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Biofinish: A Functional Wood Surface Treatment based on Aureobasidium
2020 - IRG/WP 20-40903
Xyhlo Biofinish is a natural and environmentally friendly wood protection concept based on linseed oil impregnation and a fungal-based coating. It emerged in the late 1990s and has been developed over the past 15 years into an industrially applicable process in the Netherlands. The combination of linseed oil impregnation and a surface treatment with the living fungus Aureobasidium extends the service life of wood outdoors and significantly reduces maintenance costs. Aureobasidium grows on water-repellent linseed oil surfaces in many regions of the world which enables the use of this concept in a wide range of applications. Tests demonstrate that its reproducible stable outdoor performance allows it to withstand the environmental conditions in at least the northern hemisphere. Linseed oil apparently stimulates growth of Aureobasidium on surfaces and it can function as repellent for liquid water into the wood. However, water vapour is still able to diffuse in the wood which creates a diffusion-open system that swells and shrinks slower. Research on the biofinish concept is still ongoing and more information about the mode of adhesion of the fungus to the wood surface is necessary. The aim of this study was to gain more information about the mode of adhesion of the fungus Aureobasidium to the wood surface and to investigate its relation to the fungal morphology. Aureobasidium produces extracellular polymeric substances (EPS) which enable the attachment of cells to surfaces and biofilm formation. EPS consist among other biopolymers of the polysaccharide pullulan, which is known for its mediation in adhesion and attachment. In this study, EPS was extracted from the fermentation suspension of several morphologically different Aureobasidium cultures and examined on their shear strength. Results showed that the EPS collected from shiny (more light reflecting) black cultures of Aureobasidium performed better in shear tests compared to EPS from matt black cultures and matt light grey/white fungal cultures. This suggests that the morphological appearance of Aureobasidium cultures correlates with the adhesion to surfaces.
S Rensink, M Sailer, S Roukens, J Gerber, H van der Mel, K Potgieter, J Spit, R Bulthuis, C Struck, M Bennink
The registration of wood preservatives under the Pesticides Act of 1962 in the Netherlands
1976 - IRG/WP 364
J Van der Kolk
The influence of previous anti-blue-stain preservative treatments on the fixation of CC in spruce
1997 - IRG/WP 97-30134
Freshly cut and kiln dried spruce boards were treated with 4 different anti-blue stain preservatives (ABP). After a period of 10 days allowing the samples to dry and fixate, the samples were treated with CC (chromium, copper formulation) using a vacuum pressure cycle. After impregnation the wood was steam fixed. A submersion leaching test showed differences in the leachable quantity of copper and chromium. When related to the retention of both salts after impregnation, no differences could be found between samples previously treated with anti-blue-stain preservatives and untreated samples. However, the retention of CC diminished significantly by application of quaternary ammonium compounds.
M Van der Zee, W J Homan
Some experiments with hexabutylditin against fungi
1977 - IRG/WP 388
The investigation was carried out in 1972 and 1973 to collect experimental data about the poisonousness of hexabutylditin (HBDT) against the woodrotting fungi Coniophora puteana (Coniophora cerebella), strain 15, and Chaetomium globosum, strain hexabutylditin was being manufactured by the Organisch Chemisch Instituut (O.C.I.) TNO, at Utrecht.
J W P T Van der Drift
Thermotolerant mould growth in dehumidifier kilns in New Zealand
1996 - IRG/WP 96-10169
Growth of Aspergillus fumigatus and Paecilomyces variottii is common on wood dried in dehumidifier kilns that operate within a temperature range of 35-55°C. Aspergillus fumigatus causes an unacceptable blue / grey discolouration of the woods surface and prolonged exposure to spores during handling of mouldy wood can cause health problems amongst timber workers. A survey of dehumidifier kiln operators in New Zealand was carried out to ascertain the extent of the problem and investigate control options. Significant growth only occurred if initial wood moisture content was above 80%. Results suggested that this was because high relative humidity (98-100%), for periods in excess of 5 days, was a requirement for extensive and profuse growth to occur. Only 3 of the 26 antisapstain treatments tested using a 3 week laboratory trial gave control of Aspergillus fumigatus at 40°C. Fumigation with 4 ppm (mg/litre of air) of formaldehyde gas controlled growth of Aspergillus fumigatus for periods up to 5 days and a second fumigation was often needed for long drying cycles (> 12 days). It seems likely that growth of thermotolerant moulds became a problem when use of pentachlorophenate as an antisapstain treatment was phased out (1988-89). Laboratory trials showed that this was one of the few fungicides that controlled Aspergillus fumigatus.
R N Wakeling, J G Van der Waals
Effect of wood moisture on ability of Sphaeropsis sapinea to colonise Pinus radiata
1999 - IRG/WP 99-10311
The factors influencing colonisation of unseasoned radiata pine logs by sapstaining fungi which can result in detrimental wood discolouration, are being explored. The objective of the current study was to determine the effect of wood moisture content on fungal growth and wood colouration (melanisation). Five replicate trials were set up using increment cores (10mm diameter) which were taken from bark to pith of freshly-felled Pinus radiata logs. Increment cores were pre-conditioned to different moisture content levels (< 30%, 50-70%, 120-140% and > 200%) using silica gel. After pre-conditioning, cores were individually encapsulated in wax and aseptically infected with Sphaeropsis sapinea introduced onto the outer (bark), freshly exposed (wax removed) cross-cut end. Sets of inoculated increment cores were incubated at 25°C. In the first trial, sets of incubated cores were assessed at two, six and nine days by cutting replicate cores into serial 3-mm-thick disks which were then plated on malt agar media. Four other replicate trials were assessed after nine days incubation following the procedure just described. Fungal growth on media was taken as a measure to determine depth of radial penetration (colonisation) at each wood moisture content level used. Also, melanisation was visually estimated along the core length. No apparent relationship was found between wood moisture content and ability of S. sapinea to colonise and melanise radiata pine.
B Kreber, D R Eden, R N Wakeling, C M Chittenden, J G Van der Waals, B Carpenter
The use of TCMTB in applications other than sapstain prevention: A review
1990 - IRG/WP 3606
The efficacy of TCMTB against staining fungi and surface moulds has been thoroughly investigated during the last decade. As a result, the chemical is used as an alternative to the chlorinated phenols in various parts of the world for the preservation of freshly sawn timber. Less known are the data obtained against brown rot, white rot and soft rot fungi. The termite repellent and bactericidal properties of the chemical widen the scope of application possibilities. The objective of this article is to report on the data actually available.
R Van der Eynde
1987 - IRG/WP 3431
Decay problems of spruce joinery in the Netherlands in the 1960's and 1970's led to the introduction of preservative treatment. Because of the known penetration difficulties with Spruce, the results of the treatments were not always successful. The fact that the decay was found only in the joints led to development of the philosophy of "local preservation" of the joints in remedial and preventative treatments, like preservative injections or use of rods and capsules containing preservatives. However the diffusion of the preservatives used in most of these systems is often poor in spruce. Because Spruce joinery dip-treated with bifluorides showed good penetration and protection, a pill consisting of a hydrophylic polymer and bifluorides was developed by TNO. Various laboratory tests carried out with this pill have confirmed good penetration of the bifluorides in the wood and activity against decay fungi.
J W P T Van der Drift, K J M Bonsen
Evaluating the potential of modified wood for use in marine environments using a short-term laboratory bioassay
2004 - IRG/WP 04-10525
Chemically modified wood may be an alternative to preservative treated timber for marine structures. In this study a screening laboratory test using the wood-boring isopod crustacean Limnoria quadripunctata was used to assess the durability of chemically modified Pinus sylvestris, Pinus radiata and Picea sp. Most of the treatments used a combination of one of two of types of the resin dimethyloldihydroxyethyleneurea (DMDHEU) and phosphobutane tricarboxylic acid (PBTC). Untreated Pinus sylvestris sapwood was used as a non-durable comparison. Small test sticks from different types of modified wood were prepared and leached in seawater for 8 days prior to the experiment. A wood stick with a Limnoria and 4 ml of seawater was placed in each 12mm diameter well of a cell culture chamber. The number of faecal pellets produced by the animals was measured under these forced feeding conditions, and activity and mortality was recorded. With some treatments, no faecal pellets were produced, with others more faecal pellets were produced than with untreated Pinus sylvestris. Non-production of faecal pellets was sometimes due to mortality, but in some treatments there were also evidence of antifeedant effects as there was no evidence of acute toxicity Limnoria. However, some moribund animals were observed in these treatments and there was significant reduction in the number of pellets produced, so chronic toxicity may be suspected. The Arkofix type of DMDHEU gave significantly higher protection against borers than DMDHEU NG. A dose-dependent suppression of pellet production by PBTC was also detected.
L M S Borges, S M Cragg, M van der Zee
Modelling the control of decay in freshly felled pine poles
1997 - IRG/WP 97-10206
In a recent study investigating control of decay in freshly felled pine utility poles, it became apparent that the efficacy of different treatment methods was strongly related to the size of the material being treated. A topical application of 5% w/v disodium octaborate tetrahydrate (DOT), brush applied to the cut surfaces of logs with otherwise intact bark was just as effective at excluding white rot colonisation in large diameter logs (greater than 30 cm) as it was in small diameter material (less than 15 cm diameter). In both instances, protection was effective for at least 12 months. In contrast, a biological treatment consisting of a spore suspension of a specially selected isolate of Trichoderma viride, was only effective in preventing white rot when applied to the small diameter logs. In larger logs, the extent of decay in biologically treated material was as high as that evident in the untreated controls. To ascertain why the effectiveness of the biological control was dependent on the diameter of material being protected, a simple mathematical model, describing both the growth of the Trichoderma and decay basidiomycetes, was devised. In addition to providing a valuable insight into the dynamics of biological control, this modelling exercise highlighted the benefits of applying such an approach to wood protection.
M W Schoeman, W Van der Werf, J F Webber, D J Dickinson
The efficacy of Sentry® as a treatment for the control of sapstain in pre-infected radiata pine
2001 - IRG/WP 01-30260
Experiments were conducted to determine the efficacy of Sentry® when used to control sapstain fungi on radiata pine branch billets stored under high fungal hazard conditions. Prior to antisapstain treatment, the billets were pre-infected with a mixed inoculum of staining fungi and held from zero to 10 days at 25°C and 75% relative humidity. This was done to produce billets with different degrees of fungal pre- infection. Following each holding time, replicates were dipped in Sentry® at concentrations ranging from 3.5%-14% w/v product. After antisapstain treatment, the billets were stored for one month at 30°C and 90% relative humidity, to simulate conditions that could be met during transport and storage of logs in the tropics. Each billet was then sawn into 10 discs and the newly-cut face assessed for fungal degrade. For two-day-old billets, 7.5% Sentry® w/v product gave satisfactory control of sapstain in one trial, whereas in a second trial 10% Sentry® w/v product was required. However, satisfactory protection was not achieved with any of the concentrations of Sentry® tested for billets held longer than two days before treatment.
C Chittenden, J G van der Waals, B Kreber, R N Wakeling
Comparative study on leaching of CCA from treated timber: Modelling of emission data
1994 - IRG/WP 94-50027
Results of a comparative study on leaching of CCA from treated timber are reported. The study aims at investigating the applicability of prestandard leaching test methods for modelling purposes. Prestandards used are the European standard proposed by CEN/TC38/WG11 and NEN 7345 (Dutch prestandard for building materials). Parameters of study are type of fixation, wood species (pine - spruce), specimen dimensions and leaching pH. Due to the conditions of test, a higher level of metal emission is observed in the CEN procedure. Both methods show a similar time-related decrease in leaching flux, however. The CEN small wood block test using a dynamic stirring leaching system proves to be an accellerated version of the static NEN method in which pole sections are immersed in water over a long period of time. Steam fixation generally reduces the emitted quantities of chromium. When naturally fixated, the initial chromium flux exceeds the copper flux, while in accelerated (steam) fixation tests copper is leached out to a higher level. In most tests the initial arsenicum emission flux does not exceed one tenth of the respective copper flux. With regard to hazard assessment of CCA leaching from treated timber in surface waters, an emission model is worked out taking into account a number of controlable and verifiable parameters influencing the final environmental concentration. The PEC-formula used (predictable environmental concentration) is kept short and is based on time dependency of the emission data (curve fitting on experimental data) and substraction of calculated dilution factors.
G M F Van Eetvelde, M Stevens, L Van der Mijnsbrugge
Sentry®, a new antisapstain formulation for protecting logs and lumber. - Part 2: protection of lumber
1999 - IRG/WP 99-30189
Recent research conducted by Forest Research, Chemcolour Industries (NZ) Ltd. and Fletcher Challenge Forest Ltd. has resulted in the development of antisapstain formulations that meet the efficacy requirements of the New Zealand Forest industry for export logs. One treatment, called Sentry®, is now poised for commercial use in New Zealand for treating export logs, having undergone an extensive suite of field and mill trials over a two year period. This paper presents results of field trials set up to determine the efficacy of Sentry® on block stacked radiata pine. Sawn timber was collected from a local mill, sawn into 1 meter lengths, dipped in antisapstain solution, and block stacked prior to assessment of surface fungal degrade after 6, 12 and 15 weeks over a period including a severe hazard New Zealand summer. The higher concentrations of the commercial standards were required to achieve adequate protection of block stacked radiata pine in storage for 12 weeks. After 12 weeks, Sentry®, at the lowest concentration tested (equivalent to 0.125% methylene bis thiocyanate (MBT) plus 0.025% 2-n-octyl-4-isothiazolin-3-one (isothiaz.), gave equivalent protection to the highest concentrations of all the commercial standards (0.6% 3-iodo-2-propynyl butyl carbamate (IPBC) plus 4.8% didecyldimethyl ammonium chloride (DDAC); 0.15% carbendazim plus 0.15% copper-8-quinolate (Cu-8): 0.6% MBT plus 0.6% chlorothalonil). The high level of protection achieved by Sentry® was in part attributed to the broad spectrum of fungicidal activity offered by MBT plus isothiaz. and the micro-emulsion system used.
R N Wakeling, D R Eden, C M Chittenden, J G Van der Waals, B Carpenter, I Dorset, R Kuluz, J Wakeman
Influence of concentration, catalyst, and temperature on dimensional stability of DMDHEU modified scots pine
1998 - IRG/WP 98-40119
Dimethyloldihydroxyethyleneurea (DMDHEU) is being used in textile industry to improve wrinkle recovery. Trials on solid wood have been performed to minimise swelling of the wood. This paper focuses on the effect of various types and concentrations of catalyst and reaction temperature on the dimensional stability of Scots pine. Three different catalysts, NKS (based on magnesium chloride), 3282 (based on aluminium chloride) and citric acid have been tried separately or in combination with tartaric acid. Reaction temperatures between 100° and 125°C have been investigated. The results showed that an anti shrink efficiency of up to 50% can be obtained.
M Van der Zee, E P J Beckers, H Militz
Effect of treating process on efficacy of CCA in a laboratory decay test
1990 - IRG/WP 3628
Test samples of Pinus radiata sapwood measuring 40x40x500 mm³ were treated with a range of concentrations of the copper-chrome-arsenate (CCA) formulation "Tanalith C" using Rueping (empty cell), Lowry (empty cell) and Bethell (full cell) treatment processes. Samples were then reduced to 40x40x7 mm³ test blocks and exposed to the decay fungus Coniophora puteana using an agar/block technique. Replicate blocks were analysed for preservative components. Regression analyses of percentage weight losses of test blocks against total Cu+Cr+As retentions (TAE) showed differences in efficacy of the preservative when applied by the three different processes, the order of effectiveness being Bethell > Lowry > Rueping. Two hypotheses are proposed to explain the results: (1) Disproportionation within the wood of preservative salts when applied by empty cell processes, (2) Differences in distribution of preservative elements following treatment by the three processes.
M E Hedley, K Nasheri, J G Van der Waals
Field performance of novel antisapstain formulations
1997 - IRG/WP 97-30125
The effectiveness as antisapstain formulations of combinations of oxine copper (Cu-8), carbendazim, hexaconazole, cyproconazole, flusilazole, didecyldimethyl ammonium chloride (DDAC), an alkanolamine borate (SB), benzalkonium chloride (BAC), 2-n-octylisothiazolin -3-one (isothiazoline) and p-chlorophenyl-3-iodopropagilformal (CPIPF) was determined for freshly sawn, block-stacked radiata pine in three 18-week field trials: 1. Established in summer 1992 evaluating combinations of hexaconazole, carbendazim and DDAC. 2. Established in autumn/winter 1994 evaluating combinations of hexaconazole, carbendazim, DDAC, BAC and SB. 3. Established in autumn/winter 1995 evaluating combinations of triazoles, DDAC, Cu-8, carbendazim, CPIPF, isothiazoline and SB. Reference standards included: Cu-8; Cu-8 + carbendazim; IPBC + DDAC and TCMTB. In all tests, formulations containing carbendazim + hexaconazole + DDAC gave better protection for 12 and 18 weeks than most other experimental formulations and were equal to or better than commercial standards.
D R Eden, R N Wakeling, C M Chittenden, J G Van der Waals
Laboratory trial to identify potential in-forest treatments to control fungal pre-infections of radiata pine logs
2000 - IRG/WP 00-30220
Development of fungal infections of radiata pine logs by wood degrading fungi commences immediately after tree felling. In general, subsequent antisapstain treatments are unable to control fungal degrade on logs where the pre-treatment log storage time exceeds 2-5 days. However, use of an in-forest treatment of logs may be advantageous to log exporters to control fungal pre-infections during the pre-treatment log storage time, possibly for up to four weeks. In the current study, the outer surface of each freshly cut branch wood billets (200 mm long) was damaged to simulate conditions occurring in the field, by scraping off some bark and also bruising bark with a hammer. Damaged billets were individually sprayed with biocontrol agents (Trichoderma harzianum, T. viride, Phlebiopsis gigantea, Brie fungus), integrated biocontrol agents (T. viride plus fluoride, T. viride plus Sentry® , T. viride plus fluoride and Sentry® ) and dairy products (brie, camembert, egg white and milk). After two days incubation, a cocktail of common sapstain fungi was sprayed onto each billet before incubation for four weeks. After two and four weeks of incubation, billets were cut into discs and eleven newly exposed cross-cut faces were assessed for fungal degrade. The results of this laboratory study showed that Camembert blended in pasteurised milk virtually controlled fungal degrade in billets. This treatment likely meets the criterion of being environmental acceptable.
D R Eden, B Kreber, R N Wakeling, J G Van der Waals, C M Chittenden
Effect of bioextracts on colonisation of radiata pine sapwood by three sapstain fungi
2003 - IRG/WP 03-10485
The objective of this study was to investigate the effect of aqueous bioextracts prepared following two-week incubation of forest soil, garden compost and chicken manure respectively, on the ability of Ophiostoma flocossum, Leptographium procerum and Sphaeropsis sapinea to colonise unseasoned radiata pine sapwood. The research showed that all bioextracts tested retarded the rate of fungal colonisation of radiata pine when compared to the untreated controls, irrespective of the test fungi used. Differences in the ability of bioextracts to reduce fungal colonisation on radiata pine were observed with garden compost and forest soil bioextracts being more inhibitory than chicken manure. There was no inhibitory effect if bioextracts were sterilised by autoclaving prior, or after, the two-week incubation period. The latter observations suggest that bioextracts must contain an active microbial community in order to exert inhibitory effects against test fungi on radiata pine sapwood.
J van der Waals, C Chittenden, B Kreber
Time limits for holding logs to achieve successful antisapstain treatment
1997 - IRG/WP 97-30126
The purpose of these trials was to determine the maximum time that logs can be left in winter and summer before treatment if sapstain, caused by pre-treatment infection, was to be prevented. Pre-treatment storage conditions representative of average temperature and humidity for the winter months of June, July and August, and of moderately severe summer conditions, for the Bay of Plenty, New Zealand were employed. After felling and debarking, logs were artificially inoculated with Ophiostoma piceae and Diplodia pini and stored in a well ventilated room at 8°C and 88% RH. At predetermined intervals from the time of felling, including 8 hours (no time in storage room), 24 hours and then at 24 hourly intervals up to 7 days, a sample of log billets was treated with a commercial antisapstain formulation, and stored at ambient temperatures (from July to November or from February to April) in a well ventilated, open-sided barn. Billets were cross-cut into sections 8 and 16 weeks from the time of felling (winter), 8 weeks (summer), and assessed for the presence of internal sapstain. Results showed that for representative winter conditions (8°C and 88%RH) logs could be stored for periods of up to 4 days before treatment without adversely affecting posttreatment sapstain development. However, during reresentative summer conditions (storage at 25°C and 75%RH), storage for more than 8 hours prior to treatment resulted in unacceptable posttreatment sapstain development. Reasons for these differences are discussed.
D R Eden, R N Wakeling, C M Chittenden, J G Van der Waals, B Carpenter
Variable tolerance of Ophiostoma spp. and Diplodia pinea to commercial antisapstain products
1998 - IRG/WP 98-10266
A recent survey of the occurrence of sapstain fungi in New Zealand, conducted at The University of Waikato, provided the opportunity to examine fungicidal tolerance amongst new isolates. It also enabled a comparison of tolerance amongst new isolates with those used in routine antisapstain screening trials at Forest Research. A rapid antisapstain laboratory disc trial was used to determine the extent of fungal growth after three weeks on radiata pine treated with various commercial antisapstain formulations, which was then used as an indicator of susceptibility or tolerance. The results showed that under laboratory conditions, susceptibility to antisapstain formulations varied greatly, both between species, and between isolates of the same species. None of the formulations tested gave good control of all the isolates when tested at commercial usage rates. The significance of these results is discussed in terms of design of laboratory antisapstain trials and relevance in the field.
D R Eden, C M Chittenden, B Kreber, J G Van der Waals, R N Wakeling, R L Farrell, T Harrington
Effect of origin and orientation of Radiata pine substrates on the development of fungal degrade
2000 - IRG/WP 00-30221
The objective of this study was to determine the influence of different radiata pine substrates on colonisation by sapstain fungi. Freshly-cut branch wood, stem wood and sawn lumber were used to prepare test samples with the largest wood surface area showing a transverse, radial or tangential face. Test samples were evaluated against sapstain fungi using a rapid laboratory antisapstain screening method routinely used at Forest Research. The following observations were made: Untreated test samples with a large transverse face were more susceptible to fungal degrade than samples with a radial or tangential faces. Of the different substrates treated with antisapstain products, transverse branch wood was the most susceptible to sapstain degrade. It is concluded that the standard Forest Research branch wood disc method, used routinely for evaluating antisapstain formulations, is a very severe screening test.
B Kreber, D R Eden, C M Chittenden, B Carpenter, J G Van der Waals
Sentry®), a new antisapstain formulation for protecting logs and lumber. - Part 1: advances in protection of New Zealand radiata pine logs
1999 - IRG/WP 99-30188
Until recently antisapstain formulations gave approximately 10 weeks protection to radiata pine logs and even within this time frame protection was often not consistent. Industry requires 20 weeks protection. The degree of protection sought by industry is in the order of 90-95%. For example, this equates to a maximum of 5 - 10% surface cover of sapstain in the first whole veneer produced from a peeler log. Recent research conducted by Forest Research, Chemcolour Industries (NZ) Ltd and Fletcher Challenge Forest Ltd. has resulted in the development of antisapstain treatments that meet the efficacy requirements of industry. This has been achieved by overcoming the underlying difficulties of treating logs: 1. deliverling an even layer of fungicide to the inherently non-homogenous logs surface, that remains intact for the duration of the protection period sought, 2. arresting inevitable pre-infection by sapstain fungi that occurs during commercial log handling regimes, by using specially formulated mixtures of fungicides of different mobility. One of these treatments, called Sentry®, is now poised for commercial use in New Zealand for treating export logs having undergone an extensive suite of field and mill trials over a two year period. Results of mill trials of Sentry® used on full size logs are presented. The consistently high levels of protection demonstrated by Sentry® in a large number of field trials, on-shore and export commercial mill trials, represents a quantum leap of performance for radiata pine logs over protection given by previously availabie formulations.
R N Wakeling, D R Eden, C M Chittenden, J G Van der Waals, B Carpenter, I Dorset, R Kuluz, J Wakeman, T Price, B Nairn
The lasting dehydration of wood treated by bifluorides worked up in Diffusec noticed by a continual drying of the wood
1999 - IRG/WP 99-30196
After an immersion of sound wood in a solution of Diffusec, in which a combination of acid potassium and ammonium bifluorides = FHF- in dissociated form is present, their potassium and ammonium fluoride ions together with the bifluoride ion = (FHF-) diffuse into the wood. They make use of the woodmoisture available as O-H-O bonds directly attached to the cellulose in the wood fibres to attract the dissociated ions, which after fusion are replaced by F-H-F bonds. If any substance that contains ions or centers of electric charge (from polar bonds) is brought into contact with water, sufficient electrical disturbance result in rupture of the hydrogen bonds. This means that the hydrogen bonds in water are readily broken. The released water dipoles are then attracted to these charge centers. Acid fluorides, as F- and FHF-, act permanently as F-H-F bonds upon OH groups of the cellulose. They are able to gather from the "watercoating" which surrounds the OH groups, so to speak thin layers which leave the wood in the form of vapour. Besides that they are able to occupy the vacant places. Near it watermolecules of the outer layers will easier release as those ones more directed inside. The uptake of the hydrogen in the air is dependent of the RH uptill air-dry wood is reached with the EMC belonging to it. No thermic intervention is necessary according to prof. dr. J. B. van Duijneveldt.
H F M Nijman
Environmental risk assessment of wood preservatives in the Netherlands
2001 - IRG/WP 01-50166-10
Before biocides can be introduced to the Dutch market, they have to be authorised under the Pesticides Act (1962). The criteria for authorisation of biocides have been laid down in the Dutch Decree on Environmental Requirements for the Authorisation of Pesticides Used in Fields Other than Agriculture. In 1998, the EU Biocides Directive (98/9/EC) entered into force, and it was implemented in May 2000. The authorisation currently is a national procedure. The inclusion of an active substance of a product in Annex 1 or 1a of the Biocides Directive, will follow the required EU steps. According to the first Review Regulation, existing active substances of wood preservatives are among the first to be evaluated at EU level. In the Netherlands, the Agency responsible for the authorisation is the Board for the Authorisation of Pesticides (CTB). The CTB is an independent regulatory body. With the request for authorisation, a complete dossier has to be submitted by the applicant. After a check of the admissibility of the dossier, the CTB commissions independent institutes for the evaluation of the dossier and to perform the risk assessment. In general, risk assessments are based on the information that is submitted by the applicant, but CTB can decide to include additional (literature) sources when necessary. One of the evaluating institutes is the National Institute of Public Health and the Environment (RIVM), that covers the aspects of both human and environmental health. This paper is concerned with the environmental risk assessment as it is done in the Netherlands. The environmental risk assessment consists of an exposure assessment, resulting in predicted environmental concentrations (PECs) and an effects assessment, resulting in predicted no-effects concentrations (PNECs). In the Netherlands, the active ingredient of the biocidal product is the main subject of the assessment, other components or metabolites are dealt with if they may present a concern. One of the basic tools for risk assessment in the Netherlands is the USES computer program, in which models and methods for the assessment of exposure and effects are implemented. The USES program has been developed under the supervision of a steering committee with members from government, institutes, academia and industry and is approved by CTB. USES includes EUSES and is fully in line with published EU-Technical Guidance Documents (TGDs).
E Smit, P van der Zandt, J Appelman
Decay potential of various New Zealand Phlebiopsis gigantea strains using a soil block method
1999 - IRG/WP 99-10309
The objective of the current study was to determine the decay potential of different strains of Phlebiopsis gigantea using Pinus radiata and European Fagus sylvatica, respectively. A soil block method was used to determine mass weight loss of P. radiata and F. sylvatica following 10 weeks incubation with different strains of P. gigantea. For comparison, Trametes versicolor, Postia placenta, Gloeophyllum trabeum, Poria vaillantii and Schizophyllum commune were included. For P. gigantea, mass weight losses ranged from 0.3% to 26.5% on P. radiata and 0.1% to 52.2% on F. sylvatica. Gloeophyllum trabeum caused the highest mass weight loss (~ 70%) of all fungi tested, irrespective of wood species used. Future work is under way to determine cellulolytic and and lignolytic enzyme systems of P. gigantea strains which showed a high and low decay potential, respectively.
B Kreber, J G Van der Waals