臭氧抑制木材表面光化降解的机理

本文用臭氧溅射椴木单板表面,结果表明:实施这种处理后的木材表面形成一层高氧层(氧含量高于素材),在紫外光的辐射下,集聚在该层中的臭氧也将参与木材表面的自由基反应,这大大减少了原来素材表面的氧参与自由基反应的机会,进而达到抑制木材表面光化降解之目的。     

Effect of ozone treatment of wood on its liquefaction

The effects of ozone treatment were investigated to improve the process of liquefaction of wood with polyhydric alcohol solvents. The liquefied wood having a high wood to polyhydric alcohol ratio (W/P ratio) could be prepared by using the wood treated with ozone in the liquid phase. The liquefied wood with a W/P ratio of 2 : 1 had enough fluidity to act as a raw material for chemical products. To get some information about the effects of ozone treatment toward the wood components, cellulose powder and steamed lignin were treated with ozone and liquefied. In particular, ozone treatment in the liquid phase was found to be effective for wood and cellulose powder. On the other hand, steamed lignin self-condensed during liquefaction after treatment with ozone in the liquid phase. Thus, ozone treatment provided lignin with reactive functional groups, and caused the subsequent condensation reaction. Although lignin was converted to a more condensable structure by ozone treatment, the condensation reaction was found to be suppressed for wood during its liquefaction. The wood liquefied products displayed good solubilities in N,N-dimethyl formamide (DMF) even after treatments of long duration. It was suggested that one of the main effects of ozone treatment toward wood was the decomposition of cellulose.Part of this report was presented at the 53rd Annual Meeting of the Japan Wood Research Society, Fukuoka, April 2003     

Influence of ozone and nitrogen deposition on bark beetle activity under drought conditions

Four years of severe drought from 1999 through 2003 led to unprecedented bark beetle activity in ponderosa and Jeffrey pine in the San Bernardino and San Jacinto Mountains of southern California. Pines in the San Bernardino Mountains also were heavily impacted by ozone and nitrogenous pollutants originating from urban and agricultural areas in the Los Angeles basin. We studied bark beetle activity and bark beetle associated tree mortality in pines at two drought-impacted sites in the San Bernardino Mountains, one receiving high levels of atmospheric pollutants, and one with more moderate atmospheric input. We also investigated the effects of nitrogen addition treatments of 0, 50 and 150 kg N ha⁻¹ year⁻¹ at each site. Tree mortality and beetle activity were significantly higher at the high pollution site. Differences in beetle activity between sites were significantly associated with ozone injury to pines, while differences in tree mortality between sites were significantly associated with both ozone injury and fertilization level. Tree mortality was 9% higher and beetle activity 50% higher for unfertilized trees at the high pollution site compared to the low pollution site. Tree mortality increased 8% and beetle activity increased 20% under the highest rates of nitrogen additions at the low pollution site. The strong response in beetle activity to nitrogen additions at the low pollution site suggests that atmospheric nitrogen deposition increased tree susceptibility to beetle attack at the high deposition site. While drought conditions throughout the region were a major factor in decreased tree resistance, it appears that both ozone exposure and atmospheric nitrogen deposition further increased pine susceptibility to beetle attack.     

Improvement of fiberboard made from acetylated fibers by ozonation I: effect of ozonation on mechanical properties

Acetylated fibers with a 24.8% weight gain by acetylation were ozonated with 0%–2.0% ozone on fibers. Fiberboards were then made from these treated fibers. The internal bond and bending strength of the acetylated fiberboards increased drastically with increasing ozone charge up to 0.5%–1.0%, whereas the thickness swelling of the fiberboards decreased. Ozone selectively cleaves the aromatic rings of hydrophobic lignin and introduces a hydrophilic carboxyl group into lignin. Thus, the wettability and thermoplasticity of acetylated fibers increased, and this structural modification improved the interfiber contact. Internal bond and bending strength increased as a result. In addition, steep density profiles were formed by the ozonation, resulting in high bending strength. The high compaction ratio accelerated the effect of ozonation. The optimum ozone charges for improving mechanical properties were 0.5%–1.0%.Part of this report was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

臭氧处理对冬枣果实多酚氧化酶和过氧化物酶活性的影响

以冬枣为试材,研究了不同臭氧浓度处理对冬枣果实多酚氧化酶和过氧化物酶活性的影响。结果表明:臭氧处理能抑制冬枣多酚氧化酶的活性,使过氧化物酶活性保持较高水平,其中以40mg/m3臭氧浓度处理最佳。     

Plant and soil microbial biomasses in Agrostis capillaris and Lathyrus pratensis monocultures exposed to elevated O3 and CO2 for three growing seasons

Elevated CO₂ usually promotes plant growth, whereas elevated O₃ often has a negative effect, especially on root biomass. Thus both these gases can indirectly affect the soil microbial community. We exposed Agrostis capillaris and Lathyrus pratensis to realistic levels of O₃ (40-50 ppb) and CO₂ (ambient air + 100 ppm) in open-top chambers during 2002-2004. The experiment shows negative effects of both O₃ and CO₂, especially on the bulk soil of L. pratensis, in terms of the decreased biomasses of total (25% and 31%), actinobacterial (29% and 31%), bacterial (26% and 33%) and mycorrhizal (AM fungal) (31% and 35%) indicator subgroups, analysed by the PLFA (phospholipid fatty acid) method. The fungal:bacterial PLFA biomass ratio decreased in the bulk soil of A. capillaris, especially with elevated CO₂ alone (38%). These longer-term changes are considered to arise mainly from differences between the plant functional types (i.e. grass cf. N₂-fixing legume) in litter quality and soil C:N ratio. The results also point to interactions and multi-trophic feedbacks between elevated O₃, plant, parasitic rust fungi and soil readily available P, accompanied by a shift in N balance in favour of plants rather than soil microorganisms.     

臭氧处理对冷库贮藏白菜品质的影响

为探索臭氧处理对冷库贮藏白菜的品质影响,在固定臭氧处理频率为1次·d-1的条件下,分别研究不同臭氧处理浓度、处理时间对冷库贮藏白菜主要品质指标变化的影响。结果表明,臭氧处理能够有效抑制白菜的呼吸强度,减缓白菜的Vc含量、叶绿素含量在贮藏期间的下降,降低贮藏失重率,最佳臭氧浓度为12.84mg·m-3,处理时间为30min。     

臭氧(O3)的制备及气水混合的研究

研究了非离子型表面活性剂TritonX-100存在下,用5-Br-PADAP光度法联合测定铜的方法.结果表明在pH9.0的硼砂缓冲介质中,5-Br-PADAP与铜生成紫色络合物,λmax＝575nm,∈575=9.00×104L@mo1-1*cm-1.铜量在0～18μg/25ml的范围内符合比尔定律.实测了钢样中铜的含量,结果令人满意.     

臭氧处理与低温对双孢蘑菇保鲜效果的影响

以提高双孢蘑菇的保鲜质量为目的,分析了O3气体处理时间对保鲜蘑菇的细胞膜透性、PPO和CAT活性的影响。结果表明：在相同条件下,O3气体处理10min的双孢蘑菇保鲜效果相对较好,表现为细胞膜透率和PPO活性受到有效抑制,CAT活性保持在较高水平。除外还分析了O3气体处理对保鲜蘑菇的细胞膜透率、PPO和CAT活性的影响,为O3气体处理技术应用于蘑菇保鲜领域提供参考。