An evaluation of the history of anthropogenic mercury (Hg) emissions is needed to quantify total atmospheric Hg emissions since the Industrial Revolution. Thus more long-term records of Hg accumulation rate from natural archives are needed. In the present study, a sediment core from Tianchi Lake, a crater lake in northeastern China, was used to reconstruct atmospheric Hg accumulation rates during the past 800 years. The results show that both Hg concentration and Hg accumulation rate began to increase from 29.5 to 40.2 ng g−1 and from 1.44 to 2.26 μg m−2 yr−1, respectively, at ~ 1750 AD, synchronous with the initiation of the Industrial Revolution. The Hg accumulation rate and Hg concentration increased significantly at ~ 1850 AD, and subsequently, there were two prominent peaks, at ~ 1940 AD and ~ 1980 AD, which are temporally consistent with the Second World War and the peak in commercial usage of Hg, respectively. The Hg accumulation rate and Hg concentration decreased after ~ 1980 AD, possibly because of the decrease in the global Hg background at that time. Differences in regional Hg emissions and atmospheric circulation may be responsible for the different trends in Hg accumulation rate after ~ 1980 AD in the Tibetan Plateau and northeastern China. Our results provide new data for evaluating natural and anthropogenic Hg emissions to the atmosphere in China.

中更新世转型（mid-Pleistocene Transition,简称MPT）期间,除了冰量周期由40 ka向100 ka的特征转变之外,约900 ka以后,高纬冰量、全球海平面和大气CO 2 /大洋碳库的变幅也都发生了明显变化,这些因素对东亚夏季风的演化产生了深远影响。但关于此时期东亚夏季风降水的变化趋势及其驱动机制,目前尚存在不同看法。本文在前期古地磁和光释光（optically stimulated luminescence,简称OSL）年代框架的基础上,基于东北平原QAL钻孔上部71 m的沉积物粒度重建了夏季风降水演化序列。结果表明:1)时间跨度为1180～450 ka的林甸组和令字组均为较细颗粒的湖相沉积,且林甸组明显较令字组颗粒粗; 2)粒度粗的层位代表低湖面阶段,反映降水少,为冰期,反之亦然; 3)小波分析显示约900 ka后,100 ka周期特征明显,为通过与深海氧同位素对比获得更精细的年龄序列奠定基础; 4)约900 ka后,冰期的降水有明显减弱的趋势。高纬冰量扩张造成的全球海平面下降导致更多陆地暴露出海平面,增加了大洋水汽的输送距离,可能是降水减少的一个影响因素。大西洋经向翻转流（Atlantic Meridional Overturning Circulation,简称AMOC）减弱,热带太平洋区域"热带辐合带"（Intertropical Convergence Zone,简称ITCZ）南移,可能是东亚夏季风降水减弱的另一重要原因。古湖相沉积能够用来重建长尺度夏季风降水变化,未来应加强东亚季风区不同区域古湖泊沉积研究,进而弥补长尺度夏季风演化研究存在的不足,这将有助于更好理解轨道尺度夏季风演化的动力机制。

真菌在矿物、岩石风化和元素溶解过程中发挥着重要作用.土壤中分布和生长着多种真菌,这些不同真菌在矿物和岩石风化,以及元素溶解过程中发挥的作用可能存在显著差异.为限定此差异,本研究从玄武岩风化土壤中分离获取了4种真菌(Aspergillus pesudofelis、Aspergillus viridinutans、Aspergillus undagawae和Aspergillus clavatus),设计批式溶解实验,探究了实验室条件下(28℃、30天内)4种真菌对玄武岩的风化作用,主要通过分析元素(包括Mg、Al、Si、Ca、Ti、Mn、Fe、Ni和Sr)的溶解速率和机制揭示不同属种真菌造成的玄武岩风化差异,并选取其中两种典型真菌所在的体系进行分析.实验结果显示不同属种真菌对玄武岩的风化和元素溶解的作用确实存在显著差异:1)与无机对照组相比,真菌A.pseudofelis的生长使得溶液pH值发生显著变化,元素的线性释放速率(Rli)显著升高;2)不同种真菌对体系pH值和Rli的影响差别巨大,且并非所有真菌均能加快玄武岩风化,如经过30天反应,含真菌A.pseudofelis体系溶液pH值上升了2.1,元素Mg的线性释放速率是无机对照组的22.5倍;而含真菌A.viridinutans体系溶液pH值仅上升了0.1,Mg的线性释放速率与无机对照组近似相等;3)Mg、Al、Ca、Ti元素的线性释放速率Rli最大值均出现在溶液最低pH值条件下,表明这4种元素的释放行为很大程度上受控于质子交换作用,而Fe和Ni的释放则由真菌代谢的草酸主导.由此可知,不同种真菌对有机酸代谢水平的差异影响了玄武岩中元素的释放行为.这也可能表明,在岩石早期风化过程中,具有较强有机酸(如草酸)代谢能力的真菌在Fe和Mg等生命必需元素的释放过程中起着重要作用.

喷气锥(碟)是五大连池世界地质公园内重点保护的熔岩地貌,它们是熔岩喷发冷却后形成的.目前,许多喷气锥(碟)表壳上分布有裂隙.这些裂隙造成了喷气锥(碟)的破坏.本文根据喷气锥(碟)的形成过程,分析了熔岩的温度变化.建立喷气锥(碟)的三维模型,通过数值计算得到熔岩降温后的温度应力分布.在此基础上,运用断裂力学理论分析喷气锥(碟)上裂隙的形态及分布特征.研究表明:熔岩喷发冷却形成喷气锥(碟)时会产生温度应力,并且最大主拉应力迹线呈环状分布.该温度应力作用下形成的裂隙具有竖直、相互平行、近似等距、由表及里等特征.故此认为喷气锥(碟)竖直状裂隙为熔岩冷却过程中产生的原生裂隙.本文还分析了喷气锥(碟)上裂隙尖端钝化现象以及裂隙密度差异现象的原因.

Lacustrine sediments from the Northeast Plain of China are an ideal archive for recording the climatic history and variability of the East Asian monsoon during the Quaternary in mid-latitude East Asia. However, the lack of a high-resolution stratigraphy and high-precision geochronology of these sediments has limited our understanding of the mechanisms of Quaternary climatic and environmental changes in the region. In this study, we present a high-resolution magnetic susceptibility stratigraphy and precise paleomagnetic and optically stimulated luminescence (OSL) chronologies for core Qiananlingzi (QAL) from the Northeast Plain. Paleomagnetic data were obtained using alternating-field (AF) demagnetization with a peak AF of 80 mT and increments of 2.5−10 mT. In addition, OSL dating was conducted on coarse-grained quartz (90−150 µm) using the single aliquot regenerative dose (SAR) protocol. Correlation of the recognized polarity intervals of the QAL core to the geomagnetic polarity timescale was achieved by combining the magnetostratigraphic and OSL geochronologic data. The results indicate that the sedimentary sequence spans the interval from the Olduvai normal subchron to the end of the Brunhes normal chron. According to the lithology and the magnetic susceptibility record, the core can be divided into four intervals, from bottom to top: the Qian’an Formation (fluvial yellow-green, brown-red and grey-brown silty sand, interbedded with brown-black silty clay, with gravel layers in the lower part); the Lingzi Formation and Lindian Formation (lacustrine grey-green clay interbedded with grey-white silty sand, with fossil bivalves); and a loess-like soil (predominantly brown-yellow clayey silt, alternating with fluviolacustrine grey-white, brown and black clay). The magnetic susceptibilities (MS) of the sediments of the lower fluvial Qian’an Formation and upper loess-like soil strata are generally higher, indicating the neoformation of strongly magnetic minerals under predominantly oxidizing conditions. By contrast, lower MS values occur in the lacustrine sediments of the Lingzi Formation and Lindian Formation, which indicate a reducing environment. Overall, the MS record of the QAL core exhibits clear orbital-scale variations, with higher MS values in coarse-grained silt layers, and lower values in fine-grained clay layers. After the application of a 300 mT DC field, the isothermal remanence (IRM) is only 70%, and a hysteresis loop remained unclosed at 500 mT. These characteristics indicate the substantial presence of high-coercivity magnetic minerals in the intervals with low MS values. Thermomagnetic measurements ( χ - T ) curves show an abrupt decrease in the heating curve at 580°C, indicating that magnetite is the dominant magnetic mineral, and a further decrease above 580°C indicates the presence of hematite. After the application of an applied DC field of 300 mT, the IRM reached 90%, the hysteresis loop was closed, and the heating limb of the χ - T curve did not decrease significantly after 580°C, indicating that low-coercivity magnetic minerals contributed substantially to the magnetic properties within the intervals of higher MS. The lacustrine sediments of the core were dated to ~1180‒450 ka based on paleomagnetic and QSL dating, and interpolation of the age-depth relationship suggests that Songnen paleo-lake existed for ~730 ka. The grain-size record of the loess in the northeastern monsoon region shows no evidence of drought events at 450 ka, and records of MS and FeD/FeT from the deposits of the loess Plateau indicate a trend of increasing summer monsoon precipitation at this time. Therefore, the disappearance of the paleo-lake may be related to the multiple episodes of subsidence of the Yishu fault, which caused a diversion of the discharge of the Songhua River from the Songnen paleo-lake to the Sanjiang Plain. The high-resolution MS record and the precise chronology obtained in this study indicate that the lacustrine sedimentary sequence of QAL core can potentially resolve orbital-scale paleoclimate changes during the middle Pleistocene in mid-latitude East Asia. The Mid-Pleistocene Transition (MPT) is one of the most important climatic events in Quaternary paleoclimatology, and it is necessary to understand the response of different climatic systems to the MPT. Detailed environmental magnetic, sedimentological and geochemical studies of lacustrine sedimentary strata in the Northeast Plain in China should be carried out to explore the paleoclimatic record of the area, including the regional climatic response to the MPT.

黑龙江省五大连池玄武岩风化剖面、喷气锥和喷气碟钻孔及火烧山喷气锥、碟集中发育区空间上表层岩石样品的磁化率结果表明:(1)风化剖面的xfd(频率磁化率)从剖面底部往上变大,指示化学风化作用逐渐增强.(2)频率磁化率可以指示喷气锥、碟的化学风化强度,但有时可能受喷气锥、碟逐层堆叠的结构等影响,结果较复杂.(3)空间上,火烧山玄武岩的xlf(低频磁化率)和xfd呈对数负相关关系.(4)频率磁化率可有效指示五大连池玄武岩化学风化作用的强度,并揭示出该区玄武岩化学风化速率具有非线性特征.

通过地形测量、专项调查等手段,对全新世镜泊近期玄武岩台地熔岩隧道进行研究发现,镜泊湖熔岩隧道按成因分为两种类型,一类为主熔岩隧道,此类熔岩隧道是熔岩流流淌过程中周边遇冷首先凝固,其中心保持高温液体状态,继续流空所致;另一类为走向与熔岩流方向呈一定夹角的熔岩“气洞”,是气泡沿熔岩流切线方向逃逸汇聚所致.镜泊湖镜泊近期熔岩台地上的塌陷沟谷为主熔岩隧道塌陷形成的,即熔岩塌陷沟谷位置为主熔岩隧道位置.研究为理解全球不同区域火山熔岩隧道的形成过程提供必要证据,同时为镜泊湖世界地质公园科普宣传、旅游开发提供科学理论依据.

回顾了针对我国东北季风区第四纪气候环境演化开展的研究工作,并重点论述了末次冰盛期以来气候环境演化方面取得的进展和存在的问题,同时提出今后的工作应加强东北季风区早第四纪沉积地层钻探、晚第四纪高分辨率湖泊沉积记录对比、与其他季风区气候记录对比和驱动机制等方面的研究.

Variance and mechanism of changes in the East Asian summer monsoon (EASM)are im-portant topics in climate study,and more researches on long-term changes in the EASM can provide use-ful information.In the present study,we use Singular Spectrum Analysis (SSA)method to decompose time-series of stalagmiteδ1 8 O in the past 2000 years,and then reconstruct centennial scale and multi-dec-adal scale time-series.The results show that the centennial scale variation indicates the evolution of the EASM,and the multi-decadal change is well correlated with the El Ni n~o Southern Oscillation (ENSO) variance.The significant 77-year and 44-year cycles in the multi-decadal time-series might be signals of solar activity transported by ENSO.