Riverine dominance of a nearshore marine demersal food web: evidence from stable isotope and C/N ratio analysis     

AM de Lecea  AJ Smit  ST Fennessy 《African Journal of Marine Science》2016,38(1):S181-S192

The Thukela Bank, KwaZulu-Natal, supports a diverse ecosystem and South Africa’s only prawn fishery. Oceanographic studies suggest riverine input is not important for the biology of this system, whereas biological studies suggest the contrary, with prawn catches increasing with increased fluvial run-off. The aim of this study was to determine (i) the importance of riverine and marine organic matter for the Thukela Bank food web; and (ii) whether there are seasonal changes in the Thukela River stable isotope values, and, if so, whether these are reflected in the isotope values of demersal organisms. Estuarine organic matter, sediments and demersal organisms were collected from several sites across the bank in the wet and dry seasons of 2008, 2009 and 2010. Marine particulate organic matter was also collected in 2010 and analysed for δ13C and δ15N, as well as C/N ratios. There were strong seasonal changes in isotopic values of organic matter and fauna, especially faunal δ13C. There was an apparent time-lag in organisms assimilating riverine organic matter isotopic values, with the isotopic signature of demersal organisms reflecting that of riverine organic matter from the previous season, which is likely the result of tissue turnover time. In 2010, Thukela Bank sediment organic matter was of riverine origin and this maintained the demersal food web. We conclude that Thukela River organic matter is an important input to the food web of the Thukela Bank, indicating that any future damming of the catchment area could have serious consequences for this ecosystem.  相似文献   

Hydrogeochemical and Isotopic Study of Groundwater in a Semi-arid Region: Yeniceoba Plain (Cihanbeyli-KONYA), Central Anatolia,Turkey     

Ayla BOZDAG  Güler GOCMEZ 《《地质学报》英文版》2016,90(1):230-241

Groundwater is the most important source of water supply in the Yeniceoba Plain in Central Anatolia,Turkey.An understanding of the geochemical evolution of groundwater is important for the sustainable development of water resources in this region.A hydrogeochemical investigation was conducted in the Plio-Quaternary aquifer system using stable isotopes(δ~(18)O andδD),tritium(~3H),major and minor elements(Ca,Na,K,Mg,Cl,SO_4,NO_3,HCO_3 and Br)in order to identify groundwater chemistry patterns and the processes affecting groundwater mineralization in this system.The chemical data reveal that the chemical composition of groundwater in this aquifer system is mainly controlled by rock/water interactions including dissolution of evaporitic minerals,weathering of silicates,precipitation/dissolution of carbonates,ion exchange,and evaporation.Based on the values of Cl/Br ratio(300 mg/l)in the Plio-Quaternary groundwater,dissolution of evaporitic minerals in aquifer contributes significantly to the high mineralization.The stable isotope analyses indicate that the groundwater in the system was influenced by evaporation of rainfall during infiltration.Low tritium values(generally1 tritium units)of groundwater reflect a minor contribution of recent recharge and groundwater residence times of more than three or four decades.  相似文献   

Geology and Isotope Geochemistry of the Yinchanggou-Qiluogou Pb-Zn Deposit, Sichuan Province, Southwest China   总被引：1，自引：0，他引：1  

LI Bo  ZHOU Jiaxi  LI Yingshu  CHEN Aibing  WANG Ruixue 《《地质学报》英文版》2016,90(5):1768-1779

The Yinchanggou-Qiluogou Pb-Zn deposit,located in the western Yangtze Block,southwest China,is hosted by the Upper Sinian Dengying Formation dolostone.Ore bodies occur in the Qiluogou anticline and the NS-and NNW-trending faults.Sulfide ores mainly consist of sphalerite,pyrite,galena and calcite,with subordinate dolomite and quartz.Seventeen ore bodies have been discovered to date and they have a combined 1.0 million tons of sulfide ores with average grades of 2.27wt%Zn and 6.89wt%Pb.The δD_(H2O-SMOW) and δ~(18)O_(H2O-SMOW) values of fluid inclusions in quartz and calcite samples range from-68.9‰ to-48.7‰ and 7.3‰ to 15.9‰,respectively,suggesting that H_2O in the hydrothermal fluids sourced from metamorphic water.Calcite samples have δ~(13)C_(PDB) values ranging from-6.2‰ to-4.1‰ and δ~(18)O_(SMOW) values ranging from 15.1‰ to 17.4‰,indicating C and O in the hydrothermal fluids likely derived from a mixed source of metamorphic fluids and the host carbonates.The δ~(34)S_(CDT) values of sulfide minerals range from 5.5‰ to 20.3‰,suggesting that thermal chemical reduction of sulfate minerals in evaporates were the most probable source of S in the hydrothermal fluids.The ~(206)Pb/~(204)Pb,~(207)Pb/~(204)Pb and ~(208)Pb/~(204)Pb ratios of sulfide minerals fall in the range of 18.11 to 18.40,15.66 to 15.76 and 38.25 to 38.88,respectively.The Pb isotopic data of the studied deposit plot near the upper crust Pb evolution curve and overlap with the age-corrected Proterozoic basement rocks and the Upper Sinian Dengying Formation hosting dolostone.This indicates that the Pb originated from a mixed source of the basement metamorphic rocks and the ore-hosting carbonate rocks.The ore geology and C-H-O-S-Pb isotopic data suggest that the YinchanggouQiluogou deposit is an unusual carbonate-hosted,strata-bound and epigenetic deposit that derived ore-forming materials from a mixed source of the underlying Porterozoic basements and the Sinian hosting carbonates.  相似文献   

He-Ar-S-Pb Isotopic Compositions of Pyrite: Constraints on the Source of Ore-forming Materials of the Chengchao Skarn Iron Deposit, SE Hubei Province, Eastern China     

LI Wei  XIE Guiqing  ZHU Qiaoqiao 《《地质学报》英文版》2016,90(5):1780-1794

The Chengchao iron deposit,the largest high-grade skarn iron deposit in southeastern Hubei Province,contains considerable amounts of magnetite and by-product anhydrite.To obtain better understanding of the ore-formation process,this study carried out He-Ar-S-Pb multi-isotopic analyses on the pyrites formed during two stages of mineralization.The results indicate that the δ~(34)S values(ranging from 14.0‰ to 17.6‰) of pyrites formed from the two stages have no obvious differences,suggesting that they were not derived from a single magmatic sulfur source.The δ~(34)S values of anhydrite mostly range from 21.9‰ to 28.4‰,similar to that of the Middle Triassic sedimentary anhydrite in the Middle-Lower Yangtze River metallogenic belt(MLYRB).The Pb isotopic compositions of the pyrites of both stages are homogeneous,with values of ~(208)Pb/~(204)Pb,~(207)Pb/~(204)Pb,and~(206)Pb/~(204)Pb being 38.006-38.257,15.523-15.556,and 17.806-18.052,respectively,indicating a mixed crust-mantle source.The He-Ar results exhibit different compositions of the two stages:the ~3He/~4He(R/Ra) and ~(40)Ar/~(36)Ar values for the early-stage pyrite are 0.46-0.63 and 311-322,respectively,whereas the values for late-stage pyrite are 0.23-0.34 and 305-361,respectively.Both stages of pyrites indicate the multiple sources of the ore-forming fluids,with decreasing amount of magmatic water and increasing amount of modified meteoric water(MASW) during fluid evolution.The Triassic evaporites played an important role in the mineralization process.  相似文献   

土壤元素异常成因研究及生态风险评价     

胡省英  黄丹  邓凯文  杨力  李迪 《城市地质》2016,(4):59-65

山区岩石与水系沉积物,对山前平原土壤物质组成具有控制作用。土壤地球化学调查,查明北京某地区土壤存在着大面积同心圆状的镉、铜、铅等多金属元素异常。研究表明,西北侧山区分布着种类繁多的岩浆岩、变质与沉积岩,但与山前土壤具有高度正相关的元素组合特征的主要是燕山期中酸性岩浆杂岩体,而且杂岩体周边及其下游的BY沟水系沉积物中的多金属元素也呈现出明显的高背景含量特征。同时,铅同位素组成亦指示山前平原土壤铅与山区岩浆岩铅、沉积岩铅具有一致的物质来源,从而证实山前土壤多金属元素异常主要来源于山区岩浆杂岩体。由于山前平原土壤呈现为碱性且农田仅种植旱地作物,故富含多金属的土壤对农作物生长的生态风险程度低下。  相似文献   

溶剂萃取法分离锂同位素研究进展   总被引：2，自引：2，他引：0       下载免费PDF全文

肖江  贾永忠  姚颖  石成龙  孙进贺  谢绍雷  景燕 《盐湖研究》2016,24(3):62-72

锂同位素(6Li和7Li)在原子能工业中占据着重要的地位。在众多锂同位素的分离方法和体系中,溶剂萃取法是一种具有较高分离系数,并最有望实现无毒、高效分离的工业生产方法。阐述了溶剂萃取法分离锂同位素的原理,综述了醇类与酮类、烷基膦与膦酸脂类、冠醚类及其它溶剂萃取体系在锂同位素分离中的研究现状及趋势,并展望了溶剂萃取法在锂同位素分离和未来青海、西藏盐湖锂资源高值化利用中的潜在应用前景。  相似文献   

长江口滨岸潮滩底栖泥螺受铅污染的急性毒理试验   总被引：4，自引：0，他引：4  

李丽娜  陈振楼  许世远  毕春娟 《海洋湖沼通报》2005,(2):88-92

为了评价长江口滨岸潮滩沉积物中重金属铅对底栖动物的影响，进行了底栖动物泥螺的24h急性毒理学试验研究。结果表明：泥螺的半致死剂量是0．275g／L，全致死剂量是11．5g／L；对泥螺体内重金属累积量的分析表明：泥螺体内Pb的含量随试验组浓度的增高而增多，试验组的Pb浓度和泥螺累积的Pb含量符合三次函数；泥螺体内Pb的增加对泥螺富集Cu、Zn的影响是使其富集量有所下降，在浓度为4g／L时稍有回升；Pb含量的增加对泥螺富集Cr的影响是在浓度为0．1 1 8g／L时出现富集较大量，说明底栖动物富集的重金属元素问具有一定的协同作用。  相似文献   

冲绳海槽中段表层沉积物物质来源的定量分离:Sr-Nd同位素方法   总被引：16，自引：2，他引：16  

孟宪伟  杜德文  吴金龙 《海洋与湖沼》2001,32(3):319-326

利用1994年85－904航次获取的冲绳海槽中段表层沉积物样品，测定其硅酸盐相的^87Sr/^86Cr和^143Nd/^144Nd比值，以定量研究冲绳海槽中段表层沉积物硅酸盐物质的来源，结果表明，冲绳海槽中段陆坡区表层沉积物硅酸盐相的^87Sr/^86Sr/^143Nd/^144Nd与东海陆架沉物硅酸盐相的^87Sr/^86Sr和^143Nd/^143Nd相当，槽底和东坡沉积物硅酸盐相的^87Sr/^86Cr和^143Nd/^144Nd值介于中国大陆硅酸盐物质和海槽水山碎屑的^87Sr/^86Sr,^143Nd/^144Nd比值之间，并大致具有两端员混合特征，利用以Sr同位素为参数的二端员混合方程进行物源定量分析的结果表明，冲绳海槽中段的西坡和槽底表层沉积物硅酸盐相以陆源物质为主，最大值为91．07％，由西向东，陆源物逐渐减少，在海槽东坡含量最小，最小值为9．93％，火山源物质在东坡含量最高，量大值为64．92％，由东向西，由北向东，火山源物质逐渐减少为零。  相似文献   

Abundance, size distribution, and stable carbon and nitrogen isotopic compositions of marine organic matter isolated by tangential-flow ultrafiltration     

Ronald Benner  Bopaiah Biddanda  Brenda Black  Matthew McCarthy 《Marine Chemistry》1997,57(3-4)

Tangential-flow ultrafiltration was used to isolate particulate and high-molecular-weight dissolved material from seawater collected at various depths and geographic regions of the Pacific and Atlantic Oceans. Ultrafiltration proved to be a relatively fast and efficient method for the isolation of hundreds of milligrams of material. Optical and electron microscopy of the isolated materials revealed that relatively fragile materials were recovered intact. Depth-weighted results of the size distribution of organic matter in seawater indicated that ˜ 75% of marine organic carbon was low-molecular-weight (LMW) dissolved organic carbon (< 1 nm), ˜ 24% was high-molecular-weight (HMW) dissolved organic carbon (1–100 nm), and ˜ 1% was particulate organic carbon (> 100 nm). The distribution of carbon in surface water was shifted to greater relative abundances of larger size fractions, suggesting a diagenetic sequence from macromolecular material to small refractory molecules. The average C:N ratios of particulate organic matter (POM) and HMW dissolved organic matter (DOM) were 7.7 and 16.7, respectively. Differences in C:N ratios between POM and HMW DOM were large and invariant with depth and geographic region, indicating that the aggregation of HMW DOM to form POM must be of minor significance to overall carbon dynamics. The stable carbon isotope composition (δ¹³C) of POM averaged −22.7%. in surface water and −25.2%. in subsurface water. Several possible explanations for the observed isotopic shift with depth were explored, but we were unable to discern the cause. The δ¹³C of HMW DOM samples was relatively constant and averaged −21.7%., indicating a predominantly marine origin for this material. The δ¹⁵N values of POM were highly variable (5.8–15.4%.), and the availability of nitrate in surface waters appeared to be the major factor influencing δ¹⁵N values in the equatorial Pacific. In the upwelling region nitrate concentrations were relatively high and δ¹⁵N values of POM were low, whereas to the north and south of the upwelling nitrate concentrations were low and δ¹⁵N values were high. The δ¹⁵N values of HMW DOM reflected the same trends observed in the POM fraction and provided the first such evidence for biological cycling of dissolved organic nitrogen (DON). Using the observed δ¹⁵N values and an estimate of meridional advection velocity, we estimated a turnover time of 0.3 to 0.5% day⁻¹ for HMW DON. These results suggest a major role for DON in the upper ocean nitrogen cycle.  相似文献   

东海—图们江水中Zn,Cd,Pb,Cu的形式分析          下载免费PDF全文

张首临  李泽林 《海洋与湖沼》1993,24(6):609-615

用防吸附物理涂汞电极反向极谱进行了东海至图们江水中Ｚｎ，Ｃｄ，Ｐｂ，Ｃｕ（１９９１年５－６月）的形式分析研究。结果表明，该４种元素不稳定态的平均浓度分别为５．７，０．０６０，０．０３５，０．６２μｇ／Ｌ，分布较为均匀。该结果证实了痕量金属离子（自由离子及不稳定络离子）的均匀分布规律。有机结合态Ｚｎ，Ｐｂ，Ｃｕ和颗粒态的Ｚｎ，Ｃｕ的较高含量，位于长江口及东海水中。  相似文献