生物改性玉米秸秆处理含铜废水的研究

为解决水体中铜离子污染治理及玉米秸秆资源化利用等问题,以黑曲霉为改性菌剂,采用固态发酵法改性玉米秸秆,制备出复合生物吸附剂。采用傅里叶红外光谱仪(FT-IR)和扫描电子显微镜(SEM)表征改性玉米秸秆,同时对吸附剂的投加量(0.05～0.30 g)、溶液初始浓度(10～200 mg·L~(-1))、溶液初始pH(1.0～6.0)以及动力学和等温吸附线进行了研究。结果表明,通过黑曲霉固态发酵法改性后的玉米秸秆对Cu(Ⅱ)的饱和吸附量为33.6 mg·g~(-1),是天然玉米秸秆的2.65倍。FT-IR和SEM表征结果显示,改性材料表面空隙增多,更为粗糙,更多的活性基团得以暴露,这为吸附性能的提高提供了依据。改性玉米秸秆对Cu(Ⅱ)吸附30 min后达平衡,可用准二级动力学模型较好地拟合,吸附等温线符合Langmuir方程,该吸附过程以单分子层吸附为主。利用黑曲霉固态发酵技术改性玉米秸秆,是一种快速资源化处理玉米秸秆的方法。     

油料作物秸秆生物炭对水体中铅离子的吸附特性与机制

为探索利用废弃生物质资源制备生物炭去除水体中Pb~(2+)污染的可行性,以农业废弃物胡麻秸秆和油菜秸秆为原材料,采用限氧裂解法在700℃条件下制备油菜秸秆(rape straw)生物炭和胡麻秸秆(flax straw)生物炭,通过2种生物炭对Pb~(2+)的批量吸附试验,利用4种吸附动力学模型(拟一级动力学、拟二级动力学、Elovich模型和颗粒内扩散模型)和4种等温吸附模型(Langmuir、Freundlich、Temkin和D-R模型)研究了胡麻和油菜秸秆生物炭对Pb~(2+)的吸附行为。同时,通过(brunauer emmett teller,BET)比表面积和孔径分析、扫描电子显微镜(SEM)、X射线衍射(XRD)和傅里叶变换红外光谱(FTIR)等手段对生物炭的结构和性质进行了表征,初步探讨了2种生物炭对Pb~(2+)的吸附机制。结果表明,胡麻和油菜秸秆生物炭分别在4 h和10 h达到吸附平衡,理论最大吸附量分别达到220.07和307.59 mg/g;2种生物炭对Pb~(2+)的吸附符合拟二级动力学模型,吸附等温线符合Langmuir等温吸附模型,表明其吸附过程为单分子层吸附;2种生物炭对Pb~(2+)的吸附作用为物理-化学复合过程,吸附机制主要包括静电作用、离子/配体交换、阳离子–π作用。研究结果可为油料作物秸秆的资源化利用和生物炭对水中重金属污染防治提供理论依据。     

秸秆生物炭对棕壤中Cu(Ⅱ)的吸附效应及影响因素

以棉花、花生秸秆为原料,采用限氧热裂解法分别于350℃、500℃、650℃下制备生物炭,通过等温吸附和吸附动力学实验,研究两种秸秆生物炭对棕壤中Cu(Ⅱ)的吸附特性和修复效应。结果表明:随裂解温度上升,秸秆生物炭的碳化程度和BET比表面积增加,而含氧官能团、H/C和O/C的比值则减少,且花生秸秆生物炭的芳香化程度、碳化程度和比表面积均高于棉花秸秆生物炭;不同温度梯度制备的生物炭在吸附效果及机制方面存在差异,秸秆生物炭对Cu(Ⅱ)的吸附效果与Lagergren动力学方程的二级动力学方程、Langmuir等温方程可以较好拟合;随着pH的升高,吸附量均增加,吸附量在6.5时达到最大,且花生生物炭的吸附量大于棉花生物炭;SEM电镜扫描图展示了花生秸秆生物炭的表面特征和孔隙结构比棉花明显;FTIR谱图分析表明秸秆生物炭含氧官能团含量随裂解温度的升高而减少。综上,花生秸秆生物炭对山东棕壤重金属污染的修复效果更优。     

小麦秸秆生物炭对高氯代苯的吸附过程与机制研究

以小麦秸秆为原料,分别在三种温度(400℃、500℃、600℃)下制备小麦秸秆生物炭,并标记为WSB400、WSB500、WSB600。分析了秸秆炭的元素组成,表征了其结构和表面特征,研究了秸秆炭对五氯苯和六氯苯的吸附动力学和吸附等温线。结果表明,升温热解使得小麦秸秆有机组分炭化、极性官能团消除,炭化程度增强;三种秸秆炭均可快速高效地吸附高氯代苯,且对六氯苯的吸附要快于五氯苯,假二级动力学方程能更好地拟合秸秆炭对氯苯的吸附动力学过程;不同秸秆炭对氯苯的饱和吸附量大小顺序为WSB400WSB500WSB600;对吸附等温线进行分析可得,随着秸秆炭制备温度的升高,其对氯苯的吸附等温曲线由线性变为非线性,吸附机理则由以分配作用为主过渡到分配作用与表面吸附共同作用。     

东北地区奶牛舍围护结构的低限热阻计算与验证

为探究利用废弃农业生物质制备两性吸附材料处理含Pb2+和As5+废水方法，该文通过醚化反应将2种具有"钳形"|结构的改性剂（阳离子改性剂IA和阴离子改性剂IM）接枝到小麦秸秆的纤维素上，制备高效两性吸附材料WS-IAIM。利用扫描电镜、红外光谱、X射线光电子能谱对其结构进行表征。通过批量处理试验，研究了该材料对水中Pb2+和As5+的去除能力和可能的吸附机理，探讨了其吸附动力学和热力学。结果表明：随着溶液pH值的增加，吸附剂对Pb2+的吸附量增大，对As5+的吸附量减少，吸附行为符合Langmuir吸附等温模型和拟二级动力学模型。根据Langmuir模型，在313 K时，对Pb2+和As5+的理论最大吸附量分别180.12和27.48 mg/g。吸附热力学和动力学结果表明，该吸附是一个自发的化学吸热过程。WS-IAIM对Pb2+和As5+的吸附过程吸附机理以离子交换和络合作用为主。该吸附材料重复使用5次后，对2种重金属离子的吸附量仍然可达159.3和19.8 mg/g。研究结果可为农作物秸秆的源化利用和水体环境中复杂重金属净化提供理论依据。     

小麦秸秆两性吸附剂的制备及其去除水中Pb2+和As5+的机制

为探究利用废弃农业生物质制备两性吸附材料处理含Pb2+和As5+废水方法，该文通过醚化反应将2种具有“钳形”结构的改性剂（阳离子改性剂IA和阴离子改性剂IM）接枝到小麦秸秆的纤维素上，制备高效两性吸附材料WS-IAIM。利用扫描电镜、红外光谱、X射线光电子能谱对其结构进行表征。通过批量处理试验，研究了该材料对水中Pb2+和As5+的去除能力和可能的吸附机理，探讨了其吸附动力学和热力学。结果表明：随着溶液pH值的增加，吸附剂对Pb2+的吸附量增大，对As5+的吸附量减少，吸附行为符合Langmuir吸附等温模型和拟二级动力学模型。根据Langmuir模型，在313 K时，对Pb2+和As5+的理论最大吸附量分别为180.12和27.48 mg/g。吸附热力学和动力学分析结果表明，该吸附是一个自发的化学吸热过程。WS-IAIM对Pb2+和As5+吸附过程的吸附机理以离子交换和络合作用为主。该吸附材料重复使用5次后，对2种重金属离子的吸附量仍然可达159.3和19.8 mg/g。研究结果可为农作物秸秆的源化利用和水体环境中复杂重金属净化提供理论依据。     

载镁香蕉秆基生物炭对氮磷的吸附性能研究

以香蕉秸秆为原料,氯化镁(MgCl_2)为改性剂,通过限氧热解法(温度673 K)制备生物质炭。利用扫描电镜、傅里叶红外光谱、X射线衍射等技术分析了镁改性生物质炭对氮、磷的吸附机理。结果表明,通过镁改性,生物质炭对氮、磷的吸附量得到显著提高,最大吸附量分别达13.80、18.21 mg·g~(-1);对氮、磷的等温吸附曲线均符合Langmuir曲线,为单层吸附,吸附机理主要以化学吸附为主;吸附平衡时间约为150 min,氨氮和磷的吸附动力学均符合准二级动力学拟合方程,吸附过程受多步骤控制。该载镁生物质炭可以作为潜在吸附剂去除废水和富营养化水体中过量的氮、磷。     

秸秆炭强化镁镧氧化物对沼液磷的回收效果

为回收沼液中的磷元素，前期研究采用了由镁镧金属离子调控合成的层状双金属氢氧化物（Mg/La0.1-LDO）材料，发现其具有丰富的层间离子和纳米粒子，在磷吸附方面体现了优异性能，但材料回收的分散性及原料成本高等因素降低了其应用价值。该研究利用农作物（水稻、玉米）秸秆固定强化Mg/La0.1-LDO，通过共热解法制备了不同温度（400、500和600 ℃）的秸秆炭镁镧双金属氧化物纳米复合材料（BC-LDO），考察不同条件下制备的BC-LDO对沼液磷的回收能力和机理。结果表明，高温（600 ℃）热解更有助于纳米粒子固定在秸秆炭上，秸秆炭强化镁镧氧化物复合材料（6YBC-LDO）含有丰富的介孔和微孔，更易与磷酸盐结合形成LaPO4沉淀和配体交换形成Mg3(PO4)2内球络合物，6YBC-LDO对磷酸盐具有高度选择吸附性并可多次重复利用，能在30 min内回收沼液中90%的磷，饱和吸附量达366.39 mg/g。将该材料应用于沼气工程沼液磷回收处理中，投加2 g/L吸附剂可去除沼液中90%以上的磷酸盐，表明采用6YBC-LDO处理沼液具有良好应用前景。     

热裂解温度对生物质炭吸附解吸Cd~(2+)行为的影响

以玉米秸秆、水稻秸秆、稻壳为原料分别在350℃、450℃、550℃、650℃热裂解温度下制备玉米秸秆炭(MSB)、水稻秸秆炭(RSB)和稻壳炭(RHB),比较不同热裂解温度下三种生物质炭对溶液中重金属离子Cd~(2+)的吸附解吸特性。利用准一级、准二级和颗粒内扩散模型对吸附过程进行拟合,结果表明三种生物质炭对Cd~(2+)的吸附满足颗粒内扩散方程。随着热裂解温度的升高,同一种原料制备的生物质炭达到吸附平衡的时间缩短。Langmuir方程和Freundlich方程拟合结果显示,三种生物质炭对溶液中Cd~(2+)的吸附更符合Langmuir方程。单位数量的RSB在一定浓度Cd~(2+)溶液中对Cd~(2+)的吸附量显著高于MSB和RHB。三种生物质炭对Cd~(2+)的吸附量随制备生物质炭的热裂解温度的升高而降低。三种生物质炭中玉米秸秆炭的解吸率最小。因此评价生物质炭对溶液中重金属的去除效果需要考虑原料、热裂解温度等多种因素的影响。     

重金属离子在土壤中的竞争吸附动力学初步研究Ⅱ.铜与镉在褐土中竞争吸附动力学

用液流法研究了重金属离子铜与镉的在褐土中的竞争吸附动力学特性,用LJ吸附动力学方程结合竞争系数对铜与镉的竞争吸附动力学过程进行了描述.竞争性弱的镉离子吸附曲线出现"过饱和点",镉在开始时占据的吸附位量的一部分,随着吸附过程的延续被铜逐渐交换占据,镉的吸附量由"过饱和点"逐渐下降,最后趋于竞争平衡;在试验温度区间内,单一离子及竞争离子在褐土中的吸附量均随温度的升高而增大;吸附速率随温度的升高而减小,阿仑尼乌斯经验方程不能符合本试验结果,显示出铜及镉在供试褐土中的吸附动力学有其特殊性.温度和pH值的升高对镉的竞争有利,但镉在褐土中的吸附竞争能力远小于铜.     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

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     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.     

Short-term variation in the concentration of selected ions within individual tropical rainstorms

Rainwater was collected at the campus of the University of Brunei Darussalam in Bandar Seri Begawan, Brunei Darussalam, using a funnel-in-bottle sampler. Polypropylene bottles were changed at intervals during rainstorm events. The pH and conductivity were determined immediately after collection on aliquots of the sample. Samples were refrigerated at 5°C for subsequent chemical analysis. Analyses for Na, Mg, Ca, Zn and Fe were carried out by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES); Cu and Mn were analysed by graphite furnace atomic absorption spectroscopy (GFAAS); K was analysed using flame atomic emission spectroscopy (FAES); and Cl^–, NO₃ ^– and SO₄ ^2– were analysed by ion chromatography (IC). Concentration versus time profiles are reported for three rainstorm events. All ions exhibited a decrease in concentration during the rainstorm. The first sample contained the highest concentration of ions, consistent with a first-flush effect. The contribution of the initial stages of the shower to the total quantity of ion deposited during the entire rainstorm is quite overwhelming; in many cases 20 to 30% of the mass was deposited in less than 5% of rainstorm duration. On the other hand, the pH and conductivity variation during rainstorms did not exhibit a consistent pattern.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Leaf litter selection by detritivore and geophagous earthworms

Summary Litterbag experiments with 10 different kinds of leaf litter showed that detritivore (Lumbricus species) and geophagous (Aporrectodea species) earthworms prefer certain litter types over others, since different numbers of worms were found below the litter after 50–52 days of exposure in a pasture. The detritivores preferred Fraxinus, Tilia, and predecomposed Ulmus and Fagus litter to Fagus litter and paper, while geophages preferred Tilia litter to Alnus and Ulmus litter, so that the two groups of earthworms showed different preferences. The detritivores seemed to be more selective than the geophages. The palatability of the litter was examined in relation to the C: N ratio, the lignin concentration and the initial and final polyphenol concentration. The numbers of detritivores were significantly correlated with the C: N ratio and the final polyphenol concentration, so that selection of litter seems to be related to palatability. The numbers of geophages were not significantly correlated with any of the parameters for palatability. The disappearance of litter after 50–52 days appeared to be due to detritivore activity, since the numbers found below the litter were positively and significantly correlated with the litter disappearance. There was no significant correlation with geophage activity. This indicates that detritivores use litter as food, and therefore influence the composition of the litter layer.     

Nematode succession and microfauna-microorganism interactions during root residue decomposition

The quality of plant material affects the vigor of the decomposition process and composition of the decomposer biota. Root residues from hairy vetch (Vicia villosa Roth), rye (Secale cereale L.) and vetch+rye, packed in litterbags were placed in pots of soil at 15 C and the content of the bags was analyzed after 2, 4, 8 and 12 weeks. Bacterial biomass did not differ between residues with contrasting composition. Among bacterivores groups of nematodes that require high bacterial production dominated in fast decomposing resources whereas flagellates with smaller requirements prevail in slower decomposing resources. Biomass of bacterial feeding nematodes correlated positively with early phase (0-2 wk) decomposition that increased in the order: rye< vetch+rye<vetch. Bacterial biomass therefore seems to be under top-down (predation) control during early decomposition. In contrast, the fungal biomass differed between resources with highest values for rye. Moreover, this increase in fungal biomass occurred later during succession and was correlated with decomposition activity for rye in that period. Fungal biomass therefore seems to be under bottom-up (resource) control. The composition of the nematode assemblages (composed of 25 taxa) showed a clear relationship to initial plant resource quality as well as decomposition phase. Early successional microbivorous nematodes vary according to resource quality with demanding bacterivores+predators (Neodiplogasteridae) dominating in vetch and less demanding bacterivores (Rhabditidae) and fungivores (Aphelenchus) being equally common in vetch and rye. Later in the succession (2-4 wk) bacterivorous Cephalobidae and fungivorous Aphelenchoides prevailed similarly on the different root materials whereas bacterivorous protozoa and the amoebal fraction thereof dominated in rye. At week 12 no species dominated the nematode assemblages that were similar between the resources. The differences between nematode assemblages among plant resources at 2 week were similar to the results of a field study sampled after 6 weeks with the same soil and plant resources. This lends support to the relevance of the successional patterns observed in this incubation study.     

Cycling of extracellular DNA in the soil environment

Upon entering the soil environment, extracellular DNA is subjected to dynamic biological, physical, and chemical factors that determine its fate. This review concerns the fate of both recombinant and non-recombinant sources of DNA. A schematic of DNA cycling coupled with genetic transformation is presented to understand its behavior in soil. Extracellular DNA may persist through cation bridging onto soil minerals and humic substances, be enzymatically degraded and restricted by DNases of microbial origin, and/or enter the microbial DNA cycle through natural transformation of competent bacteria. Lateral gene transfer may disseminate DNA through the microbial community. An understanding of DNA cycling is fundamental to elucidating the fate of extracellular DNA in the soil environment.