Long-term hydrological,biogeochemical, and climatological data from Walker Branch Watershed,East Tennessee,USA

In 1967, the original Walker Branch Watershed (WBW) project was established to study elemental cycling and mass balances in a relatively unimpacted watershed. Over the next 50+ years, findings from additional experimental studies and long-term observations on WBW advanced understanding of catchment hydrology, biogeochemistry, and ecology and established WBW as a seminal site for catchment science. The 97.5-ha WBW is located in East Tennessee, USA, on the U.S. Department of Energy's Oak Ridge Reservation. Vegetation on the watershed is characteristic of an eastern deciduous, second-growth forest. The watershed is divided into two subcatchments: the West Fork (38.4 ha) and the East Fork (59.1 ha). Headwater streams draining these subcatchments are fed by multiple springs, and thus flow is perennial. Stream water is high in base cations due to weathering of dolomite bedrock and nutrient concentrations are low. Long-term observations of climate, hydrology, and biogeochemistry include daily (1969–2014) and 15-min (1994–2014) stream discharge and annual runoff (1969–2014); hourly, daily, and annual rainfall (1969–2012); daily climate and soil temperature (1993–2010); and weekly stream water chemistry (1989–2013). These long-term datasets are publicly available on the WBW website (https://walkerbranch.ornl.gov/long-term-data/ ). While collection of these data has ceased, related long-term measurements continue through the National Ecological Observatory Network (NEON), where WBW is the core terrestrial and aquatic site in the Appalachian and Cumberland Plateau region (NEON's Domain 7) of the United States. These long-term datasets have been and will continue to be important in evaluating the influence of climatic and environmental drivers on catchment processes.     

Metals discharged during different flow conditions from a mixed agricultural‐forest catchment (NW Spain)

Metal loads were determined from water samples collected under different streamflow conditions (baseflow and storm events) in a rural catchment (NW Spain) during 4 years. A study at annual, seasonal and storm‐event scales was carried out. In all analysed scales, the export order was Fe > Al > Mn > Zn > Cu. A high inter‐annual, seasonal and storm‐event scale variability of metal load was observed. The total metal loads in stream were higher during baseflow conditions than during storm events, which only represented 4% of the duration of the study period and 25% of streamflow. During storm events, both Al and Fe loads accounted 45% of the total load of the study period, whereas Mn, Cu and Zn loads represented 42%, 33% and 24%, respectively. This highlights the role of high flows on metal export. Only four big events exported around 30% of load of each metal transported in events. At all time scales, a prevalence of export of particulate metals over dissolved metals was observed, more pronounced for Al, Fe and Mn than for Cu and Zn. The export of metals in the Corbeira catchment is influenced by runoff and, to a lesser extent, by the rainfall amount. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluating suspended sediment and turbidity reduction projects in a glacially conditioned catchment through dynamic regression and fluvial process-based modelling

Elevated turbidity (T_n) and suspended sediment concentrations (SSC) during and following flood events can degrade water supply quality and aquatic ecosystem integrity. Streams draining glacially conditioned mountainous terrain, such as those in the Catskill Mountains of New York State, are particularly susceptible to high levels of T_n and SSC sourced from erosional contact with glacial-related sediment. This study forwards a novel approach to evaluate the effectiveness of stream restoration best management practices (BMPs) meant to reduce stream T_n and SSC, and demonstrates the approach within the Stony Clove sub-basin of the Catskills, a water supply source for New York City. The proposed approach is designed to isolate BMP effects from natural trends in T_n and SSC caused by trends in discharge and shifts in average T_n or SSC per unit discharge (Q) following large flood events. We develop Dynamic Linear Models (DLMs) to quantify how T_n-Q and SSC-Q relationships change over time at monitoring stations upstream and downstream of BMPs within the Stony Clove and in three other sub-basins without BMPs, providing observational evidence of BMP effectiveness. A process-based model, the River Erosion Model, is then developed to simulate natural, hydrology-driven SSC-Q dynamics in the Stony Clove sub-basin (absent of BMP effects). We use DLMs to compare the modelled and observed SSC-Q dynamics and isolate the influence of the BMPs. Results suggest that observed reductions in SSC and T_n in the Stony Clove sub-basin have been driven by a combination of declining streamflow and the installed BMPs, confirming the utility of the BMPs for the monitored hydrologic conditions.     

北部湾沉积物粘土矿物分布特征及其环境意义

本文以南海北部湾SO-31沉积柱为研究对象,研究了14C年代学和粘土矿物学特征,并对部分全球气候事件进行了对比,为古环境、古气候的恢复提供基础资料,也为全球重大气候事件在该区域的响应提供信息。结果显示全新世以来地层沉积正常,平均沉积速率为0.57mm/a。粘土成分主要由蒙脱石、伊利石、高岭石和绿泥石组成,组合类型为蒙脱石-伊利石-高岭石-绿泥石型。全新世以来环境气候演变可划分为五个阶段:低温期阶段、干湿交替的寒冷气候阶段、逐渐升温阶段、干旱温暖气候阶段、湿热阶段。气候在每个阶段背景下还存在一些次级波动,总体趋势为干湿交替,温度逐渐上升。由于海域环境及矿物指标的影响,北部湾SO-31沉积柱粘土矿物记录的降温事件时间比其他指标记录的新仙女木降温事件发生时间滞后500~800a。     

The Upstream “Strong Signals” of the Water Vapor Transport over the Tibetan Plateau during a Heavy Rainfall Event in the Yangtze River Basin

A heavy rainfall event that occurred over the middle and lower reaches of the Yangtze River Basin(YRB) during July11–13 2000 is explored in this study. The potential/stream function is used to analyze the upstream "strong signals" of the water vapor transport in the Tibetan Plateau(TP). The studied time period covers from 2000 LST 5 July to 2000 LST 15 July(temporal resolution: 6 hours). By analyzing the three-dimensional structure of the water vapor flux, vorticity and divergence prior to and during the heavy rainfall event, the upstream "strong signals" related to this heavy rainfall event are revealed. A strong correlation exists between the heavy rainfall event in the YRB and the convective clouds over the TP. The "convergence zone" of the water vapor transport is also identified, based on correlation analysis of the water vapor flux two days and one day prior to, and on the day of, the heavy rainfall. And this "convergence zone" coincides with the migration of the maximum rainfall over the YRB. This specific coupled structure actually plays a key role in generating heavy rainfall over the YRB. The eastward movement of the coupled system with a divergence/convergence center of the potential function at the upper/lower level resembles the spatiotemporal evolution of the heavy rainfall event over the YRB. These upstream "strong signals" are clearly traced in this study through analyzing the three-dimensional structure of the potential/stream function of upstream water vapor transport.     

Delineation and assessment of Central Indian Suture through lineament extraction approach using Remote Sensing and Geographic Information System

Lineament extraction approach allowed mapping of larger number of lineaments in a classical manner in tectonic and structural studies. In the present study, various techniques were adopted to extract lineaments using Landsat ETM+ images. To remove the biasness of the images, some pre-processing techniques like stream ordering, band differencing, colour texturing were employed to enhance the edges of the structural features. Extracted lineaments and its distribution and orientation were mapped using ArcGIS Spatial analyst tool. Results of the study showed maximum number of lineaments were oriented in the ENE–SWS direction with 63° overall inclination. Accuracy assessment and validation were made with respect to visual interpretation and overlaying the lineament on Digital Topographic Model as well as with respect to an existing geological lineament map of the study site. The result of accuracy assessment indicates higher compatibility of Central Indian Suture with the geological map of the study area.     

阿根廷米纳毕戈塔地区水系沉积物采样粒度试验研究

中国地质调查局与阿根廷地质矿产调查局合作在阿根廷西北部米纳毕戈塔地区进行1︰25万水系沉积物测量,该区属于干旱-半干旱高寒山区,为突出找矿效果,消除或减少风积物干扰,需要确定适合于该区的水系沉积物采样粒度。为此,在该区选择一个有已知矿床的1︰5万图幅进行采样粒度试验,分别选择10~60目、-60目、60~80目、-80目4个粒度级进行粒度试验;根据我国区域地球化学勘查规范,每个粒度分析39种元素。结果表明,大部分元素在4种粒度水系沉积物中的分布形态基本一致,都能够较好地反映出区内已知矿床,说明采用的采样方法可以有效地避免风成砂干扰;金、银、铜、锡等成矿元素在4种粒度中的分布略有差异,10~60目的金、铜和锡异常对已知矿体的反应更清晰准确。因此,本区水系沉积物地球化学测量的最佳采样粒度是10~60目。根据本次试验结果,中-阿地调局在本区联合开展1︰25万水系沉积物地球化学测量时采用了10~60目水系沉积物作为采样介质,取得了很好的效果。这是本区第一次进行水系沉积粒度试验,对本区将来的地球化学调查和研究具有指导意义。     

电感耦合等离子体质谱法(ICP-MS)测定水系沉积物中的铌钽锆铪

建立电感耦合等离子体质谱法(ICP-MS)测定水系沉积物中铌、钽、锆、铪四种元素的分析方法。将样品与氢氧化钠、过氧化钠混合物放入高温炉中,熔融分解完全,用热水提取,过滤后弃去滤液,将滤纸及沉淀用酒石酸-盐酸溶液溶解,稀释至刻度测定。方法检出限(3s)为:LD(Nb)=0.08μg/g,LD(Ta)=0.04μg/g,LD(Zr)=0.5μg/g,LD(Hf)=0.04μg/g,精密度(RSD%,n=6)为:0.84%~4.21%。该测定方法具有灵敏度高、精密度好、分析速度快、线性范围宽、操作性强等优势。采用该方法对国家一级标准物质进行测定表明,其结果与标准值吻合。此方法已在实际地质调查样品分析中得到应用。     

Distribution and relative density of cetaceans in the Hauraki Gulf,New Zealand

Understanding species distributions, and how they change in space and time, is vital when prioritising conservation or management initiatives. We assessed the distribution and density patterns of common dolphins (Delphinus sp.), bottlenose dolphins (Tursiops truncatus) and Bryde’s whales (Balaenoptera edeni) in the Hauraki Gulf, New Zealand. Dedicated boat-based surveys were conducted in the inner Hauraki Gulf (IHG) and off Great Barrier Island (GBI) during 2010–2012. Generalised linear models were used to investigate temporal changes in relative densities and kernel density estimation was implemented to examine spatial trends. Common dolphins were widely distributed during all seasons, with higher densities observed during winter and spring in the IHG but during autumn off GBI. There was inter-annual variation in Bryde’s whale distribution, with high densities recorded off GBI in 2011. Bottlenose dolphins were infrequently sighted in the IHG but regularly encountered off GBI, with the highest densities during spring and summer.