基于近红外光谱快速分析东南极湖泊沉积物化学元素含量

以东南极罗斯岛地区的3个湖泊沉积剖面为研究对象,利用紫外-可见-近红外反射光谱仪获得了沉积物样品的光谱曲线,讨论了东南极罗斯岛湖泊沉积物的光谱特征。在沉积物化学元素分析的基础上将样品分成建模集和验证集,采用偏最小二乘法建立光谱与化学元素指标的对应关系矩阵,通过验证集预测值和测定值之间的误差参数比较,发现研究的20种元素含量均能和光谱曲线建立有效的计算关系,其中,N、C、H、Mn、Ba、P、Al、Fe、K、Se、As和Hg等元素能够达到相当精确的预测水平(预测值与测量值之间的相关系数r20.90)。本研究结果表明,利用近红外反射光谱快速分析东南极湖泊沉积物中元素含量是一种潜在有效的方法。     

北极新奥尔松地区湖泊沉积物色素含量变化及环境意义

大量的古气候资料和现代器测数据表明,最近100年来北极气候经历了明显的变暖过程,这必然会对脆弱的极地湖泊生态系统产生影响。以北极新奥尔松地区的湖泊沉积柱样为研究对象,对其中4种色素(叶绿素及其衍生物CD、总胡萝卜素TC、蓝藻叶黄素Myx和颤藻黄素Osc)进行了分析,结合其他物化指标如碳酸钙含量、TOC等,从历史演化的角度重点探讨了新奥尔松地区最近100年以来湖泊初级生产力演化过程。结果表明,在相对寒冷的小冰期,气候对湖泊中藻类的生长不利,湖泊生产力下降,沉积物中色素含量出现低值,生物硅含量降低;表层5cm(对应约1890AD)沉积物中有机质含量显著升高,各色素含量均明显增加,表明小冰期后气温上升,导致湖泊藻类生长迅速,湖泊生产力大大提高,但此时生物硅仍保持在相对较低的水平,这可能与其他藻类的竞争生长有关。最近100年,沉积物中Osc/Myx比值不断降低,表明该湖泊中蓝藻含量不断上升,暗示北极地区人类活动的增强可能导致湖泊营养水平增加。     

东南极拉斯曼丘陵中晚全新世湖泊生物量的变化记录

对东南极拉斯曼丘陵莫愁湖ZH沉积柱进行了生态地质学的研究,通过AMS-14C定年构建年龄框架,采用550℃烧失量、粒度和元素地球化学指标等,恢复了中晚全新世该地区较高分辨率的湖泊生物量记录。结果显示,距今6600-6100年、5400-4800年、4650-3750年和3500年-2850年为莫愁湖生物量高值期,气候相对温暖适宜,湖泊生产力旺盛;距今6100-5400年、4800-4650年和3750-3500年为湖泊生物量低值期,气候相对寒冷,湖泊生产力相对较弱。而且在整体较暖的气候环境下,出现了其它无冰区沉积物中鲜有记录的距今4800-4650年、4400年前后和3750-3500年的气候快速变冷事件。根据莫愁湖湖泊生物量恢复的东南极拉斯曼地区高分辨的气候变化特征,与太阳活动强度和东南极大陆冰芯记录相吻合,为东南极中晚全新世多样的气候格局研究提供了新的依据。     

海鸟活动在东南极中山站区莫愁湖沉积物中的记录

本文对采自东南极拉斯曼丘陵中山站区的莫愁湖沉积物的元素、氨基酸和Sr同位素组成进行了详细的地球化学分析。结果表明莫愁湖沉积物中Zn、Cu、F、S、P、Se等六种元素具有共同的物质来源,其标型组合特征很可能揭示了莫愁湖沉积物在历史时期曾受到过企鹅等海鸟粪的影响,沉积物中酸溶相Sr同位素组成则确认了海洋源Sr的生物地球化学转移过程。酸溶相87Sr/86Sr值和研究区的新鲜海鸟粪酸溶相Sr同位素组成基本一致,都非常接近于海洋来源锶同位素组成(87Sr/86Sr=0.7092),并且沉积物中的生物元素Zn、Cu、F、S、P、Se含量和酸溶相Sr浓度具有非常高的统计相关性。酸溶相的87Sr/86Sr比值和反映湖泊中藻类等生物自然生成量的氨基酸含量表现出明显的负相关关系,进一步揭示了莫愁湖沉积物在历史时期曾受到企鹅等海鸟活动的影响。上述研究结果为更深入地研究该地区的生态、气候和环境的演变历史及其相互作用提供了有价值的参考资料。     

西南极湖泊沉积类脂记录的有机质来源及生态环境变化

对西南极乔治王岛西湖沉积物XH1柱样进行了210Pb测年,建立起百余年(1885—2006年)沉积地层序列。定量分析了该柱样中的正构烷烃、脂肪酸和甾醇等类脂生物标志物,综合研究了其分子组合特征和大尺度气候事件[厄尔尼诺-南方涛动(ENSO)和南半球环状模(SAM)]指标,探讨了湖泊沉积有机质来源、沉积环境和早期成岩作用及其与生态环境变化的关系。结果表明,正构烷烃的主峰碳(n C_(23))、脂肪酸的后主峰碳(C_(24:0))、较高的C_(29)甾醇含量和较低的(50)C_(21)~–/(50)C_(22)~+比值均显示,苔藓、地衣等低等陆生植物是西湖沉积物中有机质的主要来源,而水生动植物及微生物的贡献相对较少。脂肪酸C_(18:2)/C_(18:0(比值表明,在年代际时间尺度上,与ENSO相比,SAM对南极半岛生态系统可能更具影响力,且对湖泊水生动植物的影响比陆生植物更为明显。内源输入的甾醇指标ACI显示,西风变弱、南极半岛变暖时,沉积物中水生生物贡献的有机质减少。整体而言,过去的100多年中,西湖呈弱氧化的沉积环境,早期成岩作用较弱,且气候事件对湖泊沉积环境影响不大。     

南大洋普里兹湾沉积物中生物硅的溶解度研究

本文利用中国南极科学考察航次获得的沉积物样品,采用分批（batch）实验方法,获取实验室生物硅溶解度,并结合间隙水中可溶性硅剖面,对普里兹湾沉积物中生物硅的溶出过程进行了初步研究。研究结果如下：在25℃,pH 8条件下,普里兹湾IV-10、 IS-4站表层沉积物中生物硅的实验室溶解度分别为1936、1539μmol/dm3,不同层次沉积物溶出结果显示随深度增加溶解度值降低。根据实验室溶解度数据与间隙水硅酸盐Cd的分析比较,表明研究站位沉积物生物硅的早期成岩过程中生物硅的溶出还伴随有其他化学过程。     

全新世湖泊沉积物TOC、C/N和δ^13Corg对千年尺度气候变化的响应

湖泊沉积物有机地化指标在古气候解释中具有复杂性和多解性。TOC、C/N和δ^13Corg作为3种常用的有机地化指标,现已广泛运用于东、中亚全新世气候变化研究中。以这3种指标为例综述了东、中亚全新世湖泊沉积有机地化指标的变化机制及影响因素。根据数据的综合分析与对比,大部分湖泊全新世沉积物TOC百分含量较高时,C／N比值也较高。这与沉积物有机质的来源有关,因两者TOC和C／N作用机制不同,也存在少数湖泊,其两者对应关系不明显;同一湖泊δ^13Corg与TOC及δ^13Corg与C／N对应关系相似;由于不同区域影响有机地化指标的因素不同,TOC、C／N和δ1^3Corg间的关系存在区域差异,据此可将研究区分为中纬度地区、青藏高原区和低纬度季风区。上述区域规律存在于研究中所选的大部分湖泊,由于有机地化指标作用机理的复杂性,也存在不符合这种规律的湖泊,因而上述结论有待于进一步讨论。     

南极普里兹湾沉积物中生物硅对粒度测量结果的影响

为了探讨生物硅对沉积物粒度测量结果的影响, 本文采用两种不同前处理方法对普里兹湾重力柱状样品进行了粒度测试。结果表明, 生物硅对沉积物的平均粒径以及黏土、粉砂、砂组分的影响较小, 而对沉积物的分选、偏态、峰态以及粒度频率分布的影响较显著。结合两组粒度组分相关性分析以及各粒级含量累积减小值, 认为生物硅对沉积物中砂、粉砂、黏土级组分含量的影响逐渐减小, 这也造成未去除生物硅的沉积物粒度测量结果偏粗。另外, 通过对比发现普里兹湾沉积物中生物硅粒径主要分布在<3Φ、5.25Φ—7.25Φ、8.75Φ—9.75Φ的粒径范围。极地研究中, 沉积物粒度结果为重建古环境变化提供重要参考, 本文研究认为在普里兹湾海域沉积物粒度研究中去除生物硅对研究结果有积极作用。     

九寨沟箭竹海沉积物中BSi含量及其环境指示意义

通过对九寨沟箭竹海沉积物样品中生物硅( BSi)含量的分析,讨论箭竹海沉积物中BSi含量与总有机碳(TOC)及粒度的关系,进而探讨BSi含量反映自然和人类因素对湖泊水体和沉积物的影响.箭竹海沉积物中BSi含量介于5.5～ 15.8 mg/g之间,BSi含量与TOC呈显著正相关关系.BSi含量还较显著地受到粒度影响,较细颗粒沉积物对BSi有较强的吸附作用.箭竹海沉积物中BSi含量变化与气温波动关系不密切,主要反映了森林砍伐和旅游开发等人类活动对湖泊水体和沉积物的影响.     

南极普里兹湾沉积物中生物硅对粒度测量结果的影响

为了探讨生物硅对沉积物粒度测量结果的影响,本文采用两种不同前处理方法对普里兹湾重力柱状样品进行了粒度测试。结果表明,生物硅对沉积物的平均粒径以及黏土、粉砂、砂组分的影响较小,而对沉积物的分选、偏态、峰态以及粒度频率分布的影响较显著。结合两组粒度组分相关性分析以及各粒级含量累积减小值,认为生物硅对沉积物中砂、粉砂、黏土级组分含量的影响逐渐减小,这也造成未去除生物硅的沉积物粒度测量结果偏粗。另外,通过对比发现普里兹湾沉积物中生物硅粒径主要分布在3Φ、5.25Φ—7.25Φ、8.75Φ—9.75Φ的粒径范围。极地研究中,沉积物粒度结果为重建古环境变化提供重要参考,本文研究认为在普里兹湾海域沉积物粒度研究中去除生物硅对研究结果有积极作用。     

Late holocene paleoclimatic and paleobiologic records from sediments of Devils Lake,North Dakota

An 84 cm sediment core collected from the center of Devils Lake, North Dakota, was analyzed at 1-cm intervals for,²¹⁰Pb,¹³⁷Cs, sediment conductivity, the concentrations of, biogenic silica, total organic carbon, carbon to nitrogen ratio, and the carbon and nitrogen isotopic composition of the organic fraction. Variations in²¹⁰Pb activities in the upper 20 centimeters indicate that sediment accumulations rates in Devils Lake are not constant, and that accumulation rates were highest during periods of high lake level. The mean sedimentation accumulation rate was calculated as 0.24 cm^–1 yr. The¹³⁷Cs profile is characterized by near-surface maximum concentrations, possibly the result of redistribution of¹³⁷Cs during salinity excursions.Biogenic silica is strongly correlated to lake level in Devils Lake. Periods of low lake level (characterized by high sediment conductivity) correspond to low biogenic silica concentrations. The trends in biogenic silica are attributed to variations in diatom productivity in the lake and to variations in sediment accumulation rates. Based on biogenic silica content and the composition of organic matter in the sediment (total organic carbon, carbon:nitrogen ratio and the ¹³C and ¹⁵N composition of total organic matter), paleobiologic conditions of Devils Lake during low lake stands were characterized by, (1) decreased primary productivity, (2) decreased input of detrital organic matter, and (3) increased nitrogen availability.During the 350 years of sediment accumulation represented by the 84-cm sediment core Devils Lake has experienced two periods of sustained high lake level; one between about 130 and 170 years ago (1820 to 1860 A.D.) and the second between 270 and 310 years ago (1680 to 1720 A.D.). Devils Lake experienced a period of intense drying about 260 years ago (1720 A.D.).     

新仙女木事件在热带湖光岩玛珥湖的记录

湖光岩玛珥湖沉积物总有机碳，总氮，总氢，生物硅等有机地球化学指标以及AMS^14C年代明确地指示了新仙女木事件在中国南方地区的存在，它不仅表现为降水的显著减少，而且表现为气温的降低，显示了凉干的气候环境，反映了季风系统在很短的时间内进行了大规模重组，夏季风强度显著减弱的事实，这为西北太平洋低续度区存在YD事件提供了新的来自于陆地的证据。     

Organic geochemical record of environmental changes in Lake Dianchi,China

In order to investigate the natural ecosystem of Lake Dianchi and to assess its anthropogenic impacts, a stratigraphic study of bulk and molecular compositions of organic matter was conducted using a 63-cm long sediment core. The results show that two apparent environmental changes occurred during the evolution of Lake Dianchi: (1) the first change occurred in the 43–63 cm sediment depth, and was revealed by the amount and the composition of organic matter in the stage. Natural changes were possibly major factors responsible for triggering the environmental change, but the influence of human activities could not be excluded. Subsequently, the lake entered into a relatively stable and oligotrophic stage, which maintained until 20-cm sediment depth. (2) Eutrophication started in the upper 20 cm depth. Human activities became a major factor influencing environmental changes in this stage. Vertical profiles of various organic geochemical variables in the upper 20-cm sediments show evidence that primary productivity of the lake increased progressively and that the lake started eutrophic. Especially in the uppermost 10 cm, notable excursions to less negative δ¹³C_org and δ¹⁵N_total and high TOC concentrations have recorded an abrupt change in the lacustrine environment, suggesting that the lake entered a hypereutrophic stage. In addition, enhancement of αβ-hopanes reflects the contribution of fossil fuels to the lake sediments.     

Response of a Lake Michigan coastal lake to anthropogenic catchment disturbance

A paleolimnological investigation of post-European sediments in a Lake Michigan coastal lake was used to examine the response of Lower Herring Lake to anthropogenic impacts and its role as a processor of watershed inputs. We also compare the timing of this response with that of Lake Michigan to examine the role of marginal lakes as early warning indicators of potential changes in the larger connected system and their role in buffering Lake Michigan against anthropogenic changes through biotic interactions and material trapping. Sediment geochemistry, siliceous microfossils and nutrient-related morphological changes in diatoms, identified three major trophic periods in the recent history of the lake. During deforestation and early settlement (pre-1845–1920), lake response to catchment disturbances results in localized increases in diatom abundances with minor changes in existing communities. In this early phase of disturbance, Lower Herring Lake acts as a sediment sink and a biological processor of nutrient inputs. During low-lake levels of the 1930s, the lake goes through a transitional period characterized by increased primary productivity and a major shift in diatom communities. Post-World War II (late 1940s–1989) anthropogenic disturbances push Lower Herring Lake to a new state and a permanent change in diatom community structure dominated by Cyclotella comensis. The dominance of planktonic summer diatom species associated with the deep chlorophyll maximum (DCM) is attributed to epilimnetic nutrient depletion. Declining Si:P ratios are inferred from increased sediment storage of biogenic silica and morphological changes in the silica content of Aulacoseira ambigua and Stephanodiscus niagarae. Beginning in the late 1940s, Lower Herring Lake functions as a biogeochemical processor of catchment inputs and a carbon, nutrient and silica sink. Microfossil response to increased nutrients and increased storage of biogenic silica in Lower Herring Lake and other regional embayments occur approximately 20–25 years earlier than in a nearby Lake Michigan site. Results from this study provide evidence for the role of marginal lakes and bays as nutrient buffering systems, delaying the impact of anthropogenic activities on the larger Lake Michigan system.     

Late Pleistocene and early Holocene ecological response of Lake El Trébol (Patagonia, Argentina) to environmental changes

Stratigraphy of Lake El Trébol (41°S 71°W, 758 m a.s.l.) described from an 11 m long sediment core provided a continuous record of patecenvironmental changes occurred during the last 14,000 years in southern South America east of the Andes. Located in an ecotonal area within a strong humidity gradient, this lake offers a unique opportunity to develop paleolimnological studies. Using a geochemical approach that includes elemental analysis, bulk organic matter, major nutrients and pigments combined with chironomids and pollen analysis, three zones were identified in the sedimentary record of this take. The oldest one (between 680 and 1,100 cm) corresponds to the late Glacial period. During that time, clayish laminated sediments were formed in a proglacial environment. Low organic matter, biogenic silica and nitrogen contents and the absence of pigments, pollen and chironomids characterise this period. At the end of this period, ca. 14,000 yr BP, a sharp increase in phosphorus concentrations predates major changes in limnological parameters. The transition zone (between 560 and 680 cm) is related to major changes in the drainage system that started soon after ca. 14,000 yr BP and continued to ca. 10,500 yr BP. The chemical composition of the sediments was affected by an increase in physical weathering mechanisms almost coincident with the increase in the regional volcanic activity that produced suspended volcanic detritus. The increase of mainly coarser detritical components may indicate a reorganisation of the fluvial system by that time. Simultaneously, an increase in the productivity of the lake accompanied by a gradual replacement of open vegetation with Nothofagus, Poaceae and Ericaceae, by Nothofagusforest, was observed. In the last zone (between 0 and 560 cm) the productivity of Lake El Trébol achieves maximum values. The trends in geochemical and biological indicators observed at Lake El Trébol can be up to some extent, correlated to those registered in Lake Mascardi. The results support earlier paleoctimatic scenarios from southern South America.     

抚仙湖有机碳的分布状况与动态变化

通过对位于中国西部的运动嵩原上的抚仙湖、星云湖及其上游的有机碳的分布状况和动态变化的调查，评估出这些湖泊的有机物对水质的影响。上游漂移来的有机碳对湖泊有机物动态变化的贡献比本湖泊生成的有机物的贡献小得多。抚仙湖主要有机物的增长是由于过去的20年间湖水水质退化、富营养化造成的。     

苦海沉积物有机质反映的过去840年来青藏高原东部环境变化

青藏高原对全球气候变暖响应敏感,研究青藏高原近千年来环境演化过程、规律与驱动机制对预测其未来气候可能发生的变化有重要参照意义.通过位于青藏高原东部的苦海沉积物总有机质相关指标[总有机碳(TOC)、总氮(TN)、总有机碳与总氮比值(TOC/TN)和总有机碳同位素(δ13Corg)]的研究重建了该区域过去840年来的环境演...     

Lacustrine Sedimentary Organic Matter Records of Late Quaternary Paleoclimates

Identification of the sources of organic matter in sedimentary records provides important paleolimnologic information. As the types and abundances of plant life in and around lakes change, the composition and amount of organic matter delivered to lake sediments changes. Despite the extensive early diagenetic losses of organic matter in general and of some of its important biomarker compounds in particular, bulk identifiers of organic matter sources appear to undergo minimal alteration after sedimentation. Age-related changes in the elemental, isotopic, and petrographic compositions of bulk sedimentary organic matter therefore preserve evidence of past environmental changes.We review different bulk organic matter proxies of climate change in tropical and temperate sedimentary records ranging in age from 10-500 ka. Times of wetter climate result in enhanced algal productivity in lakes as a consequence of greater wash-in of soil nutrients, and these periods are recorded as elevated Rock-Eval hydrogen indices, lowered organic C/N ratios, less negative organic 13C values, and increased organic carbon mass accumulation rates. Lowering of lake water levels, which typically depresses algal productivity, can also cause an apparent increase in organic carbon mass accumulation rates through suspension of sediments from lake margins and redeposition in deeper basins. Alternations between C3 and C4 watershed plants accompany climate changes such as glacial/interglacial transitions and wet/dry cycles, and these changes in land-plant types are evident in 13C values of organic matter in lake sediments. Changes in climate-driven hydrologic balances of lakes are recorded in D values of sedimentary organic matter. Visual microscopic examination of organic matter detritus is particularly useful in identifying changes in bulk organic matter delivery to lake sediments and therefore is important as an indicator of climate changes.