The influence of freeze-thaw cycles on the granulometric composition of Moscow morainic clay   总被引：2，自引：0，他引：2  

Ze Zhang  Vadim V. Pendin  WenJie Feng  ZhongQiong Zhang 《寒旱区科学》2015,7(3):199-205

The freeze-thaw cycling process considerably changes the composition,structure,and properties of soils.Since the grain size is the most important factor in determining soil characteristics,our current research primarily aims to investigate dynamic changes of the soil fraction when exposed to freeze-thaw conditions.We observed two series of Moscow morainic clayey specimens(g QmII):(I) the original series,and(II) the remolded series.We subjected each series of soil specimens to different frequencies of freeze-thaw cycles(3,6,20,and 40 cycles),and we used granulometric tests to analyze both series before and after exposure to freeze-thaw conditions.As a result of our experiments,the granulometric compositions tended to be distributed evenly after 40 freeze-thaw processes(i.e.,content of fraction for 0.1–0.05 mm was increased after 40 freeze-thaw cycles) because the division of coarse grains and the aggregation of fine grains were synchronized during the freeze-thaw process.The soil grains in both series changed bi-directionally.In the original series,changes of the sand grains were conjugated with the clay grains,and in the remolded series,changes of the sand grains were conjugated with the silt grains,because potential energy difference caused the division and aggregation processes to relate to the counteraction process.The even distribution of soil grain size indicated the state of equilibrium or balance.The granulometric compositions were altered the most during the sixth freeze-thaw cycle,because the coefficient of the intensity variation of the grain fineness(Kvar) had its maximum value at that time.  相似文献   

秋季东海溶解态和颗粒态氨基酸的分布与组成_*     

张鹏燕  陈岩  杨桂朋 《海洋与湖沼》2015,46(2)

本文对2012年秋季中国东海31个站位的海水样品中溶解态氨基酸（THAA）和颗粒态氨基酸（PAA）的分布与组成进行了研究。结果表明：表层海水中溶解游离氨基酸(DFAA)的平均浓度为0.12±0.04 μmol/L (0.06~0.19 μmol/L),溶解结合氨基酸(DCAA)的平均浓度为0.61±0.51 μmol/L (0.15~1.79 μmol/L),PAA的平均浓度为0.11±0.06 μmol/L (0.02~0.27 μmol/L)。THAA的水平分布特点大致为近岸高、远岸低;PAA的水平分布特点是近岸海域向远海海域分布呈现逐渐减小的趋势。THAA的垂直分布特点是由表层向底层逐渐降低。DCAA、PAA与Chl-a有很好的相关性,而DFAA与Chl-a的相关性不明显。东海表层海水中THAA的主要组分是天门冬氨酸、谷氨酸、丝氨酸、甘氨酸、苏氨酸及丙氨酸,PAA的主要组分是天门冬氨酸、谷氨酸、丝氨酸、甘氨酸、丙氨酸及亮氨酸。在表层海水中氨基酸是作为一个整体而对海洋生物地球化学过程产生影响的。  相似文献   

Microbial biomass response to different quantities and sources of organic matter in Brazilian coastal sediments          下载免费PDF全文

Cintia O. Quintana  Paula C. de Moraes  Marcos Y. Yoshinaga  Stuart G. Wakeham  Paulo Y. G. Sumida 《Marine Ecology》2015,36(3):766-779

This study investigates the benthic microbial responses to organic matter (OM) variations in quantity and sources in two shallow water bays (Fortaleza and Ubatuba Bays) on the SE coast of Brazil on six occasions during the year. The pelagic and benthic compartments of the bays were evaluated by: (i) nutrients and chlorophyll a (Chl a) in the water column; (ii) quantity and sources of OM in the sediment (Chl a, total organic carbon and total nitrogen and lipid biomarker composition); and (iii) microbial biomass in sediments as an indicator of active benthic response. Although there were changes in water‐column nutrients during the year, Chl a was fairly constant, suggesting a regular supply of microalgae‐derived OM to the sea bottom. Based on the composition of lipid biomarkers in sediments, OM sources were classified as mostly marine and with high contributions of labile (microalgae‐derived) OM. Labile OM composition varied from diatoms in the summer to phytoflagellates in the winter and tended to accumulate in areas protected by physical disturbances in one of the bays. Microbial biomass followed this trend and was 160% higher in protected than in exposed areas. This study suggests that the coupling between labile OM and benthic microbial biomass occurs primarily in protected areas, irrespective of the time of the year. Since meio‐ and macrofaunal assemblages depend upon secondary microbial production within the sediments, this coupling may have an important role for the benthic food‐web.  相似文献   

西沙群岛生物碳酸盐的成因和沉积:来自活体仙掌藻的证据   总被引：1，自引：0，他引：1  

许红  赵新伟  Gregor P. Eberli  LIU Xinyu  朱玉瑞  蔡瑛  LUO Wei  闫桂京  张柏林  魏凯  施剑 《海洋学报(英文版)》2015,34(4):62-73

A recent island survey reveals that the Xuande Atoll and the Yongle Atoll in the Xisha Islands can be classified into one of two systems: the depleted atoll system and growth atoll system; the survey also indicates that the decreased area of several shoals is an unbearable burden for the Xisha Islands, of which the largest island area is 2.13 km2 and the minimum elevation is 1.4 m. According to a survey on the ecological characteristics of Halimeda in the Laolongtou breaker zone of Shidao Island in the Xisha Islands, the green and white living Halimeda are collected,the isotopic ages of 14 C contained in the Halimeda are shown to be 27 years and 55 years, respectively, and carbonate mainly occurs in five types, i.e., luster, segment, sand, sand grain, and marl in the formation. The Halimeda segments mainly provide the carbonate sediments of long-term biogenic deposits in the reef environment and the annual productivity per area is 60–100 g/m2; the characteristics of the microstructure of the Halimeda are analyzed, the aragonite raphide carbonate is deposited and enriched in the cortexes, medullas and cysts, and the Halimeda generally contain major elements such as C, O, Ca, Cl, Mg, K, Na, S and Al, and are rich in trace elements such as tellurium(Te), rhodium(Rh) and strontium. It is believed that the Halimeda grow slowly,including the biotic community of reef corals in the reef areas, thus they possess an environmental remediation capacity, but it takes much time to remedy the environment, and it is necessary to make the law to protect the diversity and vulnerability of the Xisha marine ecology, the ecology of the reef community and the island environment in a scientific way. As indicated in the survey, under the background of global warming and sea-level rise, the discovery of large amounts of Halimeda in the Laolongtou sea area is significant for the natural increase of the depleted atoll system of the Xuande Atoll, while the Halimeda segments represent the primary form of the fossil Halimeda, of which the species can be identified and preserved in great numbers under geological conditions. The Miocene was discovered in large amounts in the Xichen-1 well, therefore the study on the characteristics and mechanism of Halimeda carbonate sediments plays a pivotal role in the formation and construction of organic reefs in the South China Sea as well as oil and gas exploration.  相似文献   

Carbon isotopic fractionation by desorption of shale gases     

《Marine and Petroleum Geology》2015

Geochemical studies of shale gas and conventional reservoirs within the Triassic Yanchang Formation of Xiasiwan and Yongning Field, Ordos Basin show that methane is isotopically depleted in ¹³C as compared to δ¹³C₁ calculated by the Ro based on the relationship between δ¹³C₁ and Ro. Geochemical fractionation during the adsorption/desorption process of shale system may play a significant part in influencing δ¹³C₁ values of shale gas. Two shale core samples from confined coring of the Yanchang Formation were adopted segmented desorption experiments to examine this phenomenon. The results show that the δ¹³C₁ of desorbed gas changes little in the first few phases of the experiments at low desorption levels, but become less negative rapidly when the fraction of desorbed methane exceeds 85%. The desorption process for the last 15% fraction of the methane from the shale samples shows a wide variation in δ¹³C₁ from −49‰ to −33.9‰. Moreover, δ¹³C₁ of all desorbed methane from the shale samples is substantially depleted in ¹³C than that calculated by Ro, according to Stahl and Carey's δ¹³C₁–Ro equation for natural gas generated from sapropelic organic matter. This shows some gases with isotopically enriched in ¹³C cannot be desorbed under the temperature and pressure conditions of the desorption experiments. This observation may be the real reason for the δ¹³C₁ of shale gases and conventional reservoirs becomes more negative in Xiasiwan and Yongning Fields, Ordos Basin. The magnitude of the deviation between the δ¹³C₁ of shale gas and that calculated by Ro may be related to the adsorption capacity of shale or the proportion of absorbed gases. In this way, we may be able to evaluate the relative adsorption capacity of shale in geological conditions by δ¹³C₁ of the shale gas, or by δ¹³C₁ of conventional gas which generated by the shale with certainty. The δ¹³C₁ of conventional gas in Dingbian and Yingwang Fields have no deviation because the TOC value of the hydrocarbon source rock is relatively low.  相似文献   

Evaluation of the “fishing down marine food web” process in the north-west of Persian Gulf(Khuzestan Province) during the period of 2002–2011     

MASHJOOR Sakineh  KAMRANI Ehsan 《海洋学报(英文版)》2015,34(10):103-110

The worldwide increase in commercial fisheries and its impact on ecosystems as well as inefficient fishery management have led to overfishing and frequent breakdown of traditional fish stocks.In this context,an analysis of Khuzestan inshore fisheries data covering the years 2002–2011,was conducted in reliance on testing for occurrence of the fishing down marine food webs(FDMFW) phenomenon in the North of Persian Gulf Large Marine Ecosystem(LME).In this study,the mean trophic level(m TL) and the fishing-in-balance(FIB)-index of Khuzestan landings during this period of time were estimated using the trophic level of 47 fishery resources.Increase in total landings(Y) was observed,which explained the high fishing yield in major fishery resources(especially demersal).Moreover,the moderates decreasing trend in m TL per decade,and the increasing trend in FIB-index were observed.The status of fishery resources in Khuzestan inshore waters(under exploited but not overexploited),the rise in Y,FIB and slightly drop in m TL can be considered as indirect indicators of the fishing impacts on the trophic structure of marine communities.Based on this result,probability occurrence of FDMFW process in Khuzestan inshore waters is low to some extent.However,we suggest that the goal of management programs in Khuzestan inshore waters should prevent the continuance of this trend in the long-term using an ecosystem-based approach.  相似文献   

Grain size composition and transport of sedimentary organic carbon in the Changjiang River (Yangtze River) Estuary and Hangzhou Bay and their adjacent waters     

ZHANG Weiyan  JIN Haiyan  YAO Xuying  JI Zhongqiang  ZHANG Xiaoyu  YU Xiaoguo  ZHANG Fuyuan  GAO Aigen 《海洋学报(英文版)》2015,34(10):46-56

Surface sediments from the Changjiang River(Yangtze River) Estuary,Hangzhou Bay,and their adjacent waters were analyzed for their grain size distribution,organic carbon(OC) concentration,and stable carbon isotope composition(δ13C).Based on this analysis,about 36 surface sediment samples were selected from various environments and separated into sand(0.250 mm,0.125–0.250 mm,0.063–0.125 mm) and silt(0.025–0.063 mm)fractions by wet-sieving fractionation methods,and further into silt-(0.004–0.025 mm) and clay-sized(0.004mm) fractions by centrifugal fractionation.Sediments of six grain size categories were analyzed for their OC andδ13C contents to explore the grain size composition and transport paths of sedimentary OC in the study area.From fine to coarse fractions,the OC content was 1.18%,0.51%,0.46%,0.42%,0.99%,and 0.48%,respectively,while theδ13C was –21.64‰,–22.03‰,–22.52‰,–22.46‰,–22.36‰,and –22.28‰,respectively.In each size category,the OC contribution was 42.96%,26.06%,9.82%,5.75%,7.09%,and 8.33%,respectively.The OC content in clay and fine silt fractions(0.025 mm) was about 69.02%.High OC concentrations were mainly found in offshore modern sediments in the northeast of the Changjiang River Estuary,in modern sediments in the lower estuary of the Changjiang River and Hangzhou Bay,and in Cyclonic Eddy modern sediments to the southwest of the Cheju Island.Integrating the distribution of terrestrial OC content of each grain size category with the δ13C of the bulk sediment indicated that the terrestrial organic material in the Changjiang River Estuary was transported seaward and dispersed to the Cyclonic Eddy modern sediments to the southwest of the Cheju Island via two pathways:one was a result of the Changjiang River Diluted Water(CDW) northeastward extending branch driven by the North Jiangsu Coastal Current and the Yellow Sea Coastal Current,while the other one was the result of the CDW southward extending branch driven by the Taiwan Warm Current.  相似文献   

温度对赤潮异弯藻生长速率及细胞体积和生化组成影响的研究     

王燕  宋洪军  李艳  李瑞香 《中国海洋大学学报(自然科学版)》2015,45(1):41-46

在实验室条件下,研究了温度对赤潮异弯藻生长速率、细胞体积和生化组成的影响。结果表明,赤潮异弯藻在10~30℃之间均能正常生长,25℃时生长速率最高,25℃为其最适生长温度;赤潮异弯藻的细胞体积随着温度的升高大致呈逐渐减小的趋势,10℃时细胞体积最大(823.89μm3),25℃时细胞体积最小(387.98μm3)。进一步分析表明,赤潮异弯藻生长速率与细胞体积(对数值)呈显著的负相关关系(P0.05)。在10~25℃之间,赤潮异弯藻单个细胞的碳、氮含量随着温度的升高呈逐渐减少的趋势,其单位体积细胞的碳、氮含量却呈单峰变化(15℃时结果为峰值)现象;叶绿素a含量在单个细胞和单位体积细胞两个层次上随温度的变化趋势一致,即其在整个温度区间内随着温度的升高均呈逐渐增加的趋势。赤潮异弯藻细胞C∶Chl a和N∶Chl a随着温度的升高呈先减小后增加的趋势,均在10℃时最大,在25℃时最小。  相似文献   

西藏羌塘盆地半岛湖地区索瓦组锶同位素组成与演化     

孙伟  陈明  何江林  曹竣锋  王东 《沉积学报》2015,33(2):265-274

西藏羌塘盆地中生代发育广泛的海相碳酸盐地层,前人对该区地层的对比研究多局限于古生物地层学,本文尝试通过锶同位素地层学方法对上侏罗-下白垩统索瓦组地层进行全球对比。根据锶同位素地层学的基本原理,本文在对样品进行显微组构分析、阴极发光分析、Ca、Si、Sr和Mn等元素含量分析及评估其对同期海水代表性和样品溶解过程合理性的基础上,测试了羌塘盆地半岛湖地区上侏罗-下白垩统锶同位素组成,并建立了相应的演化曲线,进行了全球对比研究。结果表明,样品的锶同位素组成与前人已公布的同期海水锶同位素组成数据较为接近,其演化曲线与国际上已公布的锶同位素演化曲线有着较好的可对比性,晚侏罗-早白垩世时期全球海平面的变化和侵蚀作用的强弱是控制锶同位素演化曲线的主要因素。此外,通过对索瓦组海相碳酸盐锶同位素的研究,我们认为索瓦组的顶部可能延伸到早白垩世欧特里夫期,近而说明了羌塘盆地在早白垩世欧特里夫期还存在大规模的海相地层。  相似文献   

西秦岭温泉斑岩钼矿床岩浆-热液演化   总被引：5，自引：3，他引：2  

邱昆峰  宋开瑞  宋耀辉 《岩石学报》2015,31(11):3391-3404

西秦岭北缘广泛出露印支期中酸性侵入岩和相关的斑岩-矽卡岩矿床。温泉矿床位于该矿带东段,是其内已探明规模最大的斑岩钼矿床。温泉矿床发育多阶段热液脉体,黄铁矿作为其中的贯通性金属硫化物,其化学组成蕴含着岩浆-热液演化及金属沉淀过程等诸多信息,对于斑岩系统模型的厘定具有重要意义。温泉矿床热液脉体时序为:钾长石-黑云母-石英脉(A脉)、石英-黄铜矿脉、石英-辉钼矿脉(B脉)和石英-绢云母-黄铁矿脉(D脉)。A脉是斑岩系统岩浆-热液演化的最早期脉体,主要矿物组合为钾长石+黑云母+石英+黄铁矿±磁铁矿±磷灰石±黄铜矿,代表了引起早期基性岩浆矿物被蚀变为黑云母的流体通道;B脉与钾长石化蚀变关系密切,围岩中斜长石斑晶大量被蚀变为钾长石;石英-辉钼矿脉切割所有早期黑云母化-钾化蚀变阶段的石英-硫化物网脉,并形成于所有斑岩侵位之后,少量黄铁矿和黄铜矿共生于辉钼矿裂隙及边部;D脉是斑岩系统岩浆-热液成矿作用的最晚期事件,其主要被黄铁矿和石英及少量黄铜矿填充,发育晚期的绢英岩化和泥化蚀变,长石多发生破坏性蚀变。四个阶段石英网脉中黄铁矿电子探针分析显示,A脉的黄铁矿中Cu、Mo和Au含量均较低,有少量的金属硫化物(黄铁矿+黄铜矿)沉淀,但通常不能形成规模矿体;石英-黄铜矿脉的黄铁矿中Cu含量明显较高,且多与高品位Cu矿体的空间产出位置相一致,可能是斑岩系统伴随钾化蚀变作用主要的铜沉淀阶段;B脉的黄铁矿中Mo含量明显较高,与高品位钼矿体空间产出关系密切,可能代表了斑岩系统钼成矿作用的主要阶段;D脉的黄铁矿中Au含量明显升高,可能代表了金在斑岩系统岩浆-热液成矿作用的最晚期事件中的沉淀。  相似文献