太湖蓝藻水华遥感动态监测预警模型的建立   总被引：7，自引：0，他引：7  

魏清宇  江南  吕恒  王甡 《地球信息科学学报》2008,10(2):156-160

湖泊富营养化和蓝藻水华暴发是当前我国湖泊面临的最重要的环境问题之一。本文分析了内陆湖泊太湖蓝藻监测的主要问题。并详细阐述了蓝藻水华遥感动态监测预警模型的建立,即,采用生物光学模型与气象环境预警模型相结合的方式,辅以图形图像学的模块匹配验证,对蓝藻水华暴发前进行临界状态的灾害等级警示,理论上较单纯监测微囊藻叶绿素a浓度值来实现水华暴发预警更为准确。这样,提前采取相应的技术措施,减少蓝藻水华暴发带来的影响和损失。  相似文献   

太平洋东部ES0103柱状样品中可溶有机质的组成变化及其早期成岩作用   总被引：1，自引：1，他引：0  

张海生  于培松  倪建宇  武光海  姚旭莹 《海洋学研究》2008,26(3):1-8

利用2001年采自太平洋东部ES0103站位的多管沉积物柱状样品,采用GC/MS对沉积物中的可溶有机质(氯仿沥青"A")及其族组成(饱和烃、芳烃、非烃和沥青质)、正构烷烃、类异戊二烯烃和萜类化合物进行了定量分析,结果表明:(1)氯仿沥青"A"中的非烃较饱和烃和芳烃的含量高,反映出该海区沉积物中有机质的演化程度较低.(2)正构烷烃的碳分子数范围多为nC14～nC34,CPI值略显奇偶优势,轻重烃比值(nC23-/nC24 )较低;类异戊二烯烃的Pr/Ph值较低,显示出该海区沉积物中的烃类是在较强的还原环境下形成的低成熟烃类,其母质来源主要为大型低等水生生物.(3)总有机碳与显晶蜡产率、氯仿沥青"A"均呈明显正相关关系,表明有机质相对富集层位所处的沉积环境也有利于高蜡烃的形成,成烃演化与成岩作用阶段有较好的对应关系.而萜类化合物的Ts/Tm值在表层和深部差别不大,显示出典型的低成熟烃类的特征.由此可见, ES0103柱状样品所处海区的沉积物为在较强还原环境中形成的,其有机质演化程度较低,为早期成岩作用阶段的产物.  相似文献   

山东聊城阿城地区含煤地层蜓类化石及其分带          下载免费PDF全文

宋香锁  王明镇  张锡麒  李敏 《山东国土资源》2008,24(12)

山东聊城地区隐伏的晚古生代含煤地层发育,其中晚石炭—早二叠世太原组灰岩中富含类化石。由三灰、七灰、十灰共鉴定出化石11属45种,自上而下可建立1个类组合带(Pseudoschw agerina带),2个类组合亚带(Triticites paramontiparus亚带;Pseudofusulina firma-Rugosofusulina complicata亚带),该地区所产类组合与华北其他地区及国外相关组合具可比性,Pseudoschw agerina带的时代为早二叠世早期。  相似文献   

Formation and early development of tetraspores of Polysiphonia urceolata (Rhodomelaceae, Rhodophyta)     

YAO Jianting  LI Dapeng  YU Shenhui  LIU Jidong  DUAN Delin 《中国海洋湖沼学报》2009,27(2)

Polysiphonia urceolata is one type of potential commercial red seaweeds used for breeding and cultivation, because of its significant biochemical and biomedical application. However, the information of breeding and seedling incubation for cultivation is limited, especially the early development. In this study, tetrasporohyte and gametophyte of P. urceolata were taken as the study materials in Huiquan Bay, Qingdao, China. The cleaned and sterilized tetrasporophytes and gametophytes were pre-cultured in sterilized seawater, then nurtured at 18℃, 25 μmol photons m-2 s-1 in 12:12 h (light:dark) photoperiod. Continuous observation under microscope showed that the early development consists of bipolar division stage and seedling stage. In the division stage, tetraspores germinate into bipolar sporelings that further differentiate into a colorless rhizoidal portion and a lightly pigmented upright shoot. The lightly pigmented rhizoidal cell develops to a rhizoid and the larger pigmented cell transforms to an erect axis. In the seedling stage, several quasi-protuberances appear on the erect axis and form juvenile seedlings. The results demonstrate the culture of P. urceolata from tetraspores under laboratory conditions.  相似文献   

沙漠型景区旅游环境承载力预警研究——以宁夏沙坡头为例     

宋小龙  李陇堂  王艳茹  石磊  杨萍  高秀云 《中国沙漠》2019,39(2):19-26

以沙坡头景区为例，引入预警理论，运用旅游环境承载率计算公式和BP神经网络预测模型对沙漠型景区现状和未来旅游环境承载力进行预警分析。结果表明：（1）将沙漠型景区旅游环境承载力预警警界区间划分为弱载（<0.8）、适载（0.8~1.0）、轻度超载（1.0~1.2）、中度超载（1.2~1.5）、严重超载（>1.5）等5个级别，对应的预警状态分别用黑灯、绿灯、黄灯、橙灯和红灯来警示；（2）沙坡头景区现状旅游环境承载力在旅游旺季整体上处于弱载状态，但"五一"、"十一"假期处于超载状态；（3）沙坡头景区在2016-2020年内旅游环境承载力仍会处于不断上升的趋势，但速度会放缓，"五一"、"十一"假期旅游高峰期间会处于超载状态。根据承载力预警结果，提出不同承载状态的预警方案。  相似文献   

U–Pb zircon geochronology,geochemical, and Sr–Nd isotopic constraints on the age and origin of basaltic porphyries from western Liaoning Province,China     

《International Geology Review》2012,54(9):1052-1070

Basaltic porphyries from the northeast North China craton (NCC) provide an excellent opportunity to examine the nature of their mantle source and the secular evolution of the underlying mantle lithosphere. In addition, the study helps to constrain the age and the mechanism of NCC lithospheric destruction. In this paper, we report geochronological, geochemical, and Sr–Nd isotopic analyses of a suite of mafic lavas. Detailed laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U–Pb dating yielded an age of 223.3 ± 1.1 million years, which we regard as representing the crystallization age of the basaltic porphyries. The bulk-rock analysed samples are enriched in both large ion lithophile elements (LILEs) (i.e. Ba, Sr, and Pb) and light rare earth elements (LREEs), but depleted in high field strong elements (HFSEs) (i.e. Nb, Ta, Zr, Hf, and Ti) and heavy rare earth elements (HREEs), without significant Eu anomalies (Eu/Eu*?= 089–0.98). The basaltic porphyries have undergone low degrees (～5%) of partial melting of a garnet-bearing lherzolite mantle. The rocks display very uniform (⁸⁷Sr/⁸⁶Sr) _i (0.70557–0.70583) and negative ?_Nd (t) values (–11.9 to –10.1). These features indicate that the western Liaoning basaltic porphyries were derived from a common enriched lithosphere mantle that had previously been metasomatized by fluids related to subduction of Palaeo-Asian sedimentary units. However, the mafic melts were not affected to a significant degree by crustal contamination. Based on earlier studies, these findings provide new evidence that the northeast margin of the NCC had undergone a phase of post-orogenic extensional tectonics during the Middle Triassic. Furthermore, lithospheric thinning occurring across the northern NCC might have been initiated during Early Triassic times and was likely controlled by the final closure of the Palaeo-Asian Ocean, as well as the collision of Mongolian arc terrenes with the NCC.  相似文献   

Geochronological and geochemical study of gneiss–schist complexes and associated granitoids,Beishan Orogen,southern Altaids     

《International Geology Review》2012,54(14):1705-1727

The tectonic nature of metamorphic terranes and their role in orogenesis are problematic. Here we present new U–Pb ages and geochemical data for widespread metamorphic rocks and associated granitoids from Northwest China. Orthogneisses from the metamorphic complexes have crystallization ages of ～457, ～452, and ～526 Ma. One paragneiss (schist) has a maximum depositional age of 312 ± 7 Ma. Three foliated granites were emplaced at ～450, ～349, and ～410 Ma, and all lack inherited Precambrian ages. The metamorphic terranes may have undergone multiple petrotectonic events as revealed by the metamorphic ages. Both the orthogneisses and granitoids show enrichment in large ion lithophile elements (LILEs) and light rare Earth elements (LREEs), and depletion in high field strength elements (HFSEs), which indicate that they formed in a subduction-generated accretionary arc setting. Our study demonstrates that the metamorphic terranes in the Beishan area, originally considered as Precambrian basement with suspected Neoarchaean to Palaeoproterozoic ages, are actually parts of early Palaeozoic arcs. The protoliths were probably metamorphosed arc plutonic and sedimentary rocks. Combined with other studies, we speculate that the Beishan Orogen formed by progressive arc accretion during the latest Neoproterozoic to early Palaeozoic time. This new interpretation has implications for other high-grade metamorphic terranes within orogens that have been assumed to represent ancient or pre-existing micro-continental blocks. If so, the importance of collision as a mechanism of mountain building has been overestimated, and the accretionary process as a mechanism of continental growth has been underestimated.  相似文献   

Petrogenesis and mineralization of the Hulu Ni-Cu sulphide deposit in Xinjiang,NW China: constraints from Sr-Nd isotopic and PGE compositions     

《International Geology Review》2012,54(6):711-733

The Permian Hulu intrusion is one of several sulphide-bearing Permian mafic–ultramafic intrusions in the eastern part of the eastern Tianshan located at the southern margin of the Central Asian Orogenic Belt (CAOB) in Xinjiang, NW China. The intrusion is composed of lherzolite, olivine websterite, gabbro, and gabbro-diorite. Disseminated and net-textured Ni-Cu sulphide ores are located at the bottom of the lopolith complex. Negative Zr, Hf, Nb, and Ta anomalies, whole-rock εNd(t) values of +5.7 to +8.8, and variable (Th/Nb)_PM values (from 1.06 to 8.13) suggest that the source of the Hulu complexes is depleted mantle metasomatized by subducted slab-derived fluid and/or melt (~5% global subducted sediment and 15% slab fluid) that has experienced approximately 3% lower crustal and 10% upper crustal contamination. The Hulu intrusion is characterized by low PGE abundances i.e. 0.03–1.08 ppb Ir, 0.04–0.69 ppb Ru, 0.02–2.15 ppb Rh, 0.30–48.71 ppb Pt, and 0.21–344 ppb Pd. Our calculations indicate that if the Pd, Os, Ir, and Cu contents of the primary magma were 2.1 ppb, 0.03 ppb, 0.05 ppb, and 200 ppm, respectively, a variable R-factor between 200 and 1600 with residual magma that had experienced 0.01% early-sulphide segregation can explain the variation in Pd, Os, and Ir contents of sulphide-poor and disseminated sulphide samples of the Hulu deposit. Basaltic magma fractionation and assimilation and/or contamination of sulphur-bearing crustal materials might have triggered sulphur saturation to form Cu-Ni sulphide ores. Tarim basaltic PGE contents cannot be used as the mineralized parent magma for the Hulu intrusion because of the differing evolutionary trends of the Ni/Pd and Cu/Ir values. However, similar Cu/Ni and Pd/Ir values in Tarim basalts and Hulu Cu-Ni sulphide ores, as well as the same early sulphide segregation process, show that certain genetic relationships between them and magma sources are probably similar to each other.  相似文献   

Early Carnian anoxic event as recorded in the southern Tethyan margin,Tunisia: an overview     

《International Geology Review》2012,54(15):1884-1905

Considerable attention has been given to the Carnian (Late Triassic) Pluvial and Reingraben events associated with organic-rich shale accumulation in the Germanic basin, Alps, southern Appenines as well as in northwestern Tethyan margins. Less interest has been shown to the southern Tethyan portion represented by the northern margin of Africa, including Tunisia. Tunisian basins represented by the Tellian domain, Tunisian trough, the ‘Dorsale’, and the North–South Axis (NOSA) belong to the southern Tethyan margin, where northern and central areas record the early Carnian anoxic event within an extensive carbonate platform. This short-lived (~2 million year) period of anoxia ranges within the Aonoides to Austriacum ammonite zones, and corresponds in Tunisia generally to intermediate to shallow water environments marked by organic-rich black limestone, dolomite, and shale. Interestingly, toward the south, the dysaerobic conditions in the Jeffara–southern Dahar basin appear to have prevailed locally also in the early Carnian. Here we review evidence of early Carnian anoxia in Tunisia based on the analysis of more than 17 Triassic sections and wireline logs from several petroleum exploration wells penetrating the black dolomites, limestones, and shales. In addition, biostratigraphic and complete geochemical reviews have been undertaken from published papers and unpublished internal reports to better assess this important and promising hydrocarbon source interval.  相似文献   

Ordovician volcano–sedimentary iron deposits of the Eastern Tianshan area,Northwest China: the Tianhu example     

《International Geology Review》2012,54(11):1398-1416

ABSTRACT

The stratabound Tianhu iron deposit, with a reserve of 104 Mt at 42% Fe, is located in the eastern part of the Central Tianshan zone in the southern part of the Central Asian Orogenic Belt. The deposit hosts schist, quartzite, marble, amphibolite, and granitic gneiss belonging to the Tianhu Group. Laser ablation inductively coupled plasma mass spectrometry was used to perform zircon U–Pb geochronology, bulk-rock geochemistry, and in situ zircon Hf isotope analyses of the metavolcanic host rocks for constraining the timing and genesis of the Tianhu iron deposit. According to the newly determined age constraints of 452 ± 3 and 477 ± 4 Ma, the iron deposit was concluded to be Ordovician in age. Geochemistry and zircon Lu–Hf isotope analyses suggested that the host rocks of the deposit represent metamorphosed arc-type volcanic rocks generated by the partial melting of a lower crustal source. Combined with geological and ore petrographic characteristics, the Tianhu iron deposit is interpreted to be of volcano–sedimentary origin with enrichment during subsequent metamorphism. The early Palaeozoic marks a critical iron mineralization epoch in the Eastern Tianshan area. The results also support the model of the Central Tianshan area as a volcanic-arc during the early Palaeozoic, associated with the subduction of the Northern Tianshan Ocean.  相似文献