Effect of NAPL exposure on the wettability and two‐phase flow in a single rock fracture

Surface‐wetting properties are an important cause of changing the groundwater and two‐phase fluid flows. Various factors affecting the surface wettability were investigated in a parallel‐walled glass fracture with non‐aqueous phase liquid (NAPL) (gasoline, diesel, trichloroethylene, and creosote) wetted surfaces. First, the effect of the duration of NAPL exposure on wettability change was considered at pre‐wet fracture surfaces using the various NAPL species, and the result showed that the surface became hydrophobic after the exposure time of NAPL exceeded 2000 min. Second, the initial wetting state of the surface affected the timing when the wettability change begins as well as the extent of the wettability change in an NAPL‐wetted rock fractures. Under the dry condition, the wettability change was completed within a very short time of exposure to NAPL (~5 min), and then it finally reached the intermediate and weakly NAPL wetting (contact angle of 118°). Under the pre‐wet condition, a relatively long time of exposure (~5000 min) was needed to observe the obvious change of the surface wettability, which was changed up to strongly NAPL wetting (contact angle of 142°). Third, the wettability changed by NAPL exposure was stable and maintained for a long time, regardless of water flushing rate and temperature. Finally, the wettability change by the exposure of NAPL on parallel fracture surfaces was evaluated at various groundwater flow velocities. Result showed that groundwater flow velocity has an important impact upon measured contact angle. Although fracture surfaces were exposed to NAPL at the low groundwater flow velocity, the wettability was not changed from hydrophilic to hydrophobic when the contact time between NAPL and mineral surfaces was not sufficient owing to the pulse‐type movement of NAPL. This implies that the variation of exposure pattern due to groundwater flow on the wettability change can be an important factor affecting the wettability change of fracture surface and migration behaviour at natural fractured rock aquifers in case of NAPL spill. Copyright © 2015 John Wiley & Sons, Ltd.     

Prograde evolution of Sulu UHP metamorphic rock in Yangzhuang,Junan region,deduced by combined Raman and petrological studies

The prograde metamorphic history of the Sulu ultrahigh‐pressure metamorphic terrane has been revealed using Raman‐based barometry of the SiO₂ phases and other mineral inclusions in garnet porphyroblasts of a coesite eclogite from Yangzhuang, Junan region, eastern China. Garnet porphyroblasts have inner and outer segments with the boundary being marked by discontinuous changes in the grossular content. In the inner segment, the SiO₂ phase inclusions are α‐quartz with no coesite or relict features such as radial cracks. The residual pressures retained by the quartz inclusions systematically increase from the crystal centre to the margin of the inner segment. The metamorphic conditions estimated by calculation from the residual pressure and conventional thermodynamic calculation range from 500 to 630 °C and 1.3 to 2.3 GPa for the stage of the inner segment. Coesite and its pseudomorph occur as inclusions in the outer segment of the garnet and matrix omphacite. This occurrence of coesite is consistent with the pressure and temperature conditions of 660–725 °C and 3.1 GPa estimated by conventional geothermobarometry. Our results suggest that the quartz inclusions in the inner segment were trapped by garnet under α‐quartz‐stable conditions and survived phase transition to coesite at the peak metamorphic stage. The SiO₂ phases and other inclusions in the garnet have retained evidence of the pre‐eclogite prograde stage even during exhumation stage. The combined Raman spectroscopic and petrological approaches used here offers a powerful means for obtaining more robust constraints prograde stages involving garnet growth where different SiO₂ phases are present as inclusions.     

基于S变换和瞬时旅行时属性的自动初至拾取方法研究

地震波走时拾取是地震资料前期处理过程中的一个重要步骤,同时也是后期层析成像方法中计算速度的重要依据。本文提出了一种新的自动初至拾取的方法,利用地震信号的瞬时旅行时属性进行地震波自动初至拾取,瞬时旅行时属性的计算包括两个独立但相关联的部分,首先通过S变换将地震信号转换到时频域,然后利用映射算子将时频域表征映像回时间域得到瞬时旅行时,从而实现自动拾取初至。理论模型和实际地震资料处理的结果表明,该方法可以有效地拾取地震波初至时间。     

敦煌某地铁矿中磁性铁的化学物相分析

本文选用HAC—H_2O_2和HCl—NaHCO_3作为选择性溶剂,对敦煌某地铁矿中磁性铁的化学物相分析进行了研究,将磁性铁物相从传统1项细化为3项,测定了磁性铁相态中磁黄铁矿、假象赤铁矿、磁铁中铁的含量。使用国家标准物质GBW07272对方法进行了评价,分析结果与标准值或参考值吻合良好(RE为0.28%~4.75%,RSD为0.13%~5.59%)。方法简单、准确。     

动态匹配追踪中利用连续相位求取瞬时频率

动态匹配追踪算法将信号的瞬时特征作为先验信息引入到信号分解中,缩小了时频原子库的搜索范围,提高了匹配追踪效率。但在利用瞬时相位获取瞬时频率信息时会得到无物理意义的负频率,不能直接应用于匹配追踪,已有文献并没有给出瞬时频率存在负异常时的解决方案。基于此,笔者通过研究主值相位与解缠相位之间的差异,提出了利用连续相位求取瞬时频率,并推导了连续相位的求取公式;然后通过实例分析,获得了反映三种不同相位数值变化的趋势图;最后通过对比三种相位求取的瞬时频率,证明由连续相位求取的瞬时频率不存在负异常,可直接应用于匹配追踪算法。     

长清M4.1地震前区域小震调制比异常分析

研究山东内陆地区2008年以来1级以上小震的月相调制效应,并结合地震b值变化进行分析。结果表明,2020-02-18长清M4.1地震前该区存在低b值、高调制比异常,计算综合节面解P轴方位偏转发现,其与小震b值的低值变化时段非常一致。研究区6次4 级以上地震前,有4次出现异常,调制比≥0.33;而2011年和2016年2次范县地震前未出现异常,可能与范县小震集中区受采油作用影响有关。     

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Biodiversity,ecological structure,and change in the sponge community of different geomorphological zones of the barrier fore reef at Carrie Bow Cay,Belize

Changes in the relative abundance of benthic groups on the barrier fore reef at Carrie Bow Cay, Belize, point to a significant reduction of corals and an expansion of the sponge community in 1995–2009. Fifty‐one species are now present in the four geomorphological zones of this reef: the low‐relief spur‐and‐groove zone, the inner reef slope, the outer ridge, and the fore‐reef slope (to a depth of 30 m). Five species are new additions to the sponge fauna reported for Belize, and six species account for 42.6% of the total assemblage: Niphates erecta (9.60%), Aiolochroia crassa (8.8%), Niphates digitalis (6.9%), Callyspongia plicifera (6.63%), Aplysina archeri (5.37%) and Xestospongia muta (5.37%). Species richness, average density, diversity and evenness indexes are statistically similar in these four zones but some species appear to be more dominant in certain areas. In the same 30 years, coral cover has decreased by more than 90%, while the octocoral cover has greatly increased (by as much as 10‐fold in the low‐relief spur‐and‐groove zone). Thus the Carrie Bow fore reef appears to be undergoing a transition from coral dominance in the late 1970s to algae dominance today, with other benthic groups such as sponges and octocorals showing signs of gradual recovery.     

近30a山西不同相态降水的统计特征及概念模型

利用山西省1981~2010年108站的地面降水观测数据,以降水量≥0.1 mm的日数为指标,对山西108个县市不同相态降水的时空分布特征进行了分析,结果表明:五寨(山西西北部)和陵川(山西东南部)平均降雨日数、平均降雪日数、平均雨夹雪日数都位于全省之首;30 a间山西的降雨日数和降雪日数分别以3.333 d/10 a和1.529 d/10 a的趋势减少,而雨夹雪日数则以0.34 d/10 a的趋势增多;山西区域降雪和降雨日数变化趋势的空间分布都具有西部减少趋势高于东部的特征,雨夹雪日数变化趋势的空间分布则具有东部增多趋势高于西部增多趋势的特征;朔州和忻州西部是降雪日数减少趋势最强的区域,运城是降雨日数减少趋势最强的区域,晋城是雨夹雪日数增多趋势最强的区域。应用328个多相态降水过程资料和NCEP再分析资料进行统计分析,结果表明:冷空气侵入导致中低空温度下降,0℃层高度降低是降水相态发生变化的主要原因;-3℃和0℃是山西中南部降水相态转变时850 hPa和925 hPa的临界值;3.5℃则是山西北部和高海拔地区降水相态发生转变时850 hPa温度的临界值;西北路冷空气侵入多相态降水过程,地面冷锋是降水相态的分界线,东路冷空气侵入多相态降水过程,低空切变线则是降水相态的分界线。     

鲁西陆块前寒武纪大地构造演化

鲁西陆块是中国前寒武纪研究的热点地区之一,其前寒武纪花岗岩-绿岩带地体的划分与构造演化历来为学者们注目。通过系统收集近年来鲁西陆块前寒武纪SHRIMP U-Pb测年数据,利用鲁西陆块前寒武纪花岗岩类岩石化学数据判别其形成的构造环境,综合国内大地构造相方面的研究成果,并在此基础上得出:鲁西陆块前寒武纪地壳形成与演化主要经历了中太古代-陆核形成阶段、新太古代-陆壳增生阶段、元古宙-大陆裂解阶段3个阶段。