Modification of wood with Si compounds to limit boron leaching from treated wood and to increase termite and decay resistance

In this study, we tested tetraethoxysilane and methyltriethoxysilane as modifying silicon-based compounds for their potential to limit boron leachability from modified wood and to increase biological durability of the wood against fungi and termites. Both the silane compounds were used in silane state where acidified ethanol was added and stirred at ambient temperature for 30 min. We used two different processes for preservative treatments: double treatment and single treatment. In double treatment, the specimens from sugi wood were first treated with boric acid at 1% concentration and subsequently treated with the silanes. In single treatment, boric acid was mixed with the silane compounds in the silane state yielding 1% boric acid concentration. Subsequent to the treatments, wood specimens were subjected to laboratory leaching tests, and leachates were analyzed for boron content with an inductively coupled plasma (ICP) spectrometry. ICP analyses showed that silane treatments were able to limit boron leaching from treated wood by about 40% in all cases for each silane compound. Wood specimens were then subjected to laboratory termite and decay resistance tests using the subterranean termites, Coptotermes formosanus, and the wood decaying fungi, Fomitopsis palustris and Trametes versicolor. Termite and fungal decay resistance tests revealed that resistance of modified wood with the silane and boron compounds increased when compared to untreated and boron-only treated wood specimens. More in-depth studies on the mechanisms of interactions between the silicon compounds, boron elements and wood components are in progress.     

Montan wax improves performance of boron-based wood preservatives

Importance of boron compounds in wood preservation is increasing due to their low environmental impact, high efficacy and the fact that many other active ingredients have been removed from the market after the introduction of the Biocidal Products Directive. The most important drawback of boron is prominent leaching in wet environment. In order to improve their fixation, and performance against wood decay fungi, boric acid was combined with montan wax emulsion. Possible synergistic effects of boric acid and montan wax were determined according to modified EN 113 procedure. Norway spruce and beech wood specimens were exposed to three white rot (Trametes versicolor, Pleurotus ostreatus and Hypoxylon fragiforme) and brown rot wood decay fungi (Gloeophyllum trabeum, Antrodia vaillantii and Serpula lacrymans) for 12 weeks. Boron leaching from vacuum/pressure treated Norway spruce wood was determined according to the continuous (EN 84 and ENV 1250-2) and non-continuous (OECD and prCEN/TS 15119-1) procedures. Boron was determined with ICP mass spectrometry in collected leachates. The results of the fungicidal tests clearly showed that montan wax emulsion and boric acid act synergistically against tested wood decay fungi. Approximately 50% lower boric acid retentions are required in combination with montan wax emulsions to achieve sufficient protection against wood rotting fungi. However, it is even more important that all leaching tests performed proved that the addition of montan wax decreased boron leaching from impregnated specimens for 20% up to 50%.     

Amount of leachant and water absorption levels of wood treated with borates and water repellents

Wood protection efficacy of borates against biological agents, flame retardancy, and suitability to the environment is well known. Since borates can be applied to timber as water based solutions, they are preferred economically as well. Even though they are highly mobile in wood, boron compounds are widely used in timber preservation. Borates migrate in liquid and increase the hygroscopicity of wood in damp conditions. This study deals with the physical restriction of water access in wood by impregnating water repellent agents into wood to limit amount of leachant and water absorption levels of wood after boron treatment. Borates were incorporated with polyethylene glycol-400 (PEG-400) their bulking effect in wood was considered. Results indicated that the amount of leachates from wood treated with borates in PEG-400 was remarkably higher compared to those of wood treated with the aqueous solutions of borates. Water absorption (WA) levels of wood treated with aqueous solutions of borates were higher than those of their treated samples with the solutions in PEG-400. Secondary treatments of wood with the water repellent (WR) chemicals following borate impregnation reduced the leaching of chemicals from wood in water and also WA of the specimens were less than those of the wood treated with only borates from aqueous and PEG solutions. Styrene (St) was the most effective monomer among the other agents used in terms of immobility effect on borates and WA.     

Evaluation of decay and termite resistance of wood treated with copper in combination with boron and N′-N-(1, 8-naphthalyl) hydroxylamine (NHA-Na)

This study evaluated the relative ability of various combinations of copper sulfate with either boric acid or calcium-precipitating agent, N′-N-(1, 8-naphthalyl) hydroxylamine (NHA-Na), to inhibit fungal degradation and attack by Formosan subterranean termites (Coptotermes formosanus Shiraki). Wood specimens were treated with either 1%, 0.5%, or 0.1% concentrations of copper sulfate, boric acid, NHA-Na, copper sulfate + boric acid, or copper sulfate + NHA-Na mixtures. Treated specimens were subjected to laboratory decay-resistance tests by using petri dishes inoculated with the Basidiomycetes fungi Tyromyces palustris and Trametes versicolor for 12 weeks. Treated wood specimens were also subjected to termite-resistance tests under laboratory conditions. Increased efficacy of copper sulfate against the brown-rot fungus T. palustris was observed when either boric acid or NHA-Na was added. The most effective treatments against the fungi tested were NHA-Na only treatments at 1% and 0.5% concentration levels. Boric acid treatments were not able to protect wood against decay after leaching because of excessive leaching of boron. Similar results were obtained in termite-resistance tests in comparison with decay-resistance tests. These results indicate that the efficacy of the treatments in preventing fungal and termite attack is a function of the type of preservative.     

Metal Transport and Bioavailability in Soil Contaminated with CCA-Treated Wood Leachates

A laboratory study was conducted to investigate metal transport and accumulation within soils contaminated with As, Cr, and Cu from CCA-treated wood leachates. New blocks of CCA-treated wood were leached using synthetic rainwater. Soil columns were constructed and filled with three different soils, including a sandy soil, an organic soil and a clay soil. The leachate was applied intermittently until 80 pore volumes were eluted through each column. Metal concentrations (Cu, Cr, and As) were measured in the leachate before passage through the columns as well as in each elutriate fraction collected. Chemical analysis was complemented with toxicity testing using Ceriodaphnia dubia, Selenastrum capricornutum, and MetPLATE?. Following application of 80 pore volumes of leachate, the columns were dissected and the profile of the metal concentrations within each column was determined. A comparison of the arsenic, chromium and copper leaching patterns found arsenic to be the most mobile, with copper the most retained in the soil columns (As < Cr < Cu). Transport patterns of As differed in the three soil types, with observed mobility highest in the sandy soil and lowest in the clay soil. The three metals accumulated in the top layer of soil. Arsenic posed the greatest risk when soil concentrations were compared to risk-based target levels. Although metals were detected in soil elutriates, no toxicity was detected in any of the soil column elutriates using any of the three toxicity assays.     

Fungal bioleaching of metals in preservative-treated wood

Twenty-four brown-rot and 10 white-rot fungi were screened to evaluate their applicability for detoxification of preservative-treated wood impregnated with copper and chromium (CC) salts. Brown-rot fungi generally showed higher tolerance towards copper inhibition than white-rot fungi. Additionally, brown-rot fungi were found to accumulate considerable quantities of oxalic acid (up to 44.3 mM) in liquid medium, while white-rot fungi generally accumulated only traces of this organic acid. Oxalic acid is a strong organic acid capable of complexing a variety of heavy metals. Four Antrodia vaillantii and two Poria placenta brown-rot strains that displayed both a high copper tolerance and a high oxalic acid production were selected for further study. The brown-rot fungi effectively decayed wood containing up to 4.4% CC causing corrected mass losses of up to 24.3% in 4 weeks. Fungal treatment was also found to promote extensive leaching of chromium (up to 52.4%), but only moderate leaching of copper (15.6% or less). These results indicate the potential of solid-state fermentation with copper-tolerant fungi for the remediation of preservative-treated wood. Improving the solubility of copper will be an important challenge for future research.     

Do the unique properties of nanometals affect leachability or efficacy against fungi and termites?

Nanotechnology has the potential to affect the field of wood preservation through the creation of new and unique metal biocides with improved properties. This study evaluated leachability and efficacy of southern yellow pine wood treated with copper, zinc, or boron nanoparticles against mould fungi, decay fungi, and Eastern subterranean termites. Results showed that nanocopper with and without surfactant, nanozinc, and nanozinc plus silver with surfactant resisted leaching compared with metal oxide controls. Nearly all nanoboron and boric acid was released from the treated wood specimens during leaching. Mould fungi were moderately inhibited by nanozinc oxide with surfactant, but the other nanometal preparations did not significantly inhibit mould fungi. Mass loss from Gloeophyllum trabeum was significantly inhibited by all copper preparations, while Antrodia sp. was not inhibited by nanometal treatments. Nanometals imparted high resistance in southern yellow pine to the white-rot fungus, Trametes versicolor. Unleached specimens treated with nanoboron or nanozinc plus surfactant caused 100% and 31% mortality, respectively. All specimens treated with nanozinc or nanozinc plus silver inhibited termite feeding, but the copper treatments were less effective against termites. Nanozinc possessed the most favorable properties: leach resistance, termite mortality, and inhibition of termite feeding and decay by the white-rot fungus.     

Leachability,metal corrosion,and termite resistance of wood treated with copper-based preservative

Health-awareness and concern for the environment have resulted in voluntary removal of chromated copper arsenate (CCA) from wood preservatives in residential applications worldwide. Copper-based preservatives have been formulated as replacements, but these may not provide a permanent solution to all of the related problems, including copper contamination of aquatic environments and corrosion of fasteners. In this study, the copper retention (before and after the leaching process) of five softwood specimens vacuum-treated with alkaline copper quaternary (ACQ) and copper azole (CA) at three target retention levels was investigated by X-ray fluorescence studies. The metal corrosion and termite (Coptotermes formosanus) resistance of treated specimens were studied under laboratory conditions. Except for treated Japanese larch wood, the copper retention levels of the other wood specimens were able to meet the target copper retention values (use classes 2–4) in Chinese National Standard 3000. The copper leaching rates were 6.92–19.54% for ACQ-treated wood and 9.38–22.46% for CA-treated wood. The metal corrosion rates of iron nails due to corrosion tests (CNS 6717) were influenced significantly by the 1.2% ACQ and 1.2% CA treatments; whereas the metal corrosion rates of zinc-galvanized steel nails were less than 2 and could meet the tested standard. Even though the ACQ and CA treatments caused higher copper leaching rates from the treated specimens, they also increased termite mortalities and reduced the mass loss significantly after termite-resistance tests (JIS K 1571).     

Decay resistance of wood treated with boric acid and tall oil derivates

In this study, the effect of two boric acid concentrations (1% and 2%) and four derivates of tall oil with varying chemical composition were tested separately and in combination. The tall oil derivates were chosen in a way that they consist of different amounts of free fatty, resin acids and neutral compounds. Decay tests using two brown rot fungi (Postia placenta and Coniophora puteana) were performed on both unleached and leached test samples. Boric acid showed a low weight loss in test samples when exposed to fungal decay before leaching, but no effect after leaching. The tall oil derivates gave better efficacy against decay fungi compared to control, but are not within the range of the efficacy needed for a wood preservative. Double impregnation with boric acid and tall oil derivates gave synergistic effects for several of the double treatments both in unleached and leached samples. In the unleached samples the double treatment gave a better efficacy against decay fungi than tall oil alone. In leached samples a better efficacy against brown rot fungi were achieved than in samples with boron alone and a nearly similar or better efficacy than for tall oil alone. Boric acid at 2% concentration combined with the tall oil derivate consisting of 90% free resin acids (TO-III) showed the best performance against the two decay fungi with a weight loss less than 3% after a modified pure culture test.     

Novolak PF resins prepared from phenol liquefied Cryptomeria japonica and used in manufacturing moldings

The wood of Japanese cedar (Cryptomeria japonica) was liquefied in phenol with H2SO4 and HCl as catalysts. The liquefied wood was reacted with formalin to prepare the novolak PF resin. The results showed that the reaction of liquefied Japanese cedar with formalin was an exothermic reaction, and formed a solid-like resin without extra heating. Two novolak PF resins were prepared from the liquefied wood which were identified as SF and CF that using the liquefied wood with H2SO4 and HCl as catalyst respectively. The novolak PF powder displayed thermo-melting characteristic. The resins of SF and CF had weight average molecular weight of 3638 and 3941 respectively and melting temperature of 149.4 degrees C and 127.5 degrees C respectively. Both of the novolak resins could be used to make moldings with good performance by mixing the novolak resin with wood powder, hardener and zinc stearate at the weight ratio of 60:30:10:1 and hot-pressed under 200 degrees C for 10min.     

Hydrogels obtained from an original catanionic system for efficient formulation of boron wood-preservatives

A new catanionic system associating amphiphilic carnosine (βAlaHisC8) and lauric acid forms supramolecular hydrogel at a very low concentration. This gel was investigated and we checked the validity of the concept of hydrogel utilization to reduce boron leachability and to develop new wood protection treatments. Impregnation with 5% aqueous borax solution (w/w) and 0.3% gelator agent (w/w) fosters improvement in the resistance of Scots pine sapwood subjected to water leaching toward the brown-rot fungus Poria placenta, while samples treated with 5% aqueous borax solution were partially degraded by the fungus. These results clearly indicate the effectiveness of hydrogel to retain boron in wood.     

Fungicidal properties of individual components of copper–ethanolamine-based wood preservatives

The importance of copper–ethanolamine-based wood preservatives is increasing. These preservatives usually consist of copper as a fungicide, ethanolamine as a fixative, and secondary fungicides (boron, triazoles) and other additives (water repellents, fixatives, wax emulsions, etc.). Questions arise as to how each of these ingredients interacts with wood-decay fungi, and whether there are any synergistic effects between the components. In order to elucidate these questions, Norway spruce wood specimens were impregnated with five different aqueous solutions consisting of one single component only and of complete formulation of five different concentrations. These specimens were exposed to two brown-rot fungi, Antrodia vaillantii and Gloeophyllum trabeum, as well as to the white-rot fungus Trametes versicolor for 8 weeks according to mini block procedure. In parallel, petri dishes with nutrient medium containing different quantities of ingredients and of complete wood preservative were inoculated with the same fungal species, and their growth was compared with growth on media without chemicals. The results showed that both experimental methods give similar results. In general, there was no synergistic effect determined. Ethanolamine did not decrease fungicidal properties of the system, while on the other hand octanoic acid has a positive effect on the growth of brown-rot fungi. The minimal effective concentration of tested copper–ethanolamine preservative was determined by the minimum effective concentration of the most fungi-toxic ingredient.     

Fixation,leachability, and decay resistance of wood treated with some commercial extracts and wood preservative salts

Beech (Fagus orientalis) and Scots pine (Pinus sylvestris) wood blocks were treated with some commercial extracts as well as water-based wood preservative salts at various concentrations to increase retention and fixation. The penetration, fixation, and antifungal properties of different treatment solutions were compared with statistical analysis. Retention levels of solutions were generally higher for Scots pine wood than beech wood. The highest retention levels were seen in wood treated with sumac leaf extract and oak valonia extract. Leaching tests indicated that both wood types treated with sumac extracts showed higher retention levels than wood treated with the other fruit and bark extract solutions. Adding 1% water-based wood preservative salts to valonia and sumac leaf extracts increased the retention levels. Concentrations of more than 1% did not contribute to retention either individually or with salt additions. Three percent and higher concentrations of wood-preserving salts accelerated and increased the amount of leaching. The results showed that the extract alone was resistant to leaching. Mycological tests showed that all extractives were significantly effective against wood decay.     

Effects of river red gum, Eucalyptus camaldulensis, litter on golden perch, Macquaria ambigua

Aquaria with added river red gum, Eucalyptus camaldulensis , litter became hypoxic, with decreased pH and contained up to 30 mg 1⁻¹ tannin and lignin. Survival of golden perch, Macquaria ambigua , larvae in aquaria treated with a simulated annual litter density of 450 g m⁻² for 72 h was 14·9% for 15-day-old larvae and 0% for 8-day-old larvae. A litter density of 1223 g m⁻² resulted in total mortality for both age groups of larvae. Aeration increased survival of larvae to a minimum of 68·8% in 1223 g m⁻² litter treatments compared to 89·8% in aerated controls and 86·8% in non-aerated controls. A kinetic behavioural assay was used to detect alarm responses in golden perch larvae and juveniles exposed to leachates from river red gum bark, leaves and wood. Eight-day-old larvae exposed to bark and wood leachates (0·001–10 g 1⁻¹) exhibited an initial period of hyperactivity, followed by a concentration-dependent decrease in spontaneous activity. Larvae exposed to leaf leachates displayed only a decrease in spontaneous activity. Four-month-old juveniles exposed to wood leachates were also initially hyperactive, then progressively developed mild hypoactivity at increasing leachate concentrations. Juveniles exposed to wood leachates at 20g 1⁻¹ for 30min suffered 97·5% mortality in 96 h. Wood leachates induced dose-dependent lamellar fusion, epithelial dissociation and necrosis in the gills. The presence of toxic leachates and low oxygen availability in flooded river red gum forests may make these habitats unsuitable as nursery areas for native fish.     

Chemical Composition of the Essential Oils from Different Morphological Parts of Pinus cembra L.

The essential oils from needles, twigs, bark, wood, and cones of Pinus cembra were analyzed by GC‐FID, GC/MS, and ¹H‐NMR spectroscopy. More than 130 compounds were identified. The oils differed in the quantitative composition. The principal components of the oil from twigs with needles were α‐pinene (36.3%), limonene (22.7%) and β‐phellandrene (12.0%). The needle oil was dominated by α‐pinene (48.4%), whereas in the oil from bark and in the oil from twigs without needles there were limonene (36.2% and 33.6%, resp.) and β‐phellandrene (18.8% and 17.1%, resp.). The main constituents of the wood oil as well as cone oil were α‐pinene (35.2% and 39.0%, resp.) and β‐pinene (10.4% and 18.9%, resp.). The wood oil and the cone oil contained large amounts of oxygenated diterpenes in comparison with needle, twig, and bark oils.     

Tolerance to wood preservatives by copper-tolerant wood-rot fungi native to south-central Chile

Understanding the effect of heavy metals and wood preservatives on the growth of wood-rot fungi native to a certain region may improve reliability in determining the effectiveness of antifungal products, particularly when dealing with new formulations. In this investigation, strains of copper-tolerant wood-rot fungi native to south-central Chile were evaluated against two preservatives: commercial chromated copper arsenate type C (CCA-C) and a new formulation with boron and silicon (BS). Thirteen native strains, mainly white-rot fungi, were selected for their high growth rates in solid medium containing 3 mM of copper. A short-term test was then carried out, consisting of adding cellulose disks impregnated with different concentrations of preservatives to solid culture media inoculated with selected copper tolerant strains. There was a great variability in interspecific and intraspecific responses to the presence of copper and preservatives in culture media. Among the native and commercial strains evaluated, the white-rot fungi Trametes versicolor 38 and mainly Ganoderma australe 100 were notable for their tolerance to all the CCA-C and BS concentrations. The brown-rot fungus Wolfiporia cocos, used as reference strain, showed a high tolerance to CCA-C, but not to BS preservative. T. versicolor 38 and G. australe 100 were selected for subsequent studies on preserved wood degradation.     

Degradation of Phenols Formed during Lignin Pyrolysis by Microfungi of Genera <Emphasis Type="Italic">Trichoderma</Emphasis> and <Emphasis Type="Italic">Penicillium</Emphasis>

This work presents the data on the rate of utilization of phenols formed during lignin pyrolysis by micromycetes of the genera Trichoderma and Penicillium. Trichoderma strains utilized phenols at the concentration of liquid pyrolytic products of 0.5–1%, while Penicillium strains degraded over 50% phenols at the concentration of pyrolytic products of 2%. Micromycete cultures completely utilized phenol and the cresol-xylenol fraction. Penicillium strains demonstrated a more active growth on media containing phenol, p-cresol, or guaiacum tar as the source of carbon as compared to Trichoderma. m-Cresol and m-xylenol in micromycete growth media containing products of lignin pyrolysis seem to be utilized by co-oxidation.     

Removal of copper, chromium, and arsenic from CCA-treated wood onto chitin and chitosan

Chitin and chitosan are naturally abundant biopolymers which are of interest to research concerning the sorption of metal ions since the amine and hydroxyl groups on their chemical structures act as chelation sites for metal ions. This study evaluates the removal of copper, chromium, and arsenic elements from chromated copper arsenate (CCA)-treated wood via biosorption by chitin and chitosan. Exposing CCA-treated sawdust to various amounts of chitin and chitosan for 1, 5, and 10 days enhanced removal of CCA components compared to remediation by deionized water only. Remediation with a solution containing 2.5 g chitin for 10 days removed 74% copper, 62% chromium, and 63% arsenic from treated sawdust. Remediation of treated sawdust samples using the same amount of chitosan as chitin resulted in 57% copper, 43% chromium, and 30% arsenic removal. The results suggest that chitin and chitosan have a potential to remove copper element from CCA-treated wood. Thus, these more abundant natural amino polysaccharides could be important in the remediation of waste wood treated with the newest formulations of organometallic copper compounds and other water-borne wood preservatives containing copper.     

Assessment of the genotoxicity of mine-dump material using the Tradescantia-stamen hair (Trad-SHM) and the Tradescantia-micronucleus (Trad-MCN) bioassays.

The Tradescantia-stamen hair (Trad-SHM) and -micronucleus (Trad-MCN) bioassays were used to determine the genotoxicity of two eluates derived from mine tailings. The goal was to test the suitability of the Tradescantia bioassays as screening tools for this kind of waste material. Leachates obtained using the current standard German leaching test methods (S4 eluate) as well as leachates obtained using a new eluation method (pHstat4) were tested and compared. Concentration of heavy metals in the pHstat4 eluate were much higher than in the S4 eluate. The chemical analysis corresponded well with the results of the bioassays. Exposure to solutions containing more than 1% pHstat4 eluate caused a significantly higher number of micronuclei. The Trad-SHM bioassay also showed an increased pink mutation rate when plants were exposed to 8 or 16% eluate solutions. In contrast, the S4 eluate only caused increased mutation rates when solutions containing more than 32% eluate were used. The low pH of the pHstat4 eluate was not responsible for the genotoxicity observed using both bioassays, as indicated by the lack of significant mutation rates in the nitric acid controls. This demonstrates that the Tradescantia bioassays can be used as tools to assess the genotoxic potential of environmental samples with a wide range of pH values, without the need for sample modification.     

Studies on the removal of heavy metals from sludges by leaching and uptake by plants

Sewage sludges from 19 Polish municipal treatment plants were investigated. Lysimeter leaching experiments on sludges and on sludge-quartz sand mixtures were made. A variety of plants was sowed in the lysimeters and the leachates were collected. Harvested plants as well as leachates were analysed for Pb, Cu, Cd, Ni, Zn and Cr concentration. Removal coefficients were established to characterize the mobility of these metals from the sludges. The high values of the correlation coefficient for cadmium and nickel suggested that water solubility of metal salts is mainly responsible for their mobility.