Distribution of organic carbon in sediments and its influences on adjacent sea area in the turbidity maximum of Changjiang Estuary in China   总被引：2，自引：0，他引：2  

GAO Jianhu  WANG Yaping  PAN Shaoming  ZHANG Rui  LI Jun  BAI Fenglong 《海洋学报(英文版)》2008,27(4):83-94

Distributions and sources of total organic carbon （TOC）in seabed sediments and their implications for hydrodynamics are analyzed, in the turbidity maximum of the Changjiang Estuary. Ecology ecoenvironmental effects of estuary water on the continuously increasing terrigenous organic carbon from the Changjiang River are also explored through variations of organic carbon content and water quality indicators. Results show that, hydrodynamics exert important influences on distributions of organic carbon in the tur- bidity maximum of Changjiang Estuary. For their redistribution effect of terrigenous organic carbon within the moving layer in the whole region, variations from land to sea are not indicated by surficial and vertical average values of TOC and total nitrogen （TN） contents in core sediment, as well as organic stable carbon isotopes in surface sediments. However, on the long-time scale, the trend of terrigenous organic carbon decreasing from land to sea is still displayed by variations of stable carbon isotopic average values becoming heavier from land to sea. Previous studies have shown that high content of Chl a cannot appear in the Changjiang Estuary in despite of adequate nourishment supply, because photosynthesis of phytoplankton is constrained by high suspended sediment concentration（SSC）. However, an area with a high content of Chl a occurs, which may be caused by resuspended benthic algae with bottom fine grain-size sediments. Tremendous pressures are imposed on the environment of Changjiang Estuary, because of uhrophication trends and special hydrodynamics. Phytoplankton bloom area tends to extend from the outer sea to the mouth of Changjiang River.  相似文献   

墨西哥湾布什山冷泉碳酸盐岩沉积岩石学及地球化学     

邸鹏飞  冯东  陈多福  Harry H Roberts 《海洋地质与第四纪地质》2009,(2)

对墨西哥湾布什山采集的7块冷泉碳酸盐岩样品进行了沉积岩石学及地球化学研究,结果表明:冷泉碳酸盐岩以结壳的形式产出,结壳中双壳类和管状蠕虫等冷泉生物碎屑发育,结壳主要由泥晶、微晶和亮晶文石组成(含量89%～99%,平均94%)。碳酸盐岩13C中等亏损(δ13C最负值为-29.4‰,PDB),表明碳的来源主要是非甲烷的碳烃化合物,18O相对富集(δ18O为+2.4‰～+5.0‰,PDB),可能与原地水合物分解形成富集18O的孔隙水有关。碳酸盐矿物相(5%硝酸可溶部分)的稀土元素总量较低(0.40×10-6～20.85×10-6),稀土元素Ce异常特征和页岩标准化配分模式在不同样品、甚至同一样品结晶程度不同的碳酸盐矿物相(泥晶、微晶和亮晶)中变化显著,表明布什山冷泉碳酸盐岩形成过程中氧化还原条件复杂多变,控制氧化环境变化的主要因素可能是流体的渗漏速率。  相似文献   

低层大气季节变化及与黄海雾季的关系   总被引：5，自引：1，他引：4  

张苏平  杨育强  王新功  魏建苏 《中国海洋大学学报(自然科学版)》2008,38(5)

根据2005～2006年青岛气象台逐日L波段探空雷达资料和地面观测资料,计算、分析了低层大气湍流混合高度、湍流混合强度和温度层结的季节变化,并分析了其与黄海海雾季节变化的关系.结果表明:温度层结、湍流强度和高度均有明显的季节变化,这些变化与海雾的季节变化密切关联.春、夏季节湍流强度较强,湍流混合高度相对较低,有利于近海面的凝结水汽在低空聚集而形成雾.雾季典型的层结结构是"上稳下湍",即:近地(海)面至150 m左右为条件性不稳定,其上方为大约400 m厚的稳定层.盛雾期稳定层的稳定性减弱,湍流强度加强.另外,黄海雾季由7月最盛到8月突然结束,与东海雾季逐渐结束明显不同.8月黄海终雾期迅速的原因与风向的突然转变有关.偏东风为整个黄海带来较冷的空气,使条件性不稳定发展,雾季终止.风向的突然转变与区域性海陆热性质差异和大尺度背景环流的调整有关.  相似文献   

Spatiotemporal Distributions of δD in Atmospheric Water Vapor Based on TES Data During 2004-2009     

ZHANG Xinping  ZHANG Xinzhu  GUAN Huade  HUANG Yimin  WU Huawu 《Acta Meteorologica Sinica》2012,26(6):683-699

The spatial and temporal distributions of the stable isotopes such as HD16O (or 1H2H16O, or HDO) and H218O in atmospheric water vapor are related to evaporation in source places, vapor condensation during transport, and vapor convergence and divergence, and thus provide useful information for investigation and understanding of the global water cycle. This paper analyzes spatiotemporal variations of the content of iso- tope HDO (i.e., δD), in atmospheric water vapor, namely, δDv, and the relationship of δDv with atmospheric humidity and temperature at different levels in the troposphere, using the HDO and H2O data retrieved from the Tropospheric Emission Spectrometer (TES) at seven pressure levels from 825 to 100 hPa. The results indicate that δDv has a clear zonal distribution in the troposphere and a good correspondence with atmospheric precipitable water. The results also show that δDv decreases logarithmically with atmospheric pressure and presents a decreasing trend from the equator to high latitudes and from lands to oceans. Sea- sonal changes of δDv exhibit regional differences. The spatial distribution and seasonal variation of δDv in the low troposphere are consistent with those in the middle troposphere, but opposite situations occur from the upper troposphere to the lower stratosphere. The correlation between δDv and temperature has a similar distribution pattern to the correlation between δDv and precipitable water in the troposphere. The stable isotope HDO in water vapor (δDv), compared with that in precipitation (δDp), is of some differences in spatial distribution and seasonal variation, and in its relationship with temperature and humidity, in- dicating that the impacts of stable isotopic fractionation and atmospheric circulation on the two types of stable isotopes are different.  相似文献   

The isotope hydrology of the Muskoka River Watershed,Ontario, Canada     

April L. James  Emily Dusome  Tim Field  Huaxia Yao  Chris McConnell  Andy Beaton  Arghavan Tafvizi 《水文研究》2020,34(4):914-926

Stable isotope tracers of δ¹⁸O and δ²H are increasingly being applied in the study of water cycling in regional-scale watersheds in which human activities, like river regulation, are important influences. In 2015, δ¹⁸O and δ²H were integrated into a water quality survey in the Muskoka River Watershed with the aim to provide new regional-scale characterization of isotope hydrology in the 5,100-km² watershed located on the Canadian Shield in central Ontario, Canada. The forest dominated region includes ~78,000 ha of lakes, 42 water control structures, and 11 generating stations, categorized as “run of river.” Within the watershed, stable isotope tracers have long been integrated into hydrologic process studies of both headwater catchments and lakes. Here, monthly surveys of δ¹⁸O and δ²H in river flow were conducted in the watershed between April 2015 and November 2016 (173 surface water samples from 10 river stations). Temporal patterns of stable isotopes in river water reflect seasonal influences of snowmelt and summer-time evaporative fractionation. Spatial patterns, including differences observed during extreme flood levels experienced in the spring of 2016, reflect variation in source contributions to river flow (e.g., snowmelt or groundwater versus evaporatively enriched lake storage), suggesting more local influences (e.g., glacial outwash deposits). Evidence of combined influences of source mixing and evaporative fractionation could, in future, support application of tracer-enabled hydrological modelling, estimation of mean transit times and, as such, contribute to studies of water quality and water resources in the region.  相似文献   

Estimation of mean water transit time on a steep hillslope in South Korea using soil moisture measurements and deuterium excess          下载免费PDF全文

Sanghyun Kim  Sungwon Jung 《水文研究》2014,28(4):1844-1857

A method for estimating daily mean transit time (DMTT) within a soil layer was proposed using field measurements of soil moisture. Vertical profiles of soil moisture time series were used for storage estimation. Water fluxes were evaluated through matrix and bypass flow. Variations in soil moisture and soil thickness were used to evaluate matrix flow. Exponential decay in depth of macropores was also used for bypass flow approximation. DMTT evaluation was compared to results obtained from a stable water isotope model using two years of data acquired on a steep granite hillslope in the Sulmachun watershed, South Korea. Various uncertainties in transit time evaluation such as model structure, non‐stationary assumption and data acquisition of existing approaches can be accounted for in the proposed methodology, and the flowpath contribution can be further configured in conjunction with hydrometric measurements. Probability density functions of isotope analyses were partially explained by transit time distributions that were based on soil moisture measurements. Supplementary sensitivity analyses for uncertainty configurations indicate that matrix flow is the primary process in determining transit time distribution while the impact of bypass flow is minor. The feasibility of a DMTT approach over isotope‐based methodologies highlights not only the strength of this proposed method, both in cost and time, but also its further application potential for existing soil moisture measurements. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Simulating water temperatures and stratification of a pre‐alpine lake with a hydrodynamic model: calibration and sensitivity analysis of climatic input parameters          下载免费PDF全文

Thomas Bueche  Mark Vetter 《水文研究》2014,28(3):1450-1464

We report on the calibration of the one‐dimensional hydrodynamic lake model Dynamic Reservoir Simulation Model to simulate the water temperature conditions of the pre‐alpine Lake Ammersee (southeast Germany) that is a representative of deep and large lakes in this region. Special focus is given to the calibration in order to reproduce the correct thermal distribution and stratification including the time of onset and duration of summer stratification. To ensure the application of the model to investigate the impact of climate change on lakes, an analysis of the model sensitivity under stepwise modification of meteorological input parameters (air temperature, wind speed, precipitation, global radiation, cloud cover, vapour pressure and tributary water temperature) was conducted. The total mean error of the calibration results is ?0.23 °C, the root mean square error amounts to 1.012 °C. All characteristics of the annual stratification cycle were reproduced accurately by the model. Additionally, the simulated deviations for all applied modifications of the input parameters for the sensitivity analysis can be differentiated in the high temporal resolution of monthly values for each specific depth. The smallest applied alteration to each modified input parameter caused a maximum deviation in the simulation results of at least 0.26 °C. The most sensitive reactions of the model can be observed through modifications of the input parameters air temperature and wind speed. Hence, the results show that further investigations at Lake Ammersee, such as coupling the hydrodynamic model with chemo‐dynamic models to assess the impact of changing climate on biochemical conditions within lakes, can be carried out using Dynamic Reservoir Simulation Model. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Contrasting carbon export dynamics of human impacted and pristine tropical catchments in response to a short‐lived discharge event          下载免费PDF全文

Adrian M. Bass  N.C. Munksgaard  M. Leblanc  S. Tweed  M.I. Bird 《水文研究》2014,28(4):1835-1843

Utilising newly available instrumentation, the carbon balance in two small tropical catchments was measured during two discharge events at high temporal resolution. Catchments share similar climatic conditions, but differ in land use with one draining a pristine rainforest catchment, the other a fully cleared and cultivated catchment. The necessity of high resolution sampling in small catchments was illustrated in each catchment, where significant chemical changes occurred in the space of a few hours or less. Dissolved and particulate carbon transport dominated carbon export from the rainforest catchment during high flow, but was surpassed by degassing of CO₂ less than 4 h after the discharge peak. In contrast, particulate organic carbon dominated export from the cleared catchment, in all flow conditions with CO₂ evasion accounting for 5–23% of total carbon flux. Stable isotopes of dissolved inorganic carbon (DIC) in the ephemeral rainforest catchment decreased quickly from ~1.5 ‰ to ~ ?16 ‰ in 5 h from the flood beginning. A two‐point mixing model revealed that in the initial pulse, over 90% of the DIC was of rainwater origin, decreasing to below 30% in low flow. In the cultivated catchment, δ¹³C_DIC values varied significantly less (?11.0 to ?12.2 ‰) but revealed a complex interaction between surface runoff and groundwater sources, with groundwater DIC becoming proportionally more important in high flow, due to activation of macropores downstream. This work adds to an increasing body of work that recognises the importance of rapid, short‐lived hydrological events in low‐order catchments to global carbon dynamics. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Spatial,seasonal, and source variability in the stable oxygen and hydrogen isotopic composition of tap waters throughout the USA          下载免费PDF全文

Jurate M. Landwehr  Tyler B. Coplen  David W. Stewart 《水文研究》2014,28(21):5382-5422

To assess spatial, seasonal, and source variability in stable isotopic composition of human drinking waters throughout the entire USA, we have constructed a database of δ¹⁸O and δ²H of US tap waters. An additional purpose was to create a publicly available dataset useful for evaluating the forensic applicability of these isotopes for human tissue source geolocation. Samples were obtained at 349 sites, from diverse population centres, grouped by surface hydrologic units for regional comparisons. Samples were taken concurrently during two contrasting seasons, summer and winter. Source supply (surface, groundwater, mixed, and cistern) and system (public and private) types were noted. The isotopic composition of tap waters exhibits large spatial and regional variation within each season as well as significant at‐site differences between seasons at many locations, consistent with patterns found in environmental (river and precipitation) waters deriving from hydrologic processes influenced by geographic factors. However, anthropogenic factors, such as the population of a tap's surrounding community and local availability from diverse sources, also influence the isotopic composition of tap waters. Even within a locale as small as a single metropolitan area, tap waters with greatly differing isotopic compositions can be found, so that tap water within a region may not exhibit the spatial or temporal coherence predicted for environmental water. Such heterogeneities can be confounding factors when attempting forensic inference of source water location, and they underscore the necessity of measurements, not just predictions, with which to characterize the isotopic composition of regional tap waters. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.  相似文献   

Climate warming alters thermal stability but not stratification phenology in a small north‐temperate lake          下载免费PDF全文

A. M. Paterson  E. A. Stainsby  N. Michelutti  H. Yao  J. A. Rusak  R. Ingram  C. McConnell  J. P. Smol 《水文研究》2014,28(26):6309-6319

Recent climate change represents one of the most serious anthropogenic threats to lake ecosystems in Canada. As meteorological and hydrological conditions are altered by climate change, so too are physical, chemical and biological properties of lakes. The ability to quantify the impact of climate change on the physical properties of lakes represents an integral step in estimating future chemical and biological change. To that end, we have used the dynamic reservoir simulation model, a one‐dimensional vertical heat transfer and mixing model, to hindcast and compare lake temperature‐depth profiles against 30 years of long‐term monitoring data in Harp Lake, Ontario. These temperature profiles were used to calculate annual (June–September) thermal stability values from 1979 to 2009. Comparisons between measured and modelled lake water temperature and thermal stability over three decades showed strong correlation (r² > 0.9). However, despite significant increases in modelled thermal stability over the 30 year record, we found no significant change in the timing of the onset, breakdown or the duration of thermal stratification. Our data suggest that increased air temperature and decreased wind are the primary drivers of enhanced stability in Harp Lake since 1979. The high‐predictive ability of the Harp Lake dynamic reservoir simulation model suggests that its use as a tool in future lake management projects is appropriate. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献