TG-FTIR-MS联用技术对沼渣热解特性的分析

为探究多种类沼渣废弃物的热解特性差异及在热解过程中逸出气相产物的主要成分和产量，该研究采用秸秆沼渣(SBR)、鸡粪沼渣(CMBR)、蛋白质类沼渣(PTBR)、脂肪类沼渣(FTBR)和淀粉类沼渣(STBR)为原料，利用TG-FTIR-MS对其热解进行分析。结果表明：5种沼渣废弃物失重过程相差较大，但主要热解阶段相同，可分为3个阶段，即吸附水蒸发阶段、挥发分析出阶段及炭化阶段。SBR、CMBR主要热解失重发生在170～450 ℃之间，PTBR、FTBR、STBR主要热解失重发生在130～450 ℃之间，失重率大小依次为STBR、FTBR、SBR、PTBR和CMBR；根据热解特性指数D值分析，PTBR、FTBR、STBR及SBR热稳定性较低，易于热解，CMBR热稳定性较高。沼渣挥发分成分较为复杂，受热过程中逸出的气体主要成分是CO₂、H₂O、CH₄和CO等，其中CMBR热解CH₄的释放量较低，而PTBR、FTBR、STBR热解CH₄释放量较高，该结果。     

坚果壳类生物质慢速热解动力学分析

为研究坚果壳生物质的慢速热解动力学过程，对两类坚果壳类生物质(花生壳和葵花瓜子壳)进行了低升温速率下惰性气氛的热重分析实验。采用竞争型热解反应动力学模型描述它们的热解过程。在原有动力学机理函数的基础上，提出了一种新的经验动力学机理函数。利用现代优化技术——模式搜索法，对实验数据进行了动力学分析，结果表明：新动力学机理函数能有效描述坚果壳类生物质的慢速热解动力学过程。     

积分方法改进的生物质热解反应速率模型构建

针对经典Arrhenius方程中温度积分项不可积的问题,通过设定热解过程中生物质转化率同时为时间(和温度r的函数,使温度积分项可积分,有效避免积分法动力学分析中因简化而导致的计算误差。基于此热动力学方程(Ⅱ类热动力学方程)采用等转化率线性积分法求解反应活化能E,并结合模型拟合法选取最优反应机理函数,将选取的机理函数重新代入Ⅱ类热动力学方程积分式解得指前因子A的值。基于等转化率线性积分法分别采用Ⅰ类及Ⅱ类热动力学方程对玉米芯等5种生物质热解过程进行动力学分析,结果显示2类热动力学方程求得生物质活化能E的决定系数均高于0.95。Ⅱ类动力学方程求解的动力学参数计算的动力学分析值与试验值的吻合度高于Ⅰ类动力学方程。根据热解反应的活化能E与lnA具有高度线性拟合性,且转化率0.05～0.85间活化能波动不大这一特点,采用最大热解速率处转化率对应的热解动力学参数简化热解过程的动力学参数,可减小数值模拟的计算成本,为工程上热解反应的数值模拟提供一定的基础。     

糠醛渣与稻壳混合物的共热解特性研究

通过对不同混合比糠醛渣和稻壳的混合物进行热重分析试验,发现主要热解温度区间明显的分为两个阶段,表现出不同的热解机理;糠醛渣和稻壳的混合比对热解过程有影响,共热解不是两种生物质单独热解贡献的简单叠加。在热解反应活跃区间建立与糠醛渣和稻壳混合物固有热解特性相适应的分段分级热解动力学模型,计算得到热解动力学参数。最后应用Newton-coats数值求积方法对模型进行验证,并与实验曲线进行对比,结果表明该模型具有较强的可靠性和实用性。     

基于多升温速率法的典型生物质热动力学分析

为研究典型生物质热动力学,判断反应机理,获得反应的动力学速率参数,该文采用热重分析技术对玉米秸秆、小麦秸秆、棉秆、松树木屑、花生壳、甜高粱渣等生物质原料进行了氮气气氛下不同升温速率的热解特性试验研究,利用Friedman法、Flynn-Wall-Ozawa法计算活化能,用Malek法确定最概然机理函数,建立了生物质热分析动力学模型,并讨论了不同生物质的差异性。结果表明:生物质的热解过程均包括3个主要阶段:干燥预热阶段、挥发分析出阶段、碳化阶段。典型生物质活化能随着转化率的增加而增加,在挥发分析出阶段,热解活化能介于144.61~167.34 k J/mol之间;反应动力学机理均符合Avrami-Erofeev函数,但反应级数有一定的差异;指前因子介于26.66~33.97 s-1之间。这为生物质热化学转化过程工艺条件的优化及工程放大提供理论依据。     

微藻种类对其热解质量损失规律和产物及动力学的影响

微藻是一种新型的可再生生物质资源,采用快速热解技术,可得到高品质的先进液体燃料和高附加值化学品。该文采用热重-红外联用仪、快速热解-气质联用仪和分布式活化能动力学模型(distribution activation energy model,DAEM)对莱茵衣藻(Chlamydomonas reinhardtii,CDR)、小球藻(Chlorella vulgaris,CRV)和铜绿微囊藻(Microcystis aeruginosa,MCA)的热解行为开展了研究,系统地对比了3种微藻在化学组成、热解失重规律、动力学、热解产物等方面的差异,并对微藻的热解机理进行了探讨。结果表明:1)3种微藻的热解过程可分为3个阶段,分别为干燥段、快速热解段和炭化阶段,其中铜绿微囊藻失重率最大,达到17.34%/min,且随着升温速率的增加,TG/DTG(thermogravimetry/differential thermogravimetry)曲线往高温一侧移动;2)红外光谱分析结果表明微藻热解主要产物为CH4、CO2、含C=O键的脂肪酸、含N-H键和C-N键的酰胺类化合物,其中莱茵衣藻热解产生的CH4质量分数最高,铜绿微囊藻热解产生的含C=O键化合物质量分数最高;3)铜绿微囊藻的活化能数值最高,随着转化率增加,活化能从100增加到680 k J/mol;4)Py-GC/MS分析表明小球藻热解产生的含氧化合物质量分数最高,达到30.89%,铜绿微囊藻热解产生的酚类化合物、芳香族碳氢化合物、胺和酰胺类和其他含氮化合物的质量分数最高,分别达到10.41%,13.46%,13.87%和14.27%。本文可为微藻的能源化利用提供科学和基础数据。     

玉米秸秆与油页岩混烧的热重试验

为了充分燃烧利用农业生物质与油页岩,采用热重-差示扫描量热(TG-DSC,thermogravimetric-differential scanning calorimetry)技术对玉米秸秆与油页岩混合燃料进行了热重试验,对其各燃烧特性与燃烧机理进行了分析并计算了燃烧动力学参数。结果表明,混烧试样的微分热重(DTG,differential thermogravimetric)曲线出现4个峰值,主要分别是半纤维素热解、纤维素热解、木质素和油页岩热解,以及油页岩焦炭燃烧和油页岩无机盐热解。在DTG曲线第1至第3峰之间出现DSC曲线放热峰,在DTG曲线第3峰至第4峰之间出现DSC曲线吸热峰,需要强化混合燃料的前期燃烧;玉米秸秆与油页岩的质量比例为4∶1时的混合燃料S2,其混烧的可燃特性、着火特性及综合燃烧特性指数均最大,燃尽时间最短,燃尽特性指数较大;在前3个温度区段,混合试样的活化能及频率因子均随温度区段的升高而降低,体现了活化能与频率因子变化的一致性;低温阶段与高温阶段反应级数分别约为1.5及0.7。研究结果可为生物质和油页岩的混烧利用提供参考。     

应用同步热分析仪确定小麦秸秆热解需热量

为了解决生物质热解过程需热量的定量问题,该文应用热重—差示扫描（TG/DSC）同步热分析仪对小麦秸秆进行了热解实验研究。将约5 mg的小麦秸秆粉样品装入带盖的铂铑坩锅中,放在热解炉中的DSC-cp高精度样品支架上,在流量为25 mL/min的高纯氮气吹扫下,以10 K/min的升温速率从常温升至973 K,记录生物质的热重(TG)曲线和差示扫描(DSC)曲线。通过对实验所得微分热重(DTG)曲线和DSC曲线对比分析,对小麦秸秆热解过程进行了详细的探讨。在DSC曲线上扣除水分的影响后对其积分得出热解过程需热量的规律。结果表明,要使1 kg干小麦秸秆完成从常温303 K到673 K,773 K,873 K的升温和热解,所需的总热量分别为523 kJ,558 kJ,592 kJ。     

小麦和玉米秸秆热解反应与热解动力学分析

为了对生物质快速热解液化设备进行分析和计算，该文用热重、差热分析仪分别对小麦和玉米秸秆在不同升温速率下进行了热分析研究。结果表明：小麦和玉米秸秆的热解特性基本一致，热解过程可以用同一种模型描述；随升温速率的提高，热解最高速率时的温度和热解最高速率明显提高。分析了小麦和玉米秸秆热解反应过程，提出了平行一阶反应动力学模型并计算出模型中各参数，将该模型的计算结果、现有一阶反应模型的计算结果分别和试验数据进行了对比，结果表明，平行一阶反应模型的准确程度比现有一阶反应模型有很大的提高。     

升温速率对椰壳热解特性的影响及动力学分析

利用热重分析仪对椰壳在不同升温速率（5、20、40℃/min）下的热解特性及动力学进行了研究,探讨了热解机理。结果表明：椰壳热解过程主要分为脱水、快速热解和缓慢失重;对比不同升温速率下的失重曲线表明,升温速率对热解失重率有明显影响,其最终热解产物的得率随升温速率的增加而减少。运用氮吸附仪测定其吸附等温线,获得不同热解温度对炭化料的孔结构,结果表明：热解温度越高,微孔越发达。使用TG曲线数据,利用分布活化能模型求出相应的活化能,失重率在0.1～0.8之间时,活化能在146～444 kJ/mol,呈“N”形变化。活化能的分布函数,反映了椰壳热解过程中不同阶段反应性能的变化规律,有助于了解椰壳的热解机理。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.