, with respect to decay and its control using chemical preservatives, while in Germany and the USA O2 utilization was being similarly examined. Oxygen consumption measurements during the decay of wood were made mainly using pressure differential closed systems and were shown to be reasonably sensitive and a suitable reflection of the rate and extent of decay. Carbon dioxide measurements were made using titration, conductivity and gas-chromatographic methods. The last method appears to be the most useful, being applicable to open and closed systems, flexible in application, very sensitive over a thousand-fold concentration range change without switching, and easily automated. Its application to evaluating the toxicity of wood preservatives has been intensively studied and shown to give chemical toxic thresholds after only one third of the normal incubation time, which are similar to those based on the much longer conventional weight loss method.
R S Smith


Water-based wood preservatives for curative treatement of insect-infested spruce constructions
1998 - IRG/WP 98-30171
On laying down sanitation measures for wooden constructions infested by wood boring insects, we must take into account static risks for the construction - and, thus, for the security of the user - as well as risks for humans and environment due to the chemical preservative compounds of the treated wood. Analyses on many roof constructions made with spruce (Picea abies L.) have revealed that Hylotrupes bajulus L. and Anobium punctatum De Geer have not the significance given to them for decennies. That often allows to replace solvant-based with water-based wood preservatives in old buildings, for the protection of humans and environment. Therefore, a method has been developed in Switzerland for testing wood preservatives with delayed curative efficacy against the house longhorn beetle. Like the European Anobium Standard EN 370 this method intends to prevent the emergence of Hylotrupes beetles. Laboratory tests with diverse water-based wood preservatives available on the market in Switzerland have shown that particularly boron and benzoylphenylurea derivatives containing products get a sufficient penetration in the wood and prevent the emergence of the beetles.
E Graf, P Manser, B Lanz


A bibliography of organic solvent-based wood preservatives
1973 - IRG/WP 322
H Alliot


Evaluation of wood treated with copper-based preservatives for Cu loss during exposure to heat and copper-tolerant Bacillus licheniformis
1999 - IRG/WP 99-20155
Copper-based wood preservatives need to be effective against exposure to all types of microorganisms. Wood treated with six copper-based preservatives was exposed to 121°C and 20 psi pressure for 15 minutes under standard autoclave conditions and the copper-tolerant bacterium, Bacillus licheniformis CC01, for 10 d at 28°C and 150 rpm. Sixteen to 37 percent of the copper was released from the wood during autoclaving, with copper citrate demonstrating the highest percent loss. Forty-four to 82 percent of the copper remaining in the samples following autoclaving was removed during exposure to the bacterium in liquid culture; copper naphthenate in oil and ACQ-D had losses of eighty percent or greater of the remaining copper. The bacterium removed as much or more total copper in 4 of 6 gas-sterilized samples (85-94%) than the cumulative effects of steam-sterilization and the bacterium on treated samples. Copper loss from in-service treated wood compromises the efficacy of copper-based wood preservatives.
D M Crawford, C A Clausen


Bibliography of organic solvent based wood preservatives
1971 - IRG/WP 38 E
This publication has as its objective the collection of the more important and more recent references dealing with solvent-based timber preservatives; these are often termed - sometimes wrongly - oil-borne preservatives or even organic wood preservatives. It is hoped that this review will stimulate more fundamental studies in the future in this field or on some of its aspects.
H Alliot


An appraisal of methods for environmental testing of leachates from salt-treated wood (2)
1998 - IRG/WP 98-50110
For wood preservatives for use in hazard class 4 information on the ecotoxicity of preservatives and ingredients as well as on the effect of losses from impregnated timber is needed for a proper environmental risk assessment. In the evaluation of a suitable test procedure the leaching behaviour of copper-based formulations was studied using analytical and ecotoxicological test methodology. These studies included an analytical comparison of end grain sealed and not sealed wood blocks. Using sensitive bioindicators in ecotoxicological studies, real effects of the leachates gained from EN 84 were measured. The possibility to use a laboratory test procedure based on the leaching according to EN 84 is shown and discussed for the risk assessment of treated timber.
H W Wegen, A Platen, G M F Van Eetvelde, M Stevens


Copper based water-borne preservatives: The use of a thin section technique to compare the protection of wood by copper based preservatives against soft-rot and bacterial decay
1987 - IRG/WP 2286
This paper describes the techniques developed and gives examples of results obtained for the performance of copper based wood preservatives against both the bacterial and fungal hazards.
A M Wyles, D J Dickinson


Copper based water-borne preservatives: The biological performance of wood treated with various formulations
1987 - IRG/WP 3451
Wood samples treated with the various components of CCA preservative singly and in combination were tested against a soft rot organism, a copper tolerant brown rot organism and in soil burial both unleached and after leaching. The results suggest that, of the elements tested, fixed copper is essential for preventing soft rot attack and fixed arsenic is essential for preventing attack by a copper tolerant brown rot organism in leaching environments.
S M Gray, D J Dickinson


A bibliography of organic solvent-based wood preservatives
1973 - IRG/WP 313 E
H Alliot


Fungal degradation of wood treated with metal-based preservatives. Part 2: Redox states of chromium
1996 - IRG/WP 96-10164
Concerns have arisen about the leaching of heavy metals from wood treated with metal-based preservatives, such as chromated copper arsenate (CCA). Of particular concern is the toxic redox state of chromium and arsenic in aging and decayed CCA-treated wood. Generally, hexavalent chromium is more toxic than trivalent chromium and trivalent arsenic is more toxic than pentavalent arsenic. The desired outcome from treating wood with CCA is total change of Cr(VI) to Cr(III) and As(III) to As(V). As part of an on-going study to determine the fate of copper, chromium and arsenic during aging and decay of CCA-treated wood, we detected Cr(III) and Cr(VI) in situ in CCA-treated southern yellow pine lumber. The redox states of Cr were determined using synchrotron X-ray fluorescence spectroscopy (SXRF). An SXRF microprobe was used to to detect Cr redox states by measuring X-ray absorption near-edge structure (XANES). The ratio of Cr(III) to Cr(VI) was determined (1) on the surface and interior of lumber two years after CCA treatment and (2) in lumber during decay by a CCA-tolerant fungus, Meruliporia incrassata TFFH-294. The XANES spectrum for Cr(VI) has a strong pre-edge feature that is not present in the spectrum for Cr(III). Only the Cr(III) XANES spectrum was detected on the surface and in the interior of the wood, indicating total reduction of Cr(VI). The XANES spectrum for Cr(III) was detected in wood after 12 week decay by Meruliporia incrassata TFFH-294, indicating that the fungus does not oxidize Cr(III) to Cr(VI) during the decay process. We are currently using XANES spectroscopy to detect and map in situ redox states of As in CCA-treated wood.
B Illman, S Bajt, T L Highley


The effective control of moulds on freshly impregnated wood
2004 - IRG/WP 04-30352
Beside natural timber it is known, that moulds can also groth at the surface of impregnated wood. This material shows “defects” like resistant dark spots or color changes and causes complaints. During the last years, the problem by moulds seems to increase. Laboratory studies were carried out to show the effect of impregnations against moulds. Wood samples (Pinus sylvestris L.) were impregnated by vacuum process using two industrial chromium-free copper based wood preservatives and a CCA-salt. Furthermore fungicides of isothiasoles as “mould-protection-chemicals” were added to the impregnation solutions. To consider an aging effect of this chemicals the modified solutions were stored at temperatures of 20°C or 40°C for 7 days. Direct after impregnation or after 4 weeks of conditioning the samples a mixture of moulds (Aspergillus niger, Penicillium cyclopium, Penicillium funiculosum, Paeciliomyces varioti, Trichoderma viride) were used to infect the impregnated material. The growth of moulds were observed after different times. The intensity of the growth of moulds was different during the first days, but already after 10 to 14 days all samples had complete moulds at the surface. Therefore none of the wood preservatives was protecting the samples against moulds. In the case of sample impregnations using wood preservatives with additional mould-protection-chemicals a various resistance of the impregnated wood on mould infection was found. The resistance depends on the combination of the type of wood preservative and the fungicide used. Differences caused by the aging test could be observed. It can be deduced from these results that this investigation method can help to answer questions concerning necessity, suitability and the appropriate type or content of mould-protection-chemicals in impregnation solutions.
G Cofta, K Lutomski, P Jüngel


The chemical analysis and biological evaluation of wood extractives as potential timber preservatives
1995 - IRG/WP 95-30090
Work involved the biological performance of water and organic solvent soluble extractives of four naturally durable wood species, namely; Matumi, Tamboti, Sneezewood and the Turpentine tree. These timber species are known to be naturally durable against termites and fungi (±25 to 35 years). The extractives were evaluated against termites and fungi using impregnated pine pencil stakes in field tests and soil burial trials over a 2 year period. C13NMR analysis of extractives isolated from the wood was carried out to try and identify the key chemical components which might impart durability with a view to prediction of new potential wood preservative formulations.
P Turner, D Conradie


Performance of copper-based wood preservatives in above ground and ground contact tests
1994 - IRG/WP 94-30057
The relative performance of a range of copper-based wood preservatives was compared using above ground and ground contact procedures. The data, accumulated after several years' testing, show that on an equivalent active ingredient basis, differences in performance of the preservative systems tested can vary quite markedly. The contribution of co-biocides to the overall performance of these copper-based systems is discussed.
A F Preston, K J Archer, L Jin, W Metzner, D Seepe


Assessment of the toxicity of some copper-, zinc- and boron-based wood preservatives to the cellar fungus Coniophora cerebella Schröet
1974 - IRG/WP 242
This article reports the use of a method based on the determination of the probability of the protection of timber against destruction by fungi. By converting the probability values to probit values and plotting them as a function of the amount of preservative retained in the timber, curves of the toxic effect are obtained, enabling any timber protection probability to be assessed.
V N Sozonova, D A Belenkov


Experiences with penetration of copper-based wood preservatives
2001 - IRG/WP 01-20233
In the Nordic countries there is a long tradition of result type based specifications for preservative-treated wood. A common Nordic standard for treated pine (Pinus sylvestris) wood was published in 1976. After a revision in 1989 this standard, then named INSTA 140, defined four classes of treated wood: M, A, AB and B. Treaters producing according to this standard had to be affiliated to a quality control and certification scheme. When the European standards EN 351 and EN 599 were to be implemented, the Nordic Wood Preservation Council issued a Nordic application document where the traditional wood preservation classes were defined in terms of EN 351 and EN 599. The present paper describes briefly how the European standards have been implemented in the Nordic countries. During the last years the use of CCA-preservatives has been restricted in the Nordic countries. New copper-based, chromium and arsenic free preservatives have been introduced for commodities above ground. This has by no means been without complications. The treaters have had severe problems to comply with the treatment requirements. Pilot plant treatment trials confirm that the penetrating properties of the chromium/arsenic free preservatives differ substantially from CCA. Experience from the Nordic quality control and certification scheme shows that it is often difficult to judge the penetration of the chromium and arsenic free preservatives. Different copper reagents give different results. A comparative test showed that ammoniumhydroxide and rubeanic acid as reagent for copper was the most sensitive to copper and performed better than other reagents tested.
J Jermer, F G Evans, I Johansson


The implementation of restrictions on the use of arsenic and chromium based wood preservatives in Sweden
1995 - IRG/WP 95-50062
In 1992 the Swedish National Chemicals Inspectorate introduced restrictions on the use of wood treated with arsenic and/or chromium based wood preservatives. Such wood is now in principle only allowed for use in ground contact or in water. These restrictions have had considerable influence on the use of wood preservatives for sawn timber for the Swedish domestic market. Thus only 35% of the preservative treated sawn timber for the domestic market was treated with CCAs in 1994 compared with as much as 85% in 1991. Use of arsenic and chromium free preservatives resulted in a share of more than 50% in 1994 for treated sawn timber for the Swedish domestic market.
J Jermer, M-L Edlund, K Nilsson


Serpula lacrymans, The Dry Rot Fungus and its Tolerance towards Copper-based Wood Preservatives
2005 - IRG/WP 05-10555
Serpula lacrymans (Wulfen : Fries) Schröter, the dry rot fungus, is considered the most economically important wood decay fungus in temperate regions of the world i.e. northern Europe, Japan and Australia. Previously copper based wood preservatives were the most commonly used preservatives for pressure treatment of wood for building constructions. Because of a suspicion about tolerance toward copper components, a soil block test was undertaken to clarify the effect of two copper based preservatives, copper citrate and ACQ-D, on the dry rot fungus, Serpula lacrymans compared to an alternative non-copper containing wood preservative. The extensive use of copper-based wood preservatives has hastened the need for understanding why some fungi are able to attack copper-treated wood. The copper tolerance of S. lacrymans and other brown-rot fungi is thought to be due in part to oxalic acid production and accumulation. Oxalic acid has been implicated in copper tolerance by the formation of copper oxalate crystals. Twelve isolates of the dry rot fungus, S. lacrymans and four other brown rot species were evaluated for weight loss on wood treated with 1.2% copper citrate, 0.5% ACQ-D and 0.5% N’N-naphthaloylhydroxylamine (NHA). Eleven out of 12 S. lacrymans were shown to be tolerant towards copper citrate. ACQ-D and NHA, on the other hand, were both effective against the dry rot isolates. These wood preservatives are less toxic toward the environment than traditional copper based preservatives.
A C Steenkjær Hastrup, F Green III, C A Clausen, B Jensen


Observations on the performance of copper-based wood preservatives in fungal cellar (soil-bed) tests
1994 - IRG/WP 94-20047
Fungal cellar (soil-bed) tests are considered to be an important tool for the evaluation of the performance of ground contact wood preservatives. Facilities of this type have been established world wide although caution has been exercised in their introduction into standard testing methods for the approval of wood preservatives. This is the result of concerns over the variability in the biological activity between different facilities, and thereafter the determination of effective preservative retentions. This paper presents results of tests on copper based wood preservatives from four different fungal cellar facilities. The results show consistent trends in preservative performance and the high decay rates demonstrate the value of this type of test in determining the potential of new wood preservatives for long term protection in ground contact.
G R Williams, D Rudolph, M E Hedley, J A Drysdale, R F Fox


Environmental fate of copper-based wood preservatives in different soil substrates - Part 2: Study of the metal sorption and migration potential under simulated rainfall
1998 - IRG/WP 98-50101-21 b
In order to examine the potential environmental impact of spillages of the saltborne wood preservative CCA in treatment plants, four large scale experiments are set-up so as to follow the water transport and ion mobility in various field soils. A plastic container is filled with a sand, silt, clay and potting soil, made up at their respective bulk density and wetted to a given moisture content. Using a rain simulator on top, a homogeneous spillage of a ready-to-use CCA solution is applied, followed by a rainfall simulation after 3 days and a 3 weeks redistribution period. Soil augers that are taken prior to each new perturbance reveal the distribution and migration pattern of the heavy metals. Copper and arsenic are strongly adsorbed in the upper soil layers, depending on the soil characteristics. Chromium, however, is percolated easily through the soil column and is readily extractable from the soil using pure water.
G M F Van Eetvelde, R Hartmann, J M Mwangi, H S Öztürk, M Stevens


Tolerance of Wood Decay Fungi to Commercial Copper Based Wood Preservatives
2002 - IRG/WP 02-30291
Due to the use of copper based preservatives like CCB or CCA for more than a century, copper tolerant fungi have appeared in some European countries in recent times. It is therefore important to find out whether this phenomenon is specific for only classical copper ingredients, or generally for all copper based formulation. Thus, we tested the tolerance of three commercial copper based preservatives and copper(II) sulphate as well as potassium dichromate for comparison. In this research, seven copper tolerant Antrodia isolates and copper intolerant fungus Gloeophyllum trabeum were tested using a screening test and standard laboratory test SIST EN 113. Screening test were performed on potato dextrose agar (PDA) with copper concentration between 5.0×10-4 and 2.5×10-2 mol/l. The tolerance determined by the screening test was not always comparable with results obtained with the standard laboratory test. However, results obtained on wood samples showed that various fungal isolates exhibited different levels of copper tolerance depending on the copper based biocide. Tolerant strains were able to decay copper sulfate as well as copper naphthenate preserved wood samples. On the other hand, even the most tolerant fungi could not decompose wood preserved with classical CCB or copper amine preservative. It can therefore be concluded that various fungal isolates exhibited different copper tolerance regarding copper formulations. This finding is very important for remediation of waste treated wood by fungi. For a successful detoxification of waste wood impregnated with multi salt preservatives like CCA or CCB the suitable tolerant fungal strains have to be used, simultaneously for synergistic action.
F Pohleven, M Humar, S A Amartey, J Benedik


Influence of carboxylic acids on LEACHING of copper amine based preservatives
2005 - IRG/WP 05-30365
The importance of chromium free preservatives is increasing. Leaching of copper from wood preserved with such solutions is still higher compared to leaching from wood impregnated with copper chromium ones. In order to decrease leaching, different carboxylic acids (octanoic, 2-etilheksanoic, decanoic) were added to copper/amine/boron aqueous solutions. Experiment of leaching of copper from Norway spruce (Picea abies) was performed according to the modified standard procedure (EN 1250). Results presented in this paper showed, that carboxylic acids significantly improve copper fixation. The best one was determined at specimens impregnated with the preservative solutions consisting of copper, ethanolamine, boric acid and octanoic acid.
M Humar, P Kalan, F Pohleven


Environmental fate of copper-based wood preservatives in different soil substrates - Part 1: Screening of the metal adsorption potential
1998 - IRG/WP 98-50101-21 a
In treatment plants, spillage of wood preservatives onto soil may be of environmental concern. This potential soil contamination served as an objective for a screening study. Three different mineral soils, a mineral substrate and two horticultural substrates are examined for their sorptive potential of copper through mixing with wood preservative solutions. Depending on the soil/substrate characteristics and the chemical nature of the preservatives used, copper is adsorbed to a higher extent with increasing concentration of the test solution. Soils with low organic matter and clay content show an upper limit of adsorption, irrespective of the product tested. The other soil types clearly exhibit a levelling-out effect from 2 to 4 hours on, often correlating with the initial metal concentration of the product though dependent on the chemical nature and buffering capacity of the active ingredients.
G M F Van Eetvelde, J M Mwangi, F Tack, R Hartmann, M Stevens


Applicability of supercritical carbon dioxide to the preservative treatment of wood-based composites
2001 - IRG/WP 01-40199
Treatability of five structural-use wood-based composites (medium density fiberboard, hardwood plywood, softwood plywood, particleboard and oriented strand board) was evaluated when supercritical (SC) carbon dioxide (CO2) was used as a carrier solvent. Treatments were conducted at three temperature 32 levels (25, 35 and 45°C) and two pressure levels [80 kgf/cm2 (7,845 kPa) and 120 kgf/cm2 (11,768 kPa)]. Although small changes in weight and thickness of the wood-based composites were caused by treatments with SC-CO2, all treated materials did not sustain any physical damage. These results suggest that the treatment conditions provided the immediate penetration of SC-CO2 into the wood-based composites without any critical pressure gradient between outer and inner zones. Strength properties of the treated wood-based composites significantly improved after treatments in most cases. In contrast, a remarkable drop in strength properties occurred in oriented strand board specimens. Further studies are underway to determine the optimum treatment conditions using biocides incorporated into the mixing or treating vessel.
M Muin, A Adachi, K Tsunoda


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