Examining Flood Frequency Distributions in the Midwest U.S.1

Villarini, Gabriele, James A. Smith, Mary Lynn Baeck, and Witold F. Krajewski, 2011. Examining Flood Frequency Distributions in the Midwest U.S. Journal of the American Water Resources Association (JAWRA) 47(3):447‐463. DOI: 10.1111/j.1752‐1688.2011.00540.x Abstract: Annual maximum peak discharge time series from 196 stream gage stations with a record of at least 75 years from the Midwest United States is examined to study flood peak distributions from a regional point of view. The focus of this study is to evaluate: (1) “mixtures” of flood peak distributions, (2) upper tail and scaling properties of the flood peak distributions, and (3) presence of temporal nonstationarities in the flood peak records. Warm season convective systems are responsible for some of the largest floods in the area, in particular in Nebraska, Kansas, and Iowa. Spring events associated with snowmelt and rain‐on‐snow are common in the northern part of the study domain. Nonparametric tests are used to investigate the presence of abrupt and slowly varying changes. Change‐points rather than monotonic trends are responsible for most violations of the stationarity assumption. The abrupt changes in flood peaks can be associated with anthropogenic changes, such as changes in land use/land cover, agricultural practice, and construction of dams. The trend analyses do not suggest an increase in the flood peak distribution due to anthropogenic climate change. Examination of the upper tail and scaling properties of the flood peak distributions are examined by means of the location, scale, and shape parameters of the Generalized Extreme Value distribution.     

污泥和盐渍土混配介质的性质及对5种野生植物生长的影响

将污泥与滨海盐渍土按照不同比例(污泥质量分数分别为0、20%、40%、60%、80%和100%)混配,开展三叶鬼针草(Bidens pilosa)、稗(Echinochloa crusgalli)、荆芥(Schizonepeta tenuifolia)、金叶马兰(Kalimeris indica)和蒲公英(Taraxacum mongolicm)5种野生植物的盆栽试验,研究污泥混配介质的理化性质,污泥比例对植物成活率、叶绿素含量和干质量的影响,以及植物体内各种重金属的累积浓度,探索污泥在滨海区盐渍土中的最佳施用比例,并对野生植物资源进行评价。结果表明,污泥改良滨海盐渍土是可行的,污泥质量分数为20%～60%时,混配介质的理化指标符合CJ/T 340—2011《绿化种植土壤》,Cd、Cu、Zn、Cr、Pb和Ni含量符合GB 15618—95《土壤环境质量标准》中的二级标准,并以60%污泥+40%滨海盐渍土的质量配比效果最佳,该混配介质中植物存活率达100%;三叶鬼针草、稗子、荆芥、金叶马兰和蒲公英是上海市滨海地区优良的植被恢复先锋植物。     

Minimum ignition energy of LDPE dust/ethylene hybrid mixture

An experimental device for evaluating the minimum ignition energy (MIE) of LDPE dust/ethylene hybrid mixture was built with the innovative mixing mode. The MIE of the hybrid mixture that contained ethylene below its lower explosive limit (LEL) was studied. The result indicated that adding a small amount of ethylene significantly reduced the MIE of the original dust cloud. All the MIEs with five different particle sizes were found to show similar trends of exponential attenuation with the increase of ethylene concentration; such attenuating effect grew as the dust particle size rose. When ethylene concentration increased and approached to its LEL, the reaction mechanism dominated by combustible dust turned into one dominated by combustible gas. The MIE decreased first and then increased with the dust mass and increased with the dust particle size. A multifactor mathematical correlation model of the MIE with the dust particle size and ethylene concentration was developed.     

火焰原子吸收法测定苹果中波尔多液的农药残留

通过原子吸收法测定苹果果皮、果肉上波尔多液的农药残留铜的含量,结果表明:喷洒了波尔多液的苹果果皮上铜含量明显大于果肉,在果皮上有一定的农药残留;而未喷洒波尔多液的苹果果皮和果肉中铜的含量的差异很小。     

城市可降解生活垃圾的生物综合处理模式初探

针对现有城市生活垃圾处理方式的不足,结合垃圾生物处理特点,设计了集混合菌群降解、生物过滤除臭、污水回用及植被绿化于一体的立体处理体系。结果表明,该系统在城市生活垃圾的“三化”处理中具有显著的潜势:既使生活垃圾在食物链外形成安全的闭路循环,防止有害物质向人居环境入渗;同时,处理设施的立体化、终产物的生物转化以及即刻的市场效应,有效地增强了系统的消纳能力,缓解了传统处理方式对城市空间的压力。该系统对我国中小城市生活垃圾的综合利用具有积极的参考价值。     

Modeling of n-butane ignition, combustion, and preflame oxidation in the 20-l vessel

The objective of the study reported herein is to simulate various physical and chemical phenomena accompanying fuel-rich n-butane–oxygen mixture preparation, ignition, preflame oxidation, and combustion in the standard 20-l explosion vessel, by applying mathematical models. Based on the computational fluid dynamics (CFD) simulations of the mixing process and natural convection of the ignition kernel, as well as on the analysis of the detailed reaction mechanism of n-butane oxidation, laminar flame propagation, and self-ignition, possible explanations for the phenomena observed experimentally have been suggested. The results of the study indicate that seemingly inflammable mixtures can become hazardous depending on the mixture preparation procedure and forced ignition timing.     

受限空间网状高分子材料抑制油气爆炸实验研究

为研究新型网状高分子材料对油气爆炸的抑制作用,搭建了狭长受限空间油气爆炸抑制实验系统,进行了油气爆炸抑制实验,通过对比是否按留空率规范填充抑爆材料所达到的3种工况,分析了爆炸超压值、升压速率、火焰强度和火焰持续时间等特性参数变化情况。实验结果表明:新型网状高分子材料对油气爆炸产生的最大爆炸超压值、升压速率和火焰强度有明显的抑制作用;新型网状高分子材料对火焰的传播有明显的阻滞作用,使火焰传播速度减小;当新型材料按照规范填充时,最大爆炸超压值和升压速率分别下降了84.36%和 39.18%以上,火焰被完全熄灭,并且距离点火端越远,抑爆效果越明显。     

基于光谱混合分析和反照率-植被盖度特征空间的土地荒漠化遥感评价

采用线性光谱混合分析模型对Landsat TM遥感影像进行混合像元分解,获取植被、裸土和水体组分的相对丰度分布;在反演地表反照率的基础上,构建了基于Albedo-Vegetation特征空间的土地荒漠化遥感监测模型;以黑河中游部分区域为例,进行了实证研究,并利用实地调查数据进行精度验证。结果表明:此方法充分利用了多维遥感信息,反映了荒漠化土地地表覆盖、水热组合及其变化,具有明确的生物物理意义,而且指标简单、易于获取,精度较高,有利于荒漠化的定量分析与监测。     

高岭石、针铁矿及其二元体对胡敏酸的吸附特性

研究了高岭石、针铁矿及其混合物(KGM)和复合物(KGC)的表面性质及吸附胡敏酸的特性.结果表明,4种物质的比表面积(SSA)表现为针铁矿KGCKGM高岭石,KGM的SSA接近两种纯物质的平均值,而KGC的SSA明显升高.高岭石、针铁矿、KGM和KGC的等电点(IEP)分别为3.2、7.9、6.1和6.7;初始p H=5.0时,其表面Zeta电位分别为-13.9、38.2、14.3和19.7 m V.4种样品对胡敏酸的动力学吸附过程适合用准二级动力学模型描述,表明化学吸附是主要作用机制.一、二位Langmuir模型可较好地拟合等温吸附数据(R~2为0.962~0.993),其中二位Langmuir模型对KGM和KGC吸附数据的拟合度R~2分别为0.989和0.993;Freundlich模型对等温吸附数据的拟合度较低,但两种二元体的拟合度高于两种纯物质.初始p H=5.0时,高岭石、针铁矿、KGM和KGC对胡敏酸的吸附容量(q_(max))分别为6.02、61.83、35.13和42.10 mg·g~(-1);两种二元体的q_(max)都高于两种纯物质q_(max)的平均值,其中KGC的q_(max)明显升高.热力学参数表明,4种样品对胡敏酸的吸附均属于吸热反应,其中高岭石的吸附为非自发过程,其余样品的吸附为自发过程.     

烟台夹河河口海水混合过程的地球化学特征研究

海(咸)水混入是河口河水重要的地质过程,深刻地影响河水地球化学过程。本文系统采集夹河河口水样,分析海淡水混合过程的地球化学特征。结果表明,远离河口段(J10~J14)为淡水性质,主要受水-岩作用及人类活动等影响;近河口段(J1~J8)海水混入严重,F~-、Cl~-、Br~-、SO~(2-)_4、Na~+、K~+、Mg~(2+)、Ca~(2+)、盐度等明显较高,主要受海水混入影响。近河口段存在Na-Ca离子交换过程,约占Na~+总量的0.9%~1.5%,离子交换量随海水混入比例增加而增加,Na~+离子交换量与K~+,Ca~(2+)、Mg~(2+)、Br~-、F~-、SO~(2-)_4离子交换量相关,且河水离子含量与盐度回归系数略低于与盐度、Na~+交换量回归系数,表明河口段河水离子交换影响河水地球化学特征。