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变化有重要意义。本文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年来环境演化过程。结果表明,苦海沉积物中的有机质主要来自于内源水生植物。由于暖期(冷期)时黄河上游径流量较高(低),苦海水位随之升高(降低),湖泊水动力增强(减弱),浅水区沉水植物对研究岩芯中的有机质贡献率提高(降低),导致沉积物TOC、TN、TOC/TN升高,δ¹³Corg值正(负)偏。人类活动导致的青藏高原近50年气候异常变暖可能是~1950 AD之后δ¹³Corg反映的黄河上游径流量变化与重建的中国温度记录之间的关系发生转变的原因。苦海沉积物δ¹³Corg记录与万象洞石笋δ¹⁸O记录和太阳总辐射强度记录变化特征的相似性说明青藏高原东部地区气候变化的控制因素为太阳辐射驱动下的季风降雨量变化。     

猪野泽沉积物有机地球化学指标与花粉组合的关系及其对环境变化的响应

探讨晚冰期以来猪野泽沉积物中的总有机碳（TOC）、碳氮比（C/N）、有机碳同位素（δ13C）3种有机地球化学指标与花粉组合之间的相互关系。结果表明,猪野泽沉积物中有机地球化学指标和孢粉组合对环境变化的响应程度不同,3种有机地球化学指标对环境变化的整体趋势反应敏感,孢粉组合适于对细节变化的分析。猪野泽沉积物整个剖面中（除~13.0 cal ka BP之前的底部砂层沉积段外）TOC和C/N较低值,δ13C较高值,对应总花粉浓度较低时期;TOC和C/N较高值,δ13C较低值,对应总花粉浓度较高时期。     

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...     

滇池流域宝象河水库沉积物中有机碳的来源

通过对滇池流域宝象河水库沉积物TOC、TN、C/N、δ13C及粒度等指标的测定,分析了沉积物中有机碳的主要来源及其变化趋势。结果表明:水体中不同位置沉积物有机碳来源并不相同,距三岔河入库河口相对较近的沉积柱芯A中C/N比值介于2.93~11.73,δ13C值介于-23.66‰~-21.78‰,有机碳主要来源于水生生物,陆源输入贡献较小,有机碳含量受粒径大小影响显著;距三岔河入库河口相对较远的沉积柱芯B中,其TOC和TN含量较高,分别介于14.62~24.93 g?kg-1和2.11~3.3 g?kg-1,δ13C值变化范围为-28.36‰~-26.36‰,粒度以黏土和细粉砂为主,有机碳主要来源于水库周边陆源输入,受人类活动影响强烈。     

气候成因、要素与气候变化

P4672006010009兰州与江汉平原有机碳同位素的古气候指示意义对比研究=Paleocli matic i mplication of Lanzhou and Jianghan plain:acli mate proxy study of organic carbonisotope/杨桂芳,彭红霞…∥长江流域资源与环境.—2005,14(4).—486~490研究结果表明:在兰州地区,δ13Corg值波动反映C3/C4植物比例的改变,指标温度变化.δ13Corg值偏正时,表明C4植物含量较大,反映温度较高.而δ13Corg值偏负时,表明气候较冷;汉江平原δ13Corg值主要反映降水信息,δ13Corg值偏负时指示相对暖湿气候,δ13Corg值偏正反映气候偏干.δ13Corg等指标…     

江陵地区全新世早期人类活动的孢粉记录

江陵剖面沉积物孢粉提供全新世早期人类活动的证据。早期人类活动始于6 200 a B.P.,人类大规模活动始于3 400 a B.P.。随着定居点扩大和人类活动加强,地表土壤侵蚀严重,入湖的陆源粗颗粒物质和营养物质增多。湖泊沉积物表现为粗颗粒含量迅速增加,各粒径波动频繁,TOC、TN和C/N的高值以及有机质δ¹³C的低值。2 500 a B.P.以后,沉积环境发生了显著变化,由湖泊及湖沼堆积转化为洪水漫滩堆积,气候变干,人类逐渐撤离该地区。     

广西北部山地沼泽20 ka以来的 碳同位素组成与气候变化

根据广西北部山地泥炭沼泽沉积的有机碳同位素组成、TOC和C/N等古气候指标对末次盛冰期以来该区植被与气候演变过程进行研究,结果发现：末次盛冰期（21―14 cal. ka B.P.）偏正的δ13Corg数据反映了山地植被面貌曾发生显著变化,指示冰期气候的冷干变化,但并未导致山地森林向地带性草地退化,C3植物仍占优势。沉积物岩性和TOC等数据表明：在14―10 cal. ka B.P.期间沼泽湿地逐渐形成,指示了东亚夏季风降雨的增强,与石笋指示的季风增强起始年代基本一致。冰消期碳同位素曲线负偏的变化要早于TOC指示的泥炭沼泽堆积,即10―9 cal. ka B.P.前后富有机质的泥炭堆积进入旺盛期。碳同位素组成在9―8 cal. ka B.P.存在一个正偏的变化波动,可能与8.2 ka降温事件或局地物源输入变化有关。7.0―2.8 cal. ka B.P.期间古田湿地的有机质输入较高,碳同位素偏负,指示气候暖湿。从1.7 cal. ka B.P.至今,δ13Corg值的再次正偏可能指示夏季风强度减弱,但考虑到该阶段为人类农业活动快速发展期,因此不排除人为因素的影响。此外,末次盛冰期广西山地与雷州半岛沿海低地的碳同位素值对比发现：沿海平原区与华南山地的沉积记录存在明显差别,其主要原因是山区因山地降雨效应使山区的湿度即便在盛冰期也能保持较高水平;而低地平原冰期阶段的降雨则显著减少,加上平原区较高的蒸发量使干旱程度增加,C4草本也相应增多。实际上,影响亚热带山地沼泽δ13Corg值变化的原因比较复杂,在利用δ13Corg值推论古气候时需要同时考虑气候因素和湿地沉积体的物源及其地貌环境等背景。     

亚热带季风区湖沼流域表生地球化学元素研究——以江西定南大湖为例

湖沼沉积物地球化学元素对地球气候环境变化敏感性强。本文以江西定南大湖湖沼沉积物地球化学元素为研究对象,使用主成分分析法,并结合总有机碳(TOC)、有机碳同位素(δ13Corg)、中值粒径(Md)、化学蚀变指数(CIA)等相关气候代用指标,以元素组对的形式阐释不同地化元素响应不同气候环境下的地球化学行为和迁移规律。研究结果显示:第一主成分(PC1)包括Al2O3、Ti O2、Si O2、Nb、Rb、Ga、Ba、S等元素,曲线变化与CIA相似,指示湖泊流域的化学风化强度,气候暧湿,PC1含量高;第二主成分(PC2)包括Co、Zr、Hf元素,曲线变化与中值粒径较为一致,指示湖泊流域的水动力条件,气候冷干,PC2含量高;第三主成分(PC3)包括Sc、Cu、U、V元素,曲线变化与TOC、δ13Corg含量变化一致。大湖沉积物的物质来源为:在气候暧湿、流域化学风化作用强的条件下,地表径流冲刷流域周边花岗岩风化壳物质并搬运至湖盆沉积,但不排除在冷干时期,风力携带粉尘物质堆积的影响,粉尘物质可能主要源于周边的风化碎屑物。     

河西走廊盐池晚冰期以来沉积地层变化综合分析——来自夏季风西北缘一个关键位置的古气候证据

盐池位于祁连山北麓的河西走廊中段,是研究长时间尺度亚洲夏季风影响区北部边界变化的关键区域。现代气候学证据显示,亚洲夏季风的水汽输送限于祁连山东部地区,但是在全新世长尺度气候变化的背景下,夏季风西北边界是否会南北向移动是一个关键的科学问题。本研究对盐池古湖泊沉积物进行了孢粉浓缩物AMS14C测年,并分析了岩性、粒度、矿物及地球化学等指标。年代结果显示剖面下部湖相沉积层主要形成于晚冰期和早全新世期间,配合指标研究,该时期盐池沉积物体现了湖泊扩张的特征;剖面中部湖相沉积层主要形成于早、中全新世过渡时期,该段年代序列混乱,且普遍偏老,与之对应的指标结果显示湖泊开始退缩。湖泊退缩过程中,湖泊边缘附近水动力作用较强,导致再搬运及再沉积作用明显,从而使得年代结果较老且混乱。中全新世以来盐池古湖泊退缩明显,沉积速率较低,以泥沼相沉积为主。盐池晚冰期以来湖泊演化过程与青藏高原区和典型季风区的古气候记录具有一致性,整体表现为晚冰期及早全新世湖泊扩张,中、晚全新世期间湖泊退缩明显,这种变化模式与西风区湖泊演化存在差异,显示了千年尺度亚洲夏季风对该区域的影响,证明了夏季风北部边界摆动的事实。     

全球变暖对青藏高原不同补给类型湖泊生产力的影响

研究以青藏高原阿翁错和托素湖湖泊沉积物为研究对象,通过多指标(总有机碳含量、有机碳同位素和有机碳埋藏速率等)综合分析,重建不同补给类型湖泊的生产力变化及碳循环过程。结果显示：全球变暖对不同类型湖泊的生产力的影响存在显著差异。在以降水和冰川融水为主要补给源的阿翁错,全球变暖造成冰川融水补给增加。当指示冰川融水补给量变化的δ¹⁸O_carb值逐渐偏负时,湖泊沉积物TOC含量逐渐升高;指示冰川融水输入造成湖泊面积持续扩张,营养物质增加,湖泊生产力提高;当湖泊面积扩张较快,即冰川融水在短时间内快速输入时,TOC含量下降,可能是由于当冰川融水输入过多,造成湖水温度下降过快时,底栖藻类生产力下降,进而湖泊固碳能力下降。对于受人类活动影响的托素湖,全球变暖对湖泊水文过程及生产力的影响较小,δ¹⁸O_carb值变化主要受控于农业灌溉活动引起的湖泊补给水量的变化。当δ¹⁸O_carb值升高时,TOC含量增加;推测是由于农业灌溉耗水量增加导致湖泊补给水量减少,湖泊水位下降,湖泊底部...     

A 15.4-ka paleoclimate record inferred from δ<Superscript>13</Superscript>C and δ<Superscript>15</Superscript>N of organic matter in sediments from the sub-alpine Daping Swamp,western Nanling Mountains,South China

We inferred past climate conditions from the δ¹³C and δ¹⁵N of organic matter (OM) in a sediment core (DP-2011-02) from the sub-alpine Daping Swamp, in the western Nanling Mountains, South China. In the study region, a 1000-m increase in altitude results in a ~0.75‰ decrease in δ¹³C and a ~2.2‰ increase in δ¹⁵N. Organic carbon stable isotope (δ¹³C) values of the dominant modern vegetation species, surface soils, and the core samples taken in the swamp exhibit a strong terrestrial C3 plant signature. Comprehensive analysis of the core indicates both terrestrial and aquatic sources contribute to the OM in sediment. Temperature and precipitation are most likely the critical factors that influence δ¹³C: warm and wet conditions favor lower δ¹³C, whereas a dry and cool climate leads to higher δ¹³C values. Higher δ¹⁵N values may result from greater water depth and increased primary productivity, promoted by large inputs of dissolved inorganic nitrogen, induced by high surface runoff. Lower δ¹⁵N values are associated with lower lake stage and reduced productivity, under drier conditions. Therefore, stratigraphic shifts in these stable isotopes were used to infer past regional climate. Measures of δ¹³C and δ¹⁵N in deglacial deposits, in combination with total organic carbon (TOC) and nitrogen (TN) concentrations, the TOC/TN ratio, coarse silt and sand fractions, dry bulk density and low-frequency mass magnetic susceptibility, reveal two dry and cold events at 15,400–14,500 and 13,000–11,000 cal a BP, which correspond to Heinrich event 1 and the Younger Dryas, respectively. A pronounced warm and wet period that occurred between those dry episodes, from 14,500 to 13,000 cal a BP, corresponds to the Bølling–Allerød. The δ¹³C and δ¹⁵N data, however, do not reflect a warm and wet early Holocene. The Holocene optimum occurred between ~8000 and 6000 cal a BP, which is different from inferences from the nearby Dongge cave stalagmite δ¹⁸O record, but consistent with our previous results. This study contributes to our understanding of climate-related influences on δ¹³C and δ¹⁵N in OM of lake sediments in South China.     

Climatic and environmental change in Yanchi Lake, Northwest China since the Late Glacial: A comprehensive analysis of lake sediments

Modern climate research has shown that the Asian summer monsoon water vapor transport is limited to the eastern part of the Qilian Mountains. On the Holocene millennial-scale, whether the northwest boundary of the summer monsoon varies according to climate change is a key scientific issue. Yanchi Lake is located in the northern Qilian Mountains and the middle of the Hexi Corridor, where the modern climate is less affected by the Asian summer monsoon. It is a key research area for examining the long-term variations of the Asian summer monsoon. Paleoclimatic data, including AMS ^14C dates of pollen concentrates and bulk organic carbon, lithology, grain-size, mineral composition and geochemical proxies were acquired from sediments of Yanchi Lake. The chronological results show that the lower part of the lacustrine section is formed mainly in the Late Glacial and early Holocene period, while the proxies＇ data indicate the lake expansion is associated with high content of mineral salts. The middle part of this section is formed during the transitional period of the early and middle Holocene. Affected by the reworking effect, the pollen concentrates AMS^14C dates from the middle part of the section are generally older than those from the lower part. Since the mid-Holocene, Yanchi Lake retreated significantly and the deposition rate dropped obvi- ously. The Yanchi Lake record is consistent with the Late Glacial and Holocene lake records in the Qinghai-Tibet Plateau and the climatic records in typical monsoon domain, which indicate the lake expansion and the strong Asian summer monsoon during the Late Glacial and early Holocene. The long-term monsoonal pattern is different from the lake evolution in Central Asia on the Holocene millennial-scale. This study proves the monsoon impacts on the northwestern margin of the summer monsoon, and also proves the fact that the northern boundary of the summer monsoon moves according to millennial-scale climate change.     

Response of Sandy Lake in Schirmacher Oasis,East Antarctica to the glacial-interglacial climate shift

Freshwater lakes in Antarctica fluctuate from ice-free state (during austral summer) to ice-cover state (during austral winter). Hence the lakes respond instantly to the seasonal climate of the region. The Antarctic seasons respond sharply to the glacial and interglacial climates and these signatures are archived in the lake sediments. A sediment core from Sandy Lake, a periglacial lake located in Schirmacher Oasis of East Antarctica records distinct changes in grain-size, C, N, C/N ratios (atomic), δ¹³C_OM and δ¹⁵N_OM contents during the last 36 ky. The contents of the sedimentary organic matter (OM) proxies (C_org ~ 0.3 ± 0.2%, C/N ratios ~9 ± 5 and δ¹³C_OM ~?18 ± 6‰) indicate that the OM in this lake sediment is a product of mixing of terrestrial and lacustrine biomass. Distinctly lower contents of C_org (~0.2%) and sand (~50%), low C/N ratios (~8) and depleted δ¹³C_OM (~?20‰) during the Last Glacial Maximum (LGM: 32–17 ky BP based on Vostok Temperatures) suggest greater internal (autochthonous) provenance of organic matter and limited terrestrial (allochthonous) inputs probably due to long and intense winters in the Antarctic. Such intense winters might have resulted the lake surface to be ice-covered for most part of the year when the temperatures remained consistently colder than the Holocene temperatures. The denitrification within the lake evident by enriched δ¹⁵N_OM (>10‰) during Antarctic LGM might have resulted from oxygen-limitation within the lake environment caused by insulated lake surface. The gradual increases in δ¹³C_OM, C/N and sand content starting at ~11 ky BP and attaining high values (~?11‰, ~10 and ~80% respectively) at ~6 ky BP together suggest a subtle change in the balance of sources of organic matter between algal and macrophyte/bryophyte nearly 8–9 ky later to the beginning of the deglaciation. Thus the seasonal opening-up of the Sandy Lake similar to the modern pattern started with the establishment of the optimum temperature conditions (i.e., 0 °C anomaly) in the Antarctic, prior to which the lake environment might have remained mostly insulated or closed.     

Lakes of the Jom-Bolok Volcanoes Valley in the East Sayan Mts., Baikal region

Journal of Geographical Sciences - This article describes the lake basins of the Jom-Bolok volcanic region in the East Sayan (the largest manifestation of the Holocene eruptions in Central Asia)....     

贝加尔地区萨彦山东部Jom-Bolok火山谷湖泊古环境研究（英文）

This article describes the lake basins of the Jom-Bolok volcanic region in the East Sayan(the largest manifestation of the Holocene eruptions in Central Asia). The geomorphological position, origins, aspects of the structure and development are reviewed considering its sedimentary filling. The limnic morphogenesis here develops under the conditions of contrasting relief, high energy of neotectonic and exogenous processes. We established that Lake Khara-Nur, formed as a result of lava-damming of the Jom-Bolok river valley, emerged in its present form approximately 6500 years ago. A complex record on the environment and climatic changes, acquired from its sediments, made it possible to determine for the first time in this region the long-term trends in the development of the Middle and Late Holocene mountain geosystems and also the distinction of several paleogeographic stages of the formation of the natural environment. An average geochemical record resolution for the bottom sediments of the lake was made uniquely for the East Siberian lake records and is equal to 35 years, while the palynological record approximates 110 years.     

Sediment geochemical records of environmental change in Lake Wuliangsu, Yellow River Basin, north China

We present a paleolimnological record from shallow Lake Wuliangsu in the Yellow River Basin, north China, using a short (56 cm) sediment core. Our objective was to investigate environmental changes in this semi-arid region over the past ~150 years. The sediment core was dated using ¹³⁷Cs and ²¹⁰Pb. We examined stratigraphic trends in core lithology, nutrients, stable isotopes (δ¹³C and δ¹⁵N) and trace element concentrations in the Lake Wuliangsu core to discern between natural sediments and those affected by human agency. A lithologic transition from yellow, coarse-grained sediment to grey, fined-grained sediment marked the lake’s formation about 1860. Until ~1950, sediments displayed relatively low and constant heavy metal concentrations, indicating little human influence. In the 1950s, enrichment factors (EFs) increased, reflecting greater impact of human activities. Carbon and nitrogen stable isotopes in organic matter (OM), along with heavy metal concentrations, were used to infer past shifts in trophic state and identify pollutants that came from agriculture, industry and urbanization. In the late 1950s, the first evidence for environmental change is recorded by increases in total organic carbon (TOC), total organic nitrogen (TN), TOC/TN, EFs, δ¹³C and a decrease in δ¹⁵N. After about year 2000, a more rapid increase in trophic status occurred, as indicated by greater total phosphorus (TP), EFs, δ¹⁵N and lower δ¹³C values. Changes in isotope and TOC/TN values in the lake sediments may reflect a shift in lake ecology during this period. The first increase in trophic status during the late 1950s was mainly a result of agricultural development in the catchment. In contrast, the change after ca. AD 2000 was driven largely by urban and industrial development. Agreement between paleolimnologic data from Lake Wuliangsu, and both instrumental and written records, indicates that the lake sediments provide a reliable archive for investigating the formation and environmental history of the lake.     

Paleoclimate changes inferred from stable isotopes and magnetic properties of organic-rich lake sediments in Arctic Norway

Stable isotope measures in organic matter are frequently used as indicators of past climate change. Although such analyses can provide valuable information, there is considerable uncertainty associated with studies of organic-rich sediments, especially those from Arctic lakes and bogs. We studied stable isotopes of carbon and nitrogen, and magnetic properties in a sediment core from a small alkaline lake with a high sedimentation rate, Lake Nattmålsvatn, Norway. There is good correspondence among the different sediment variables during the late glacial, and they seemingly reflect major climate variations such as the Allerød Interstade and the Younger Dryas, as well as the transition into the current interglacial. During the early Holocene, however, these relationships are more complex and δ¹³C and δ¹⁵N values do not stabilize until ~7,500 cal year BP. A significant excursion in all variables occurs between 6,850 and 6,500 cal year BP and is interpreted to represent climate deterioration. Holocene δ¹³C values vary little and indicate that isotopically-depleted dissolved inorganic carbon (DIC) in the lake, possibly influenced by methanotrophy and high pCO₂, dominated the lake’s carbon cycle. Holocene δ¹⁵N is similarly muted, likely due to the availability of abundant dissolved nitrogen. Bulk organic matter is probably dominated by phytoplankton remains produced beneath the ice cover in late spring and during ice breakup when isotopically-depleted DIC, pCO₂ and ammonium availability were maximal. Thus, use of δ¹³C and δ¹⁵N as indicators of Holocene paleoclimate and paleoproductivity variation can be challenging in a lake such as Nattmålsvatn, where ice cover isolates the basin for large parts of the year, allowing dissolved respiratory gases to accumulate in the water column. In contrast, magnetic variables appear to better track climate variations. In particular, runoff-driven influx of minerogenic sediments shows high variability that can be attributed to regional changes in Holocene winter precipitation. The most striking shifts occur between 4,000 and 2,300 cal year BP.