Determination of Radiogenic 87Sr/86Sr and Stable δ88/86SrSRM987 Isotope Values of Thirteen Mineral,Vegetal and Animal Reference Materials by DS‐TIMS     

Jean‐Michel Brazier  Anne‐Dsire Schmitt  Eric Pelt  Damien Lemarchand  Sophie Gangloff  Tho Tacail  Vincent Balter 《Geostandards and Geoanalytical Research》2020,44(2):331-348

This work presents new ⁸⁷Sr/⁸⁶Sr and δ^88/86Sr_SRM987 isotopic values of thirteen mineral, vegetal and animal reference materials. Except for UB‐N, all our results are consistent with previously published data. Our results highlight intermediate precisions among the best presently published and a non‐significant systematic shift with the calculated δ^88/86Sr_SRM987 mean values for the three most analysed reference materials in the literature (i.e., IAPSO, BCR‐2 and JCp‐1). By comparison with the literature and between two distinct digestions, a significant bias of δ^88/86Sr_SRM987 values was highlighted for two reference materials (UB‐N and GS‐N). It has also been shown that digestion protocols (nitric and multi‐acid) have a moderate impact on the δ^88/86Sr_SRM987 isotopic values for the Jls‐1 reference materials suggesting that a nitric acid digestion of carbonate can be used without significant bias from partial digestion of non‐carbonate impurities. Different δ^88/86Sr_SRM987 values were measured after two independent Sr/matrix separations, according to the same protocol, for a fat‐rich organic reference material (BCR‐380R) and have been related to a potential post‐digestion heterogeneity. Finally, the δ^88/86Sr_SRM987 value differences measured between animal‐vegetal and between coral‐seawater reference materials agree with the previously published results, highlighting an Sr isotopic fractionation along the trophic chain and during carbonate precipitation.  相似文献   

Capture Versus Capture Zones: Clarifying Terminology Related to Sources of Water to Wells          下载免费PDF全文

Paul M. Barlow  Stanley A. Leake  Michael N. Fienen 《Ground water》2018,56(5):694-704

The term capture, related to the source of water derived from wells, has been used in two distinct yet related contexts by the hydrologic community. The first is a water‐budget context, in which capture refers to decreases in the rates of groundwater outflow and (or) increases in the rates of recharge along head‐dependent boundaries of an aquifer in response to pumping. The second is a transport context, in which capture zone refers to the specific flowpaths that define the three‐dimensional, volumetric portion of a groundwater flow field that discharges to a well. A closely related issue that has become associated with the source of water to wells is streamflow depletion, which refers to the reduction in streamflow caused by pumping, and is a type of capture. Rates of capture and streamflow depletion are calculated by use of water‐budget analyses, most often with groundwater‐flow models. Transport models, particularly particle‐tracking methods, are used to determine capture zones to wells. In general, however, transport methods are not useful for quantifying actual or potential streamflow depletion or other types of capture along aquifer boundaries. To clarify the sometimes subtle differences among these terms, we describe the processes and relations among capture, capture zones, and streamflow depletion, and provide proposed terminology to distinguish among them.  相似文献   

Regeneration and utilization of nutrients during collapse of a <Emphasis Type="Italic">Mesodinium rubrum</Emphasis> red tide and its influence on phytoplankton species composition     

Yafeng Zhang  Xiuxian Song  Paul J. Harrison  Sheng Liu  Zhiming Yu  Jinjun Kan  Peiyuan Qian  Hao Liu  Kedong Yin 《中国科学:地球科学(英文版)》2018,61(10):1384-1396

High-biomass red tides occur frequently in some semi-enclosed bays of Hong Kong where ambient nutrients are not high enough to support such a high phytoplankton biomass. These high-biomass red tides release massive inorganic nutrients into local waters during their collapse. We hypothesized that the massive inorganic nutrients released from the collapse of red tides would fuel growth of other phytoplankton species. This could influence phytoplankton species composition. We tested the hypothesis using a red tide event caused by Mesodinium rubrum (M. rubrum) in a semi-enclosed bay, Port Shelter. The red tide patch had a cell density as high as 5.0×10⁵ cells L^?1, and high chlorophyll a (63.71 μg L^?1). Ambient inorganic nutrients (nitrate: \(\rm{NO}_3^-\), ammonium: \(\rm{NH}_4^+\), phosphate: \(\rm{PO}_4^{3-}\), silicate: \(\rm{SiO}_4^{3-}\)) were low both in the red tide patch and the non-red-tide patch (clear waters outside the red tide patch). Nutrient addition experiments were conducted by adding all the inorganic nutrients to water samples from the two patches followed by incubation for 9 days. The results showed that the addition of inorganic nutrients did not sustain high M. rubrum cell density, which collapsed after day 1, and did not drive M. rubrum in the non-red-tide patch sample to the same high-cell density in the red tide patch sample. This confirmed that nutrients were not the driving factor for the formation of this red tide event, or for its collapse. The death of M. rubrum after day 1 released high concentrations of \(\rm{NO}_3^-\), \(\rm{PO}_4^{3-}\), \(\rm{SiO}_4^{3-}\), \(\rm{NH}_4^+\), and urea. Bacterial abundance and heterotrophic activity increased, reaching the highest on day 3 or 4, and decreased as cell density of M. rubrum declined. The released nutrients stimulated growth of diatoms, such as Chaetoceros affinis var. circinalis, Thalassiothrix frauenfeldii, and Nitzschia sp., particularly with additions of \(\rm{SiO}_4^{3-}\) treatments, and other species. These results demonstrated that initiation of M. rubrum red tides in the bay was not directly driven by nutrients. However, the massive inorganic nutrients released from the collapse of the red tide could induce a second bloom in low-ambient nutrient water, influencing phytoplankton species composition.  相似文献   

Soil erosion in the Anthropocene: Research needs   总被引：6，自引：0，他引：6       下载免费PDF全文

Jean Poesen 《地球表面变化过程与地形》2018,43(1):64-84

Soil erosion is a geomorphological and, at the same time, a land degradation process that may cause environmental and property damage, loss of livelihoods and services as well as social and economic disruption. Erosion not only lowers soil quality on‐site, but causes also significant sediment‐related problems off‐site. Given the large number of research papers on this topic, one might therefore conclude that we know now almost everything about soil erosion and its control so that little new knowledge can be added. This conclusion can be refuted by pointing to some major research gaps. There is a need for more research attention to (1) improved understanding of both natural and anthropogenic soil erosion processes and their interactions, (2) scaling up soil erosion processes and rates in space and time, and (3) innovative techniques and strategies to prevent soil erosion or reduce erosion rates. This is illustrated with various case studies from around the world. If future research addresses these research gaps, we will (1) better understand processes and their interactions operating at a range of spatial and temporal scales, predict their rates as well as their on‐site and off‐site impacts, which is academically spoken rewarding but also crucial for better targeting erosion control measures, and (2) we will be in a better position to select the most appropriate and effective soil erosion control techniques and strategies which are highly necessary for a sustainable use of soils in the Anthropocene. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Gully head modelling: A Mediterranean badland case study          下载免费PDF全文

Dino Torri  Jean Poesen  Mauro Rossi  Valerio Amici  Daniele Spennacchi  Cati Cremer 《地球表面变化过程与地形》2018,43(12):2547-2561

Predicting the location of gully heads in various environments is an important step towards predicting gully erosion rates. So far, field data collection and modelling of topographic thresholds for gully head development has mainly focused on gullies that formed in forested areas, rangelands, pastures and cropland. Such information for gullies in badlands however is very scarce. Therefore, this paper aims to extend the database on gully head topographical thresholds through data collection in a badland area and to improve the prediction of gully heads forming at sites with a very low erosion resistance value. For this, we chose a badland site located in central Italy that is characterized by biancana forms and both active and dormant gullies. The definition of the conditions under which present‐day gully heads developed allowed a better modelling of the gully head threshold equation, with modification of a previous model and the exemplification of how to use the updated model. The model shows that the resistance to gully head retreat depends on slope gradient and drainage area at gully heads, land use at the moment of gully development (as numerically expressed using parameters derived from the Runoff Curve Number method), surface rock fragment cover, presence of joints, pipes, and factors/processes affecting detachment rate. This study attempted to better understand environmental conditions that control the development of gully heads in badlands through a combination of field data collection of gully heads, an analysis of land use changes over 10 centuries, focusing on the period 1820–2005, and land use management through repeat photography and a critical examination of historical documents. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Long‐term sediment yield from a small catchment in southern Brazil affected by land use and soil management changes          下载免费PDF全文

Jean P.G. Minella  Gustavo H. Merten  Claúdia A.P. Barros  Rafael Ramon  Alexandre Schlesner  Robin T. Clarke  Michele Moro  Leandro Dalbianco 《水文研究》2018,32(2):200-211

Sediments produced from eroding cultivated land can cause on‐site and off‐site effects that cause considerable economic and social impacts. Despite the importance of soil conservation practices (SCP) for the control of soil erosion and improvements in soil hydrological functions, limited information is available regarding the effects of SCP on sediment yield (SY) at the catchment scale. This study aimed to investigate the long‐term relationships between SY and land use, soil management, and rainfall in a small catchment. To determine the effects of anthropogenic and climatic factors on SY, rainfall, streamflow, and suspended sediment concentration were monitored at 10‐min intervals for 14 years (2002–2016), and the land use and soil management changes were surveyed annually. Using a statistical procedure to separate the SY effects of climate, land use, and soil management, we observed pronounced temporal effects of land use and soil management changes on SY. During the first 2 years (2002–2004), the land was predominantly cultivated with tobacco under a traditional tillage system (no cover crops and ploughed soil) using animal traction. In that period, the SY reached approximately 400 t·km^?2·year^?1. From 2005 to 2009, a soil conservation programme introduced conservation tillage and winter cover crops in the catchment area, which lowered the SY to 50 t·km^?2·year^?1. In the final period (2010–2016), the SCP were partially abandoned by farmers, and reforested areas increased, resulting in an SY of 150 t·km^?2·year^?1. This study also discusses the factors associated with the failure to continue using SCP, including structural support and farmer attitudes.  相似文献   

Assessment of soil factors controlling ephemeral gully erosion on agricultural fields   总被引：1，自引：0，他引：1       下载免费PDF全文

Paul Ollobarren Del Barrio  Miguel A. Campo‐Bescós  Rafael Giménez  Javier Casalí 《地球表面变化过程与地形》2018,43(9):1993-2008

The soil factor is crucial in controlling and properly modeling the initiation and development of ephemeral gullies (EGs). Usually, EG initiation has been related to various soil properties (i.e. sealing, critical shear stress, moisture, texture, etc.); meanwhile, the total growth of each EG (erosion rate) has been linked with proper soil erodibility. But, despite the studies to determine the influence of soil erodibility on (ephemeral) gully erosion, a universal approach is still lacking. This is due to the complex relationship and interactions between soil properties and the erosive process. A feasible soil characterization of EG erosion prediction on a large scale should be based on simple, quick and inexpensive tests to perform. The objective of this study was to identify and assess the soil properties – easily and quickly to determine – which best reflect soil erodibility on EG erosion. Forty‐nine different physical–chemical soil properties that may participate in establishing soil erodibility were determined on agricultural soils affected by the formation of EGs in Spain and Italy. Experiments were conducted in the laboratory and in the field (in the vicinity of the erosion paths). Because of its importance in controlling EG erosion, five variables related to antecedent moisture prior to the event that generated the gullies and two properties related to landscape topography were obtained for each situation. The most relevant variables were detected using multivariate analysis. The results defined 13 key variables: water content before the initiation of EGs, organic matter content, cation exchange capacity, relative sealing index, two granulometric and organic matter indices, seal permeability, aggregates stability (three index), crust penetration resistance, shear strength and an erodibility index obtained from the Jet Test erosion apparatus. The latter is proposed as a useful technique to evaluate and predict soil loss caused by EG erosion. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Achievability of Municipal Solid Waste Compost for Tea Cultivation with Special Reference to Cadmium          下载免费PDF全文

Tanmoy Karak  Ornella Abollino  Ranjit K. Paul  Amrit K. Dutta  Agnese Giacomino  Puja Khare  Romesh K. Boruah 《洁净——土壤、空气、水》2018,46(6)

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Evidence of multiple evaporite recycling processes in a salt‐tectonic context,Sivas Basin,Turkey          下载免费PDF全文

Alexandre Pichat  Guilhem Hoareau  Jean‐Paul Callot  Etienne Legeay  Kaan Sevki Kavak  Sidonie Révillon  Corinne Parat  Jean‐Claude Ringenbach 《地学学报》2018,30(1):40-49

The isotopic composition of evaporites can shed light on their environment of precipitation and their subsequent recycling processes. In this study, we performed Sr, O and S isotopic analyses on evaporitic sulphates in the halokinetic Sivas Basin. The main objectives were to decipher the age and origin of the evaporites responsible for the salt tectonics, and to test whether diapir dissolution acts as the source of younger evaporitic layers in continental mini‐basins. The Sr isotopes demonstrate that the first evaporites precipitated from seawater during the Middle–Late Eocene. The similar isotopic values measured in the halokinetic domain confirm that the Eocene evaporites triggered the salt tectonics and were continuously recycled in Oligo‐Miocene mini‐basins as lacustrine to sabkha evaporites. Modern halite precipitates suggest that the dissolution and recycling of diapiric halite is ongoing. This study demonstrates the efficiency of isotopic analyses in constraining evaporite recycling processes in continental halokinetic domains.  相似文献   

The 1‐million‐year‐old quartz assemblage from Pont‐de‐Lavaud (Centre,France) in the European context          下载免费PDF全文

Jackie Despriée  Marie‐Hélène Moncel  Marta Arzarello  Gilles Courcimault  Pierre Voinchet  Jean‐Jacques Bahain  Christophe Falguères 《第四纪科学杂志》2018,33(6):639-661

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