航空煤油薄油层燃烧特性实验研究

为研究薄油层燃烧特性,开展航空煤油薄层油池火实验,分析油品燃烧的整个过程、燃烧速率、火焰高度和辐射反馈等参数随时间的变化规律。结果表明:整个薄层燃烧过程除发展、稳定和熄灭阶段外,还存在薄层燃烧衰减阶段。稳定阶段的燃烧速率与初始油层厚度相关,但随着厚度的增加其逐渐趋于稳定;薄层燃烧衰减阶段,燃烧速率会随着实时油层厚度的下降逐渐降低。对比火焰高度的实测值和模型预测值发现,Heskestad模型的预测更接近实际结果;燃烧发展阶段后,火焰辐射反馈基本维持稳定,受初始厚度的影响较小,但辐射透射强度会随着油层厚度的降低而增加,且增速逐渐加快,表明辐射透射在薄层燃烧衰退阶段中起到关键作用。结合辐射透射的变化规律,将辐射反馈分为可吸收和不可吸收2部分,并提出用于预测辐射透射大小的经验模型。     

Flame propagation through dust clouds of nano and micron scale aluminum particles

Temperature measurement on propagating flame and minimum explosible concentration are investigated. The dust explosion experiments of nano-particle dust clouds exhibit higher temperature gradient in preheat zone and lower MEC than those of micron particle dust clouds. A heterogeneous model is proposed to describe the oxidation process under two extreme conditions: whether the alumina film is involved in the reaction or not. The new methodology allows the estimation of oxidation kinetics of growing alumina. For micron particle, the model clarifies that the activation energy which has been wrongly considered to be for aluminum oxidation should be for lattice diffusion, and the initial reaction rate is proved to be dominated by the diffusion rate of oxygen through alumina shell as diffusion controlled reaction. For nano-particle, the model explained that why the reported activation energy shows significantly lower than that for micron particle, due to initially ignorable alumina film or considered as kinetically controlled reaction. However, as reaction occurs and alumina builds up on the surface, the interference of alumina somewhat increases the activation energy.     

秸秆添加对长期施肥旱地红壤N2O和CO2排放的影响

秸秆还田作为农田土壤培肥的一种重要措施,显著影响N₂ O和CO₂ 等温室气体排放.为探明长期施肥土壤N₂ O和CO₂ 排放对秸秆添加的响应规律及关键影响因素,采集对照（CK,不施肥）、当地推荐化肥施用量（F）、200 %当地推荐化肥施用量（2F）、猪粪（M）和化肥配施猪粪（FM）这5种长期施肥（30 a）处理的旱地红壤,分别设置添加秸秆和不添加秸秆处理,在恒温恒湿条件下培养（65 %田间持水量,25 ℃）20 d.结果表明,施肥显著促进了N₂ O排放.相较不施肥处理[（22.05 ±2.09） μg·kg^-1,以N计,下同],施化肥处理N₂ O累计排放量显著增加了119 %~195 %[F和2F处理分别为（48.38 ±20.81） μg·kg^-1和（65.13 ±12.55） μg·kg^-1],施粪肥处理N₂ O累计排放量显著增加了275 %~399 %[M和FM处理分别为（82.72 ±12.73） μg·kg^-1和（1 101.99 ±425.71） μg·kg^-1].土壤硝态氮（NO₃ ^--N）、可溶性有机碳（DOC）和可溶性总氮（DTN）是影响不同施肥处理N₂ O排放的主要因素.相较未添加秸秆,添加秸秆对CK、F和FM处理的N₂ O累计排放无显著影响,显著增加了2F（345 %）和M处理（247 %）的N₂ O累计排放.秸秆添加通过增加DOC和消耗DTN从而影响N₂ O排放.施肥显著促进了CO₂ 排放.相较不施肥处理,施粪肥处理CO₂ 累计排放量显著增加了120 %~130 %[M和FM处理累计排放量（以C计,下同）,分别为（122.11 ±4.3） mg·kg^-1和（116.47 ±4.55） mg·kg^-1],2F处理CO₂ 累计排放量显著增加了28 %[（65.13 ±12.55） mg·kg^-1].微生物量碳（MBC）、DOC和DTN是影响不同施肥处理CO₂ 排放的主要因素.相较未添加秸秆,添加秸秆条件下CO₂ 累计排放量显著增加了660 %~1 132 %.秸秆添加后DOC和MBC含量显著提高,促进了CO₂ 排放.综上,秸秆添加通过增加土壤DTN消耗和DOC含量显著促进施肥处理的N₂ O和CO₂ 排放.在施用粪肥的旱地红壤中应合理考虑秸秆还田,以平衡肥力提升与温室气体排放的综合效益.     

Short- and Longer-Term Effects of Fire and Herbivory on Sagebrush Communities in South-Central Montana

To better understand the role of herbivory and fire as potential disturbance processes in sagebrush communities, we examined responses of a grazing ungulate, elk (Cervus elaphus), following prescribed burning of sagebrush (Artemisia tridentata ssp. vaseyana) in south-central Montana (USA.) with concurrent monitoring of changes in plant production, nutritional quality, and community diversity from 1989–1999. Burning transformed low-diversity, sagebrush-dominated communities into high-diversity, graminoid-forb communities that persisted for 10 years without significant reestablishment of sagebrush. Elk increased use of burned sites one year after burning, but elk use returned to pre-burn levels over the next two to nine years. Forage biomass and nutritional quality declined after initial increases that coincided with increased elk use. Increases in elk use appeared to be influenced by increases in combined graminoid and forb production and changes in structural vegetation characteristics that permitted greater foraging efficiency. Declines in use were associated with loss of nutritional enhancement and declines in combined graminoid and forb production. Managers may observe only short-term responses from grazing ungulates to prescribed fire in sagebrush communities, but can expect longer-term increases in plant diversity and establishment of graminoid-forb communities.     

羧基稻草阳离子吸附剂的制备及其去除水溶液中亚甲蓝的研究

为促进工业废水处理并降低废水处理费用,研究了柠檬酸热化学酯化法改性稻草制备可生物降解阳离子吸附剂的方法.实验比较了天然和改性稻草去除溶液中阳离子染料(亚甲蓝)的能力,研究了不同实验参数(pH值、吸附剂量、染料浓度、离子强度、吸附时间)对亚甲蓝吸附效果的影响在pH为2～10范围内,天然稻草去除亚甲蓝的能力随pH值的增加而增加,而改性稻草在pH≥3时对染料的去除率达到最大.改性稻草用量大于1.5g·L-1时几乎能完全去除浓度为250mg·L-1亚甲蓝溶液中的染料.改性稻草用量为2.0g·L-1对浓度为50～450mg·L-1的亚甲蓝溶液去除率保持在98%以上.增加溶液的离子强度会导致亚甲蓝去除率降低.染料吸附等温线符合Langmuir模式.吸附过程符合准一级反应动力学方程.酯化改性使染料的吸附剂粒子内扩散速率常数(kid)大大增加.研究结果表明,改性稻草是良好的亚甲蓝吸附剂.     

微波辐照麦秸制造活性炭

研究了微波辐照经氯化锌浸渍的麦秸制造活性炭。实验结果表明,经微波辐照８ｍｉｎ,所得到活性炭的亚甲蓝脱色力为１７０ｍＬ／ｇ,为国家标准一级品（ＬＹ２１６－７９）的１．４２倍,时间仅为传统方法的１／４５。     

改性稻草吸附铜离子的热力学研究

研究表明稻草改性后吸附铜离子的能力得到很大提高。在4种温度下（15、27、37、50℃）,改性稻草吸附铜离子的最大吸附量分别为1．10、1．24、1．34、1．50mmol／g。不同温度下,吸附自由能△G大大小于零,吸附过程具有强烈的自发趋势。吸附焙△H和吸附熵△S都大于零,吸附过程是熵增加推动的。     

Source profiles of particulate organic matters emitted from cereal straw burnings

Cereal straw is one of the most abundant biomass burned in China but its contribution to fine particulates is not adequately understood. In this study, three main kinds of cereal straws were collected from five grain producing areas in China. Fine particulate matters （PMzs） from the cereal straws subjected to control burnings, both under smoldering and flaming status, were sampled by using a custom made dilution chamber and sampling system in the laboratory. Element carbon （EC） and organic carbon （OC） was analyzed. 141 compounds of organic matters were measured by gas chromatography-mass spectrum （GC-MS）. Source profiles of particulate organic matters emitted from cereal straw burnings were obtained. The results indicated that organic matters contribute a large fraction in fine particulate matters. Levoglucosan had the highest contributions with averagely 4.5% in mass of fine particulates and can be considered as the tracer of biomass burnings. Methyloxylated phenols from lignin degradation also had high concentrations in PM2.5, and contained approximately equal amounts of guaiacyl and syringyl compounds. 13-Sitostrol also made up relatively a large fraction of PMz5 compared with the other sterols （0.18%-0.63% of the total fine particle mass）. Normal alkanes, PAHs, fatty acids, as well as normal alkanols had relatively lower concentrations compared with the compounds mentioned above. Carbon preference index （CPI） of normal alkanes and alkanoic acids showed characteristics of biogenic fuel burnings. Burning status significantly influenced the formations of EC and PAHs. The differences between the emission profiles of straw and wood combustions were displayed by the fingerprint compounds, which may be used to identify the contributions between wood and straw burnings in source apportionment researches.     

Preparation1 and utilization of wheat straw anionic sorbent for the removal of nitrate from aqueous solution

In order to reduce the impact of eutrophication caused by agricultural residues (i.e. excess nitrate) in aqueous solution, economic and effective anionic sorbents are required. In this article, we prepared anionic sorbent using wheat straw. Its structural characteristics and adsorption properties for nitrate removal from aqueous solution were investigated. The results indicate that the yield of the prepared anionic sorbent, the total exchange capacity, and the maximum adsorption capacity were 350%, 2.57 mEq/g, and 2.08 mmol/g, respectively. The Freundlich isotherm mode is more suitable than the Langmuir mode and the adsorption process accords with the first order reaction kinetic rate equation. When multiple anions (SO42-, H2PO4-, NO3-, and NO2-) were present, the isotherm mode of prepared anionic sorbent for nitrate was consistent with Freundlich mode; however, the capacity of nitrate adsorption was reduced by 50%. In alkaline solutions, about 90% of adsorbed nitrate ions could be desorbed from prepared anionic sorbent. The results of this study confirmed that the wheat straw anionic sorbent can be used as an excellent nitrate sorbent that removes nitrate from aqueous solutions.     

秸秆还田对稻田温室气体排放的影响:Meta分析——以长江中下游地区为例

全球气候变暖是人类面临的严峻挑战,稻田生态系统在全球气候变暖中起到重要的作用。目前已有许多学者通过大田试验的方法研究了不同秸秆还田方式下温室气体排放的特征,但由于试验地点等因素的不同导致最终的结果差异很大。通过整合这些结果来研究区域内不同秸秆还田方式(翻耕秸秆还田(CTS)、免耕秸秆还田(NTS)和旋耕秸秆还田(RTS))下稻田温室气体排放的特征,能够准确地反映一定区域内稻田生态系统的净减排潜力。本文基于长江中下游地区32篇关于秸秆还田对稻田温室气体排放的文献收集173组数据,利用Meta分析方法研究了3种秸秆还田方式下稻田CH_4和N_2O排放的特征,并估算出不同秸秆还田方式下稻田的全球增温潜势和净增温潜势。结果表明,CTS、NTS和RTS处理下稻田CH_4周年排放的效应值分别为0.76、0.37和0.68,稻田N_2O周年排放的效应值分别为0.44、0.36和0.52;在两熟制下,不同秸秆还田方式下稻田CH_4周年排放的效应值的大小为RTSCTSNTS,但N_2O周年排放的效应值的大小为RTSNTSCTS。在三熟制下,三种秸秆还田方式下稻田CH_4的周年排放的效应值的高低为CTSRTSNTS,而N_2O周年排放的效应值的高低为RTSNTSCTS。在相同的秸秆还田方式下,三熟制稻田温室气体周年排放的效应值都高于两熟制。此外,不同的还田秸秆种类影响稻田温室气体的排放;结合前期研究,估算出CTS、NTS和RTS处理下稻田的净增温潜势分别为12 375.55、11 232.36和15 982.87 kg CO_2-equivalent·hm~(-2)。因此,免耕秸秆还田是长江中下流地区稻田净减排条件下适宜的秸秆还田方式。