玉米芯骨料生态混凝土的制备及性能

农村大量玉米芯焚烧或占地堆放,严重污染环境且造成资源浪费。玉米芯具有轻质、保温等建筑性能,可用于制备生物质建筑材料,该研究将破碎后的玉米芯颗粒掺入再生砂浆中制备玉米芯骨料生态混凝土,通过改变胶砂比及玉米芯体积分数探讨生态混凝土的基本性能。试验结果表明：玉米芯小颗粒与大颗粒的质量比为1∶1.5时骨料的级配较合理,生态混凝土的强度较高;生态混凝土的胶砂比对干密度影响不大,但导热系数和强度则随胶砂中再生砂比重的增加而降低;随生态混凝土中玉米芯含量的增加,混凝土的干密度、导热系数及强度均明显降低。试验范围内,生态混凝土的干密度为1 200～1 550 kg/m3,导热系数为0.20～0.26 W/m•K,28 d强度为2.0～5.7 MPa。玉米芯骨料生态混凝土的研究可为开发轻质保温的墙体材料用于农业农村建设提供参考。     

纤维改性再生骨料透水混凝土力学性能透水性和耐磨性研究

再生骨料透水混凝土是利用再生骨料制备透水混凝土,具备再生混凝土和透水混凝土的功能优势,但导致强度、耐磨性变差,故该文进行再生骨料透水混凝土改性研究。将聚丙烯纤维和碳纤维以不同的体积分数(其中聚丙烯纤维掺量分别为0.3%、0.6%、0.9%、1.2%,碳纤维掺量分别为0.2%、0.4%、0.6%、0.8%)掺入再生透水混凝土中,采用WAW-1000电液伺服万能试验机测定力学强度,自制透水装置测定透水系数,洛杉矶磨耗试验机测定耐磨性,获取不同种类和掺量纤维对透水性、力学性能和耐磨性的影响。试验结果表明,聚丙烯纤维和碳纤维的掺入对混凝土的孔隙率和透水系数影响不大,但可提高强度和耐磨性。随着纤维掺量的增加,抗压强度和劈裂抗拉强度呈先增大后减少的趋势;质量损失率也先减少后增大趋势。经优化分析可知聚丙烯纤维最优掺量为0.6%,碳纤维最优掺量为0.4%。该成果可为纤维改性混凝土以及再生骨料透水混凝土的推广应用提供参考。     

荷载与腐蚀冻融耦合作用下再生混凝土耐久性能试验

现有的荷载与环境多因素研究大多是通过给试块设计安装一套夹具,然后拧紧螺丝或者用千斤顶对试块施加荷载（应力）,再用此带着夹具的试块进耐久性试验,此方法操作困难、繁琐,极易发生应力损失,使研究的准确性急剧降低。该文提出了一种具有操作简便、控制精准等优点的耦合作用机制,采用先加载再腐蚀冻融,且以此循环作用的方式来模拟混凝土真实工作状态,并对普通混凝土及再生混凝土在多因素耦合作用下耐久性能进行研究。该文试验加载制度分别采用0、40%、70%应力水平的重复荷载与25次腐蚀冻融交替2次,并对此耦合作用下再生混凝土与普通混凝土进行了宏观和微细观试验研究。试验结果显示：在宏观方面,随着应力水平的从0增加至70%,再生混凝土和普通混凝土的抗压强度损失率分别增加27.2%和100%,再生混凝土在多因素耦合作用下的耐久性能表现更佳,荷载会使普通混凝土和再生混凝土的劣化速度加快;在微观方面,在腐蚀冻融50次后,再生混凝土和普通混凝土的显微硬度损失率分别为8.1%和23.8%,环境扫描电镜（environmental scanning electron microscope, ESEM）结果也可以看出界面过渡区是混凝土中较薄弱的环节,且在冻融循环作用前,天然粗骨料界面过渡区处黏结强度和塑性变形能力较强,冻融循环作用后,再生粗骨料界面过渡区处抗冻融腐蚀能力更好。该结果为普通混凝土耐久性改进及再生混凝土的推广应用提供理论参考。     

再生骨料透水混凝土强度及透水性能试验

利用再生废弃混凝土骨料制备透水混凝土是目前研究的热点和趋势,其中强度和透水性是其关注及目前亟待突破的关键性能。以废弃的预制混凝土梁构件为再生骨料来源制备透水混凝土,并以水胶比0.3,砂率10%为基准,设计6组配合比,并通过标准养护下的立方体试块试验,研究了单一因素下再生骨料透水混凝土的孔隙率、透水性及其强度性能,其范围分别为孔隙率17.8%~23.8%,渗透系数0.27~0.57 cm/s以及抗压强度4.0~9.63 MPa。结果表明,再生骨料透水混凝土基本性能够满足要求,其中内掺粉煤灰能大幅提高其抗压强度,提高约44%,外掺钢纤维提高透水性,掺入萘系高效减水剂及硅粉的效果不明显。此外,再生骨料透水混凝土的毛细吸水过程与普通混凝土类似,即前期吸水快,后期趋于平缓。     

一种静压成型混凝土透水砖的制备与物理性能试验

 透水铺装具有缓解城市防洪压力、涵养地下水源、改善城市热环境等特点。针对混凝土透水砖的特点,设计孔隙率和水灰比不同的4种混凝土透水砖,采用体积法进行配合比设计,通过水泥裹料投石法搅拌,在自制的模型中静压成型,对其物理性能包括抗压强度、孔隙率、透水性进行率定,并对透水能力最强的砖体进行成本预算。结果表明:设计的透水砖透水系数达到了1.18～1.60mm/s,抗压强度超过了30MPa;采用体积法设计配合比是合理、可行的;利用15%粉煤灰和5%的硅灰配合使用等量代替水泥,设计的透水砖成本仅为28.25元/m2。     

高寒灌区风沙吹蚀对农业水利工程混凝土抗冻耐久性的影响

针对内蒙古引黄灌区农业水利工程混凝土实际服役环境,同时加大风积沙资源化利用效率,配制满足农业水利工程设计要求的风积沙混凝土,并研究风沙吹蚀作用对风积沙混凝土抗冻耐久性的影响。结果表明:相对动弹性模量可准确表征风积沙混凝土受风沙吹蚀影响下的冻融破坏,且风沙吹蚀影响下混凝土冻融循环后的内部损伤是未受风沙吹蚀影响下混凝土冻融循环后的2倍;在风沙吹蚀影响下的冻融过程中,风积沙混凝土水泥浆体在冻融过程发生"酥化",同时在风沙流的持续撞击、削切下,"酥化"的水泥浆体进一步剥落,迫使破坏表面水泥浆体与骨料连接处的界面过渡区较光滑;风积沙替代率为40%可以配制满足抗冻性要求的风积沙混凝土,但风积沙混凝土气泡间距系数不能准确评价其抗冻性,气泡盒维数与细骨料细度模数可反映气泡结构特征和细骨料颗粒级配,且二者呈负相关趋势,二者结合可对风积沙混凝土抗冻耐久性优劣进行初步判定。     

改性玉米芯制备太阳能界面蒸发体及其性能分析

针对天然生物质材料应用于海水淡化领域,蒸发效率较低、材料容易降解等问题,采用多巴胺对天然玉米芯进行改性处理,以改性玉米芯为基底,在其表面包覆炭黑-纤维素薄膜,制备了一种集光热转换、输水、隔热于一体的太阳能界面蒸发体。对改性玉米芯蒸发体的光学吸收性能、输水性能、接触角进行表征,并搭建了室内蒸发试验和户外蒸发试验系统,测试了改性玉米芯的蒸发性能,与天然玉米芯相比,改性玉米芯蒸发体的蒸发速率相对未改性的提升了约10.4%。对改性玉米芯蒸发体进行了30次循环试验,蒸发体均保持稳定的蒸发速率,整个循环测试中蒸发速率波动不超过1%。并且,长期工作后,蒸发体表面没有盐分沉积,没有出现材料软化、降解现象。改性玉米芯蒸发体在海水环境中能够保持良好、稳定的蒸发性能,且能够有效降低海水中的Na⁺、K⁺、Mg²⁺、Ca²⁺等离子浓度,达到世界卫生组织所规定的饮用标准中的相应限值。改性玉米芯蒸发体的制备方法简单、成本低廉、蒸发性能稳定,为扩展生物质材料在海水淡化领域的应用提供了有效途径。     

秸秆土聚物保温建筑材料工艺及界面结构分析

为研究开发强度高、耐腐蚀性好的保温建筑材料,以节省建筑能源消耗,拓宽秸秆工业化利用途径,该文将秸秆掺入到土壤聚合物中制备秸秆土聚物,以抗压强度为指标,优选秸秆土聚物的较优工艺,并测定了秸秆土聚物的导热系数,确定其保温性能。用X射线衍射、傅立叶红外光谱以及扫描电镜对秸秆土聚物复合材料的晶相成分、化学键合和微观结构进行了分析。结果表明秸秆土聚物较优工艺配方如下:反应体系中Si O2与Al2O3摩尔比为3.9,Na2O与Si O2摩尔比为0.30,秸秆掺量4%,长度1 mm,水灰比0.10,制备得到的试块置于(20±2)℃、相对湿度为70%±2%的环境中养护,其7 d抗压强度可达54.58 MPa,导热系数为0.0681 W/(m·K)。X射线衍射、傅立叶红外光谱以及扫描电镜分析表明秸秆土壤聚合物为Si,O,Al组成的半晶态,无定形层状结构,与纯土聚物红外特征峰相同,无新化学键生成。秸秆土聚物界面处出现间隙和裂纹,裂纹遇秸秆后转向,产生二次裂纹,形成弱结合界面。初步判断秸秆与土聚物之间没有发生化学结合。研究结果为秸秆的工业资源化利用开辟了一条新途径,也为绿色保温建筑材料的研究提供依据。     

固化剂与糯米浆固化土的工程性能对比分析

[目的] 通过分别掺入离子固化剂、糯米浆对工业废料铁尾矿砂与黄土混合土进行固化试验,研究对比两种固化剂对目标土样的固化效果差异,为后续的工程应用及研究提供理论支持。[方法] 采用离子固化剂与糯米浆分别对目标混合土进行固化研究,通过干湿、冻融循环试验和自然风化试验对试件抗压强度的改变,综合评价两种固化剂对试件强度和耐久性的影响,并根据扫描电镜试验与比表面积试验测得孔隙结构对强度的影响。[结果] 掺入1.5%离子固化剂的混合土强度改善效果优于其他掺量的离子固化剂改良土,比素土提升50%强度;掺入10%糯米浆的混合土强度使素土强度增加110%。经过耐久性试验之后,掺入1.5%离子固化剂的混合土强度损失率更小,掺入10%糯米浆的混合土强度残余更高。[结论] 离子固化剂与糯米浆作为固化剂,均可提升土体材料的强度性能。糯米浆作为固化剂的固化效果优于离子固化剂。     

内蒙古砒砂岩的性能及其对水泥力学性能影响的研究

砒砂岩地区是黄河泥沙的主要来源地之一。为了实现对砒砂岩的资源化利用,对砒砂岩基本物理化学性质进行了研究,并探讨了其作为混凝土掺合料的可行性。通过X射线荧光光谱分析(XRF)、X射线衍射分析(XRD)和扫描电镜(SEM)研究发现,红色、白色砒砂岩的矿物成分差别不大,主要包含石英、长石、蒙脱石、高岭土、方解石等,还含有一定量活性的Si O2、Al2O3和Ca O(能够促进水泥水化)。砒砂岩作为水泥掺合料对水泥胶砂性能影响的研究试验结果表明,掺入砒砂岩会缩短水泥的初凝时间,掺量30%时初凝时间会缩短69%;当砒砂岩掺量不多于20%时水泥胶砂的28 d抗压强度和抗冻性能会提高,当掺量大于20%时水泥胶砂的抗压强度和抗冻性能(冻融循环后抗压强度)会显著降低。同时,研究还发现掺入砒砂岩会显著提高水泥胶砂28 d抗折强度。     

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,     

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.     

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.     

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.     

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.     

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,     

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.