洋壳渗透率结构对其内部热液对流的影响研究——基于热力学数值模拟

洋底特殊环境的限制使数值模拟成为研究海底热液对流与成矿机制的有效方法.本文通过数值模拟的方法,研究洋壳渗透率单因素变化对热液对流系统的形态和输出参数(热液喷发温度和热流值)进行研究.模拟结果表明,洋壳平均渗透率分别与热液喷发温度和热量输出呈反相关和正相关关系,符合达西流体热对流的基本解析规律.另外,洋壳渗透率的垂向变化不会使洋壳内部的对流系统产生明显的横向偏移,只使热液羽规模在垂向上产生规律性变化,且渗透率越大,热液羽规模越小.渗透率在水平方向的变化则是引发热液羽和热液喷发位置横向偏移的主要因素,且只有在特定的渗透率水平变化率范围内,上涌热液羽才会发生向高渗区的明显偏移,这也从一定程度上解释了现今拆离断层相关的热液系统均未发育于断层终止线上的事实.以大西洋Trans-Atlantic Geotraverse(TAG)热液区为例,断裂带高渗区必然影响相邻洋壳内部热液的上涌路径,但受区内拆离断裂带周缘的渗透率水平变化规律的影响,上涌热液羽不至于完全偏移至断裂带,从而产生拆离断层上盘的热液活动.     

基于不同模型的河口区水产养殖塘水-气界面CH4气体传输速率及扩散通量研究

模型估算法是水-气界面甲烷（CH₄）通量监测的主要方法.本研究选择6种不同的参数化模型方法估算了2015年6、8和10月两个亚热带河口养殖塘水-气界面CH₄传输速率（k_x）及其扩散通量,探讨了河口养殖塘k_x及CH₄扩散通量的变化特征和影响因子.结果表明：研究期间,不同模型估算下的k_x及其扩散通量均值在闽江河口养殖塘变化范围分别为1.60±0.75~6.29±1.30 cm/h和9.19±2.67~30.64±6.28 μmol/（m²·h）,在九龙江河口养殖塘的变化范围分别为0.89±0.19~6.07±0.61 cm/h和3.18±0.48~21.03±2.13 μmol/（m²·h）;k_x及其扩散通量在两个河口区均呈现随时间推移而升高的特征;整个养殖期间,养殖塘水-气界面平均CH₄传输速率k_x呈现闽江河口略高于九龙江河口（P>0.05）,但水-气界面平均CH₄扩散通量呈现闽江河口显著高于九龙江河口的特征（P<0.05）;风速、水体溶解CH₄浓度和盐度是调控河口区养殖塘水-气界面CH₄扩散通量变化的重要因子;不同模型估算出的河口养殖塘水-气界面CH₄传输速率k_x存在差异,表明模型估算法获得的水-气界面CH₄扩散通量存在一定的不确定性.     

青海湖泉湾镭同位素的空间分布与沿岸地下水排放评价

青海湖是青藏高原的重要组成部分,它是维系青藏高原东北部生态安全的重要水体.其沿岸地下水的排放直接影响了青海湖的水文生物地球化学过程,然而对该问题的研究仍然不充分.本研究于2014年对青海湖泉湾湖水、河水和地下水进行223Ra和224Ra活度的测定分析,并对泉湾湖水水平向和垂直向的Ra活度分布进行深入分析,最后估算并探讨了泉湾水体的停留时间和布哈河口沿岸地下水的排放通量.表层湖水、河水、地下水不同端元的水体223Ra和224Ra活度值分别为0.441和0.026 dpm/100 L、0.22和0.016 dpm/100 L以及0.061和1.30 dpm/100 L,最高值为地下水,其次湖水,河水最小;总体上泉湾湖水223Ra和224Ra活度随离岸距离增加分别由0.047到0.011 dpm/100 L和1.4到0.2 dpm/100 L的减小,垂向上Ra活度呈楔形分布,Ra活度在不同方向上的非保守性分布主要受到悬浮颗粒物解析的影响;通过水体滞留时间模型计算获得青海湖泉湾水体的平均停留时间为1.8天,进一步分析泉湾水体Ra的源汇项,应用镭同位素质量平衡模型获得泉湾布哈河口沿岸地下水排放通量为0.054～0.109 m3/(m2·d).     

Interaction of multiple courses of wave‐induced fluid flow in layered porous media

Different theoretical and laboratory studies on the propagation of elastic waves in layered hydrocarbon reservoir have shown characteristic velocity dispersion and attenuation of seismic waves. The wave‐induced fluid flow between mesoscopic‐scale heterogeneities (larger than the pore size but smaller than the predominant wavelengths) is the most important cause of attenuation for frequencies below 1 kHz. Most studies on mesoscopic wave‐induced fluid flow in the seismic frequency band are based on the representative elementary volume, which does not consider interaction of fluid flow due to the symmetrical structure of representative elementary volume. However, in strongly heterogeneous media with unsymmetrical structures, different courses of wave‐induced fluid flow may lead to the interaction of the fluid flux in the seismic band; this has not yet been explored. This paper analyses the interaction of different courses of wave‐induced fluid flow in layered porous media. We apply a one‐dimensional finite‐element numerical creep test based on Biot's theory of consolidation to obtain the fluid flux in the frequency domain. The characteristic frequency of the fluid flux and the strain rate tensor are introduced to characterise the interaction of different courses of fluid flux. We also compare the behaviours of characteristic frequencies and the strain rate tensor on two scales: the local scale and the global scale. It is shown that, at the local scale, the interaction between different courses of fluid flux is a dynamic process, and the weak fluid flux and corresponding characteristic frequencies contain detailed information about the interaction of the fluid flux. At the global scale, the averaged strain rate tensor can facilitate the identification of the interaction degree of the fluid flux for the porous medium with a random distribution of mesoscopic heterogeneities, and the characteristic frequency of the fluid flux is potentially related to that of the peak attenuation. The results are helpful for the prediction of the distribution of oil–gas patches based on the statistical properties of phase velocities and attenuation in layered porous media with random disorder.     

对东日本大地震序列潜热通量异常现象的讨论

用美国国家环境预报中心的表面潜热通量数据,对2011年东日本大地震序列前后所出现的潜热通量异常展开讨论,结合主震震中周边区域在1991~2011年的中强地震序列数据,分析了潜热通量异常与地震之间的关系。结果表明:(1)东日本大地震前的潜热通量剧烈变化不一定是异常,且不一定由此次地震活动引起;(2)该研究区域内20年间出现过多次有疑似"热异常"却无明显震例与之相对应的情况;(3)该研究区域内20年间有超过60%的中强地震震前并无"热异常"出现;(4)在研究潜热通量变化是否属于异常时,应尽量多地考虑各个方面的影响因素,科学合理地设定判断参数;(5)在研究潜热通量异常与地震的关系时,应对特定区域作长时间序列分析,而不是单纯针对短期内的个别震例进行判别。     

鄱阳湖入湖、出湖污染物通量时空变化及影响因素(2008-2012年)

研究鄱阳湖入、出湖污染物通量是加强鄱阳湖及长江水功能区限制纳污红线管理的前提,是建立鄱阳湖水质预测模型的基础.基于2008-2012年鄱阳湖8条主要入湖河流、出湖口的逐月水量、水质同步监测资料,根据污染源特征优选算法,计算总磷(TP)、氨氮(NH3-N)、高锰酸盐指数(CODMn)的入、出湖污染物通量,并分析时空变化特征及影响因素.结果表明:(1)出湖口和乐安河入湖口断面的NH3-N、TP及昌江入湖口断面的TP,以点源污染为主,采用每月瞬时通量作为月平均通量的算法更准确;其余以非点源污染为主,采用瞬时污染物浓度与月平均流量之积来计算月平均通量更准确.(2)2008-2012年CODMn、NH3-N和TP年平均人湖通量分别为304398、53063和9175 t,年平均出湖通量分别为367436、45814和8452t.8条入湖河流每年的入湖水量、CODMn通量和个别年份的NH3-N、TP通量小于出湖,这主要是因为未计算区间产流及相应排污和采砂引起的内源污染.(3)入、出湖污染物通量在年际间主要受水量影响而呈现W型波动变化趋势,CODMn、NH3-N、TP入湖通量及CODMn出湖通量均集中在汛期,NH3-N、TP出湖通量则是冬季较多(低水位下湿地植被净化作用受限).入湖TP、NH3-N、CODMn通量主要来自赣江、信江、乐安河,而NH3-N、TP浓度最高的是乐安河、信江.     

Comparison of three remote sensing based models for the estimation of latent heat flux over India

The aim of this work is to compare three remote sensing based models: two contextual and one physically-based single-pixel model for the estimation of daytime integrated latent heat flux without the use of any ground measurements over Indian ecosystems. Satellite datasets from the MODIS sensors aboard the Terra and the Aqua satellites were used. The latent heat flux estimated from the remote sensing models was compared with that estimated from Bowen ratio energy balance towers at five sites in India. The root mean square error (RMSE) of the latent heat flux estimated from the contextual and the physically-based models was found to be in the order of 40 and 70 W m^?2, respectively. The relatively inferior performance of the more complex physically-based model in comparison with the contextual models was found to be largely due to inaccurate parameterizations estimated only from remote sensing datasets without any ground data.     

Video-monitoring of wood discharge: first inter-basin comparison and recommendations to install video cameras

Wood in rivers plays a major role both ecologically and morphologically. In recent decades, due to human activities in the river channels and along the riparian zone, wood obstruction and jamming has exacerbated flooding hazards and infrastructure damage. Therefore, it is necessary to quantify the wood flux and discharge in rivers to improve wood hazard management. Among the various methods for monitoring the wood flux in a river, the streamside videography technique is effective given its high temporal and spatial resolution. Previous work monitored the wood discharge (m³/s) using this technique in the Ain River (France) during three floods (MacVicar and Piégay, 2012), and the same method is implemented on the Isère River (France) to obtain the statistics of wood discharge for two floods. Comparison between the two sites supports the generalization of both the monitoring technique and the link between wood discharge and flood characteristics. We first show that the maximum wood discharge is observed at bankfull discharge, and we confirm the three stage model proposed by MacVicar and Piégay (2012). Additionally, transverse distributions of the number of wood pieces and corresponding wood length appear to be similar for different flood magnitudes on each site. As a technical contribution, the use of the same technique on two sites allows for recommendations on key decisions related to the location and implementation of the equipment. Both statistical and technical contributions can be used by decision makers to implement this monitoring technique, acquire the wood transport parameters, and evaluate the potential wood hazards at local scale or along a river. © 2020 John Wiley & Sons, Ltd.     

模拟强震后高压输电接续管漏磁的检测方法研究

为维持强震影响下电力系统安全运行,改善高压输电效率及输电质量,提出强震影响下高压输电接续管漏磁检测方法。采用磁敏传感器获取漏磁通内的漏磁信号,通过计算提取接续管内漏磁信号特征量,依据这些特征实现高压输电接续管漏磁检测。构建高压输电接续管三维有限元几何模型,通过对模型的单元类型确定、材料选择、边界条件与荷载设置、传感器部署位置等,完成高压输电接续管仿真分析。实验结果表明：在Ⅸ度罕遇北京波影响下,接续管内漏磁信号特征量可评判缺陷深度,实现接线管漏磁检测。通过对DL/T1192-2012标准输电线接续管上表面和下表面两端的漏磁信号峰值检测等,证明了本文方法对强震影响下高压输电接续管漏磁进行检测的有效性。     

The magnetic field strength and energy flux of energetic electrons in a microwave burst source region

The observations of a microwave burst with multiple impulses on 1993 Oct 2, 073940–074100 UT are analysed. This event consists of multiple impulses superimposed on a slowly varying burst background. Our formula for coronal magnetic field diagnostics was used here for the first time to derive the field strength and information on the energetic electrons. The results are: 1) The mean spectral index of the impulsive component in the optically thin part is less than that of the slow background by 1 (a harder spectrum). The mean brightness temperature at 19.6 GHz of the former is 6 times that of the latter. 2) The mean magnetic strengths of the impulse and slow burst regions are 158 G and 531 G, respectively. The time variation in the slow burst region is saddle-shaped, being 50% lower in the middle than at the beginning and end. 3) The column density NL and number density N of energetic electrons in the impulsive component are 4% and 8% of those of the slow component, but the energy flux and emission coefficient are 100% and 800% greater. The two components appear to be produced by two different electron groups with different energy distributions in two different regions.