Effect of Compression Wood on Leaching and Fixation of CCA-C Treated Red Pine

In this study, we investigated the effect of compression wood on the release rate of chromium, copper, and arsenic elements from red pine (Pinus resinosa Ait.) and the rate of fixation of hexavalent chromium in the wood. Wood blocks from red pine, some containing compression wood and some with normal wood, were treated with a 1.0% CCA-C solution and then allowed to fix at 23°C ± 2 (74°F ± 4) for 0, 6, 24, 48, 96, 192, and 336 h. After each fixation period, sets of blocks removed from the conditioning room were subjected to 336 h of leaching. The percentage of hexavalent chromium reduced to the trivalent state was determined for solution pressed from matched sets of blocks. The blocks containing compression wood released significantly less chromium and copper elements. For chromium, the biggest effect was seen after the 192- and 336-h fixation periods. In the normal wood blocks fixed for 336 h, the average chromium release rate after 6 h of leaching was almost five times greater than that of the compression wood blocks. Copper and arsenic release was also affected by compression wood, but for these two elements, the effect diminished during the later stages of fixation. A higher percentage of hexavalent chromium was reduced to trivalent chromium in compression wood compared with that in normal wood after most fixation periods, and this difference was significant after 0, 48, 96, and 192 h

Interactions of ammoniacal copper zinc arsenate (ACZA) wood preservative with Douglas-fir

The use of the waterborne wood preservative, ammoniacal copper zinc arsenate (ACZA), is likely to increase in the near future because of environmental concerns associated with oilborne preservatives. Developing an understanding of the permanence of this preservative in wood will become important from both environmental and performance standpoints. Conventional thinking suggests that ACZA components are stabilized in the wood by the precipitation of metal/arsenate complexes as the ammonia evaporates, but little work has been done to confirm this theory. Experiments were conducted to clarify the mechanisms which stabilize, or "fix" copper, arsenic and zinc within ACZA treated wood. Studies were undertaken to determine the effect of ACZA composition on fixation, the role of wood components in fixation, the role of precipitation in fixation, the order of precipitation of ACZA components, the sites of copper and zinc adsorption within the treated wood, the bonding environment of adsorbed copper, and the microdistribution of copper, zinc and arsenic within treated wood. The results of these experiments generally support the finding that arsenic fixation occurs by precipitation of metal/arsenate, complexes as ammonia evaporates from the treated wood. Arsenic leaching was minimized when the metal oxide:arsenic pentoxide ratio in the treating solution exceeded 2.0, and when a portion of the copper was replaced with zinc. Subsequent tests revealed that zinc precipitated the majority of arsenic when the ammonia was allowed to evaporate from the treating solution. In contrast, the metal cations are not dependent on arsenic for fixation because they have low water solubility and undergo adsorption reactions with the wood. Copper, in particular was readily adsorbed by the lignin and heartwood components of wood, suggesting that phenolic groups were primary reaction sites. Further tests with lignin model compounds also suggested that copper reacted preferentially with the hydroxyl groups of phenolic compounds. Adsorption of the metals to the wood can interfere with arsenic fixation by reducing the availability of metal cations in the preservative solution. The severity of arsenic leaching due to metal adsorption could be affected by many treatment variables, and more work is needed to determine how these variables could be manipulated to minimize arsenic fixation

Efficacy of alternative copper-based preservatives in protecting decking from biodegradation

The above-ground performance of decking treated with two alternative copper-based preservative formulations is being evaluated at a test site near Madison, Wisconsin, USA. Southern pine sapwood lumber specimens (38 mm by 140 mm by 910 mm) were pressure treated with 0,93 %, 1,40 % or 2,34 % (oxide basis) actives concentrations of a boron-copper formulation (BC) composed of 7,2 % copper hydroxide and 92,8 % sodium tetraborate decahydrate. Similar specimens were pressure-treated with 0,66 % or 1,32 % actives concentrations of a copper-zinc formulation (CZDP) composed of 18 % copper (CuO basis), 12 % zinc (ZnO basis), 14 % dimethylcocoamine and 56 % propanoic acid. In both cases untreated specimens and specimens treated with a 1% concentration of chromated copper arsenate Type C (CCA-C) were included for comparison.  The specimens were installed on racks approximately 760 mm above the ground and periodically evaluated for extent of fungal decay and surface microbial growth. After 18 years in test specimens treated with the lowest solution concentration of BC (0,93 %) suffered substantial degradation and all but three replicates have failed. Obvious decay has not yet been detected in specimens treated to the highest BC concentration (2,34 %), but decay is suspected in one of these specimens. Decking specimens treated with CZDP exhibited no evidence of decay until year 17 when a fruiting body was observed on one specimen treated with a 0,66 % solution concentration. There has been no evidence of decay in specimens treated with 1,32 % CZDP or in either set of specimens treated with 1 % CCA-C. Both BC and CZDP-treated specimens were at least as effective as 1 % CCA-C in minimizing noticeable surface microbial growth. These decking studies confirm that relatively low copper concentrations can provide substantial protection for decking exposed in a moderate climate, and that the CZDP formulation is potentially more effective than the BC formulation. However, caution is warranted in extrapolating these findings to more severe climates and to construction designs that are more likely to trap moisture

Migration of creosote from wood and its effects on marine borer attack

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Interactions of ammoniacal copper zinc arsenate (ACZA) with Douglas-fir

Tests were conducted to determine the effect of ACZA composition on fixation and the roles of adsorption and precipitation in fixation. The sites of copper and zinc adsorption within the treated wood and the bonding environment of adsorbed copper were also examined. The results generally support the finding that arsenic fixation occurs by precipitation of metal/arsenate complexes. Arsenic leaching was minimized with high solution ratios of metal oxide:arsenic pentoxide, and with formulations containing zinc. Zinc precipitated the majority of arsenic when ammonia was allowed to evaporate from the treating solution. The metal cations were leach-resistant regardless of ACZA formulation because of their low water solubility and their ability to adsorb to the wood. Copper was readily adsorbed by lignin and by model compounds that possessed phenolic hydroxyl groups, which suggests that phenolic hydroxyl groups were the primary reaction sites. Fourier Transform Infrared (FTIR) and Fast Atom Bombardment (FAB) mass spectroscopy analysis also supported this conclusion. Multiple copper species and increased free radical content were detected within lignin that had adsorbed copper. Adsorption of copper and zinc has important ramifications for arsenic fixation.Keywords: leaching, adsorption, Douglas-fir, fixation, ACZA, precipitation, ammoniacal copper zinc arsenat

Methylisothiocyanate fumigant content of Douglas-fir heartwood at various moisture levels after treatment with solid sodium N-methyldithiocarbamate

The relationship between moisture content and the presence of methylisothiocyanate (MITC) in wood following various applications of sodium n-methyldithiocarbamate (NaMDC) was investigated with small Douglas-fir heartwood blocks. While MITC levels were initially higher in wetter blocks, MITC levels in drier blocks remained more stable over the 8-week test period. The addition of water as well as NaMDC to blocks enhanced MITC levels only initially; this effect declined over the test period for blocks at 30% MC or greater. In comparing the effect on MITC levels of applying the NaMDC in powder or pellet form, no significant difference between the two application methods emerged.Keywords: fumigants, MITC, Douglas-fir heartwood, methylisothiocyanate, decomposition, sodium n-methyldithiocarbamate, moisture content, NaMD

The Application of Near Infrared (Nir) Spectroscopy to Inorganic Preservative-Treated Wood

There is a growing need to find a rapid, inexpensive, and reliable method to distinguish between treated and untreated waste wood. This paper evaluates the ability of near infrared (NIR) spectroscopy with multivariate analysis (MVA) to distinguish preservative types and retentions. It is demonstrated that principal component analysis (PCA) can differentiate lumber treated with CCA, ACZA, or ACQ preservatives. Furthermore, separation according to wood species and assay zone was also observed. Within the range of preservative concentrations available, partial least squares (PLS) regression was also performed on the NIR data, from which retention levels were predicted. The results highlight the potential for this technique to predict the concentration, as well as identify the type, of inorganic preservatives present

Northeastern united states species treated with copper-based preservatives: Durability in mississippi stake tests

This paper reports on the ground-contact durability of lesser-used wood species of the northeastern United States after treatment with copper-based preservatives. Stakes (19 by 19 by 457 mm) cut from balsam-fir (Abies balsamea), eastern hemlock (Tsuga canadensis), eastern spruce (mixture of Picea glauca, Picea mariana and Picea rubens), red maple (Acer rubrum) or eastern white pine (Pinus strobus) were treated with one of four concentrations of chromated copper arsenate type C (CCA-C), copper citrate (CC), alkaline copper quat type C (ACQ-C) or copper azole type A (CBA-A) and placed into the ground at a test site in southern Mississippi. Similarly treated southern pine (Pinus spp.) stakes were included for comparison. The stakes were rated for decay and termite attack after 1, 2, 3, 4, 5, 8, 10 and 12 years. Eastern white pine and incised eastern hemlock and balsam-fir had durability similar to southern pine when treated with CCA or the other copper-based preservatives. Eastern spruce was less durable than the other softwood species, apparently because of low preservative uptake. Red maple had the least durability at all retentions and for all preservatives. This study indicates that several northeastern softwoods can be adequately durable when pressure-treated with CCA-C or copper-based preservatives

Interactions of Ammoniacal Copper Zinc Arsenate (ACZA) with Douglas-Fir

Tests were conducted to determine the effect of ACZA composition on fixation and the roles of adsorption and precipitation in fixation. The sites of copper and zinc adsorption within the treated wood and the bonding environment of adsorbed copper were also examined. The results generally support the finding that arsenic fixation occurs by precipitation of metal/arsenate complexes. Arsenic leaching was minimized with high solution ratios of metal oxide:arsenic pentoxide, and with formulations containing zinc. Zinc precipitated the majority of arsenic when ammonia was allowed to evaporate from the treating solution. The metal cations were leach-resistant regardless of ACZA formulation because of their low water solubility and their ability to adsorb to the wood. Copper was readily adsorbed by lignin and by model compounds that possessed phenolic hydroxyl groups, which suggests that phenolic hydroxyl groups were the primary reaction sites. Fourier Transform Infrared (FTIR) and Fast Atom Bombardment (FAB) mass spectroscopy analysis also supported this conclusion. Multiple copper species and increased free radical content were detected within lignin that had adsorbed copper. Adsorption of copper and zinc has important ramifications for arsenic fixation

Northeastern United States species treated with copper-based preservatives: Durability in Mississippi stake tests

This paper reports on the ground-contact durability of lesser-used wood species of the northeastern United States after treatment with copper-based preservatives. Stakes (19 by 19 by 457 mm) cut from balsam-fir (Abies balsamea), eastern hemlock (Tsuga canadensis), eastern spruce (mixture of Picea glauca, Picea mariana and Picea rubens), red maple (Acer rubrum) or eastern white pine (Pinus strobus) were treated with one of four concentrations of chromated copper arsenate type C (CCA-C), copper citrate (CC), alkaline copper quat type C (ACQ-C) or copper azole type A (CBA-A) and placed into the ground at a test site in southern Mississippi. Similarly treated southern pine (Pinus spp.) stakes were included for comparison. The stakes were rated for decay and termite attack after 1, 2, 3, 4, 5, 8, 10 and 12 years. Eastern white pine and incised eastern hemlock and balsam-fir had durability similar to southern pine when treated with CCA or the other copper-based preservatives. Eastern spruce was less durable than the other softwood species, apparently because of low preservative uptake. Red maple had the least durability at all retentions and for all preservatives. This study indicates that several northeastern softwoods can be adequately durable when pressure-treated with CCA-C or copper-based preservatives