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Qualifying ecotoxicity research on tropical hardwood leachates
1997 - IRG/WP 97-50096
Almost as a rule, quantification and identification of various types of environmental contamination is grounded on chemical evaluation principles. Yet for monitoring surface water pollution, aquatic bio-assays may provide a more direct way to assess the potential hazard of environmental samples. A battery of such tests is experienced onto leachates of tropical hardwoods used in ground and water contact. Four of seven wood species tested exhibited no acute toxic profile, whilst afzelia, afrormosia and mainly merbau revealed a considerable toxicity response for all organisms tested. These results, although at screening level, demonstrate the natural toxicity of particular tropical hardwood extractives towards the aquatic compartment. Hence, a welcome source of information is obtained, so as to weigh the ecotoxicity results previously gathered on preservative treated wood.
G M F Van Eetvelde, P Marchal, M Stevens


Danish wood preservatives approval system with special focus on assessment of the environmental risks associated with industrial wood preservatives
2001 - IRG/WP 01-50166-01
The following is a description of the procedure used by the Danish Environmental Protection Agency to assess the environmental risks associated with preservatives used in the pressure impregnation of wood. The risk assessment covers issues considered to be of significance for the environment and which are adequately documented so as to allow an assessment. Such issues are persistence and mobility in soils, bioaccumulation and the impact on aquatic and terrestrial organisms. Unless required in special circumstances, the assessment does not apply to birds and mammals as the normal use of preservative treated wood is not expected to involve any noteworthy exposure of these groups. Approval of wood preservatives will be based on a general assessment of the environmental risk associated with the normal use of wood treated with the preservative in a realistic worst case situation. The assessment may address other aspects such as disposal and total life cycle.
J Larsen


Biological screening assays of wood samples treated with creosote plus chemical additives exposed to Limnoria tripunctata
1980 - IRG/WP 408
Laboratory methods for exposure of treated wood coupons to Limnoria tripunctata are described. Chemical additions to creosote were screened using this method. Three pesticides, Endrin, Kepone, and Malathion proved particularly effective. The addition of varying percentages of naphthalene to creosote using several treatment methods are currently being assayed. Results to date show that the coupons treated by the empty cell method have better performance than those prepared by the toluene dilution method. The naphthalene coupons treated by the full cell method show no attack after six months' exposure.
B R Richards, D A Webb


Use of vermiculite as substrate in assays on phytotoxicity of treated wood
1989 - IRG/WP 3547
It is considered the possibility of using vermiculite instead of soil as substrate in assays on phytotoxicity of wood treated with preservatives for agricultural use. Three organic preservatives were used. It had been tested the behaviour of both, vermiculite and soil in case of preservative leaking due to a leach. So that, assays of germination with cucurbitaceous were carried out, mixing a dose of preservatives with both substrates.
M V Baonza Merino, D Franco


Utility, deterioration and preservation of marine timbers in India
2005 - IRG/WP 05-40314
Timber is extensively used in India in the marine environment for various purposes due to its several advantages over modern materials. Infact, its use is increasing in recent years, finding wider and wider applications and this scenario is not going to change in the near future. Though, the bio-deterioration problem is found very severe in tropical waters, still indigenous methods are widely employed for the protection of fishing craft and the present level of chemical treatment is well below 5% of total timber used. This is due to socio economic problems of the potential timber user groups, unavailability of treatment plants in the coastal areas, lack of awareness in user groups, etc. In this paper, types of fishing craft used in the country, timber uses in the marine environment, bio-deterioration losses, research conducted on bio-deterioration aspects at various places and methods applied for the protection of wooden structures are presented.
B Tarakanadha, M V Rao, M Balaji, P K Aggarwal, K S Rao


Creosote movement from treated wood immersed in fresh water: Initial PAH migration
2003 - IRG/WP 03-50201
Creosote has a long history of successful use as a wood preservative, but polycyclic aromatic hydrocarbons (PAHs) in this preservative have raised environmental concerns, particularly when creosote-treated wood is used in aquatic environments. A number of models have been developed to predict the risk of creosote use in aquatic environments, but one limitation of these models is a lack of data on the initial rates of creosote migration from treated wood. We examined the effect of flow rates on creosote migration from freshly treated wood immersed in fresh water. Creosote component levels declined to a steady state within 7 days, suggesting that creosote migration decreased sharply after an initial spike. The data will be used to enhance existing predictive models.
Sung-Mo Kang, J J Morrell, J Simonsen, S T Lebow


Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic conditions. Part 2: Semi-industrial investigation
1995 - IRG/WP 95-50040-13
In continuation of previous leaching research on the quantification and modelling of metal elements released from CCA treated timber, a series of experiments has been carried out dealing with the influence of temperature and pH of the relative aquatic environment. The leaching method used is the Dutch prestandard for building materials, a long term static leaching test simulating practical bank-shoring situations. Parameters of study are type of fixation, wood species and specimen profiles. With decreasing water temperature, significantly less leaching of copper, chromium and arsenic is observed. An outdoors/indoors temperature ratio of 0.7 could be established. Increasing acidity of the leaching water mainly enhances the release of copper, whereas chromium and arsenic show a minimum leaching tendency at neutral pH. Both conditioning chamber fixation and steam fixation prove to be effective in fixing the metal elements in the wood substrate. With steam fixed timber, however, a higher loss of copper is observed during the early leaching cycles, due to the presence of copper salts on the wood surface. With regard to specimen profiles, boards in comparison with posts demonstrate a remarkable resistance to leaching of active ingredients, presumably due to the different heartwood/sapwood distribution and the specimen dimensions. In conclusion, the observations made confirm the results obtained from previous leaching studies. Converting the emission data into leaching fluxes, a highly correlated double logarithmic flux formula is regarded the best tool for curve fitting, however, for a limited time span. Other models which are more suitable for extrapolation of emitted quantities over a longer period of time are still under investigation. Likewise, proprotional metal ratios versus retention levels highlight the relativity of experimental data obtained with standard emission tests.
G M F Van Eetvelde, W J Homan, H Militz, M Stevens


Wood preservation in Kenya
2000 - IRG/WP 00-40191
Current research on wood preservation in Kenya is mainly on the development of biological control of wood-destroying termite species, using mycoinsecticides. The major research institutions include the Kenya Agricultural Research Institute (KARI), Kenya Forestry Research Institute (KEFRI), Moi University and the International Centre for Insect Physiology (ICIPE). Training institutions include Forestry Training College, Forest Products Training Institute and Moi University. A number of publications, mostly an biological control of termites, are available and they range from workshop and conference proceedings to theses and journal publications. Wood-destroying termite species include several genera in Macrotermitidae and one drywood termite genus. Wood preservation facilities are available in Kenya, mainly for assorted timber products, sleepers and utility poles. The major preservatives used are CCAs, PCP and Creosote oil. There are still no set standards, specifications and requirements for wood preservatives and little, if any information exists on the marketing aspects of wood preservatives. The yet to be established Industrial Chemicals Act and the recently introduced Environmental Management and Coordination Bill (1999) may be able to handle regulatory, environmental, health and safety aspects of wood preservation in Kenya.
G Ochiel


Laboratory simulation of leaching from creosote treated wood in aquatic exposures
2000 - IRG/WP 00-50157
Creosote has a long history of use as a preservative particularly in industrial wood products, but its use has come under increasing scrutiny as a result of concerns about its potential effects on aquatic and terrestrial non-target organisms. Despite its long use, there is relatively little data on the rates of creosote loss in many exposures. In this report, we describe small scale leaching tank procedures for evaluating migration from creosote-treated Douglas-fir lumber exposed at 35°C under 0 flow rate conditions. Creosote component concentrations in the water column were quantified using solid phase microextraction and gas chromatography. As expected, migration rates were higher for lower boiling point fractions. Leaching in the first eight hours followed a linear relationship for acenaphthene, dibenzofuran, fluorene, phenanthrene and fluoranthene. Chemical concentrations arrived at a steady state after 24 hrs of leaching. Concentrations of all creosote components tested tended to be lower than their reported water solubilities, suggesting that other factors were influencing migration. Further analyses of the leaching system are planned. The results will be used to expand a model that simulates creosote loss from treated wood in flowing fresh water.
Ying Xiao, J Simonsen, J J Morrell


A case for adopting a standardised protocol of field and laboratory bioassays to evaluate a potential soil termiticide
2003 - IRG/WP 03-20275
The rationale for adopting a new approach to the field testing of potential soil termiticides is advocated on the grounds that current testing methods are limited to termite bioassays and do not address quantitatively the persistence and bioavailability of soil termiticides to foraging subterranean termites over time and in different soil types. Furthermore, the present testing regimes assume field situations of uniform high termite hazard across field sites. Our testing procedures require the random sampling of soil cores from test soil pads (500 x 500 mm) at several geographically different locations. The soil cores from treated and untreated soil pads are returned to the laboratory and the soil residues in half of the samples examined for each year of test by gas chromatography. The bioavailability of termiticide residues in the remaining soil samples are evaluated by termite bioassays using the field collected subterranean termite, Coptotermes acinaciformis (Froggatt). Both tunnelling distance and mortality are used as indicators of termiticide activity and availability. This paper compares the traditional soil test methods with our new approach, which addresses the problems of security with longevity of test, variability of termite hazard levels at different field sites, and a practical method for managing variables in assessing potential soil termiticides. Importantly, this technique prevents the direct destruction of natural populations of subterranean termites or the indirect contamination by contact from soil residues of termiticides applied in and around active termite colonies.
J R J French, B M Ahmed


Preliminary studies of the decay mechanism of some brown-rot fungi
1989 - IRG/WP 1402
The importance of the enzymatic degradation of hemicellulose and cellulose by brown-rot fungi is still under discussion. Endo-ß-1,4-xylanase and endoglucanase activities of Coniophora puteana and Poria placenta cultures were measured by the increase in reducing groups. Enzymes were produced in liquid and solid sawdust based culture media. Enzyme activities were measured in two, four and eight week intervals from the beginning of the test. The ability of brown-rot fungi to degrade crystalline and noncrystalline cellulose by an enzymatic pathway was studied by measurement of total cellulase activities from Coniophora puteana and Serpula lacrymans. Low enzyme activities were noted. This result indicates strongly that these fungi possess a complete cellulose-degrading enzymatic pathway.
A-C Ritschkoff, H Viitanen


An appraisal of methods for environmental testing of leachates from salt-treated wood; part 1
1998 - IRG/WP 98-50115
The magnitude and diversity of leaching tests with salt-treated wood, performed by institutes as well as industry, strongly appeal for harmonisation towards one single method. That procedure should be well-defined, cost- and time-effective and moreover be extended with a clear detection and interpretation scheme. The paper(s) presented here tend to evaluate 2 existing leaching methods, the ENV 1250.2 and the EN 84, for their potential use as an environmental standard in high hazard class wood preservation. The leachates obtained are chemically examined for their patterns and levels of metal emission and are biologically screened for their releavance towards in service biomonitored samples. Upon strengthening the objectives and characteristics of the EN 84 ageing test, the results reported here justify the support and upgrading of this procedure as an early stage leaching method within the standard efficacy testing of new or renewed wood preservatives.
G M F Van Eetvelde, M Stevens, F Mahieu, H-W Wegen, A Platen


Composting of waste building up in sawmill dipping basins
1990 - IRG/WP 3570
We have studied composting of waste building up in dipping basins at sawmills although this waste can also be disposed of by incineration. Controlled composting within the sawmill area seems to be a feasible method. Another possibility is to accomplish composting directly at the local dumping site. Waste containing antistain chemicals is generally classed as hazardous. It cannot therefore be placed as such at common dumps. However after successful composting the permission to do so can probably be obtained. The composted dipping basin waste might also be suitable as land filling or in some cases as soil improvement material - at least in parks and green belt areas.
I A Linderborg, U Ek


Detection of a brown-rot fungus using serological assays
1986 - IRG/WP 1305
Polyclonal antisera produced to Poria placenta (Fr.) Cooke were used in two tests to qualitatively assay for the fungus. Fungal hyphae were fixed to slides and fluorescent antibody (FA) techniques used to visualize the hyphae under the microscope. Fluorescence of non-Poria fungi, when present, could be reduced but not eliminated by cross-absorbing the sera with these fungi. The antisera was also used in an enzyme-linked immunosorbent assay (ELISA) to distinguish between Poria placenta and a non-Poria control fungus Rhizoctonia solani.
B Goodell, J Jellison


Protection of southern pine using N,N-Napthaloylhydroxylamine: Field tests, soft-rot cellars and aquatic bioassay leach testing
1999 - IRG/WP 99-30204
Recent environmental restrictions are limiting the use of broad-spectrum biocides for wood preservation. There is an urgent need for new, sharply targeted, environmentally benign wood preservatives. N'N-Napthaloylhydroxylamine (NHA), a water-soluble calcium-precipitating agent, has been shown to inhibit decay by brown-rot and white-rot fungi in soil-block tests and prevent damage by Eastem subterranean termites under lab conditions. In order to further evaluate the capacity of NHA to prevent decay and termite damage, SYP stakes were pressure treated with three concentrations of NHA (0.1, 0.5 and 1.0%) and CCA (1.0%) and placed in-ground at the Harrison Experimental Forest, Gulfport, Mississippi, in June, 1997. Similarly, treated sticks were placed in soft-rot fungal cellars at FPL. One percent NHA-treated stakes were also leached for 72 hours in water and the leachates tested by an acute, five dilution bioassay using Ceriodaphnia dubia in EPA Protocol 600/4-90/27F. Results to date: 1) NHA stakes (0.5 and 1.0%) are as durable as CCA; 2) NHA does not inhibit soft-rot fungi and, 3) NHA is a relatively benign molecule with LD50 130-fold less than copper for C. dubia.
D M Crawford, F Green III


New approaches to practical evaluation method of bio-degradation of wooden construction - Non-destructive detection of defects using radar technique
2000 - IRG/WP 00-20214
There have been a number of researches and developments on the techniques and apparatus for the nondestructive evaluation of the biological deterioration in wood and wooden constructions, such as decay or insect attack in house, public buildings or in historically important architectures. As for the detection of the decay in wood, techniques using sound in audible or in ultrasonic frequency ranges, stress waves, heat wave and X- ray have been investigated, where the changes in the physical properties expressed in the wave form were related to decay. The change in the velocity, the attenuation or the frequency spectrum of these physical energy waves can be associated with the decrease of the specific gravity or the structural change due to decay. Some mechanical properties such as the boring resistance and the elastic properties of wood surface could be an indicator of decay. The dielectric property of wood and its relation to decay is also useful. Miller et al. (1989) applied a radar technique to diagnosing of standing trees. However the techniques previously developed are not always feasible. One of the possible reasons is that these physical or mechanical properties change not only on decay but also on other factors, such as the water content or the grain direction in wood. In addition, sometimes the techniques are less practical, strictly not non- destructive or too expensive. In practical maintenance operation of wooden constructions, visual inspection together with sampling method plays an important roll, however a specialized training is needed for the operator to get the skill of the diagnosing. In this study, to establish a practical evaluation method of bio- degradation in wooden construction, scanning using a newly developed portable radar apparatus was investigated. By comparing the results with other methods, a more practical method to evaluate the bio-degradation in wood was proposed.
Y Fujii, Y Komatsu, Y Yanase, S Okumura, Y Imamura, M Tarumi, H Takiuchi, A Inai


Laboratory testing of wood natural durability - In soil-bed assays
1998 - IRG/WP 98-20141
Laboratory methods for assessing wood decay resistance are being investigated in the framework of an ongoing European research project. This paper summarizes the main results obtained for soil-bed tests based on the European prestandard ENV 807-Test 2. The data suggest that this testing methodology is suitable for evaluating the natural durability of timber species in soil-contact under conditions which promote soft rot. Results after 16 weeks of exposure were found to enable the assessment of wood durability. Both, mass and strength (MOE) loss determination proved suitable for hardwood testing. In contrast, only the MOE losses recorded for softwood species were correlated with their expected decay resistance. The lack of correlation between mass loss and durability data is likely related to the very slow decay rates found for softwood timbers in the soil bed. Furthermore, artificial weathering prior to testing was shown to affect the susceptibility of some timber species to soft rot decay. This suggests that a weathering step may be required prior to biological testing. Wood leaching by the protocol described in EN 84 deserves attention as a possible alternative to the very expensive and time consuming artificial weathering pretreatment. In conclusion, laboratory soil testing using a modified ENV 807-Test 2 methodology can be recommended for assessing the durability of timbers to be used in ground contact. Such tests can provide useful information to complement the results from basidiomycete tests. The potentials of basidiomycete tests based on EN 113 to assess the natural durability of timbers were also investigated. The main findings will be presented at this conference by van Acker et al. (1998).
R Sierra-Alvarez, I Le Bayon, J K Carey, I Stephan, J Van Acker, M Grinda, G Kleist, H Militz, R-D Peek


Fumigation of New Zealand grown western red cedar for export markets
2001 - IRG/WP 01-30262
The objective of this study was to demonstrate that methyl bromide fumigant penetrates into the centre of western red cedar (Thuja plicata L.) timber to meet the standard for export markets. Kiln dried western red cedar was used and a cavity (50x 30 x 13mm3) was prepared into the centre of each sample board (500 x 200 x 26 mm3 thick). An absorbent sachet used in industry for cross checking that the concentration of methyl bromide meets the standard during fumigation of export commodities was then inserted into the cavity. Two sample boards with individual sachets separated by aluminium foil and positioned at 13 mm below the wood surfaces, were then glued together. After curing of the glue, an aluminium tape was used to seal the four edges of the sample to prevent penetration of methyl bromide through the boards' edges. Fumigation was performed for 24 hours in the laboratory and also in a commercial environment using 80g of methyl bromide/m3 of wood prior to the cross checking of sachets. The results of this study demonstrated penetration of methyl bromide into the centre of kiln dried western red cedar (26 mm thick) in sufficient quantity to meet the specification for export to overseas markets.
B Kreber, G Durbin, D Wilson


Scandinavian experience – 25 years’ experience in transforming used creosoted wood into bio-fuel
2005 - IRG/WP 05-50224-18
Swedish experiences show that the best and most efficient way to handle the creosoted wood waste is through combustion. The preparation of creosoted waste wood to fuel chips at IQR AB’s plant in Trollhättan is done by splinting the wood according to a special method. Mainly railroad sleepers, but also other wooden commodities, from all over Europe are delivered to the plant. The wood material is crushed in a number of steps to achieve the appropriate size of the chips. The wooden chips are then delivered to combustion facilities in Sweden. The PAH emissions can be kept at a low level due to good mixing, high temperature and a high retention time in the furnace.
T Karlström


The biological effectiveness of wood modified with heptadecenylsuccinic anhydride against two brown rot fungi: Coniophora puteana and Gloeophyllum trabeum
1992 - IRG/WP 92-3705
A modified soil block test was carried out using wood samples reacted with heptadecenylsuccinic anhydride (ASA). This modification gave good resistance to decay brought about by the brown rot fungi Coniophora puteana and Gloeophyllum trabeum during the twelve week exposure period. Results indicated that there was a good correlation between increased loading of modifying reagent and an increase in effectiveness paralleled by a marked reduction in wood moisture content. The effective resistance threshold level was calculated to be about 30% weight gain of ASA. Further discussions regarding the mode of action are included.
C Codd, W B Banks, J A Cornfield, G R Williams


Étude de l'impact d'un xénobiotique sur le milieu aquatique: Approche méthodologique
1990 - IRG/WP 3586
L'action de xénobiotiques sur les communautés vivantes des écosystèmes lénitiques a été abordée à des échelles spatiotemporelles différentes. Dépassant le niveau des tests monospécifiques, nous avons effectué des essais en laboratoire sur des microcosmes contenant des végétaux ( Lemna minor ) et des bactéries et également sur des bassins de quelque m³ contenant une grande variété d'organismes. Les essais ont porté jusqu'à présent sur le Pentachlorophénol; ils seront poursuivis prochainement sur d'autres composés. Les résultats obtenus au laboratoire se sont avérés être transposables aux effets obtenus dans les bassins: le développement de souches bactériennes résistantes au PCP et l'inhibition de l'activité photosynthétique des différents groupes de végétaux constituent les principaux résultats de la contamination par le fongicide. Ces effets reposent sur les caractéristiques de dispersion et d'accumulation du produit étudiées par ailleurs. Il s'avère que l'approche méthodologique multidimensionnelle utilisé içi est très efficace et elle sera utilisée pour vérifier les effets d'autres xénobiotiques sur la structure et le fonctionnement des écosystème aquatiques.
G Blake, G Merlin


Comparison of Temporal Changes in Metal Leaching and Aquatic Toxicity from Wood Treated with CCA and Alternative Preservatives
2005 - IRG/WP 05-50236
This study compares the temporal variation of chemical leaching and aquatic toxicity of wood treated with chromated copper arsenate (CCA) and other copper-based wood preservatives (alkaline copper quaternary (ACQ), copper boron azole (CBA), copper citrate (CC) and copper dimethyldithiocarbamate (CDDC)). Treated wood blocks were leached for 21 days and the leachate collected was analyzed for preservative chemicals and aquatic toxicity. The measured rate of copper leaching was fit using the recently proposed diffusion model for predicting preservative leaching rates. An unpreserved wood sample was tested as a negative control. In general the predicted values for flux rate were on the same order of magnitude as calculated using the experimental data. In natural water, several physical and chemical factors may affect the bio-availability and toxicity of chemicals. Copper concentrations and resulting aquatic toxicity obtained using two natural waters as leaching solutions were found to be lower compared with data obtained using de-ionized water as the leaching fluid.
B Dubey, T G Townsend, G Bitton, H M Solo-Gabriele


Screening of the technical performance and aquatic toxicity of N-methylolacrylamide treated wood
2000 - IRG/WP 00-40166
In the course of the last decades chemical modification of wood species, with a limited natural durability, has been subjected to intensive research. As a possible alternative and supplementary treatment of non-durable wood in a range of applications it remains one of the major topics in the wood preservation world. Different modification systems have been scaled-up and are now in an industrialising phase. In this paper a possible new chemical modification technique, with N-methylolacrylamide (NMA), is described. The main objective of chemical modification with this monomer is to improve the dimensional stability and the decay resistance of non-durable wood species. Data on the latter will be reported on comparative bases. The fact that NMA-monomer is a water-soluble monomer, can be put forward as one of the plus-points. This aspect on the other hand results in a possible risk for the aquatic food chain, which comprises a possible drawback in view of scaling-up. In this framework several aquatic toxicity tests have been executed on leachates of wood treated with NMA under different reaction conditions.
V Rijckaert, S De Geyter, J Van Acker, M Stevens


Performance of Copper-Chrome-Arsenic (CCA) and Copper-Chrome-Boric (CCB) treated panels of Bombax ceiba and Paraserianthus falcataria against bio-deterioration at Krishnapatnam harbour, east coast of India
2003 - IRG/WP 03-30310
Results of investigations on the durability of light weight timber species (Specific gravity below 0.4) i.e., Bombax ceiba and Paraserianthus falcataria in treated and untreated condition conducted at Krishnapatnam harbour (Lat 13o28’ to 13o59’ N; Long: 80o10’ to 80o16’E) along the east coast of India are reported in the paper. Exposure trails were conducted with panels (Size: 30 x 3.8 x 3.8 cm.) treated with CCA (Copper–Chrome–Arsenic) and CCB (Copper-Chrome-Borate) at four retention levels (8, 16, 24, and 32 kg/m3), for a period 3 years from August, 1997 to July, 2000. Control panels of both the species were heavily attacked by shipworms and pholads and rejected in a period of 3 months. On these, panels, shipworms attained maximum growth of 2.3 cm. and pholads 1.4 cm. On these panels. borer species identified were: Martesia striata, M. nairi, Teredo furcifera, T. fulleri, Lyrodus pedicellatus, and Bankia campanellata. Timber panels treated with CCA at lower loadings (8 and 16 kg/3) had greater number of shipworms (>200) than pholads. Shipworms and Pholads attained maximum growth of 2.6 and 1.8 cm respectively. Panels treated with higher loadings (24 and 32 Kg/m3) had more pholads (>150) than shipworms. Pholads and shipworms attained maximum growth of 3.1 and 6.8 cm respectively on these panels. The CCB treated panels of lower loadings also had heavier shipworms (>300) that attained maximum growth of 16 cm, whereas, pholads attained a maximum of 2.2 cm. On higher loadings of CCB treated panels, pholads intensity was observed to be greater and attained a growth of 3.4 cm while shipworm attained 1.9 cm. Overall, shipworm intensity was found to be greater on CCA and CCB panels with lower retentions (8 and 16 Kg/m3), whereas penetration was not deep on higher loadings (24 and 32 Kg/m3). CCA treated panels with lower loadings (8 and 16 Kg/m3) were found to be better than those of lower loadings of CCB. However, at higher loadings (24 and 32 Kg/m3) variations were not significant.
B Tarakanadha, N R Raveendra Prasad, K S Rao


Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic applications. Part 1: Laboratory scale investigation
1995 - IRG/WP 95-50046
In order to investigate the applicability of current prestandard leaching test methods, a series of experiments has been performed on CCA impregnated wood dealing with the influence of pH, temperature and agitation of the surrounding water. The leaching method used in this first part of the investigation is the European prestandard drafted by CEN/TC38/WG11, a short term dynamic leaching test under laboratory conditions of test. Parameters of study are water acidity, stirring of the leaching water, type of fixation and wood species. With increasing acidity of the leaching water, the release of copper is strongly enhanced whereas chromium is lost on a low and fairly constant rate irrespective of pH. In general, significantly greater quantities of metal elements were leached when stirring the leaching water compared with the static experiments performed. Both natural and steam fixation appear to be effective in fixing the CCA components to a large extent. However, the overall detectable copper quantities still indicate incomplete Cu fixation. Likewise, with steam fixed timber a higher loss of copper is observed in the early leaching cycles, likely due to the presence of copper salts on the wood surface. With regard to the wood species investigated, no major differences in loss patterns are observed with pine and spruce specimens. However, the difficulties met when impregnating spruce at toxic limit level attempting full penetration of the wood blocks seem to be reflected in the loss data obtained. The results obtained in this leaching study tend to support the prestandard test procedure examined. However, more detailed information is required on certain parts of the test method as described in this study as well as on data-interpretation procedures to evaluate the results obtained and translate them to conditions under service.
G M F Van Eetvelde, R J Orsler, G E Holland, M Stevens


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