Testing a theoretical resistance law for overland flow on a stony hillslope

Overland flow, sediments, and nutrients transported in runoff are important processes involved in soil erosion and water pollution. Modelling transport of sediments and chemicals requires accurate estimates of hydraulic resistance, which is one of the key variables characterizing runoff water depth and velocity. In this paper, a new theoretical power–velocity profile, originally deduced neglecting the impact effect of rainfall, was initially modified for taking into account the effect of rainfall intensity. Then a theoretical flow resistance law was obtained by integration of the new flow velocity distribution. This flow resistance law was tested using field measurements by Nearing for the condition of overland flow under simulated rainfall. Measurements of the Darcy–Weisbach friction factor, corresponding to flow Reynolds number ranging from 48 to 194, were obtained for simulated rainfall with two different rainfall intensity values (59 and 178 mm hr⁻¹). The database, including measurements of flow velocity, water depth, cross-sectional area, wetted perimeter, and bed slope, allowed for calibration of the relationship between the velocity profile parameter Γ, the slope steepness s, and the flow Froude number F, taking also into account the influence of rainfall intensity i. Results yielded the following conclusions: (a) The proposed theoretical flow resistance equation accurately estimated the Darcy–Weisbach friction factor for overland flow under simulated rainfall, (b) the flow resistance increased with rainfall intensity for laminar overland flow, and (c) the mean flow velocity was quasi-independent of the slope gradient.     

泰山玉的外观特征及分类分级研究

泰山玉的主要矿物成分为蛇纹石,另外有少量的磁铁矿、绿泥石等,因其所含矿物及其含量的不同,产生了不同的外观特征。泰山玉的颜色主要有绿色、黑色、褐色和花色4个系列,根据玉石颜色结合市场上普遍认可的分类名称,将泰山玉划分为4类,即泰山碧玉、泰山墨玉、泰山紫檀玉和泰山花斑玉。从颜色、质地、透明度、光泽、净度、块度几方面对泰山玉进行了质量评价,并将每一玉石类型划分了3个质量等级。     

CBERS-02星CCD波段平均太阳辐照度反演及应用

卫星图像波段平均太阳辐照度是计算表观反射率的重要参数。本文采用两种方法对CBERS-02星CCD波段平均太阳辐照度进行了计算,一种方法是利用大气辐射传输软件SBDART模拟大气顶部的太阳光谱曲线,结合CBERS-02星CCD波段响应曲线,计算1～4波段的平均太阳辐照度;另一种方法是用6S模型对波段平均太阳辐照度进行计算。为验证计算结果,用同样的方法,计算了LandsatTM5和ETM的波段平均太阳辐照度,与Landsat公布的数据进行对比,结果表明,用模拟的太阳光谱曲线的计算结果更准确。以2005年8月24日的一景图像为例,计算了图像的表观反射率,经6S模型大气校正后,反演了地表反射率,与地面实测的地表反射率进行了对比,除第四波段误差为4%外,其余1～3波段误差仅为0.01%。     

海拉尔盆地乌尔逊凹陷片钠铝石及研究意义

海拉尔盆地乌尔逊凹陷含片钠铝石砂岩与CO2气井、燕山期花岗岩的分布一致,均产于苏仁诺尔构造带乌西断裂控制的区域.在偏光显微镜和扫描电镜下观察发现片钠铝石的产状有3种:①部分或全部交代长石、石英等碎屑颗粒,多呈长柱状、片板状集合体;②作为胶结物充填于碎屑颗粒间的孔隙中,呈放射状、束状、毛发状、菊花状集合体;③充填在碎屑矿物的溶洞或裂隙中,呈纤维状集合体.含片钠铝石砂岩的成岩共生序次和油气包裹体及现今地层水特征均表明,片钠铝石的生长时间晚于任何其它自生矿物.电子探针及INCA能谱仪分析表明,片钠铝石主要由Na、Al、O、C等组成.研究表明,海拉尔盆地乌尔逊凹陷片钠铝石可作为深部CO2热流体活动的示踪矿物.     

两类多河道河流的形式模式及河道稳定性比较

在多河道河流中，网状河流作为有别于分汊河流和辫状河流的河型而提出已经引起人们的注意，但它与分汊河流的区别常常被忽略。为了阐明二者的根本差别，力求从多河道形成模式上对二者进行比较研究。通过对长江下游分汊河流及荆江风状河流特定河段形成历史及方式的探索，提出河道内的江心洲化模式和河漫滩上的河道化模式分别是分汊河流和网状河流形成的基本途径。由此而决定了网状河道具有分汊河流更高的稳定性。     

一种基于星形的星图识别算法

针对卫星自主定姿问题,提出了一种基于星形的星图识别算法.该算法直接以星对角距为匹配特征,先确定影像中亮星为中心星,并以此星与相邻星像点构建辐射状星图,统计所有满足星对角距匹配条件的导航星出现次数,次数最多的即为中心星所对应的导航星.实验表明,该算法构造的导航星表容量小,抗星等干扰,与多边形角距匹配算法相比,具有匹配速度快、识别率高、可靠性好的特点.     

广州市大气颗粒物PM2.5显微形貌特征和来源解析

PM_2.5是近年来影响我国城市大气环境的首要污染物,其成因机制复杂。本文采用扫描电镜和ICP-MS研究了广州市大气颗粒物PM_2.5的显微形貌及其化学组成特征,并应用富集因子法进行源解析。结果表明,PM_2.5的颗粒形态以无定形态为主;主要物质表现为含Fe、Mg、Al、K、Na的硅酸盐组合,具有道路扬尘、建筑施工排放等一次粒子特征;单个无定形颗粒物能谱表现出硫酸盐+硝酸盐的组合特征,为汽车尾气所排放的前体污染气体NO_x和SO₂进入大气环境中,在特定的物理化学条件下通过成核作用发生相态改变所形成的二次粒子。PM_2.5中高度富集Cd、Se、Zn、Cu、Pb、As等重金属,异常富集的Br主要为当地普遍使用的阻燃剂十溴联苯醚和拆解电子垃圾所致,稀土元素的浓度在0.022~0.582 ng/m³之间,具有重稀土元素富集的特征。这些特征反映出广州市PM_2.5颗粒物的组成既有一次粒子,也有二次粒子,物质来源具有多重性。     

PALEONTOLOGY

正20141596 Liu Yunhuan(School of Earth Sciences and Resources,Chang’an University,Xi’an 710054,China);Shao Tiequan Early Cambrian Quadrapyrgites Fossils of Xixiang Boita in Southern Shaanxi Province(Journal of Earth Sciences and Environment,ISSN1672-6561,CN61-1423/P,35(3),2013,p.39-43,3 illus.,20 refs.)     

地浸砂岩型铀矿镭—氡放射性平衡对伽玛测井解释结果的影响研究

地浸砂岩型铀矿钻探勘查过程中,由于钻孔内＂压氡现象＂的存在,使钻孔内铀矿层的镭—氡含量出现暂时的不平衡现象,往往会造成伽玛测井解释结果系统偏低,影响了铀矿资源量评价的准确程度。因此在地浸砂岩型铀矿勘查过程中,必须设计一定数量的物探参数孔,及时开展镭—氡放射性平衡系数的研究和评价。     

Within-reach spatial variability of snails and molluscivory by brown trout

Linking habitat distributions of prey to the probability of predation is important to understanding consumptive effects of predators on prey populations. This study reports how within-reach spatial variability of two snails, the hydrobiid Potamopyrgus antipodarum and the physid Physella acuta, was linked to habitat-based predation risk by young brown trout (Salmo trutta) of different age classes. Potamopyrgus is endemic to New Zealand streams and lakes, where it commonly co-exists with the invader P. acuta, but both snails are worldwide invaders to many freshwater systems. Examination of egested snails revealed Potamopyrgus and Physella were consumed in similar numbers within age classes. However, 10-month-old trout consumed, on average, fewer snails than 20-month-old trout, and 8-month-old trout ate essentially no snails, suggesting snails were a more important prey item for larger age-1 fish than smaller age-0 fish. No Physella were egested alive by any trout age class. However, 38% and 16% of the Potamopyrgus consumed were egested alive by 10- and 20-month-old trout, respectively, with some passing live after ~70 h in digestive tracts. Physella and the spiny-shell form of Potamopyrgus were significantly denser on macrophytes than on stony sediments in midchannel, and these habitat distributions affected their odds of consumption. Risk of consumption by trout was ~10 times greater for Physella than Potamopyrgus on stones, but their risk was similar in protective macrophytes. Odds of consumption were similar for spiny and smooth shell forms of Potamopyrgus on stones, suggesting spines do not provide protection from large predators like trout. My results suggest that brown trout can potentially exert stronger population regulatory effects on Physella than on Potamopyrgus and that these effects are partly mediated by macrophyte cover.