Research on the carbon isotopic composition of organic matter from Lake Chenghai and Caohai Lake sediments

The carbon isotopic composition of organic matter from lake sediments has been extensively used to infer variations in productivity. In this paper, based on the study of the contents and δ13C values of organic matter in different types of lakes, it has been found that δ13C values of organic matter have different responses to lake productivity in different lakes. As to the lakes dominated by aqutic macrophytes such as Lake Caohai, organic matter becomes enriched in 13C with increasing productivity. As to the lakes dominated by aquatic algae such as Lake Chenghai, δ13C values of organic matter decrease with increasing productivity, and the degradation of aquatic algae is the main factor leading to the decrease of δ13C values of organic matter with increasing productivity. Therefore, we should be cautious to use the carbon isotopic composition of organic matter to deduce lake productivity.

The Correlation of Inorganic C, O Isotopic Values for Lake Chenghai Sediments and Its Environmental Implications

As one of the lakes on the Yunnan-Guizhou plateau, Lake Chenghai, which is a typical closed lake with the precipitation accounting for one-third or more of the annual water input, has a high total salinity (almost like a saline lake).The inorganic C,O isotopic composition of lake sediments bears much sensitive information about environmental change in the catchment, while their correlations revealed the hydrological conditions under which the lake was closed. Their compositional variations are controlled by temperature, precipitation, photosynthesis, dissolving equilibrium of the carbonate system and hydrological condition. According to our research on inorganic C, O isotopic composition of Lake Chenghai sediments, we investigated the environmental change of this catchment several decades ago. The results showed that Lake Chenghai has kept good hydrological closing conditions in the past several decades, as indicated by the good correlation of inorganic C, O isotopic composition of sediments; and that the environmental change in this catchment shows a tendency of periodical evolution on a 10\+\{-11\}-years scale, although the signal noise is relatively high at the bottom of the sediment core. And we also can extend C, O isotopes, a sensitive environmental indicator, to nearly saline lake environments with a high degree of mineralization.

Isotopic Tracing of Trophication Processes over the Last Millennia on Lake Chenghai

Multi-parameter studies (stable isotopes in carbonate and or ganic matter, pigment, organic carbon and nitrogen contents) from a 660-yr cont inuous sediment core from Lake Chenghai, a closed, eutropic lake in southern Chi na, provide information on lake historical eutrophication. During the last 660 y ears, great changes have taken place in productivity and eutrophication of Lake Chenghai in response to human activities. In 1690, the productivity of the lake began to increase as Lake Chenghai became closed from agriculture in the lake’s watershed. In 1942, Lake Chenghai evolved to eutrophic state, marked by an incr ease in organic carbon, nitrogen, CaCO\-3, pigment contents and obvious negative values of stable isotopes, which is more or less simultaneous with the large-s cale population immigration during the period. In 1984, intensive human activiti es induced modern lacustrine productivity and eutrophic level. Human-induced tr ophic changes during the past few decades have affected the Lake Chenghai ecosys tem to such an extent that it has never experienced before in the last 660 years .

Environmental evolution recorded by multi-proxy evidence in Lake Chenghai sediments, Yunnan Province during recent 100 years

Lacustrine sediments can provide potential information about environmental changes in the past. On the basis of high-resolution multi-proxy analysis including carbon and nitrogen contents of organic matter, C/N ratios, inorganic carbon contents, and carbon and oxygen isotopic composition of carbonate, together with precise 137Cs dating, the environmental evolution of Lake Chenghai, Yunnan Province, during the past 100 years has been investigated. It is shown that the carbonate in Lake Chenghai is authigenic, and the organic matter is mainly derived from aquatic plants and algae, instead of terrestrial-source materials. The environmental evolution of Lake Chenghai can be diverged into three periods with the contrasting characteristics during the past 100 years. Before 1940, the stable carbon and oxygen isotope values, the poor correlation between them and the lower carbon and nitrogen contents of organic matter suggested that Lake Chenghai was open, and the lake water was oligotrophic during that period. During 1940-1993, the negative δ13C values and the gradual increase of carbon and nitrogen contents of organic matter and C/N ratios indicated that the eutrophication was aggravated. The closeness of Lake Chenghai and human activities may be responsible for this eutrophication. After 1993, notable increases in carbon and oxygen isotopic values of carbonate, carbon and nitrogen contents of organic matter, C/N ratios and inorganic carbon contents demonstrated that the increase of lacustrine productivity and the serious eutrophication were resulted from strong human activities. Therefore, the multi-proxy in Lake Chenghai sediments has reliably recorded the natural environmental evolution and the impacts from human activities.

Initiation and evolution of coarse-grained deposits in the Late Quaternary Lake Chenghai source-to-sink system:From subaqueous colluvial apron(subaqueous fans)to Gilbert-type delta

Investigating the formation and evolution of coarse-grained deposits in modern lakes and the relevant controlling conditions is indispensable to the prediction of reservoir sandbodies, disaster prediction,and limnological research. The source-to-sink system of coarse-grained deposits in Lake Chenghai, a deep,scarped Late Quaternary lake, was investigated in this study based on 62 outcrops, Advanced Land Observing Satellite(ALOS) digital elevation model(DEM) data, and regional geological survey data. The findings include the following:(1) the source areas of coarse-grained deposits in Lake Chenghai were lithologically classified into carbonate source areas, basaltic source areas and siliciclastic source areas, and were geomorphically categorized as scarp type or confluence type. Subaqueous colluvial aprons have formed downstream of the carbonate source areas and scarp-type basaltic source areas, while Gilbert-type deltas have formed downstream of siliciclastic source areas and confluence-type basaltic source areas.(2) The formation and evolution of coarse-grained deposits are controlled by the sediment flux that evolves in synchrony with the geomorphic evolution of the source areas and the sink regimes. Scarps represent the initial landform of the source areas.Source material rolls off or slides down scarps or forms small-scale debris flows before entering the lake. The source material initially formed subaqueous colluvial apron(synonymous with subaqueous fans) where sufficient space was present to accommodate sediments and the basement angle exceeded than the natural angle of repose. As weathering and denudation have progressed, the initial scarps have transformed into confluencetype slopes, and the source material has formed medium-and large-scale debris flows that have entered the lake, resulting in an increase in sediment flux. Consequently, the subaqueous colluvial aprons have rapidly grown and developed subaerial deposits, which have evolved into larger-scale Gilbert-type deltas that overlie the initial aprons.(3) The morphology and distribution of coarse-grained deposits vary in response to differences in quantity and composition of materials from different source areas, which resulting from different rates of weathering and denudation and different sediment input regimes. Firstly, the size and surface slope angle of a subaqueous colluvial apron from a carbonate source are smaller than those of a subaqueous colluvial apron of basaltic origin. Secondly, a Gilbert-type delta from a basaltic source features a greater slope angle and a thicker topset than does a Gilbert-type delta of siliciclastic origin, and the latter exhibits a longer foreset and a thicker bottomset than in the former. Thirdly, the sizes of subaqueous colluvial aprons are not strongly correlated with the sizes of the source areas, while the sizes of Gilbert-type deltas are.

Sudden enhancement of sedimentation flux of^(210)Pb_(ex) as anindicator of lake productivity as exemplified by Lake Chenghai

The fundamental assumption of 210Pbsediment dating is the stable flux of 210Pbse, which was derived from atmosphere and then transferred into sediments via lake water. When the sedimentation rate is relatively constant, the 210Pbse activity in sediments will be exponentially reduced with sedimentation age. 210Pbse in lake water is incorporated into sediments mainly via organic particulates. If the sedimentation flux of organic matter in lake water is suddenly in- creased, 210Pbse will be significantly deposited and then transferred into sediments. On the one hand such sudden purification effect is obviously unfit for the fundamental assumption of 210Pbse dating; on the other hand, the sudden enhancement of 210Pbse flux would be indicative of the conspicuous variation of primary productivity of lake water. This problem will be discussed in accordance with the variation trend of 210Pbex in the vertical profile of recent sediments of Lake Chenghai, Yunnan Province. The sediment core was collected from the deep-water area of Lake Chenghai in June 1997. The vertical profile of 137 Cs activity is characterized by a tree-peak pat- tern. This profile gave reliable ages, and also showed the stability of sediment accumulation in the recent ten years. The vertical profile of210Pbse activity displays a specific distribution of peaks, and is similar to the vertical profile of Corg. This phenomenon seems to be related to the mecha- nism of constraining the transfer of 210Pbse into lake sediments. The average atomic ratios of Horg/Corg and Corg/Norg in Lake Chenghai sediments are 5.51 and 7.04, respectively, indicating that the organic matter was predominantly derived from the remains of endogenic algae. In terms of the three-stage evolutionary characteristics of organic matter in sediments, i.e., “deposition-de- composition-accumulation”, the sedimentation fluxes （F（Corg）） of organic carbon （Corg） since 1970 were calculated by modeling. The sedimentation fluxes of 210Pbse (F(210Pbse)) in different years display good synchronous relations with the sedimentation flux of organic carbon （F（Corg））, es- pecially in the years of 1972─1974 and 1986─1989. The variation of F（Corg） led to the variation of F(210Pbse); the variation of F（210Pbex） reflects, to some extent, the historical variation of lake pro- ductivity.

以河长制为抓手构建河湖管理保护机制探讨——以云南省程海为例

程海属于内陆封闭型湖泊,近年来程海周边旅游业崛起,人为活动日渐频繁,对湖水需求量逐日增加,导致本不能对外出水的程海流域沉积了超出湖体自身净化能力的污染物质,从而影响整个生境的自然循环能力。深入贯彻落实习近平生态文明思想,积极践行“绿水青山就是金山银山”理念,按照中央、省、市决策部署,坚持问题导向和目标导向,制定《关于全面推行河长制的实施意见》,在全县范围内全面推行河长制、湖长制,推动山水林田湖草沙系统治理,既治乱又治病治根,打造生态美丽河湖,使程海流域的河湖面貌得到初步改善。

高原深水湖泊程海氮磷形态分布特征及其与叶绿素a的相关性

湖泊水体氮、磷形态分布特征及其与藻类生长的关系是湖泊富营养化研究的重要方面。采用GPS定位,在程海湖设置了3个断面9个采样点,研究了氮、磷形态分布特征,并分析了各形态氮磷与叶绿素a的相关性。结果表明:总氮(TN)质量浓度为0.773 mg.L-1,总磷(TP)质量浓度为0.046 mg.L-1,叶绿素a质量浓度为0.024 mg.L-1。氮素的赋存形态特征是以溶解态总氮(DTN)占大部分,DTN中又以溶解态有机氮(DON)占绝大部分;磷素的存在特点是溶解态无机磷(DIP)含量比重较大。各形态氮、磷都有明显的季节性波动但区域性差异不明显,叶绿素a则有明显的季节节律和时空差异。叶绿素a很好地响应了总氮(TN)、总磷(TP)、溶解态总氮(DTN)、溶解态总磷(DTP)、颗粒态总氮(PTN)、颗粒态总磷(PTP)的变化。程海富营养化受氮和磷共同限制,控制富营养化必须同时削减氮和磷。

云南程海近500年来湖泊初始生产力的演化

程海为富营养化封闭湖泊。通过对程海 CH0 1孔沉积物色素分析 ,定性恢复了近 5 0 0 a来程海湖泊初始生产力演化过程。结果表明 ,近 5 0 0 a来程海湖泊初始生产力总体上呈现由低到高的上升趋势。其中 170 0 AD前后、1790 AD前后是湖泊初始生产力出现变化的界限。另外 ,色素含量变化揭示研究时期内存在 175 0 AD前后、1930

云南省高原深水湖泊程海磷形态分布和变化

采用GPS定位,在程海设置了3个断面9个采样点,对各种形态磷进行了为期1 a的研究,分析了高原深水湖泊程海磷形态分布和变化.结果表明:程海中总磷含量范围为0.008～0.155 mg/L,年平均值为0.046 mg/L,含量水平已经较高.存在形态是颗粒态总磷占54.35%;溶解态有机磷占19.56%;溶解态无机磷占26.09%.各形态磷时间分布和变化与水生生物特别是浮游植物生命活动和周期变化密切相关;水平分布格局受浮游生物活动、湖流风动等综合影响;由水表层-亚底层垂直分布比较均匀,湖底层含量不同程度升高.

青藏高原东缘近2000年湖泊气候记录及全球联系

掌握青藏高原东缘气候变化历史对认识区域乃至全球气候动力成因有重要意义。本文基于我们近年来在青藏高原东缘获取的湖泊记录，并汇总他人研究成果，探讨了高原东缘近2000年气候变化历史。我们的工作表明青藏高原东缘北部（N-ETP）和南部（S-ETP）近2000年水文气候存在显著的区域差异。N-ETP 地区中世纪总体温暖湿润，小冰期寒冷干燥，近100-200年温暖湿润，表现为“暖湿-冷干”气候模式；而S-ETP地区中世纪温暖干旱，小冰期寒冷湿润，近100-200年温暖干旱，表现为“冷湿-暖干”气候模式。对比分析表明，N-ETP地区气候模式与东亚夏季风广泛区域气候模式相似；而S-ETP地区气候模式与多数印度夏季风地区气候模式相似。我们怀疑这样大尺度的水文气候差异可能与不同区域大气环流差异以及赤道太平洋-印度洋海表面温度变化及其引起的大气环流的强度及位置的变化有关。

云南程海富营养化过程的碳氧稳定同位素示踪

近 5 0 0年来程海生物成因碳酸盐δ1 8O和δ1 3C及其有机质δ1 3C同位素记录了程海湖泊环境由贫营养到中富营养的演化过程。碳酸盐δ1 8O记录显示 ,大约 1 690年程海成为封闭湖泊后 ,当时湖泊贫营养环境并没有发生变化 ,但造成了湖泊水体交换周期加长 ,碳酸盐δ1 3C、有机质δ1 3C及其色素含量、碳酸盐含量变化指示湖泊生产力开始增高。 1 91 1～ 1 942年碳酸盐δ1 8O和δ1 3C及有机质δ1 3C突然显著偏负 ,表明湖泊生物种群结构发生转变 ,湖泊初级生产力迅速增加 ,湖泊由贫营养向中营养转化。湖泊沉积物色素含量及碳酸盐含量变化也记录了这一湖泊环境的转换过程。约 1 986年以来 ,随着藻类养殖业及其农业耕作方式的转变 ,程海水环境渐渐转变成目前的中富营养化状态。

云南程海沉积物碳酸盐来源辨识

碳酸盐是湖泊沉积物的组成部分,其碳、氧同位素组成是恢复湖区古气候/古环境的有效代用指标.沉积物碳酸盐包括物源区带来的外源碳酸盐和湖泊内生沉淀产生的自生碳酸盐,其中只有自生碳酸盐才具有古气候指示意义.故沉积物碳酸盐来源辨识是开展碳酸盐古环境记录研究的基础和前提.通过多种方法的综合判别,证明了程海沉积物碳酸盐主要是自生碳酸盐,为开展碳酸盐记录研究提供了可靠依据.程海是开展碳酸盐碳氧同位素与古气候研究的理想场所,尤其值得深入研究.

永胜金沙江寨子村古滑坡和古堰塞湖的发现

在滇西北地区永胜南部金沙江的右岸,发现了总方量为2.5×108 m3的超大型古滑坡。滑坡后缘及两侧断壁为近直立的石灰岩峭壁,高5～30 m。滑床发育有规模不一的冲沟,覆盖有发育植被的坡积物、倒石堆和巨石。该滑坡曾造成过严重的堵江事件,在金沙江左岸仍然可以看到垄岗状残留滑坡坝,坝体方量约180×104 m3,滑坡坝和坝体后侧基岩界限清晰,两者之间岩性区别较大。滑坡堵江事件在上游形成了沿江连续分布长度约46 km的古堰塞湖沉积,沉积物主要由粉土、粉质粘土及粉细砂构成,偶夹卵石层,以水平层理为主,粉细砂层中见有小型交错层理,湖相沉积特征显著,而沉积物的树枝状平面分布进一步证实其形成于堰塞湖环境。

程海藻类植物种群结构和数量的周年变化特征

2009年10月—2010年9月,在程海湖设置了3个断面9个采样点,对程海藻类植物进行了逐月采样调查。结果表明：程海藻类植物种类175种（变种）,种类组成结构特点以硅藻、绿藻、蓝藻为主;数量组成结构特点则是蓝藻占绝对优势,表现出典型的富营养化蓝藻型特征。细胞丰度为390.16×104~51 435.0×104个.L-1之间,年平均4 851.75×104个.L-1。年内时间分布呈现出3次波峰与3次波谷,每一次高峰的出现都伴随着不同种类为主的蓝藻水华暴发;水平分布在种类上无明显差异,数量上则表现出南部断面最低,中部断面次之,北部断面最高;垂直分布以表层最多,底层最低,5.0~20.0 m水柱中差异不明显。与1985年相比,种类组成中硅藻比重下降而蓝绿藻比重上升,一些对环境敏感的种类消失,优势种群发生演变,年内数量变动由单峰型发展为多峰型,湖泊富营养化进一步发展。提出了大力削减入湖污染物、增强湖泊生态系统的功能等控制富营养化的对策建议。

程海的环境问题及其管理对策探讨

程海水污染和富营养化程度日趋严重，ｐＨ值和氟化物浓度超过国家《地面水环境质量标准》Ｖ类，非离子氨和总磷浓度也较高，矿化度趋近咸水湖标准，湖水已达到富营养水平。然而，程海目前的水质仍主要由自然演化进程决定，ｐＨ值、氟化物和总磷浓度适宜分别控制在背景值９．１１～９．３０之间、１．８８～２．２３ｍｇ／Ｌ之间和０．０５８ｍｇ／Ｌ以下。程海是磷限制型，富营养化控制重点应放在人湖磷负荷上。目前程海最大的污染源是降雨径流，其次是仙人河引水（含县城污水）、螺旋藻养殖废水和湖面大气沉降。水污染控制首先要实现点污染源零排放，而后将重点放在农田暴雨径流人湖污染负荷控制方面，侧重荒山造林、小流域综合治理和农田养分有效管理。另外，要有计划地引水人湖，控制提灌水量，防止程海水位继续下降。

程海近代气候变化的化学记录

通过对程海沉积物化学组分及其比值变化剖面的精细剖析 ,辨识了程海沉积物碳酸盐含量、Ca O/ (Mg O· Al2 O3)和 (Ca O+K2 O+Na2 O) / Al2 O3比值的环境指示意义 ,初步探讨了程海区域的气候短尺度波动。研究结果表明 ,程海区域主要表现为暖干与冷湿相交替的气候演替类型 ,且存在约 5 0

云南程海现代沉积物环境记录研究

本文通过对程海沉积物C、H、N等元素的含量及其比值的综合分析 ,辨识了程海沉积物有机质H/C及C/N值的环境指示意义 ,发现它们均可作为程海水位波动及区域气候干湿变迁的替代性指标。研究结果表明 :程海的水位和区域气候干湿变化明显经历了两个不同的阶段 ,但整体上程海水位一直呈下降趋势 。

程海的水质状况及咸化趋势

程海又名黑坞海,位于东经100°38—41′,北纬26°27—38′之间,即今云南省永胜县城西南20km处,是横断山区最大的一个内流高山湖泊。长期以来,程海的水量出湖略大于入湖,湖水量逐年减少,水质向咸化方向发展。本文根据1981年5月27日—6月5日对程海的综合调查资料,重点分析了1972年至1981年水质演变情况,对水质状况及成化趋势进行了初步研究。

高原深水湖泊程海中氮元素时空分布特征

采用GPS定位,在程海设置了3个断面9个采样站14个采样点,对氮元素及其赋存形态进行了为期1年的动态研究。结果表明：总氮（TN）浓度范围0.490~2.827 mg/L之间,平均0.773 mg/L,赋存形态及其组成为：溶解态总氮（DTN）占TN含量的64.3%;颗粒态总氮（PTN）占TN的35.7%;溶解态有机氮（DON）占TN的53.3%;溶解态无机氮（DIN）占TN的11.0%;氨态氮（NH3-N）占TN的6.9%;硝态氮（NO3--N）占TN的3.4%;亚硝态氮（NO2--N）占TN的0.8%,使湖泊具备富营养化易发条件。氮素形态转化及其年内时间分布特征与浮游植物生长、衰老、死亡、分解等生命活动的周期变化密切相关。空间分布格局受浮游生物活动、湖流风动、湖水补给和水化学特征等综合影响。文章为认识高原深水湖泊水中氮赋存形态、时空分布及其动态变化提供资料,为揭示氮素生物地球化学循环过程和蓝藻水华爆发的内在联系提供参考。