基于木质素部分脱除及其含量对生物质热解特性的影响

该研究采用固定床热解炉,研究不同木质素含量花生壳、核桃壳样品的裂解行为,利用元素分析、工业分析、气相色谱-质谱联用以及气相色谱法对原料和热解产物进行分析,探究木质素与综纤维素在原始交联结构下的交互作用及其对热解产物分布特性影响。研究结果发现,300℃热解条件下,随着木质素含量的增加,样品中固体产率增加,液体产率和气体产率下降。500、700℃热解条件下,固体产率相比300℃有大幅度的下降,且随样品中木质素含量的增加,固体产率无明显变化,液体产率稍微增加,气体产率下降。500℃时,H2产率很低,随样品中木质素含量的增加,CO2含量减少,CH4含量增加,CO含量有稍微的上升。而700℃时,综纤维素的脱氢、缩合、成环会生成大量的H2。同时,木质素能够促进综纤维素分解生成大量左旋葡聚糖,并抑制其分解;而综纤维素抑制木质素单体愈创木基的脱甲氧基反应,促进苯丙烷基的脱烷基反应,形成更多的酚类化合物。该研究对于生物质组分间交互和产物形成特性研究具有积极意义。     

纤维素木聚糖和木质素含量对生物质热解特性及产物的影响

采用热重法研究了纤维素、木聚糖和木质素含量对生物质热解特性的影响,分析了三组分相互混合热解时的交互作用规律,及其对热解动力学参数的影响;同时,在生物质真空热解液化系统上考察了三组分含量对热解液化产物分布及生物油组成的影响。结果表明,纤维素热解较为剧烈,生物油中芳香族、糖类、醛类和醇类含量较高;木聚糖的热稳定性较差,生物油中芳香族、酮类和酸类物质较多;木质素热解较为平缓且固体残留物较多,生物油成分主要为芳香族化合物。纤维素对活化能和指前因子的影响较大,木聚糖和木质素对反应级数的影响较大;纤维素的热解有利于减少固体残留物,而木质素的热解产物有利于促进糖类的分解;木聚糖对纤维素的热解具有明显的抑制作用;木聚糖能促进木质素的低温热解,两者混合热解对生物油组成影响较小。因此,高纤维素含量的生物质可以获得更高的生物油产率,且适量的木质素有利于促进纤维素的分解,为进一步提高生物油产率和品质提供了理论依据。     

熔融盐-镍协同催化生物质热解制取富氢气体

在固定床反应器中研究了(Na_2CO_3-NaOH)熔融盐和镍对生物质三组分纤维素、半纤维素和木质素热解制氢的影响。结果表明,熔融盐中的氢氧化钠能吸收三组分热解产气中CO_2,从而有利于合成气中的CO转化成H2。熔融盐含有的碱金属Na~+和OH~-分别能促进半纤维素与纤维素、木质素的热解,木质素热解产氢量最高可达到1 148 m L/g,H2体积分数达到90.7%。熔融盐-镍协同作用时可以降低三组分产气中CH_4含量,与单独添加熔融盐相比,纤维素、半纤维素和木质素的CH_4产量分别下降35.0%、24.5%和12.0%。在熔融盐-镍的存在下,纤维素、半纤维素和木质素的最高产氢量分别达到910、714和1 106 m L/g,H2体积分数分别为77.6%,77.8%和91.6%。     

活性炭催化生物质与低密度聚乙烯共热解

为探究生物质主要组分与聚烯烃塑料在活性炭共催化热解过程的相互作用机理,该研究采用磷酸活化法制备了活性炭催化剂,利用固定床反应器对纤维素、木聚糖、木质素、花旗松单独催化热解及其与低密度聚乙烯共催化热解产物的产率及组成进行了分析。结果表明,活性炭催化纤维素和木聚糖单独热解的主要产物为呋喃类物质,其质量分数分别为78.6%和83.2%;而活性炭催化木质素热解的主要产物为简单酚类物质（86.6%）。与理论计算值相比,四种混合物共催化热解所得液体产率降低了8.7%～11.4%,气体产率提高了22.6%～64.0%;液体产物中芳烃和轻质脂肪烃（C9～C16）的质量分数增加而氧化物的质量分数降低;气体产物中H2的体积分数有所增加而CO和CO2的体积分数明显降低。活性炭催化剂作用下,生物质三组分与低密度聚乙烯之间相互作用的影响程度有所不同。     

“木质素优先解聚”策略下生物质定向解聚研究进展

木质素的来源、催化剂和溶剂对木质素整体转化和产物分布起着至关重要的作用。该文主要综述了国内外有关木质素优先解聚的最近研究进展，分析比较了酸催化剂、碱催化剂、贵金属催化剂以及非贵金属催化剂的优势与不足，指出金属负载型催化剂能有效促进木质素苯丙烷单元间C-C键或C-O键的断裂转化为芳烃化合物，并对木质素脱出率和单体产率进行了评述与分析。对比分析了不同种类的溶剂对木质素的脱出率、碳水化合物的脱出率以及浆液的宏观结构造成的影响，发现醇类溶剂不仅可以断开木质素和半纤维素之间的酯键，而且可以保护纤维素和半纤维素不受破坏，从而达到生物质高值化利用的效果。最后对当前生物质解聚所面临的挑战以及未来研究趋势进行了总结与展望，指出通过催化剂和溶剂结合可以有效地解聚出木质素单体，因此催化剂开发和溶剂的选择将是该领域未来研究重点。     

流通加压热水液化木质生物质

在160～280℃温度范围内,10 MPa,10 mL/min条件下,考察了反应温度对木粉溶解百分比、水溶解部分中半纤维素来源糖类、纤维素来源糖类及降解产物生成的影响,研究了流通加压热水液化生物质的过程。随着温度的升高,木粉溶解百分比逐渐增大,280℃条件下,96.5%的木粉可溶解于水中。水溶解部分中,半纤维素来源糖类和纤维素来源糖类均随温度升高而增大,并分别在250℃和280℃时达最大值,降解产物5-羟甲基糠醛产率和糠醛产率也随温度升高而增大。同时,采用X射线衍射分析水不溶性残渣发现,随着处理温度的升高,残渣相对结晶度逐渐升高,但当温度达到280℃时,相对结晶度骤然下降且（002）晶面衍射峰消失,表明纤维素结晶结构被彻底破坏。残渣的傅立叶红外光谱分析表明,半纤维素在250℃即被完全水解;280℃时,半纤维素和纤维素特征峰均消失,残渣特征峰主要为木质素来源芳香环。研究表明,流通加压热水可以用于木质生物质的全水解来获取糖类。     

反应温度和停留时间对纤维素水热解产物理化特性的影响

为了解纤维素在水热降解过程中产物的理化特性及其形成机制,该文对生物质主要组分—纤维素的水热降解特性进行了系统地研究,全面分析了反应温度和停留时间对纤维素水热产物分布的影响,并从产物的化学结构入手,对纤维素水热解机理进行了探索。随着温度的升高,重质油产率在250℃时达到最大,重质油组分变得复杂,焦炭产率逐渐降低。随着停留时间的延长重质油产率呈现先增加后降低的趋势,焦炭产率变化趋势较小,然而通过对焦炭的热重、红外、元素、电子扫描显微镜和X射线光电子能谱仪分析表明停留时间的延长可以提高焦炭的化学官能性,这为生物质水热机理的研究提供了依据。     

农田不同肥力条件下玉米秸秆腐解效果

为了探讨农田不同肥力对玉米秸秆腐解转化和能态变化的影响,该文采用砂滤管法在陕西关中高、中等、低3种肥力塿土上进行了480 d的玉米秸秆腐解试验,研究了腐解进程中玉米秸秆的分解率以及有机碳组成和能态变化。结果显示,随着腐解进行,腐解产物中的苯–醇溶性、水溶性组分下降,半纤维素和纤维素含量先上升后下降,而木质素增加;腐解物的能态呈现上下起伏、下降和相对稳定3个阶段的变化,总体是一个放能过程。腐解产物的热值与其有机碳、苯–醇溶性组分、水溶性组分、半纤维素和纤维素呈显著正相关,但与其灰分、木质素、腐殖物质含量呈显著负相关。腐解480 d,3种肥力间比较发现,玉米秸秆在中等肥力田块上矿化率最高,低肥力田块上的最低;中等肥力土壤能够促进玉米秸秆中的水溶性有机组分和木质素的分解,而高肥力土壤能够促进苯–醇溶性组分和半纤维素、纤维素分解,并有利于腐殖物质的形成,而且腐解物的能态最高。     

生物质三组分燃烧特性及动力学分析

采用热重分析法对纤维素、木聚糖和木质素的燃烧特性及动力学进行研究,考察了不同升温速率(20、40、60、80℃/min)对燃烧特性的影响,求出了生物质三组分的燃烧特性参数和动力学参数。研究表明:纤维素和木质素的燃烧失重分别集中在挥发分和焦炭的燃烧阶段,而木聚糖的燃烧在这2个阶段失重都比较大。纤维素和木质素在低温段和高温段燃烧的最佳反应级数分别为1和2,而木聚糖在这2个温度区间燃烧的最佳反应级数都为1。     

改性生物质炭对棉秆热解挥发分析出特性的影响

生物质焦炭由于其复杂的结构特点和无机矿物质的存在,使得其对快速热解过程中挥发分的析出有着重要的影响。此外生物质本身所含的大量金属盐也促进了焦炭与挥发分的反应。该文通过酸洗和负载Na、K、Mg、Fe金属氯盐等探讨棉杆热解焦炭对生物质热解特性的影响。试验温度为500℃,研究发现棉秆热解炭对酸类、脂类和醛类有明显抑制作用;对酚类、呋喃类以及糖类有促进作用;酸洗以及负载不同金属盐后生物炭的存在使得生物油的产量降低,而气体产率增加;金属离子对酚类富集作用顺序为:KNaFeMg,Fe Cl3的添加有利于氢气的增加,氢气体积分数达12.96%,而KCl和Mg Cl2对CO的生成促进作用明显,产量分别为49.22%和49.38%;金属离子对挥发分裂解影响要强于单纯增加下层催化段焦炭质量。     

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。     

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.     

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.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

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,     

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,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

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.