岩芯XRF扫描在湖泊年纹层研究中的应用——以青藏高原东南缘新路海为例

湖泊年纹层以其精确到年乃至季节尺度的高分辨率优势, 成为研究古气候环境变化的重要载体. X射线荧光(XRF)岩芯扫描由于其有分辨率高、分析快速等特点, 在湖泊年纹层研究中发挥了重要的作用. 本文以青藏高原东南缘新路海年纹层为研究对象, 采用X射线荧光(XRF)岩芯扫描, 对新路海湖泊纹层计年、纹层形成机理及古气候重建进行了研究. 结果表明: 利用X射线图像明暗层、Rad峰值、Zr和Fe元素峰值标记法获得的年代序列基本一致, 并且与独立的放射性测年(²¹⁰Pb/¹³⁷Cs)结果吻合, 证实了上述各种纹层计年方法的可行性和可靠性. 新路海年纹层层偶是由粗颗粒碎屑层和细颗粒碎屑层交互组成的, 较厚且Zr和Si元素高的粗颗粒层形成于春、夏季, 而较薄且Fe元素含量高的细颗粒层形成于秋、冬季. 纹层的厚度能够指示西南季风降水量的大小, 近100年以来新路海纹层厚度反映的西南季风演化, 与利用昆明地区历史文献重建的湿度记录(干旱/洪水指数)、树轮δ¹⁸O重建的尼泊尔喜马拉雅地区的季风降水基本一致. 近100年来新路海的纹层厚度具有7~8、4~5和2年的周期, 表明新路海纹层厚度记录的近100年的西南季风演化可能与厄尔尼诺—南方涛动、太平洋年代际振荡、印度洋偶极子和准两年周期震荡有关.     

内陆干旱区柴达木盆地苏干湖年纹层的发现及其意义

柴达木盆地北缘苏干湖若干钻孔岩芯发现, 水深大于3.0 m的沉积物均具有裸眼可分辩的由深色层和浅色层组成的纹层层理. 以湖泊中心SG03I孔上部5.5 m具有纹层结构的沉积岩芯为研究对象. 基于沉积物收集装置的现代过程研究发现, 苏干湖夏秋季以浅色的单水方解石为主, 冬半年以深色有机质为主, 现代湖泊能够形成冬半年深色层和夏半年浅色层的纹层沉积. 岩芯中有四种类型的纹层沉积: 单水方解石-有机质纹层、白云石-有机质纹层、碎屑-硅藻(碎屑)纹层与文石-有机质纹层, 均具有季节特征, 属可靠的年纹层, 且顶部纹层计年与210Pb测年结果一致. 根据纹层计年, 年纹层沉积形成于距今2670 a以来. 苏干湖纹层沉积是中国西部干旱区发现的第一个能够确认为是年纹层的湖泊沉积, 4种不同类型的年纹层指示了不同气候类型及其季节差异, 具有重建高分辨率气候变化的重要意义.     

1990s长江下游干流径流量演变趋势

利用M-K相关分析方法和大通站1950-2000年逐月径流资料,研究了长江下游干流径流的趋势变化.研究结果表明:1950s以来长江下游径流量呈增加趋势,1990s平均径流量(30415.3 m³/s)比所有其他年代平均径流都大,为近50a以来的最大值;就季节和月份而言,秋季径流明显减少;夏、冬两季径流量,增加的趋势明显,尤以冬季枯水季节径流增加最为突出.洪水、枯水季节径流增加明显,但以枯水季节径流增加占优势.冬季枯水径流的增加,可能在一定程度上能够缓解长江口生态环境的巨大压力.1990s径流量的增加与全球变暖、水循环加快、长江流域降水量增加密切相关.     

全球变暖对长江洪水的可能影响及其前景预测

要长江流域近150a间发生的1870、1931、1935、1954与1998年特大洪水灾害损失严重;长江洪水是我国的心腹之患.1990年以来,长江大洪水高频发生,达6次.长江洪水的发生,除湖泊蓄洪功能减弱等因素外,与全球变暖有关.20世纪90年代为近千年中全球最暖的年代,水循环加快,长江中下游夏季降水量为近120a最多的十年,高出1961-1990平均值112mm;而降雨集中和大暴雨降水事件的增加是洪水增加的主要原因.区域气候模式模拟在CO₂倍增时,长江流域温度升高2.2℃,夏季降水增加10%-20%,气溶胶的增加可能使此值降低一些.考虑气候变暖可能促进潜在蒸发增加9%-15%的假定情景,计算在降水增加10%,蒸发增加9%条件下,最大洪峰流量在大通站将会达到8.4×10⁴ m³/s左右,己超过1998年洪峰流量;汉口站7.9×10⁴ m³/s,超过有记录以来所有的洪峰流量;而在宜昌站高达6.94×10⁴ m³/s,超过自有实测记录以来的除1896年和1981年以外所有的洪峰流量.假定情景的最高值出现在降水增加20%,蒸发增加15%时,大通站流量将达到9.45×10⁴ m³/s,超过该站近百年最大值,1954年的9.26×10⁴ m³/s;宜昌站将出现7.82×10⁴ m³/s流量,超过1882年以来所有实测记录值,但比1870年据洪痕推算的10.5×10⁴ m³/s仍有逊色.未来气候若继续变暖,降水量增加将给长江洪水防御带来巨大的压力.但上述估算是粗糙的,有一定的不确定性,需在以后的研究中进一步改进.     

粤东五华河流域的化学风化与CO2吸收

基于对粤东五华河干流和支流水体的物理、化学组成测试数据,应用质量平衡法和相关分析法探讨湿热山地丘陵地区岩石化学风化过程对大气CO₂的吸收.结果表明:五华河水体的总溶解性固体含量(77.11 mg/L)接近于世界河流的平均值(65 mg/L);离子组成以Ca²⁺、Na⁺和HCO₃^-为主,可溶性Si次之.五华河流域化学径流组成主要源自硅酸盐矿物化学风化过程的贡献,碳酸盐矿物的贡献较少;大气和土壤CO₂是流域内岩石化学风化的主要侵蚀介质.与同一气候带其他河流相比较,五华河流域岩石化学风化过程对大气CO₂的吸收通量(2.14×105mol/(km²·a))较低,这主要是由于流域内缺乏碳酸盐岩所导致.     

乌梁素海悬浮颗粒物和沉积物有机碳同位素特征及来源

悬浮颗粒物和沉积物是湖泊有机污染物的主要承载物质,其稳定同位素研究对有效识别有机质污染导致的湖泊富营养化具有重要意义.本研究选取乌梁素海为研究区,于2019年4月（融冰期）、7月（夏灌期）和10月（秋灌期）对湖区及入湖渠道的表层沉积物和悬浮颗粒物中有机碳的δ¹³C、C/N比及总有机碳（TOC、POC）和总氮（TON、PON）含量进行测定分析,联合采用δ¹³C、C/N及同位素多元混合模型研究湖泊有机碳来源及其贡献率.结果表明,乌梁素海悬浮颗粒物有机碳δ¹³C_POC的变化范围为-23.29‰~-29.75‰,呈现10月>4月>7月、入湖渠道>湖区的趋势,悬浮颗粒物POC/PON比变化范围为4.10~21.35,呈现出4月<7月<10月的时间变化,悬浮颗粒有机质主要来源于浮游植物（51.59%）、入湖渠道泥沙（34.60%）和大型水生植物（13.76%）.沉积物有机碳δ¹³C_TOC变化范围为-27.58‰~-22.68‰,呈现4月<10月<7月的变化,沉积物TOC/TON比变化范围为3.06~23.77,时空变化明显,沉积物有机质则主要源于入湖渠道挟带的泥沙,贡献达72.79%以上,而浮游植物与大型水生植物的贡献率相差较小,分别为11.85%和15.36%.本研究可以初步判定受入湖渠道影响的富营养化湖泊中悬浮颗粒物和沉积物有机碳来源,为改善湖泊有机污染和研究有机碳来源提供更多理解.     

贵阳市百花湖近10年(2009-2018年)的水质时空变化

百花湖是贵阳市重要的城市饮用水源地,并且近年来经常发生水质异常现象.本文利用2009-2018年百花湖长时间序列的监测数据,采用综合营养状态指数法和Pearson相关性分析,研究了百花湖10年间的水质变化特征和影响因素.结果表明：1）库区叶绿素a（Chl.a）、总磷（TP）、总氮（TN）、高锰酸盐指数（COD_Mn）和透明度（SD）的浓度范围分别是3.43~39.72 mg/m³、0.034~0.115 mg/L、1.200~2.759 mg/L、1.41~5.51 mg/L和0.75~2.07 m,且高氮磷比（12~63）表明百花湖是磷限制型.2）在空间上,TP、TN、氨氮、COD_Mn和Chl.a浓度沿水体流向逐渐降低,SD呈相反变化趋势.3）10年来,百花湖水质由Ⅳ类转变为Ⅲ类,综合营养状态由轻度富营养化状态转变为中营养状态,水质整体向好.4）入库支流是影响百花湖库区水质的主要因素,长期以来,东门桥河、南门河水质TP和TN等超标严重,给库区水质稳定达标带来威胁.5）百花湖Chl.a浓度与气温、水位、风速和TP等指标显著相关,是受水文、气象及营养盐因素的综合控制.未来在百花湖水环境保护治理过程中,应加大对东门桥河、南门河等重点支流的污染治理,加强对水动力学、气候变化等水文气象因素影响库区水质（藻类水华）的机制研究.     

巢湖形成演变与现代沉积作用

通过地质调查, 钻孔样品分析及历史资料对比, 得出:1.巢湖位于在中新生代形成的巢湖断陷盆地南部, 形成于更新世发育的河谷平原上, 由于全新世受气候及相应海平面变化和长江河道演变等三者共同影响而积水成湖。成湖历史大约2000年左右, 属河成型浅水湖。2.湖底沉积物平均中值粒径5-6ф, 并形成有三角洲沉积, 开阔湖沉积等五种沉积类型, 东、西、中三湖区的沉积物中分別为0.21, 0.37, 0.14cm/a, 全湖年淤积总量为93×l0⁴t/a。3.湖泊污染加重起始于70年代, 磷除来自外源外, 内负荷引起的释放量达220.56t/a, 这对巢湖富营养化亦有着重要的影响。     

崇明岛"闸控型"河网水体富营养化特征及其影响因素

为研究崇明岛"闸控型"河网水体富营养化特征及其与环境因子的相互作用,以2010年各季节崇明岛河网水质数据为基础,探讨了环境因子与藻类的变化规律及其相互作用机制.结果表明:崇明岛河网水环境中营养盐水平较高,氮污染尤为严重.长江引水进入岛内河网水环境后,营养盐(除SiO₃-Si)、Chl.a含量和营养状态都出现了明显的升高.与长江引水相比,河网内藻类群落Chl.a贡献比例的变化主要表现为硅藻比例的下降以及蓝藻和绿藻比例的上升.尽管水温、pH、浊度以及营养盐中的TN、TP、NO₃^--N、DOC的变化均与Chl.a含量显著相关,但藻类群落对环境因子的响应关系存在较大差异.蓝藻的增加主要与水温和TP含量的升高有关;绿藻与TN、NO₃^--N的关系最为密切;硅藻的变化只与浊度存在明显正相关,营养盐并不是硅藻生长的促进因子.     

柴达本盆地沙下盐湖的卤水化学及矿物沉积特征——以察尔汗盐湖区北部外围地带为例

对柴达木盆地察尔汗盐湖区外围沙下盐湖的卤水及沉积进行了综合研究。沙下盐湖卤水化学组成与地表径流和开放性盐湖卤水之间存在明显的差异性,具有高Na⁺+Cl^-、低Mg²⁺+Ca²⁺+SO₄^2-、贫K⁺+CO₃^2-+HCO₃^-等特征。沙下盐湖析盐层位含有新生矿物并夹带碎屑矿物,其盐类矿物组合为:石盐+羟氯镁铝石+光卤石。25℃等温蒸发相图表明,其卤水演化方向往光卤石析出区迁移,在穿越上覆盖层通道中卤水发生的物理化学反应与独特的沉积特征,可以作为继续寻找沙下盐湖的指导。     

洞庭湖冲淤变化分析(1956-1995年)

根据１９５６－１９９５年洞庭湖水文泥沙原型观测和地形测绘等翔实资料,运用输沙量法和地形法对洞庭湖冲瘀变化进行了认真的统计分析,分析结果表明,洞庭湖来水量以四水为主,占５７．８％,来沙量以四口为主,多年平均沉积率为７４．０％,出湖仅占２６．０％;淤积量及湖水沙量随着四分流分沙比的减少而减少。     

The last 40 ka tephrostratigraphic record of Lake Ohrid,Albania and Macedonia: a very distal archive for ash dispersal from Italian volcanoes

A 1075 cm long core (Lz1120) was recovered in the south-eastern part of the Lake Ohrid (Republics of Macedonia and Albania) and sampled for identification of tephra layers. Magnetic susceptibility investigations show rather high magnetic values throughout the core, with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment. Naked-eye inspection of the core allowed us to identify of two tephra layers, at 896–897 cm and 1070–1075 cm. Laboratory inspection of the grain-size fraction > 125 μm allowed for the identification of a third cryptotephra at 310–315 cm. Major element analyses on glass shards of the tephra layers at 896–897 cm and 1070–1075 cm show a trachytic composition, and indicate a correlation with the regionally dispersed Y-3 and Y-5 tephra layers, dated at ca 30 and 39 cal ka BP. The cryptotephra at 310–315 cm has a mugearitic–benmoreitic composition, and was correlated with the FL eruption of Mt. Etna, dated at 3370 ± 70 cal yr BP. These ages are in agreement with five ¹⁴C AMS measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core.     

Ultrahigh-pressure metamorphic records hidden in zircons from amphibolites in Sulu Terrane, eastern China

Abstract The amphibolites occur sporadically as thin layers and blocks throughout the Sulu Terrane, eastern China. All analyzed amphibolite from outcrop and drill cores from prepilot drill hole CCSD‐PP1 and CCSD‐PP2, Chinese Continental Scientific Drilling Project in the Sulu Terrane, are retrograded eclogites overprinted by amphibolite‐facies retrograde metamorphism, with characteristic mineral assemblages of amphibole + plagioclase + epidote ± quartz ± biotite ± ilmenite ± titanite. However, coesite and coesite‐bearing ultrahigh‐pressure (UHP) mineral assemblages are identified by Raman spectroscopy and electron microprobe analysis as inclusions in zircons separated from these amphibolites. In general, coesite and other UHP mineral inclusions are preserved in the cores and mantles of zircons, whereas quartz inclusions occur in the rims of the same zircons. The UHP mineral assemblages consist mainly of coesite + garnet + omphacite + rutile, coesite + garnet + omphacite, coesite + garnet + omphacite + phengite + rutile + apatite, coesite + omphacite + rutile and coesite + magnesite. Compositions of analyzed mineral inclusions are very similar to those of matrix minerals from Sulu eclogites. These UHP mineral inclusion assemblages yield temperatures of 631–780°C and pressures of ≥2.8 × 10³ MPa, representing the P–T conditions of peak metamorphism of these rocks, which are consistent with those (T = 642–726°C; P ≥ 2.8 × 10³ MPa) deduced from adjacent eclogites. These data indicate that the amphibolites are the retrogressive products of UHP eclogites.     

近百年鄱阳湖湿地格局演变研究

鄱阳湖是我国最大淡水湖和长江中游仅存的两个通江湖泊之一,重建其近百年自然通江的湖泊湿地演变过程,对于鄱阳湖湿地生态修复与保护具有重要意义.本研究基于两期历史时期地形图和遥感产品,构建了 1930s、1970s、1990s、2000s和2010s鄱阳湖湿地格局变化数据集,探究了土地利用方式改变和水文连通变化对鄱阳湖湿地变...     

Kyanite-anthophyllite schist and southwest extension of the Dabie Mountains ultrahigh- to high-pressure belt

Abstract Kyanite-anthophyllite schist preserves the first record of high pressure in the amphibolite-facies unit of the SW Dabie Mountains, whereas ultrahigh- and high-pressure (UHP and HP) metamorphism has been well documented by the occurrence of coesite, diamond and mafic eclogite in the SE Dabie Mountains. Textural evidence indicates that minerals of the kyanite-anthophyllite schist formed mainly in two stages: (i) garnet + kyanite + antho-phyllite + rutile formed at pressure in excess of 1.2 GPa at T < 650°C; (ii) cordierite±staurolite formed by reaction of anthophyllite + kyanite at P < 0.5 GPa, T∼530°C. Plagioclase and ilmenite replaced garnet and rutile respectively during decompression. In a still later stage, secondary biotite recrystallized, accompanied by sillimanite replacing kyanite, and spinel replacing staurolite. The P-T information suggests that the amphibolite unit in the SW Dabie Mountains is part of the Triassic collision belt between the Sino-Korean and Yangtze cratons. The P-T paths of the UHP eclogite in the eastern Dabie Mountains and the HP kyanite-anthophyllite schist in the SW Dabie Mountains show similar decompression and equivalent late stage Barrovian-style metamorphism. Emplacement of voluminous granitoid at middle crustal levels between 134–118 Ma contributed to the development of the Barrovian-type metamorphism in the Dabie Mountains.     

古生态记录揭示的长江中下游太白湖生态系统稳态转换过程

长江中下游浅水湖泊在过去百年内受到强烈的人类活动影响,生态系统状态发生显著的变化,服务功能逐渐丧失.为了更科学有效地管理浅水湖泊,当前迫切需要了解湖泊的生态系统转变过程.以长江中下游典型富营养化浅水湖泊太白湖为例,结合历史资料和监测数据,基于铅铯同位素重建年代序列,利用粒度、地化指标和沉积物中硅藻群落的时间序列数据,对太白湖过去百年间生态系统转变进行分析.基于T检验的STARS法检测硅藻群落的结果显示,有2个稳态转换分别发生在1950s末和1990s末.1950s末太白湖硅藻群落代表的生态系统状态发生了显著突变,这主要归因于由于建闸筑坝造成的水文条件和营养条件的改变;1990s期间的湖泊生态系统整体转变则是由长期营养输入和渔业活动加强导致的生态系统弹性损失引起的.讨论了不同阶段太白湖生态系统主要要素间反馈机制在水文条件改变和营养富集影响下的变化,加深了对人类活动干扰下太白湖生态系统结构变化过程的理解,为建立浅水湖泊系统动力学模型提供基础.     

Effect of mining and related activities on the sediment trace element geochemistry of Lake Coeur D'Alene,Idaho, USA part II: Subsurface sediments

During the summer of 1990, 12 gravity cores were collected in Lake Coeur d'Alene, Idaho at various depths and in a variety of depositional environments. All core subsamples were analysed to determine the bulk sediment chemistry; selected subsamples were analysed for trace element partitioning and ¹³⁷Cs activity. The purpose of these analyses was to determine the trace element concentrations and distributions in the sediment column and to try to establish a trace element geochemical history of the lake in relation to mining and mining-related discharge operations in the area. Substantial portions of the near-surface sediments in Lake Coeur d'Alene are markedly enriched in Ag, As, Cd, Hg, Pb, Sb and Zn, and slightly enriched in Cu, Fe and Mn. Variations in the thickness of the trace element-rich sediments, which range from more than 119 cm to as little as 17 cm, indicate that the source of much of this material is the Coeur d'Alene River. An estimated 75 million tonnes of trace element-rich sediments have been deposited on or in the lake bed. Estimated trace element masses in excess of those considered representative of background conditions range from a high of 468 000 tonnes of Pb to a low of 260 tonnes of Hg. The similarity between the trace element-rich surface and subsurface sediments with respect to their location, their bulk chemistry, their interelement relations and their trace element partitioning indicate that the sources and/or concentrating mechanisms causing the trace element enrichment in the lake sediments have probably been the same through-out their depositional history. Based on a Mt St Helens'ash layer from the 1980 eruption, ages estimated from ¹³⁷Cs activity and the presence of 80 discernible and presumably annual layers in a core collected near the Coeur d'Alene River delta indicate that deposition rates for the trace element-rich sediments have ranges from 2.1 to 1.3 cm/year. These data also indicate that the deposition of trace element-rich sediments began, at least in the Coeur d'Alene River delta, some time between 1895 and 1910, dates consistent with the onset of mining and ore processing activities that began in the area in the 1880s.     

“引江济太”水系有色溶解有机质的特征与来源

在"引江济太"水系的调查基础上,分析了有色溶解有机质(CDOM)的吸收光谱、荧光特性及其主要来源,探讨了CDOM与pH、DO、叶绿素a等水质指标的关系。结果表明:水体吸收系数a(355)与CDOM浓度呈显著正相关,均具有明显的空间差异,它们在河道出入湖口及开阔湖区较低,而在望虞河和太浦河中游较高,这显然与中游河道受纳了两岸污水有关,S值也表明望虞河受外源输入影响最大。通过三维荧光激发-发射矩阵(EEM)分析,发现了5种荧光团,包括2种类蛋白荧光团和3种类腐殖质荧光团,其中类蛋白荧光(特别是T峰)明显强于类腐殖质荧光。研究发现,水体DO浓度、pH值均随CDOM浓度呈指数函数递减。荧光指数(FI)明显偏向生物来源(约1.9),因此,"引江济太"水系CDOM以生物的本地生产为主,河道局部污染水体中的类腐殖质荧光可能来源于污水微生物对藻类产生的溶解有机质的转化,在局部河道中也有一定的外源输入。     

洞庭湖近几十年来湖盆变化及冲淤特征

洞庭湖是我国著名的五大淡水湖泊之一,位于长江中游荆江段南岸,湖南省境内.历史时期,曾经是我国第一大淡水湖,直至新中国成立初期,湖泊面积仍然有4350km2,居我国淡水湖泊之首位.但由于洞庭湖承纳“四水”,吞吐长江,长江大量水沙涌入洞庭湖,造成了湖盆迅速淤高,加之由此诱发的人类大规模地湖泊垦殖活动,湖泊急剧萎缩.目前,洞庭湖已退居鄱阳湖之后,为我国第二大淡水湖泊.湖泊的严重泥沙淤积,已经造成了湖泊调蓄长江中游洪水功能的严重衰退,不但危及湖南省的防洪的安全,而且危及长江中下游地区的防洪安全,研究洞庭湖的湖盆冲淤演变具有重要意义.本文根据1974、1988和1998年洞庭湖125000水下地形资料,并针对洞庭湖具有显著上下游水位落差的实际,分不同高程和不同水位情况下,分析洞庭湖湖泊面积和容积演变特征,探讨洞庭湖近几十年来的湖盆变化及冲淤规律,试图揭示洞庭湖湖泊调蓄能力的变化过程.     

Chemical composition of short sediment cores from Thermaikos Gulf (Eastern Mediterranean): Sediment accumulation rates, trawling and winnowing effects

Four cores recovered within the framework of the INTERPOL Project have been analysed for their grain size and geochemistry; sediment accumulation rates (SARs) were also determined from ²¹⁰Pb and ¹³⁷Cs profiles. Two cores are representative of the Axios and Aliakmon Rivers depositional environment, whilst the third core represents the Pinios River province; the fourth core represents an environment of outer shelf relict sands. Apparent SARs ranged between 0.667 g cm⁻² yr⁻¹ (Axios and Aliakmon Rivers) and 0.414 g cm⁻² yr⁻¹ (Pinios River). Trawling activities and biomixing are critical processes that may be responsible for the mixing of the surface sediments, as observed from the excess ²¹⁰Pb profiles. The thickness of the surface mixed layer was 4.5 cm in the vicinity of Axios and Aliakmon Rivers and in the area of Pinios River, 3.75 cm on the outer shelf and 1 cm in the area where no trawling was observed. Sediment accumulation appeared to be regulated by variations in the riverine discharge, shelf transport pathways and winnowing processes. Major element variations, such as Si, Al, Ti, V and Ni, were dominated by terrigenous supply as aluminosilicate minerals and quartz, whereas most Ca and Sr were biogenic. Si/Al and Ca/Al ratios have been used to express changes in sediment accumulation and winnowing. Redox processes were depicted by Mn, which showed an increase in the depth of its redoxcline, from 1 cm in inshore stations to 2 cm on the outer shelf. Si/Al ratios follow the Ca/Al ratios and can be used to assess percentage winnowing in the sediment. Increases in these ratios indicate a decrease in sediment input rates and are seen in the upper parts of most of the cores. Anthropogenic or ‘excess’ metal contents have been calculated from Zn/V and Pb/V ratios. Their distributions in the cores showed that by far the highest contamination is associated with the Axios River output, whilst sediments influenced by the Pinios River were relatively uncontaminated.