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Depletion of boron and copper from CCB treated test specimens using different leaching protocols
2004 - IRG/WP 04-50208
The objective of this study was to measure the depletion of inorganic wood preservative components regarding the proposed OECD guideline "Estimation of emissions from preservative-treated wood to the environment: laboratory method for wooden commodities exposed in the use class 4 and 5" as part of the project "Investigations concerning the influence of test parameters on the release of biocidal actives from treated timber in leaching tests". Pine sapwood specimens (50x10x150) were pressure impregnated with CCB according to European Use Class 4. Before leaching all samples were stores 4 weeks for fixation. In addition leaching tests were performed according to the European Standard EN 84 by means of EN 113 blocks. Parallel investigations were carried out between two laboratories to assess the repeatability and comparability of the methods. The results of chemical analysis of leachates taken at different time intervals show that similar depletion rates were determined for copper and boron independent on the leaching protocol used. However, the loss of copper as well as chromium in short term dipping experiments was often lower than the detection limit. Furthermore it can be stated that the difference between parallels was higher for the results which were obtained for the OECD guideline that EN 84. A comparison of both laboratory results indicate that a quite good repeatability is given in case of the CCB treated material.
E Melcher, R-D Peek, U Schoknecht, R Wegner


Analysis of creosote posts after 40 years of exposure
1994 - IRG/WP 94-50035
In the early 1950s The Western European Institute for Wood Preservation (WEI) started a program for testing creosote and salt treated posts in three exposure sites in Europe. Of these only the site in Simlångsdalen in south western Sweden remains today. The purpose with this investigation was to demonstrate which creosote components are still retained in the posts after 40 years of exposure and which components have migrated or evaporated. Three posts, impregnated with three different creosotes, from the site in Simlångsdalen have been studied. The retention, composition and distribution of creosote in the posts have been determined and compared with data on the original creosote. After 40 years of exposure creosote loss is greatest in the post impregnated with creosote containing the highest fraction of low-boiling constituents. The loss is greatest in the top sections of all three posts. The concentrations of low-boiling compounds (b.p. < 270°C), e.g. naphthalene and 2-methylnaphthalene are very low. The residual creosotcs have the greatest percentage of high-boiling constituents (> 315°C), especially phenanthrene and anthracene (b.p. 340°C). The soil close to those posts which were "over-loaded" with creosote during the treatment process, contains increased concentrations primarily of the heavier components fluoranthene, pyrene and chrysene. The small number of posts analyzed limits the possibility to generalize the conclusions.
G Bergqvist, S Holmroos


Depletion of wood preservatives after four years' marine exposure in Mt. Maunganui harbour, NZ
1994 - IRG/WP 94-50036
This paper reports on chemical analysis of marine test samples exposed in Mt. Maunganui harbour, New Zealand from 1977 to 1981. Depletion data for a Class II CCA, a CCA-A formulation, acid copper chromate and ammoniacal copper arsenate are presented. The results suggest differences in the rate of loss of individual preservative components among the four formulations and redistribution of individual preservative components within the wood.
K J Archer, A F Preston, C M Chittenden, D R Page


Stability and performance of tributyltin compounds
1984 - IRG/WP 3275
Based on the critical examinations of the disputable permanence of tributyltin compounds in wood, this paper deals with a number of examinations of the relative evaporation, thermal stability and oxidation stability of some TBT-compounds. While thermal and oxidative stability is high for all TBT-species, the relative evaporation at elevated temperature is highly variable, and lowest for the TBT-esters examined. Evaporation measurements on treated wood confirm this order of precedence and stress the importance of the preservative formulation. The results also indicate that TBTO evaporates 2-3 times faster than TBTN. It is established that at high retention of TBT in wood the decomposition is slower than at low retention. This fact combined with the extra high retention of TBT in vacuum treated joints of window frames explains the fine record of non-failure for such windows, and the paper ends up with a calculation indicating the presence of sufficiently high amounts of tributyltin for effective fungicidal protection of Nordic class B impregnated windows for at least 20 years.
F Imsgard, B Jensen, H A B Landsiedel, H Plum


Polyflavonoid tannins - From a cause of CCA soft-rot failure to the "missing link" between lignin and microdistribution theories
1986 - IRG/WP 3359
Polyflavonoid tannins are proven to be fast-reacting with CCA solutions and hence, to be strong competitors of the structural wood constituents for fixation of CCA preservatives. The consequence of this effect is that even relatively small amounts of tannin cause severe undertreatment of the structural wood constituents which in turn badly affects the long term durability of CCA-treated timber. The effect is compounded by heavy disproportionation between tannins and structural wood constituents of Cu, Cr and As. This leads to the well-known high susceptibility to soft-rot attack in Eucalyptus species and in vineyard posts even experienced with some susceptible softwoods. Relationships found by other authors between soft-rot incidence and lignin content in CCA-treated timber are shown here to be only part of the total failure mechanism. The total mechanism of resistance and failure is due to the balance of distribution of reactions among the various proportions of highly reactive tannins and more abundant but less reactive lignin and carbohydrates present in any wood. As a consequence of the clarification of these mechanisms the liability of different woods to soft-rot attack may then be determined. Solutions to the problem are presented and discussed. Lignin and microdistribution theories are shown to be both correct and different facets of a single unified theory. Better-performing CCA formulations for tannin-containing softwoods are proposed and proved to be effective. Directions under investigations for better performing CCA formulations for hardwoods are discussed. Inorganic waterborne preservatives formulations "precipitating", not "fixing", such as simple CrIII arsenates or ammoniacal copper arsenites, can be deduced to be better suited for Eucalyptus preservation than CCA itself.
A Pizzi, W E Conradie, M Bariska


Sludge formation in timber treatment with CCA preservatives. Origin and elimination
1984 - IRG/WP 3276
The exact distributions between lignin and holocellulose and retentions on wood of copper, chromium and arsenic as a function of various sets of conditions in a factorial experiment in which combinations of three temperatures of treatment, three CCA solution concentrations, four pH&apos;s of the initial CCA solution and two timber species, namely Pinus radiata and Eucalyptus grandis, are reported. Temperature and concentration appear to have an equally important effect on the preservative chemicals retentions and distribution in timber. pH, has also an effect but somewhat less marked than temperature and concentration, with the exception of the formation of sludges. Multivariable regression equations describing the amounts of Cu, Cr and As fixed on lignin and holocellulose for both pine and eucalyptus are also presented. The timber species treated also appears to have an important influence on the amounts of chemicals fixed and their distribution. Eucalyptus appears to be much less tolerant than pine to extremes of treating conditions. The influence of treating time under the most common treating conditions is also briefly discussed.
A Pizzi, W E Conradie, A Jansen


An investigation into the influence of soil cation exchange capacity on preservative component depletion
1994 - IRG/WP 94-20050
The mobility of preservative components from treated wood into the soil environment is regarded as an important determinant of preservative performance. Standard procedures for the investigation of this phenomenon have not been developed to any great extent. Soil bed studies conducted in this laboratory using natural soil and modified soil media have provided interesting comparative data on the influence of cation exchange capacity on preservative depletion. Some of these data are discussed with reference to the development of a standard soil contact depletion procedure.
K J Archer, L Jin


Effect of soil parameters on biocide depletion: laboratory and field studies of water- and emulsion-borne preservatives
2000 - IRG/WP 00-30234
Two field test sites with different soils were selected. Soil analysis showed that the soil at the two sites had considerable texture, base saturation, acidity, and cation exchange capacity differences. Five sets of field stakes were treated as follows: three with water-borne CCA to about 0.4 pcf (6.4 kgm-3) retention, one with 0.75% DDAC, and one with 0.75% DDAC:0.25% chlorothalonil. The last two sets were treated using oil-in-water emulsions. Samples from all five sets were installed at both field sites. In addition, wood samples which had been co-treated with the five sets of field stakes were installed in a lab environment in fungus cellar tubs using soils from the two sites. All wood samples were defect-free southern yellow pine (SYP) sapwood, with the field stakes measuring 19 x 19 x 457 mm3 and the fungus cellar samples measuring 5 x 19 x 250 mm3. The field samples were exposed for two or three years and the fungus cellar samples for 36 weeks, after which depletion of the various biocides was measured. No consistent pattern in CCA depletions between the two soils were observed in either the fungus cellar or field exposure tests, despite the large chemical and physical differences between the two soils. The fungus cellar method may be useful to conduct relatively rapid depletion studies. The authors also discuss problems with depletion studies, including possible influences by soil, wood, and microorganisms present in the soil.
T Schultz, D D Nicholas, D E Pettry, M G Kim


Black Stain of Western red-cedar by Aureobasidium pullulans and its Relationship with Tropolone Depletion
2005 - IRG/WP 05-10564
Western red-cedar is valued for its natural durability conferred by fungicidal tropolone chemicals. However, weathered surfaces of WRC products are still susceptible to ‘black stain’ caused by fungi such as Aureobasidium pullulans. The effect of weathering on the tropolone content of heartwood was characterized and correlated with the ability of this fungal species to colonize the same weathered surfaces. UV plus water spray severely reduced tropolone content but did not lead to increased fungal colonization compared to un-weathered wood. When WRC was treated with UV only, the tropolone content was less affected but the fungal colonization increased significantly. A.pullulans exhibited high tolerance to the tropolone &#946;-thujaplicin in vitro; thus loss in tropolone content may not be required for colonization. In addition to UV resistance from melanization and ability to use lignin breakdown products as a carbon source, resistance to tropolones may confer considerable competitive advantage to A.pullulans growing on WRC exposed to weather. The application of water spray most likely washed away products of lignin photo-degradation, leaving the wood surface void of accessible carbon sources which resulted in decreased colonization.
R Chedgy, R Daniels, P I Morris, C Breuil


Losses of preservatives from treated wood during service. Results from a questionnaire
1994 - IRG/WP 94-50031
From environmental as well as from performance point of view it is of interest to know how much of the preservatives in treated wood that is leached out or evaporated from the wood during service. Many laboratory studies are carried out on leaching from small samples in distilled water or water with different pH. These studies give a good picture of the relative leaching from wood treated with different preservatives, but the results are only true for the actual conditions and not representative for treated wood in service. In many reports on studies concerning treated wood in service the remaining preservatives are analysed, mainly to get to know if the remaining amount of preservatives can prevent the wood from biological attack. Seldom is the initial preservative retention known and therefore the leached amount is not known. To get more facts a questionnaire on leaching during service was sent out to all IRG-members in 1991. 29 answers were received, most of them in form published documents but also information from some unpublished studies. Many of the answers concern results from analyses of field test stakes and very few results from analyses of treated timber in constructions. In some cases laboratory studies of leaching are reported in the same documents. Several documents report only on laboratory experiments. All relevant results are put together in Table 1. Reports only referring to laboratory studies are not included. The reports in Table 1 are in the same order as they were received. In Table 2 all results concerning CCA are put together. These results give a good picture of the difficulties to draw conclusions on leaching during service.
M-L Edlund


Laboratory studies of CCA-C-leaching: influence of wood and soil properties on extent of arsenic and copper depletion
2002 - IRG/WP 02-50186
The extent which a wood preservative leaches is important for efficacy studies and environmental concerns. However, little information exists on the effect soil properties have on leaching. This study investigated leaching of stakelets which had been cut from five different southern yellow pine (SYP) sapwood boards then treated with CCA-C to a target retention of 6.4 kgm-3 (0.4 pcf). All stakelets were leached for 12 weeks by a common laboratory method in five different soils or water, with five replicate stakelets per board/soil. The physical and chemical properties of the five different soils were determined and the average leaching of the individual components of CCA was correlated with the various soil properties. Unfortunately, migration of a soil component (likely iron) into the stakelets from at least one of the five soils interfered with Cr determination by X-ray fluorescence; consequently, Cr depletion was not studied. Stakelets cut from one board tended to have lower Cu and As losses than the average of the other four boards for all five soils and water, and stakelets from another board tended to have higher Cu losses. Stakelets from all five boards had similar initial Cu and As levels, suggesting that the board effect was not due to differences in initial retentions. Cu loss was approximately equal to or greater than As loss for stakelets exposed to all five soils, but for wood leached in water the As loss was about twice the Cu loss. The soil property which was most statistically correlated to Cu loss was % Base Saturation (r2 of 77%), with Soil Acidity (pH) also important as a single predictor, and the Cr and Cu Soil Contents important as secondary predictors. The relationship between % Base Saturation (or Soil Acidity) and % Cu leached was not linear, however. A negative correlation was observed between Soil Cu Content and the metal leached from wood. The best factor to predict As loss was the Soil Cu Content, with Exchangeable K and % Silt also contributing to give an overall r2 of 72.3%. The % Organic Matter and the Soil As Content were also important as secondary predictors. We conclude that depletion of CCA is extremely complex and that Cu and As depletion appears to be influenced differently by the soil properties. Furthermore, extent of leaching can vary between different wood samples of the same species and even samples cut from the same board; thus, leaching data are not precise. Recommendations are given for a standard laboratory method for ground-contact leaching.
D Crawford, R F Fox, D P Kamden, S T Lebow, D D Nicholas, D Pettry, T Schultz, L Sites, R J Ziobro


The efficacy of polymer/preservative treatments in soil-bed exposure
1992 - IRG/WP 92-3729
Southern pine was treated with CCA, CCB, sodium borax/boric acid, or disodiumoctaborate, alone or in combination with an acrylic polymer system containing a water repellent. Treated samples were subjected to an unsterile soil burial test. The addition of polymer reduced the weight loss in borontreated samples at the lower retentions but not at the higher retention. Results with borates indicate that polymers may improve performance in above-ground applications. Polymer treatments improved the performance of CCA and CCB at retentions below threshold, indicating the potential for modifying CCA/CCB formulations.
R J Murphy, H M Barnes, S M Gray


Working plan: Second international collaborative field trial
1995 - IRG/WP 95-20056
This paper describes the scope, objectives, and approaches to be used in the second international collaborative field trial approved by the Scientific Programme Committee for partial funding in 1994. The trial is designed to develop a broad data base on causal mechanisms, interactions, and factor affecting the performance of treated wood in ground contact. The trial encompasses 12 different field test sites representing all continents except Antarctica. Preservatives were chosen to represent new technologies and include oilborne, waterborne copper-organic, and water-dispersible systems. CCA is used as the reference system. Task forces to research the following areas are described: accelerated soilbed testing, decay types/modes of failure, preservative depletion, abiotic factors, and copper tolerance.
H M Barnes, T L Amburgey


A comparison of the leaching resistance of copper 2-ethanolamine and copper ethylenediamine treated Scots pine
2000 - IRG/WP 00-30233
The depletion of copper from copper 2-ethanolamine and copper ethylenediamine treated Scots pine blocks was investigated. A greater leaching resistance was found for copper 2-ethanolamine, which retained ca. 86% and ca. 50% copper after water and buffer leaching, respectively. Leached amine treated blocks also contained significant residual amine. This was consistent with other observations linked to the formation of amine acid salts in amine treated wood. The results also suggested that significant loss of copper, due to formation of copper acetate can occur.
Xiao Jiang, J N R Ruddick


A trial of "sour" felling to prevent bluestain by depletion of sapwood nutrients
2001 - IRG/WP 01-10404
Discoloration of conifer wood caused by bluestain causes large economic losses in Canada. Most deep stain develops in the log stage during storage or transport. In a search for control strategies that will not disrupt woodlands productivity we tested "sour" felling, termed "hagarashi" in Japan. The practice involves delaying the delimbing of freshly harvested trees. The tree continues to transpire and to respire. This could result in partial drying of the wood and/or faster depletion of sapwood nutrients needed for the growth of bluestain fungi. Field experiments were done compared sour-felled trees with ones immediately processed by a harvester/delimber. We examined the development of stain and also analyzed sapwood nutrients. The latter included lipophilic extractives, phenolics, soluble sugars, starch and total nitrogen. There was no stain in both sets of trees, attributable to unfavourably cool weather. The viability of ray parenchyma cells and the moisture content remained similar in both sets of trees. Despite being unable to show a benefit in reduced stain this work provided baseline data for the levels of the extractives in fresh and stored lodgepole pine trees. Starch was depleted to 20-30% of its original amount over the six week period, presumably as it was used by the dying tree.
A Byrne, A Uzunovic, D Minchin, C Breuil


Quantification of creosote migration down wooden poles and the prevention of its depletion during flood irrigation
1994 - IRG/WP 94-50032
Polyethylene field liners heat-shrunk onto soil-contact surfaces prevented decay of creosote-treated Eucalyptus grandis vineyard poles under flood-irrigation. The present work quantified losses of creosote from these poles after six and 24 months&apos; service. After six months&apos; service the mean creosote retention of unlined poles above the ground line was 12.62% (m/m dry wood), with sample retentions decreasing progressively to 4-6% at the ground line and 2-3% throughout their sub-soil profiles. These values remained similar after 24 months&apos; service. The mean creosote retention above the ground line of lined poles after six months&apos; service was 13.06%, however sample retentions did not decrease towards the ground line, and these remained between 13-17% throughout the sub-soil profile. After 24 months&apos; service the mean creosote retention above the ground line of the lined poles had fallen somewhat, but sample retentions remained over 12% at, and below, the ground line. The results showed that, while slight creosote evaporation from wood above ground may have ocurred, the major phenomena affecting creosote retentions in unlined poles in soil were gravitational migration and leaching to soil, and it seemed that these factors were coupled. Primarily, the results confirmed that creosote was lost from poles by leaching to soil, and that such loss was prevented by the application of the field liners.
M Behr, A A W Baecker


Depletion of preservatives from treated wood: Results from laboratory, fungus cellar and field test
1993 - IRG/WP 93-50001-07
This paper compares results of preservative component losses using a range of test procedures with several different water-borne preservatives. The data shows that laboratory leaching tests are in some cases comparable to, but in other cases significantly underestimate preservative component losses when compared with field or fungus cellar depletion tests. The results also suggest that preservative component losses are treatment retention and formulation dependent. It is apparent that the changing nature of wood preservative formulations, coupled with the different types of treated commodities and applications now being used, mandates the use of a wider range of test methods with multiple retentions to comprehensively assess likely loss of wood preservative components in service. The paper addresses a number of these issues and also presents test methods which may be suitable for further development in the area of preservative depletion.
L Jin, A F Preston


Leaching of components from CCF treated timber in ground contact
1998 - IRG/WP 98-50108
In order to investigate the depletion of different CCF-salts during service small stakes (10*10*450mm³) were treated with five water-borne wood preservatives and after fixation brought into ground contact for several years. After failing some of the broken down stakes were used to determine the remaining concentration of relevant ions and their distribution in different segments of the stakes. As expected the content of the components in the stakes decreased with time. Furthermore the results show that the remaining concentration of copper, chromium and fluorine differ depending from the wood preservative used and from the position of the segment in the stake. Only up to 20% of the fluorine was found in the stakes whereas up to 100% of chromium or copper was left. The highest F concentration was determined in the samples when hexafluorosilicate was used in the formulation of the water-borne wood preservative. On the other hand the results show clearly that irrespective of the ion investigated, by far the largest amount was analysed in the fracture zone.
E Melcher


Effect of soil chemistry and physical properties on wood preservative leaching
1998 - IRG/WP 98-50111
When treated wood is placed in contact with soil, complicated mass transfer and chemical reactions occur which causes the preservative components to leach from the wood. There are several factors that are known to affect the amount of chemical leached from wood. These are properties of the preservative and carrier, preservative retention, degree of fixation, exposure time, grain orientation, surface area of the product, wood species, and site factors. With regard to site factors, the chemical and physical properties of soil play an important role in the depletion of biocides from treated wood. The effect of soil properties on the leaching of wood preservatives has only been studied to a limited degree but appears to be a major factor in the performance of treated wood. In this study the effect of five soils with widely different physical and chemical properties on the leaching of chromated copper arsenate (CCA-C), pentachlorophenol (Penta) and didecyldimethylammonium chloride (DDAC) from southern pine was evaluated.
Joan-Hao Wang, D D Nicholas, L S Sites, D E Pettry


CCA type C depletion of Southern yellow pine utility poles
1995 - IRG/WP 95-50049
Depletion and redistribution of preservative components were evaluated on five CCA-C treated poles in service for over six years in Conley, Georgia. A statistical approach was taken in which retentions below ground were compared to retentions above ground due to a lack of initial data on individual poles. It was hypothesized that the below ground retentions should be lower than the corresponding above ground retentions based on the premiss that wood in ground contact is subject to a higher leach potential than wood above ground contact. There were no significant differences between above ground and below ground CCA-C retentions in any of the six 12.5 mm zones. Linear regression performed on the retentions across zones showed no significant difference between the slopes of the gradient curves on either exposure for any of the components indicating there has been no redistribution of chemicals among zones.
P D Osborne, R F Fox


Is Field Test Data from 20 x 20mm Stakes Reliable? Effects of Decay Hazard, Decay Type and Preservative Depletion Hazard
2006 - IRG/WP 06-20327
Effects of decay hazard, decay type and preservative depletion hazard on the performance of variously preservative treated 20 x 20 x 500 mm Radiata pine and Fagus sylvatica test stakes across 13 field test sites in New Zealand and Queensland Australia were determined. Radiata pine treated with an ammoniacal copper quaternary preservative (ACQ) (1.56% m/m a.i.) and copper chrome arsenate (CCA) (0.72% m/m a.i.) was susceptible to sudden failure at some of the sites that had a high brown rot hazard whereas pine treated with copper-azole (CuAz) (0.59% m/m a.i.) was not affected, suggesting that CuAz was particularly effective against brown rots. At the most severe brown rot sites ACQ treated pine was more susceptible than CCA and its performance in service may be compromised as a result, as previously occurred for pine treated with acid copper chromate (ACC). Based on overall performance across all sites pine treated with chlorothalonil plus chlorpyriphos (1.07% m/m a.i.) (11% mean soundness reduction (MSR)), creosote/oil treated pine (37% m/m a.i.) (14% MSR) and CuAz (15%MSR) all gave significantly better protection (5% P) than pine treated with CCA (19% MSR) and ACQ (19% MSR). The decay hazards encountered, as determined by mean soundness reduction after 6.5 years, were more severe than encountered in previous studies at some of the same sites and this was linked to differences of intra-site decay type between test plots and associated decay hazard differences. Greater decay rates encountered in this study were, in part attributed to high preservative depletion. At very wet sites, particularly those likely to have a high soil organic acid content, 20 x 20 x 500 mm stakes are probably too small for accurate interpretation of long-term durability of preservative treated wood. Knowledge of the distribution of different decay types across sites tested, coupled with associated decay hazards and preservative depletion hazard, suggested that 4 test sites of clearly defined features would enable comprehensive field testing of preservative treated wood. Selection of sites is not straightforward and requires a rudimentary knowledge of soil type, geology, vegetation and climate, or comprehensive knowledge of the decay types present. In view of the cost of maintaining test facilities, adequate multi-site testing of new wood preservatives may be achievable through cooperation between research establishments. Possibly, current test site selection criteria fall short of ensuring adequate test site parameters are incorporated and maximum cost effectiveness of testing may not always be achieved through duplication of test site parameters between sites of similar but unrecognised properties. Scope for artificial creation of intra-site decay hazard differences is discussed.
R Wakeling


Above and Below-Ground Depletion of Copper, Chromium and Arsenic from Pinus radiata and Fagus sylvatica at Thirteen Test Sites in New Zealand and Australia
2006 - IRG/WP 06-30402
The objective was to determine the significance of site and wood species on preservative depletion for a copper chrome arsenate preservative (CCA) from 20 x 20 x 500 mm field test stakes after 5.5 and 4.5 years for pine and beech respectively. At least 5 sacrificial stakes were used to produce site means. Site and wood species had a major effect on copper, chromium and arsenic loss from CCA treated pine and beech. At the most severe site above and below ground percentage losses for pine were, 36 and 73 for copper, 22 and 22 for chromium and 31 and 49 for arsenic. At the least severe site losses were close to zero for both above and below ground. Based on mean loss across all sites, the above ground portion of CCA treated pine lost less than 1% copper compared to 8% for chromium and 15% for arsenic. Increased copper (30%) loss for the below ground portion compared to the above ground portion (<1%), was much greater than for chromium (8 versus 9%) and arsenic (15 versus 22%). Whereas copper loss was most affected by below ground exposure for pine, for beech arsenic was most affected. All three elements were more susceptible to loss from beech than pine for both above and below ground exposure, except below ground copper (30% loss for pine and 28% for beech). Arsenic in particular was more susceptible to loss from beech for both above ground (32% for beech versus 15% for pine) and below ground (53% for beech versus 22% for pine). The finding that waterlogged sites, and/or sites with low pH caused greatest loss to all treatments irrespective of wood species, in the light of low loss at horticultural sites suggested that the influence of extremes of water availability and of low pH was more important than other mechanisms such as cationic exchange reactions with soil. Particularly high loss occurred at sites where soil was likely to have contained a high organic acid concentration.
R Wakeling


Above and Below-Ground Copper-Azole and Copper, Chrome Arsenate Depletion from Pinus radiata and Fagus sylvatica at Thirteen New Zealand & Australian Sites
2008 - IRG/WP 08-30460
The objective was to determine the significance of site on preservative depletion from Pinus radiata D. Don and Fagus sylvatica L. 20 x 20 x 500 mm field test stakes treated with a ground contact retention of copper amine plus tebuconazole (CuAz) and copper chrome arsenate (CCA) after approximately 5 years exposure to widely different soil and climate conditions. Site, wood species and their interactions had a dramatic and statistically significant effect on CCA and CuAz-treated pine and beach. Mean Cu depletion for radiata pine treated with 0.72% m/m a.i. CCA after 5.5 years, across 13 sites was less than 1% for above ground portions of stakes compared to 30% for below ground. However, below ground depletions at acidic sites located at a peat bog and a Nothofagus (southern hemisphere beech) forest were 43 and 73% respectively. Mean below ground chromium and arsenic depletions were 9 and 21% respectively but were 22 and 41% at the most severe depletion site (Nothofagus forest). Across all sites, mean above ground depletion of Cu and tebuconazole from radiata pine treated with 0.59% m/m a.i. CuAz, was 19 and 42% compared to 47 and 55% for below ground. Substantially greater loss of copper from CuAz treated wood compared to CCA treated wood, especially for above ground exposure, across all sites, may be significant for wood in service situations where aquatic toxicity of copper is an issue. Beech was more susceptible than pine to loss of copper for both CCA and CuAz. This may have been attributable to less efficient fixation reactions and preservative distribution (macro- and micro-) in beech. The finding that waterlogged sites, and/or sites with low pH caused greatest loss to all treatments irrespective of wood species, in the light of low loss at horticultural sites suggested that the influence of extremes of water availability and of low pH was more important than other mechanisms such as cationic exchange reactions with soil. Particularly high loss occurred at sites where soil was likely to have contained a high organic acid concentration.
R Wakeling


Depletion and Redistribution of Boron in Bundles of Commercially Treated Lumber Exposed to Artificial and Natural Rainfall
2008 - IRG/WP 08-30474
The depletion and redistribution of boron from stacks of Southern Yellow Pine lumber pressure treated with disodium octaborate tetrahydrate (DOT) and exposed to artificial and natural rainfall was examined. When the lumber was exposed to periodic simulated rainfall, 5.7-8.1% of the measured boron present leached from the lumber after exposure to over 300 mm of rainfall. In tests which exposed boards to natural rainfall for 6-8 months, an estimated 9.7-14.9% of the calculated boron migrated from the stacks. In both tests, the majority of the exposed lumber retained boron levels at or above the AWPA standard suitable for exposure to Formosan termites of 4.48 kg/m3. In a harsher exposure test, DOT treated boards were submerged for over one month and representative boards were periodically removed to examine changes in boron levels. After 18 days of submergence a significant amount of boron had depleted from the test lumber. However, subsequent samplings showed lower levels of boron leached from submerged test boards. These results demonstrate that depletion of boron from dimensional lumber exposed to moderate amounts of liquid water should not result in significant decreases to boron levels in the wood.
M E Mankowski, M J Manning


Effect of a biological treatment on below ground decay of Douglas-fir pole sections
2008 - IRG/WP 08-40433
The use of exogenous sugars to accelerate microbial growth and eventually limit available oxygen in soil surrounding wood in soil contact was investigated on untreated Douglas-fir poles exposed over a 3 year period in Western Oregon. Isolation frequencies differed markedly between treated and untreated poles and the treatment did appear to shift the frequency of some basidiomycetes. The treatment was also associated with slight, but not significant delays in loss of surface integrity for the first 2 years of the test. These differences, however, disappeared after 3 years. The results suggest that exogenous sugars can alter the composition of the fungal flora in the soil surrounding untreated wood in soil contact, but the decay capabilities of that modified flora do not differ markedly from that present in the unaltered soil.
C Freitag and J J Morrell