低温胁迫对6种珍贵树种苗木光合荧光特性的影响

以格木（Erythrophleum fordii）、降香黄檀（Dalbergia odorifera）、闽楠（Phoebe bournei）檀香（Santalum album）、铁刀木（Cassia siamea）和樟树（Cinnamomum camphora）6种珍贵树种苗木为研究对象,分析自然降温过程中苗木相对叶绿素含量、气体交换参数及叶绿素荧光参数等指标的变化,探讨低温胁迫对这6种苗木光合荧光特性的影响,并利用隶属函数法对6种珍贵树种耐寒能力进行了评价,以期了解这几种植物的抗寒能力差异及低温对其光合能力的影响,为扩大引种和栽培提供依据。结果表明,与对照相比,低温胁迫下6种珍贵树种苗木净光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr）均有不同程度的下降,其中,格木、降香黄檀、闽楠、檀香、铁刀木净光合效率的下降很大程度上来源于非气孔因素抑制,而樟树净光合速率下降可能来源于气孔限制因素。闽楠、檀香和樟树水分利用效率（WUE）呈上升趋势,而格木与降香黄檀WUE均有不同程度的降低,表明闽楠、檀香和樟树能较好地协调碳同化和水分耗散。低温胁迫下6种珍贵树种Fm均有所下降,表明低温可对珍贵树种苗木叶片PSII反应中心的电子传递潜力产生明显的抑制,致使珍贵树种PSII的光能转换效率降低。降香黄檀、闽楠、檀香、铁刀木和樟树经历2次低温胁迫后qP呈现出持续下降的趋势,表明珍贵树种PSII反应中心的开放程度降低。在2次低温胁迫间格木、降香黄檀、闽楠和铁刀木qN差异不显著（p〉0.05）,表明珍贵树种具有过剩光能耗散机制,保护光合机构免受破坏。相关性分析结果表明,Pn与Gs、Tr、Fv/Fm、qP、qN、ETR和Fm存在极显著相关关系（p〈0.01）,表明Gs、Tr、Fv/Fm、qP、qN、ETR和Fm均可作为衡量植物光合能力的参数。隶属函数法分析结果表明,6种珍贵树种抗寒能力依次为格木〉樟树〉闽楠=檀香=铁刀木〉降香黄檀。总之,?     

Simultaneous removal of arsenate and fluoride from water by AI-Fe （hydr）oxides

A1-Fe （hydr）oxides with different A1/Fe molar ratios （4：1, 1：1, 1：4, 0：1） were prepared using a co- precipitation method and were then employed for simultaneous removal of arsenate and fluoride. The 4A1 ： Fe was superior to other adsorbents for removal of arsenate and fluoride in the pH range of 5.0-9.0. The adsorption capacity of the A1-Fe （hydr）oxides for arsenate and fluoride at pH 6.50.3 increased with increasing A1 content in the adsorbents. The linear relationship between the amount of OH released from the adsorbent and the amount of arsenate or fluoride adsorbent by 4A1 ： Fe indicated that the adsorption of arsenate and fluoride by A1- Fe （hydr）oxides was realized primarily through quantita- tive ligand exchange. Moreover, there was a very good correlation between the surface hydroxyl group densities of A1-Fe （hydr）oxides and their adsorption capacities for arsenate or fluoride. The highest adsorption capacity for arsenate and fluoride by 4A1 ： Fe is mainly ascribed to its highest surface hydroxyl group density besides its largest pHpzc. The dosage of adsorbent necessary to remove arsenate and fluoride to meet the drinking water standard was mainly determined by the presence of fluoride since fluoride was generally present in groundwater at much higher concentration than arsenate.     

Thermodynamic and kinetic studies on Cs+- and Sr2+-exchange in natural zeolite from Akita,Japan

Thermodynamic and kinetic studies on the adsorption of Cs⁺ and Sr²⁺ by Na-exchanged clinoptilolite-rich zeolite rock from Akita (Northern Japan) were performed for the purpose of nuclear waste treatment. The thermodynamic parameters such as selectivity coefficient, thermodynamic equilibrium constant, and standard free energy of exchange were evaluated. These values indicated that the selectivity order was determined as Cs⁺ > Na⁺ > Sr²⁺. In order to discuss the adsorption mechanism of Cs⁺ and Sr²⁺ onto Na-exchanged clinoptilolite, the effective diffusion coefficients were calculated and two kinetic models, pseudo-first-order and pseudo-second-order kinetic model, were tested. For all systems studied, chemisorption seems significant in the rate-controlling step, and the pseudo-second-order kinetic model provided the best correlation of the experimental data.     

Defluoridation of drinking water using Al3+-modified bentonite clay: optimization of fluoride adsorption conditions

Al³⁺-bentonite clay (Alum-bent) was prepared by ion exchange of base cations on the matrices of bentonite clay. Intercalation of bentonite clay with Al³⁺ was performed in batch experiments. Parameters optimized include time, dosage, and Al³⁺ concentration. Physicochemical characterization of raw and modified bentonite clay was done by X-ray fluorescence, X-ray diffraction, energy dispersive X-ray spectrometry attached to scanning electron microscopy, Brunauer–Emmett–Teller analysis, cation exchange capacity (CEC) by ammonium acetate method, and pH_pzc by solid addition method. Chemical constituents of water were determined by atomic absorption spectrometry (AAS), ion selective electrode (Crison 6955 Fluoride selective electrode) and a Crison multimeter probe. For fluoride removal, the effect of contact time, adsorbent dosage, adsorbate concentration, and pH were evaluated in batch procedures. The adsorption capacity of fluoride by modified bentonite clay was observed to be 5.7 mg g^?1 at (26 ± 2) °C room temperature. Maximum adsorption of fluoride was optimum at 30 min, 1 g of dosage, 60 mg L^?1 of adsorbate concentration, pH 2–12, and 1:100 solid/liquid (S/L) ratios. Kinetic studies revealed that fluoride adsorption fitted well to pseudo-second-order model than pseudo first order. Adsorption data fitted well to both the Langmuir and Freundlich adsorption isotherms, hence, confirming monolayer and multilayer adsorption. Alum-bent showed good stability in removing fluoride from ground water to below the prescribed limit as stipulated by World Health Organization. As such, it can be concluded that Alum-bent is a potential defluoridation adsorbent which can be applied in fabrication of point of use devices for defluoridation of fluoride-rich water in rural areas of South Africa and other developing countries. Based on that, this comparative study proves that Alum-bent is a promising adsorbent with a high adsorption capacity for fluoride and can be a substitute for conventional defluoridation methods.     

In vitro assessment of genotoxic and oxidative effects of zinc borate

Zinc borate is used as flame retardant for plastics and cellulose fibers, paper, rubber, and textiles. Despite its wide industrial use, there is limited information concerning its toxicity. The aim of the present study was to investigate the concentration dependence (0–280 mg L^?1) of its genotoxic activity on cultured human lymphocytes by using sister chromatid exchange and chromosomal aberration assays. Total antioxidant capacity and the extent of oxidative stress were also determined. Zinc borate was found to be non-genotoxic at all tested concentrations. It exhibited antioxidant activity at concentrations lower than 40 mg L^?1, and total oxidative stress levels were not changed at any applied concentration of zinc borate.     

持久性有机污染物在大气与植物间交换过程研究进展

大气、植物间持久性有机物污染物(POPs)的交换行为是控制POPs进入食物链,及影响其全球范围内迁移、分布的重要环节.本文着重介绍了大气、植物间POPs交换过程方面的研究现状;总结了其影响因素,主要包括POPs本身的理化性质(lgKOA)、植物特性(叶片表面形态、脂质含量、表皮的可渗透性)以及环境温度;提出了目前大气、植物间POPs交换过程研究中存在的部分问题,以及今后可能的发展方向.     

不饱和聚酯树脂钮扣粉尘静电爆炸敏感性研究

针对某不饱和聚酯树脂钮扣厂在除尘设备维修过程中发生的粉尘爆炸事故,探究静电引起此次事故的可能性并提出防护措施。通过实验测定不饱和聚酯树脂钮扣粉尘的爆炸特性参数,进而确定其静电爆炸敏感性。结果发现:不饱和聚酯树脂钮扣粉尘云最小点火能MIE为4～10 mJ、最低着火温度MIT为480 ℃、粉尘层最低着火温度LIT＞400 ℃。表明,此粉尘属易燃粉尘,其粉尘爆炸敏感度极高,被静电火花点燃的可能性极大,在生产过程中,应采取静电防护措施。     

大气汞浓度升高对水稻叶片生理效应的影响研究

采用大田开顶式气室熏气实验,研究大气汞浓度升高对水稻叶片气体交换参数、脯氨酸、丙二醛的积累以及超氧化物歧化酶活性的影响。实验结果显示,水稻叶片净光合速率(Pn)和气孔导度(Gs)随大气汞浓度的升高均较对照略微下降,表明大气汞浓度的升高对水稻光合作用和气孔开放程度有一定影响;扬花期水稻胞间CO2浓度(Ci)随大气汞浓度的升高明显降低(P0.05)表明Pn的略微下降属于气孔限制,同时蒸腾速率(Tr)显著增加(P0.01)表明大气汞对水稻的蒸腾生理功能有一定的影响。乳熟期水稻叶片气体交换参数与大气汞浓度无显著差异(P0.05),且各指标均低于扬花期。水稻叶片脯氨酸(Pro)含量在拔节期随大气汞浓度的升高而显著增加(P0.05),扬花期先升高后下降,在45 ng·m-3时达到最大,成熟期无显著差异(P0.05);水稻叶片丙二醛(MDA)含量在拔节期先升高后下降,45 ng·m-3时达到最大,扬花期和成熟期均无显著差异(P0.05);水稻叶片超氧化物歧化酶(SOD)活性在拔节期先升高后下降,15 ng·m-3时达到最大,扬花期无显著差异(P0.05)。以上结果表明大气汞浓度的升高可以引起水稻叶片膜脂过氧化以及脯氨酸和丙二醛含量的积累,且随着体内Pro、MDA和SOD对大气汞胁迫的协同反应,水稻对逆境的适应能力增强,对汞胁迫产生了耐受性。     

林业企业产权问题的探讨

本文针对目前多数林业企业缺乏市场活力、生产经营不景气这一现状,从改革途径、产权重组和产权交易方式三个方面,阐述了林业企业所有制改革的思路和看法,认为只有用价值规律这一杠杆来调节林业经济活动,才能实现林业企业资源的合理配置,促使林业生产力的不断提高。