Effect of moisture content on manufacturing cement-bonded particleboard using supercritical CO<Subscript>2</Subscript>

This study examined the effects of moisture content (MC) on the manufacture of cement-bonded particleboard (CBP) using supercritical CO₂ in the curing process. Significant correlations were found between MC and the performance of CBP: the internal bond strength, modulus of rupture, and modulus of elasticity values of CBP achieved their maximums, when the MC of boards was approximately 30%. This finding indicated that during the curing phase of manufacturing CBP, a MC of about 30%, which is nearly equal to the water–cement (w/c) ratio of about 0.34, contributes to improved mechanical properties. However, the mechanical properties decreased when the MC was below 30%, which had a negative effect on board performance, indicating that carbon dioxide could not fully react and no carbonation occurred during the curing process. Maintaining a MC of approximately 30% as an ordinary condition of the cement required in the curing of CBP could promote the reaction of carbon dioxide to form calcium carbonate (CaCO₃), which leads to increased final strength of CBP. Both X-ray diffractometry and thermal gravimetry observation agreed well with these results and clarified that the increase of CaCO₃ content caused by carbonation with increased MC of boards contributed to improving the mechanical properties of CBP.     

Manufacturing oil palm fronds cement-bonded board cured by gaseous or supercritical carbon dioxide

This study dealt with the effects of a curing method that uses gaseous and supercritical CO₂. Its effects on the properties of oil palm fronds cement-bonded board manufactured by the conventional cold-press setting method were recorded. The effect of MgCl₂ as an accelerator of cement setting was also investigated. The hydration of cement was examined using X-ray diffractometry, thermal gravimetry, and scanning electron microscopy. The results are as follows. (1) High-performance cement-bonded boards made from oil palm fronds were successfully manufactured using the CO₂ curing method. (2) The curing method using either gaseous or supercritical CO₂ resulted in accelerated curing of cement (within several minutes). Accelerated formation of the hydration products (e.g., calcium carbonate and calcium silicate) is the main reason for the high strength of CO₂-cured boards. (3) The CO₂ curing technology does not require setting accelerators, which cause a decrease in the dimensional stability of cement-bonded board.     

Rapid production of high-strength cement-bonded particleboard using gaseous or supercritical carbon dioxide

This study deals with the effects of curing treatment with gaseous and supercritical carbon dioxide on the properties of cement-bonded particleboard (CBP) manufactured by the conventional cold-pressing method. The hydration of cement and the mechanism of improvement were examined using X-ray diffractometry (XRD), thermal gravimetry (TG-DTG), and scanning electron microscopy (SEM) observations. The results are as follows: (1) The curing of cement was accelerated concomitantly with the improvement in mechanical and dimensional properties of CBP significantly by curing with gaseous or supercritical carbon dioxide. (2) Supercritical carbon dioxide curing imparted boards optimal properties at a faster rate than did gaseous curing. (3) Accelerated formation of calcium silicate hydrate and calcium carbonate and the interlocking of those hydration products on the wood surface are potentially the main reasons for the superior strength of carbon dioxide-cured boards.     

Effect of carbon dioxide-air concentration in the rapid curing process on the properties of cement-bonded particleboard

This study deals with the effects of carbon dioxide (CO₂)-air concentration in the rapid curing method on the properties of cement-bonded particleboard manufactured using conventional cold pressing as the setting method. The hydration of cement was examined using X-ray diffractometry, thermal gravimetry, and scanning electron microscopy. The results are as follows: (1) The properties of CO₂-cured boards improved with increasing CO₂ concentration. When 10% or 20% CO₂ was applied for 10 min of curing time, the properties of the CO₂-cured boards were comparable to those obtained by conventional 2-week curing. (2) The hydration process of cement could be accelerated within several minutes using CO₂ curing, even with a low concentration of 10%–20% CO₂; a reduction in calcium hydroxide was observed followed by rapid formation of calcium carbonate.     

Branch CO<Subscript>2</Subscript> efflux in vertical profile of Norway spruce tree

Branch CO₂ efflux of Norway spruce tree [Picea abies (L.) Karst.] was measured in ten branches at five different whorls during the growing season 2004 (from June till October) in campaigns of 3–4 times per month at the Beskydy Mts., the Czech Republic. Branch CO₂ efflux was measured using a portable infrared gas analyzer (LI-6250, LI-COR, Inc., USA), operating as a closed system. Branch woody-tissue temperature was measured continuously in 10-min intervals for each sample position during the whole experiment period. On the basis of relation between CO₂ efflux rate and woody-tissue temperature, a value of Q₁₀ and of normalized CO₂ efflux rate (E₁₀–CO₂ efflux rate at 10°C) was calculated for each sampled position. Estimated Q₁₀ values ranged from 2.12 to 2.89, and E₁₀ ranged from 0.41 to 1.19 μmolCO₂m⁻²s⁻¹. Differences in branch CO₂ efflux were found between orientations, east-side branches presented higher efflux rate than west-side branches. The highest branch CO₂ efflux rate values were measured in August and the lowest in October, which corresponds with woody-tissue temperature and growth processes during these periods. Branch CO₂ efflux was significantly and positively correlated with branch position within canopy and woody-tissue temperature. Branches from the upper whorls showed higher CO₂ efflux activity and seasonal dynamics than branches from the lower whorls.     

Soil CO<Subscript>2</Subscript>, CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O emissions from production fields with planted and remnant hedgerows in the Fraser River Delta of British Columbia

Planting hedgerows on farm field edges can help mitigate greenhouse gas (GHG) emissions from agricultural landscapes by sequestering carbon (C) in woody biomass and in soil. Sequestration rates however, must be assessed in terms of their overall global warming potential (GWP) which must also consider GHG emissions. The objectives of this study were to (1) compare carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) emissions from two types of hedgerows and adjacent annual agricultural production fields, and 2) better understand how climate, soil properties and plant species configurations affect hedgerow GHG emissions. At eight study sites in the lower Fraser River delta of British Columbia, we measured emissions from soil in both planted (P-Hedgerow) and remnant hedgerows (R-Hedgerow), as well as in adjacent annual crop production fields over 1 year using a closed-static chamber method. CO₂ emissions were 59 % higher in P-Hedgerow than R-Hedgerow, yet there were no significant differences of relative emissions of CH₄ and N₂O. The environmental variables that explained the variation in emissions differed for the three GHGs. CO₂ emissions were significantly correlated with soil temperature. CH₄ and N₂O and emissions were marginally significantly correlated with soil organic carbon (SOC) and soil water-filled pore space (WFPS), respectively. Emissions were not significantly correlated with hedgerow plant species diversity. While hedgerows sequester carbon in their woody biomass, we demonstrated that it is critical to measure hedgerow emissions to accurately ascertain their overall GHG mitigation potential. Our results show that there are no CO₂e emission differences between the management options that plant new diverse hedgerows or conserve existing hedgerows.     

Consumption of O<Subscript>2</Subscript>, evolution of CO<Subscript>2</Subscript> and reduction of Cr(VI) during fixation of chromium based wood preservatives in wood

Norway spruce dust was impregnated with aqueous solutions of chromated copper wood preservatives. Immediately after treatment, observation of CO₂ evolution and O₂ consumption were performed. Significant quantities of CO₂ were released during reaction of chromium (K₂Cr₂O₇) containing solutions with wood or brown rotted wood. Nevertheless, during reaction of cellulose with these preservatives we did not observe evolution of CO₂. The presence of copper did not influence on concentration of CO₂. Opposite to CO₂ evolution, treatment of wood and brown rotted wood resulted in O₂ consumption. The oxygen concentration decrease in the measuring chamber was approximately 5 times greater than increase of concentration of carbon dioxide. Electron paramagnetic resonance (EPR) observations of chromium fixation showed that chromium is reduced from Cr(VI) to Cr(III) with Cr(V) as an intermediate on wood, brown rotted wood and cellulose. However, the reduction on wood and brown rotted wood was faster than the reduction on cellulose, as determined from changes of Cr signals in EPR spectra. So, evolution of CO₂ and consumption of O₂ as well as EPR signals of Cr species thus indicate that brown rotted wood, consisting of lignin and hemicelluloses in contact with Cr(VI) reacts more intensively than cellulose, and possibly, oxidation mechanisms of lignin and cellulose with Cr(VI) are different. Received: 20 July 2000     

Soil CO<Subscript>2</Subscript> emissions in agricultural watersheds with agroforestry and grass contour buffer strips

The potential for agricultural soils to act as a sink and sequester carbon (C) or a source and emit carbon dioxide (CO₂) is largely dependent upon the agricultural management system. The establishment of permanent vegetation, such as trees and grass contour buffer strips, may cause accumulation of above- and below-ground C over time, thereby acting as a sink for tropospheric CO₂. However, the effects of contour grass strips and grass-tree strips (agroforestry) on soil CO₂ emissions have not been extensively studied in row-crop watersheds in the temperate regions. The objective of this study was to determine the effects of agroforestry and grass contour buffer strips and landscape position on soil surface efflux rate of CO₂ in three adjacent agricultural watersheds with claypan soils in northeast Missouri. The three watersheds were in a corn-soybean rotation, and contained (1) cropped only (CR), (2) cropped with grass contour strips (GR), or (3) cropped with tree-grass contour strips (AF) management systems. Soil surface CO₂ efflux was measured throughout the 2004 growing season at the upper (UBS), middle (MBS), and lower (LBS) backslope landscape positions within the three watersheds. The cumulative soil CO₂ production was lowest in the CR (0.9 kg CO₂-C m⁻²) compared to the AF (1.5 kg CO₂-C m⁻²) and GR watersheds (1.5 kg CO₂-C m⁻²). The lower backslope position (1.6 kg CO₂-C m⁻²) across all three watersheds produced 32 and 40% greater cumulative soil CO₂ than the upper and middle backslope positions, respectively. A 72-day incubation study determined the effects of 40, 60, 80, and 100% soil water-filled pore space (WFPS) and N rate (0 and 1.39 g KNO₃ kg soil⁻¹) on soil CO₂ efflux from bulk soil collected under each management system. The cumulative CO₂ production was highest in the grass soil (1,279 mg CO₂-C kg soil⁻¹) compared to the agroforestry (661 mg CO₂-C kg soil⁻¹) and cropped (483 mg CO₂-C kg soil⁻¹) soils regardless of WFPS and N rate. The highest cumulative CO₂ production for the grass soil (1,279 mg CO₂-C kg soil⁻¹) occurred at 80% WFPS, and was approximately 2 to 2.6 times greater than the agroforestry and cropped soils at 80% WFPS. The results of this study indicate that conservation management practices, such as grass and grass-tree contour buffer strips, and landscape position affect soil surface CO₂ production and accumulation of soil organic C that may influence soil C sequestration.     

Difference in cutting age for highest profit by methods for calculating CO<Subscript>2</Subscript> emission trading and the price of CO<Subscript>2</Subscript>

 The amounts of CO₂ that are absorbed and emitted by forest in a model stand area were determined using two calculation methods, namely the flow approach and the stock approach for emission trading, to understand the relationships between the cutting age for the highest profit rate (CAHPR; optimum tree ages to be cut so as to maximize the profit) and (1) the prices of CO₂ and (2) the balance between CO₂ emission and absorption. The resultant CAHPR differed between these two CO₂ accounting methods, which give different tree ages for maximum log volume yield. A rise in CO₂ price caused the CAHPR to approach the tree age of maximum log volume in the flow approach method, and to deviate from the tree age of maximum log volume in the stock approach method. Even at the same CO₂ price, the CAHPR differed between the CO₂ accounting methods. At low CO₂ prices, the CAHPR did not affect situations where the difference of average profit is large by cutting age. On the other hand, the CAHPR was greatly affected at low CO₂ prices when the mean log volume growth changed with tree age. These trends were found to be universal. Received: September 18, 2001 / Accepted: October 25, 2002 Acknowledgments This study is one of the fifth science study subsidy projects of the Japan Forest Technology Association. Correspondence to:K. Sakata     

Effects of long-term elevated CO<Subscript>2</Subscript> on N<Subscript>2</Subscript>-fixing,denitrifying and nitrifying enzyme activities in forest soils under <Emphasis Type="Italic">Pinus sylvestriformis</Emphasis> in Changbai Mountain

A study was conducted to determine the effects of elevated CO₂ on soil N process at Changbai Mountain in Jilin Province, northeastern China (42°24′N, 128°06′E, and 738 m elevation). A randomized complete block design of ambient and elevated CO₂ was established in an open-top chamber facility in the spring of 1999. Changpai Scotch pine (Pinus sylvestris var. sylvestriformis seeds were sowed in May, 1999 and CO₂ fumigation treatments began after seeds germination. In each year, the exposure started at the end of April and stopped at the end of October. Soil samples were collected in June and August 2006 and in June 2007, and soil nitrifying, denitrifying and N₂-fixing enzyme activities were measured. Results show that soil nitrifying enzyme activities (NEA) in the 5–10 cm soil layer were significantly increased at elevated CO₂ by 30.3% in June 2006, by 30.9% in August 2006 and by 11.3% in June 2007. Soil denitrifying enzyme activities (DEA) were significantly decreased by elevated CO₂ treatment in June 2006 (P < 0.012) and August 2006 (P < 0.005) samplings in our study; no significant difference was detected in June 2007, and no significant changes in N₂-fixing enzyme activity were found. This study suggests that elevated CO₂ can alter soil nitrifying enzyme and denitrifying enzyme activities. Foundation project: This research was supported by the National Natural Science Foundation of China (No. 90411020) and Major State Basic Research Development Program of China (973 Program) (2002CB412502).     

Crop residue effect on crop performance,soil N<Subscript>2</Subscript>O and CO<Subscript>2</Subscript> emissions in alley cropping systems in subtropical China

Land management practices that simultaneously improve soil properties are crucial to high crop production and minimize detrimental impact on the environment. We examined the effects of crop residues on crop performance, the fluxes of soil N₂O and CO₂ under wheat-maize (WM) and/or faba bean-maize (FM) rotations in Amorpha fruticosa (A) and Vetiveria zizanioides (V) intercropping systems on a loamy clay soil, in subtropical China. Crop performance, soil N₂O and CO₂ as well as some potential factors such as soil water content, soil carbon, soil nitrogen, microbial biomass and N mineralization were recorded during 2006 maize crop cultivation. Soil N₂O and CO₂ fluxes are determined using a closed-based chamber. Maize yield was greater after faba bean than after wheat may be due to differences in supply of N from residues. The presence of hedgerow significantly improved maize grain yields. N₂O emissions from soils with maize were considerably greater after faba bean (345 g N₂O–N ha⁻¹) than after wheat (289 g N₂O–N ha⁻¹). However, the cumulated N₂O emissions did not differ significantly between WM and FM. The difference in N₂O emissions between WM and FM was mostly due to the amounts of crop residues. Hedgerow alley cropping tended to emit more N₂O than WM and FM, in particular A. fruticosa intercropping systems. Over the entire 118 days of measurement, the N₂O fluxes represented 534 g N₂O–N ha⁻¹ (AWM) and 512 g N₂O–N ha⁻¹ (AFM) under A. fruticosa species, 403 g N₂O–N ha⁻¹ (VWM) and 423 g N₂O–N ha⁻¹ (VFM) under Vetiver grass. We observed significantly higher CO₂ emission in AFM (5,335 kg CO₂–C ha⁻¹) from June to October, whereas no significant difference was observed among WM (3,480 kg CO₂–C ha⁻¹), FM (3,302 kg CO₂–C ha⁻¹), AWM (3,877 kg CO₂–C ha⁻¹), VWM (3,124 kg CO₂–C ha⁻¹) and VFM (3,309 kg CO₂–C ha⁻¹), indicating the importance of A. fruticosa along with faba bean residue on CO₂ fluxes. As a result, crop residues and land conversion from agricultural to agroforestry can, in turn, influence microbial biomass, N mineralization, soil C and N content, which can further alter the magnitude of crop growth, soil N₂O and CO₂ emissions in the present environmental conditions.     

Effects of elevated atmospheric CO<Subscript>2</Subscript> on two southern forest diseases

Research into the effects of rising atmospheric carbon dioxide (CO₂) on plant diseases remains limited despite the economic importance of this subject. Loblolly pine (Pinus taeda) seedlings were exposed to ambient and twice ambient levels of atmospheric CO₂ prior to inoculation with the fusiform rust fungus (the obligate pathogen Cronartium quercuum f.sp. fusiforme, CQF) or the pitch canker fungus (the facultative pathogen Fusarium circinatum, FC). Additionally, northern red oak seedlings (Quercus rubra; an alternate host of CQF) were exposed to ambient or elevated levels of atmospheric CO₂ prior to inoculation with CQF. In all cases, disease incidence (percent of plants infected) and disease severity (proportion of each plant affected) were determined; with the oak seedlings, the latent period (time to sporulation) was also monitored. In general, disease incidence was decreased by exposure to elevated CO₂. This exposure also increased the latent period for CQF on oak seedlings. In no instance did exposure to elevated CO₂ affect disease severity. This research demonstrated that plants may benefit from exposure to the increasing concentration of CO₂ in the atmosphere through decreases in fungal disease incidence.     

Seasonality of vertically partitioned soil CO<Subscript>2</Subscript> production in temperate and tropical forest

Soil CO₂ production seasonality at a number of depths was investigated in a temperate forest in Japan and in a tropical montane forest in Thailand. The CO₂ production rates were evaluated by examining differences in the estimated soil CO₂ flux at adjacent depths. The temperate forest had clear temperature seasonality and only slight rainfall seasonality, whereas the tropical montane forest showed clear rainfall seasonality and only slight temperature seasonality. In the temperate forest, the pattern of seasonal variation in soil respiration was similar at all depths, except the deepest (0.65 m–), and respiration was greater in summer and less in winter. The contribution of the shallowest depth (around 0.1 m) was more than 50% of total soil-surface CO₂ flux all year round, and the annual mean contribution was about 75%. CO₂ production mostly appeared to increase with temperature in shallower layers. In contrast, in the tropical forest, soil CO₂ production seasonality appeared to differ with depth. The CO₂ production rate in the shallowest layer was high during the rainy season and low during the dry season. Soil CO₂ production at greater depths (0.4 and 0.5 m–) showed the opposite seasonality to that in the shallower layer (around 0.1 m). As a result, the contribution from the shallow depth was greatest in the tropical forest during the rainy season (more than 90%), whereas it decreased during the dry season (about 50%). CO₂ production appeared to be controlled by soil water at all depths, and the different ranges of water saturation seemed to cause the difference in seasonality at each depth. Our results suggest the importance of considering the vertical distribution of soil processes, particularly in areas where soil water is a dominant controller of soil respiration.     

CaCO<Subscript>3</Subscript> in situ treated bamboo pulp fiber reinforced composites obtained by vacuum-assisted resin infusion

The aim of this study is to investigate the properties of CaCO₃ in situ treated bamboo pulp fiber (BPF) composites that have been filled with epoxy resin by means of vacuum-assisted resin infusion (VARI). Un-treated and treated BPF were processed at a pressure of 0.24 MPa into BPF preforms. VARI was used to infuse epoxy resin through the BPF preforms to make BPF composites. The flexural properties, impact property, and thermal properties of the BPF composites were analyzed. CaCO₃ with the loading of 30 wt% affects the performance of the composites. The flexural strength did not decrease and modulus of the treated BPF composites increased by 9.38%, while the impact strength decreased by 50.98%, compared to the control sample. Dynamic mechanical analysis revealed the maximum elastic moduli of the treated specimens increased by 1.19 times in the temperature range of ?20 to 120 °C. The thermal decomposition temperature of the composites was influenced by the effect of the crystal field and size effect of CaCO₃.     

Nutrient contents and efficiencies of beech and spruce saplings as influenced by competition and O<Subscript>3</Subscript>/CO<Subscript>2</Subscript> regime

Saplings of Fagus sylvatica and Picea abies were grown under conditions of intra and interspecific competition in a 2-year phytotron study under combinations of ambient and elevated ozone (+O₃ which is 2 × O₃, but <150 nl l⁻¹) as well as carbon dioxide concentrations (+CO₂ which is amb. CO₂ + 300 μl CO₂ l⁻¹) in a full factorial design. Saplings were analysed for various mineral nutrients in different plant organs as well as biomass production and crown development. The study was based on the assumption that nutritional parameters important for growth and competitiveness are affected by stress defence under limiting nutrient supply. The hypotheses tested were (1) that nutrient uptake-related parameters (a) as well as efficiencies in nutrient use for above-ground competition (b) of beech rather than spruce are impaired by the exposure to elevated O₃ concentrations, (2) that the efficiency in nutrient uptake of spruce is enhanced by elevated CO₂ concentrations in mixed culture, and (3) that the ability to occupy above-ground space at low nutrient cost is co-determinant for the competitive success in mixed culture. Clear nitrogen deficiencies were indicated for both species during the 2-year phytotron study, although foliar nitrogen-biomass relationships were not so close for spruce than for beech. O₃ stress did not impair nutrient uptake-related parameters of beech; thus hypothesis (1a). was not supported. A negative effect of elevated O₃ (under amb. CO₂) on the N and P based efficiencies in above-ground space occupation (i.e. lower crown volume per unit of N or P invested in stems, limbs and foliage) of beech supported hypothesis (1b). It appeared that ozone stress triggered a nutrient demand for stress defence and tolerance at the expense of above-ground competition (trade-off). Crown volume of beech under O₃ stress was stabilized in monoculture by increased nutrient uptake. In general, the +CO₂-treatment was able to counteract the impacts of 2 × O₃. Elevated CO₂ caused lower N and S concentrations in current-year foliage of both tree species, slightly higher macronutrient amounts in the root biomass of spruce, but did not increase the efficiencies in nutrient uptake of spruce in mixed culture. Therefore hypothesis (2) was not supported. At the end of the experiment spruce turned out to be the stronger competitor in mixed culture as displayed by its higher total shoot biomass and crown volume. The amounts of macronutrients in the above-ground biomass of spruce individuals in mixed culture distinctly exceeded those of beech, which had been strongly reduced by interspecific competition. The superior competitiveness of spruce was related to higher N and P-based efficiencies in above-ground space occupation as suggested in hypothesis (3). This article belongs to the special issue “Growth and defence of Norway spruce and European beech in pure and mixed stands”.     

在长白山生态系统中长期的高浓度CO2熏蒸对土壤酶的影响

从1999年到2006年在中科院长白山森林生态系统定位站（42°24＇N,128°28＇E,海拔738m）对长期高浓度CO2熏蒸对土壤酶活性的影响进行了研究.采用开顶箱（OTC）的方式对红松和长白松进行高浓度CO2处理, CO2浓度分别受控于高浓度CO2箱（500 μmol·mol^-1）、对照箱（370 μmol·mol^-1））和裸地（370 μmol·mol^-1）.经高浓度CO2（500 μmol·mol^-1）熏蒸8年后,土壤样品分别在2006年春季、夏季和秋季进行采集和分析.结果表明：在高CO2浓度（500 μmol mol^-1）条件下,转化酶活性除了红松夏季样品之外都是显著降低的;而脱氢酶活性却是增加的,但只有部分结果显著;长白松的多酚氧化酶活性都显著降低;过氧化氢酶活性在春季增加,而在其他季节均降低.总而言之,在高CO2浓度条件下,土壤酶的活性与树种有关.     

Photocatalytic activity of TiO<Subscript>2</Subscript> crystallite-activated carbon composites prepared in supercritical isopropanol for the decomposition of formaldehyde

 An effort was made to develop photocatalytic TiO₂ crystallite–activated carbon (TiO₂-AC) composites from tetraisopropyl titanate (TPT)-soaked activated carbon in supercritical isopropanol. It was subsequently found that TPT in supercritical isopropanol could be effectively converted to the anatase form of the TiO₂ crystallites. The prepared composites, composed of activated carbon as an adsorbent and the anatase form of TiO₂ as a photocatalyst, were evaluated for their adsorption capacity and subsequent photocatalytic activity against formaldehyde, one of the harmful air pollutants in the environment. As a result, the supercritically treated TiO₂–AC composites, particularly at 300°C and 350°C, had much higher formaldehyde-decomposing ability compared to a noncomposite comprising a simple mixture of activated carbon and TiO₂ granules. This indicates that the supercritical treatment can be effective for preparing the photocatalytic composites that have a high synergetic effect of adsorption and photocatalytic decomposition of formaldehyde for environmental cleaning. Received: May 18, 2001 / Accepted: March 8, 2002 On leave from Fujian Forestry College, Fujian 353001, P.R. China Acknowledgments The authors express their sincere thanks to Miss H. Tokoro and Mr. D. Kusdiana for their kind, valuable help and cooperation and to Dr. H. Miyafuji for SEM observations of samples, all at the Graduate School of Energy Science, Kyoto University. Correspondence to:S. Saka     

Cyproconazole impregnation into wood using sub- and supercritical carbon dioxide

Supercritical fluid (SCF) impregnation is a promising preservative treatment method for wood. In order to commercialize the sub- and supercritical CO₂ biocide treatment, better understanding of the fluid phase and its effect on treatment results have to be demonstrated and developed. Preservative treatability under super- and subcritical fluid conditions was evaluated using radiata pine sapwood, and treating characteristics in relation to different fluid phases and treatability were discussed. Various treatment conditions resulted in varying biocide retentions and distributions. Higher pressure conditions enhanced biocide retentions resulting from increasing biocide input in the applied saturation method. Subcritical CO₂ condition produced higher biocide retentions and little retention gradients from face to core. Subcritical CO₂ treatment has a couple of benefits such as investment costs and energy consumption compared with supercritical CO₂.     

外源糖溶液和高浓度CO2处理对白桦叶片糖和蛋白质含量的影响

3年生白桦同时接受3种外源糖溶液(蔗糖、果糖、葡萄糖)和3种高浓度CO2(700、1400、2100μL·μL-1CO2)处理.处理1个月后,测定了叶片的总糖、蔗糖、果糖和蛋白质含量.结果表明:在700μL·L-1和1400μL·L-1 CO2下,外源糖溶液增加了叶片的可溶性糖和蛋白质含量,其中外源蔗糖的效果最好:外源糖溶液与2100μL·L-1CO2结合,会抑制叶片积累总糖和蛋白质:在700μL·L-1和1400μL·L-1CO2下,喷施葡萄糖、果糖的叶片在蛋白质含量上没有明显差别:同700、1400μL·L-1CO2相比,除喷施果糖植株外,2100μL·L-1 CO2明显增加了叶片的总糖、蔗糖、果糖和蛋白质含量:在喷施同种外源糖溶液的情况下,叶片的糖含量与CO2浓度呈正相关性.图6参7.     

Seasonal dynamics and impact factors of urban forest CO<Subscript>2</Subscript> concentration in Harbin,China

CO₂ concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and annual dynamics and factors that impact CO₂ concentration in different spaces. CO₂ concentration in different communities in green lands had an obvious diurnal variation, chronically decreasing, and temperature influenced the lilac area and the grassland. Seasonally, CO₂ was lowest in the larch green land (344.03 ± 23.03 μmol/mol) and highest in the grassland (360.13 ± 22.43 μmol/mol). The overall trend in CO₂ concentration was autumn > spring > summer; temperature is the main factor controlling variation in CO₂ concentrations during the growing season; the CO₂ concentration at the larch, birch, lilac, and grassland types of sites was negatively correlated with land surface temperature and air temperature, and the CO₂ concentration at the larch and birch sites was positively correlated with atmospheric pressure. Without any obvious annual change law, further study and observation are needed.