长江中下游典型湖泊近代环境变化研究

选择长江中下游的典型湖泊洪湖、巢湖、石臼湖和太湖,采集了沉积柱样,测定了总有机碳、总氮、总磷,并采用210Pb和137Cs定年以研究湖泊近代环境演变。根据洪湖137Cs蓄积峰得到过去50 a里洪湖沉积速率经历了一个由慢到快再变慢的过程,1963~1986年之间沉积速率最大,达0.174 cm/a,这可能是因为当时湖区大规模开垦有关。巢湖钻孔核素的研究发现20世纪70年代以来随着深度的减少,巢湖钻孔中沉积通量在增加,可能与流域内水土流失逐步加重有关。对营养盐的分析表明,洪湖50年代以来沉积物中营养元素急剧增加,巢湖70年代以来营养元素开始增加,在太湖中体现为80年代,石臼湖中则为近百年来营养元素开始快速增加。从营养盐增加的幅度来看,草型湖的洪湖、石臼湖要大于藻型的巢湖以及太湖藻型区域。本文尝试利用总有机碳、总磷获取了湖泊环境变化的速率。研究表明总有机碳和总磷的变化速率存在波动性,这可能与湖泊的自我调节有关。而总有机碳的变化速率在最近时间阶段内基本呈正值,对于洪湖来说在80年代初,石臼湖在1970年左右,太湖在80年代初,巢湖在60年代。总有机碳、总磷变化速率的振荡幅度与周期也许对理解当今湖泊处于何种位置,由此采取何种湖泊管理手段提供重要认识。     

Geochemistry of Renuka Lake and wetland sediments,Lesser Himalaya (India): implications for source-area weathering,provenance, and tectonic setting

The geochemical investigation of sediments deposited in the Renuka Lake basin and its adjoining wetland has shown variation in the distribution and concentration of major, trace and REEs. The major elements are depleted in the lake in relation to wetland and that of Post Archaean Australian, Shale (PAAS), except for CaO which is strikingly in excess and has a dilution effect on SiO₂ and other oxides and trace elements. The Wetland sediments, on the other hand, are enriched in Al₂O₃, Fe₂O₃, K₂O and TiO₂ and the latter three show a positive correlation with Al₂O₃ in both wetland and lake sediments suggesting their association with phyllosilicates and similar source rocks. The enrichment of Y, Zr, Ni, Th, U and Nb in wetland compared to lake and their similarity with PAAS in the former, suggests more clay fractions in the wetland. A high Zr/Hf ratio in wetland and lake sediments and a positive correlation of Zr with Y and HREE indicate Zr control on HREEs. However, higher Zr/Yb and Zr/Th ratios in wetland compared to lake indicate mineral sorting during the process of lighter particles (clays) being trapped in wetland soil. This is also reflected from negative correlation of Gd_N/Yb_N with Al₂O₃ and a strong positive correlation with SiO₂ in wetland sediments. The wetland in this context has a control on lake sediment chemistry. The chondrite normalized REE patterns are essentially the same for lake as well as wetland sediments but abundance decreases in the former. The similarity of pattern with that of PAAS and negative Eu anomaly indicates a cratonic source of sediments. In a plot of the individual samples, wetland samples cluster while lake samples are separated indicating fractionation of lake sediments. A strong positive correlation of La_N/Yb_N with Al₂O₃ and a positive correlation of Zr-∑LREE and Zr-La_N/Yb_N suggest that LREEs are controlled by both phyllosilicates and zircon. The chemical index of alteration (CIA) indices in lake sediments and in wetland are higher than PAAS indicating moderate chemical weathering in the source area. The petrography, lack of felsic magmatic rock fragments, and negative correlation between Zr-(Gd/Yb)_C indicate sedimentary source rocks for the detritus. This is in conformity with the Lesser Himalayan sedimentary sequence belonging to neo-Proterozoic–Proterozoic age and constituting lake catchment of Renuka. The tectonic delineation and discriminant function plots of lake and wetland sediments indicate their cratonic and/or quartzose sedimentary orogenic terrain source that has been deposited in a passive margin setting.     

Environmental effects of river sand mining: a case from the river catchments of Vembanad lake,Southwest coast of India

Rivers in the southwest coast of India are under immense pressure due to various kinds of human activities among which indiscriminate extraction of construction grade sand is the most disastrous one. The situation is rather alarming in the rivers draining the Vembanad lake catchments as the area hosts one of the fast developing urban-cum-industrial centre, the Kochi city, otherwise called the Queen of Arabian Sea. The Vembanad lake catchments are drained by seven rivers whose length varies between 78 and 244 km and catchment area between 847 and 5,398 km². On an average, 11.73 million ty⁻¹ of sand and gravel are being extracted from the active channels and 0.414 million ty⁻¹ of sand from the river floodplains. The quantity of instream mining is about 40 times the higher than the sand input estimated in the gauging stations. As a result of indiscriminate sand mining, the riverbed in the storage zone is getting lowered at a rate of 7–15 cm y⁻¹ over the past two decades. This, in turn, imposes severe damages to the physical and biological environments of these river systems. The present paper deals with the environmental effects of indiscriminate sand mining from the small catchment rivers in the southwest coast of India, taking the case of the rivers draining the Vembanad lake catchments as an example.     

Heavy metal concentrations (Cd,Cu and Pb) in five aquatic plant species in Tasik Chini,Malaysia

The purpose of this study was to determine the levels of heavy metals namely cadmium (Cd), copper (Cu) and lead (Pb) in the five aquatic plants. For this purpose, the concentration of heavy metals were measured in water and in the five aquatic plant species, Lepironia articulata, Pandanus helicopus, Scirpus grossus, Cabomba furcata and Nelumbo nucifera, in 15 sites from Tasik Chini. The concentrations were different among the plant species as well as among the parts of plants. The highest concentration of heavy metals among the aquatic plants and plant parts was found in the roots of S. grossus. The concentrations of Cd in the leaves and stems of submerged aquatic plant, C. furcata, were higher than concentration of Cd in the leaves and stems of emergent aquatic plant and floating leaf plant. The concentration of Cu in the stem of C. furcata was greater than that in the leaf, while the concentration of Cd was more in the leaf than in the stem. The heavy metal contents of the aquatic plants were in descending order of Pb > Cu > Cd. The metal concentration quotient of leaves/roots and stems/roots (ML/MR and MS/MR) were calculated. The highest internal translocation was found in P. helicopus, while the lowest internal translocation was found in S. grossus.     

青藏高原中部扎布耶茶卡142 ka以来石英砂表面特征及环境意义

石英抗风化能力强,表面特征保留了许多环境信息,用扫描电镜方法对石英砂表面结构进行了研究.结果表明: 扎布耶茶卡的石英颗粒以次棱角状、次圆状为主,撞击坑、贝壳状断口、平行解理和水下磨光面等机械特征出现频率较高;化学特征有二氧化硅沉淀、蜂窝状溶蚀面、硅质球和蚀坑/洞.石英颗粒经历冲洪积作用,搬运至湖泊后又经历了水下机械和化学作用.在142～60 ka BP扎布耶茶卡湖区气候寒冷,但无冰川作用存在,石英颗粒搬运距离近,机械特征主要是强烈的物理风化与冲洪积作用形成的,化学特征与弱的水动力条件有关;8.5～3.7 ka BP湖区气候温暖,但变化频繁,湖水进一步咸化、退缩,山坡后退变缓,机械特征主要由物理风化及搬运中的碰撞造成,化学特征则与弱的水动力条件和高盐环境有关.     

Responses of landscape pattern of China’s two largest freshwater lakes to early dry season after the impoundment of Three-Gorges Dam

The effects of hydrologic cycle change (caused by human activity and global climate change) on ecosystems attract the increasing attention around the world. As a result of impounding of the Three Gorges Dam (TGD), climate change and sand mining, the dry season of Poyang Lake and Dongting Lake (China’s two largest freshwater lakes) came early after the TGD impoundment. It was the primary cause of the increasing need for sluice/dam construction to store water in the Lakes and attracted increasing attention. In this paper, we compared the landscape pattern between three hydrologic years with early dry season (EY) and three normal hydrologic years (NY) of each lake by remote sensing technology, to reveal the effect of early dry season on landscape pattern. The results showed that early dry season caused expanding of Phalaris to mudflat zone in Poyang Lake, while caused expanding of Carex to Phalaris zone and expanding of Phalaris to mudflat zone in Dongting Lake. In landscape level, there was no significant difference in landscape grain size, landscape grain shape, habitat connectivity and landscape diversity between EY and NY in the two lakes. While in habitat class level, there were significant changes in area of mudflat and Phalaris and grain size of mudflat in Poyang Lake, and in area of Carex, grain size of Phalaris and grain shape of Carex and Phalaris in Dongting Lake. These changes will impact migrating birds of East Asian and migratory fishes of Yangtze River.     

卫星测高数据监测青海湖水位变化

为了验证Cryosat-2/SIRAL数据监测湖泊水位的能力,提高其提取湖泊水位变化的精度,以青海湖为研究对象,利用主波峰重心偏移法、主波峰阈值法、主波峰5-β参数法、传统重心偏移法、传统阈值法和传统5-β参数法6种算法对Cryosat-2/SIRAL LRM 1级数据进行波形重跟踪,提取青海湖2010—2015年湖泊水位,对比不同算法获取水位的精度,并结合Envisat/RA-2 GDR数据,延长水位变化时间序列,获得青海湖2002年—2015年的水位变化信息。结果表明,主波峰5-β参数法提取湖泊水位的精度最好,均方根误差为0.093 m;对于GDR产品中LRM模式的3种数据,基于Refined OCOG算法的数据更适合湖泊水位的提取;青海湖2002年—2015年水位整体上涨,水位平均变化趋势为0.112 m/年,年内水位变化呈现明显的季节性。     

基于landsat 8-OLI/TIRS和HJ-1B太湖叶绿素含量和温度反演研究

水体的表面温度是研究环境气候变化的一个重要参数,同时,也是研究生物物理过程的一个不可或缺的因子。卫星遥感对大面积水体表面温度的监测有着传统的测量手段无法比拟的效率。水体表面的温度变化不仅对水中生物的生存有着重要的意义,同时,水温的变化也常常会导致水中浮游生物和植物疯长,进而引起水资源的污染,对人们的生活造成严重的影响。本文利用ENVI/IDL 5.1对Landsat 8卫星的OLI/TIRS数据和HJ-1CCD多光谱数据在太湖水体区域开展了其在温度反演和叶绿素含量的监测等领域的研究。研究结果表明:1)使用HJ_1B反演的结果和Landsat 8反演的结果呈现一致性。2)通过实测的数据和反演数据建立了模型并通过同名点实测数据对实验结果进行了验证,证明了建立的模型的可靠性,找到了误差来源。最后分析了造成叶绿素含量较高的原因及反演的难点。     

基于环境一号卫星遥感数据的南京市市区湖泊信息提取研究

环境一号卫星系统是专门用于环境和灾害监测的,对地观测系统由两颗光学卫星HJ-1A和HJ-1B组成,拥有光学、红外、超光谱多种探测手段,具有大范围、全天候、动态的环境和灾害监测能力。本文以南京的环境一号卫星影像为例,运用归一化差异水体指数法提取并分析了南京市市区湖泊分布信息,得到了较为满意的结果。     

冰湖的界定与分类体系——面向冰湖编目和冰湖灾害研究

冰川湖泊（简称冰湖）不仅是高山区重要的水资源,而且是许多冰川灾害的孕育者和发源地,在冰冻圈科学、气候变化和山地灾害研究中具有重要地位。本文系统讨论了现有冰湖定义及存在的问题,从冰湖编目和冰湖灾害研究视角提出冰湖的定义,指出现有冰湖研究主要是基于“以现代冰川融水为主要补给源或在冰碛垄洼地内积水形成的天然水体”这一冰湖定义的。同时,从冰湖形成机理、地貌形态和空间分布位置将冰湖划分为冰川侵蚀湖（冰斗湖、冰川槽谷湖和其他冰川侵蚀湖）、冰碛阻塞湖（终碛阻塞湖、侧碛阻塞湖、冰碛垄热融湖）、冰川阻塞湖（冰川前进阻塞湖和其他冰川阻塞湖）、冰面湖、冰下（内）湖和其他冰川湖6大类及8个亚类,并给出各冰湖类型相应的遥感判识指标和定量指标,以期建立具有普适性和可操作性的冰湖分类体系。