Strontium in coral aragonite: 1. Characterization of Sr coordination by extended absorption X-ray fine structure

Aragonite was analyzed from Porites lobata, Pavona gigantea, Pavona clavus, and Montastrea annularis corals by Sr K-edge extended absorption X-ray fine structure (EXAFS) and compared with aragonite, strontianite, and mechanically mixed standards. Bulk analyses were performed and data compared with equivalent micro-EXAFS analyses on small (∼400 μm³) analytical volumes with a microfocused X-ray beam. As a result of the architecture of the coral skeleton, the crystals within the microanalytical volume are not randomly oriented, and the microanalytical X-ray absorption spectra show orientational dependence. However, refinement of bulk and microanalytical data provided indistinguishable interatomic distances and thermal vibration parameters in the third shell (indicative of Sr speciation). The Sr K-edge EXAFS of all the coral samples refine, within error, to an ideally substituted Sr in aragonite, in contrast to previous studies, in which significant strontianite was reported. Some samples from that study were also analyzed here. Strontianite may be less widely distributed in corals than previously thought.     

The role of rainfall temporal and spatial averaging in seasonal simulations of the terrestrial water balance

The partitioning of rainfall into surface runoff and infiltration influences many other aspects of the hydrologic cycle including evapotranspiration, deep drainage and soil moisture. This partitioning is an instantaneous non-linear process that is strongly dependent on rainfall rate, soil moisture and soil hydraulic properties. Though all rainfall datasets involve some degree of spatial or temporal averaging, it is not understood how this averaging affects simulated partitioning and the land surface water balance across a wide range of soil and climate types. We used a one-dimensional physics-based model of the near-surface unsaturated zone to compare the effects of different rainfall discretization (5-min point-scale; hourly point-scale; hourly 0.125° gridded) on the simulated partitioning of rainfall for many locations across the United States. Coarser temporal resolution rainfall data underpredicted seasonal surface runoff for all soil types except those with very high infiltration capacities (i.e., sand, loamy sand). Soils with intermediate infiltration capacities (i.e., loam, sandy loam) were the most affected, with less than half of the expected surface runoff produced in most soil types when the gridded rainfall dataset was used as input. The impact of averaging on the water balance was less extreme but non-negligible, with the hourly point-scale predictions exhibiting median evapotranspiration, drainage and soil moisture values within 10% of those predicted using the higher resolution 5-min rainfall. Water balance impacts were greater using the gridded hourly dataset, with average underpredictions of ET up to 27% in fine-grained soils. The results suggest that “hyperresolution” modelling at continental to global scales may produce inaccurate predictions if there is not parallel effort to produce higher resolution precipitation inputs or sub-grid precipitation parameterizations.     

Preface to the special issue on electromagnetic phenomena related to seismic and volcanic activities from EMSEV in 2016

<正>EMSEV,Electromagnetic Studies of Earthquake and Volcanoes,set up in 2002,is a joint academic organization by multi-associations in IUGG(International Union of Geodesy and Geophysics),including IAGA(International Association of Geomagnetism and Aeronomy),IASPEI(International Association of Seismology and Physics of the Earth’s Interior),IAVCEI(International Association of Volcanology and Chemistry of the Earth’s Interior).On     

Notes on the origin of inertinite macerals in coals: Observations on the importance of fungi in the origin of macrinite

Macrinite is a, generally, rare inertinite maceral, often incorporating remnants and fragments of other macerals, including vitrinite, liptinite, and other inertinite. The associated inertinites include multiple forms of funginite. Funginite is also commonly found in association with vitrinite of slightly elevated reflectance and with degraded varieties of vitrinite. Together with the highly degraded macrinite, the latter two associations are here inferred to be part of a continuum of fungal and microbial degradation of peat. In any case, the origin of some macrinite is potentially distinct from that of inertinite generated by fire.     

Climate Change Impacts for the Conterminous USA: An Integrated Assessment

During this century global warming will lead to changes in global weather and climate, affecting many aspects of our environment. Agriculture is the sector of the United States economy most likely to be directly impacted by climatic changes. We have examined potential changes in dryland agriculture (Part 3) and in water resources necessary for crop production (Part 4) in response to a set of climate change scenarios. In this paper we assess to what extent, under these same scenarios, water supplies will be sufficient to meet the irrigation requirement of major grain crops in the US. In addition, we assess the overall impacts of changes in water supply on national grain production. We apply the 12 climate change scenarios described in Part 1 to the water resources and crop growth simulation models described in Part 2 for the conterminous United States. Drawing on data from Parts 3 and 4 we calculate what the aggregate national production would be in those regions in which grain crops are currently produced by applying irrigation where needed and water supplies allow. The total amount of irrigation water applied to crops declines under all climate change scenarios employed in this study. Under certain of the scenarios and in particular regions, precipitation decreases so much that water supplies are too limited; in other regions precipitation becomes so plentiful that little value is derived from irrigation. Nationwide grain crop production is greater when irrigation is applied as needed. Under irrigation, less corn and soybeans are produced under most of the climate change scenarios than is produced under baseline climate conditions. Winter wheat production under irrigation responds significantly to elevated atmospheric carbon dioxide concentrations [CO₂] and appears likely to increase under climate change.     

东南极冰盖Lambert冰川流域的物质平衡研究

Lambert冰川流域是南极冰盖最大的冰流系统, 因而在整个南极冰盖的物质平衡中占有非常重要的地位. 近年来穿越该冰川流域的路线考察所获得的现场观测资料和浅冰芯研究结果显示, 该冰川东、西两侧的积累速率分布和近期变化有明显差异: 东侧积累速率较高且近几十年来呈增加趋势, 西侧积累速率较低且过去几十年为明显减小. 冰体运动速度测量和冰流通量计算表明, 该冰川东侧运动速度较快, 冰流量也较大, 说明该冰川冰量补给主要来源于东侧区域. 计算出的考察断面上游物质积累总量大于流出的冰通量约13%, 意味着该流域目前处于物质正平衡状态, 如果保持目前气候状态, 冰盖将会增厚.     

Morphodynamic evolution of a lower Mississippi River channel bar after sand mining

In‐channel sand mining by dredge removes large quantities of bed sediment and alters channel morphodynamic processes. While the reach‐scale impacts of dredging are well documented, the effects of the dredged borrow pit on the local flow and sediment transport are poorly understood. These local effects are important because they control the post‐dredge evolution of the borrow pit, setting the pit lifespan and affecting reach‐scale channel morphology. This study documents the observed morphological evolution of a large (1·46 million m³) borrow pit mined on a lateral sandbar in the lower Mississippi River using a time‐series of multibeam bathymetric surveys. During the 2·5 year time‐series, 53% of the initial pit volume infilled with sediment, decreasing pit depth by an average of 0·88 m yr^?1. To explore the controls of the observed infilling, a morphodynamic model (Delft3D) was used to simulate flow and sediment transport within the affected river reach. The model indicated that infilling rates were primarily related to the riverine sediment supply and pit geometry. The pit depth and length influenced the predicted magnitude of the pit bed shear stress relative to its pre‐dredged value, i.e. the bed‐stress reduction ratio (R*), a metric that was correlated with the magnitude and spatial distribution of infilling. A one‐dimensional reduced‐complexity model was derived using predicted sediment supply and R* to simulate patterns of pit infilling. This simplified model of borrow‐pit evolution was able to closely approximate the amount and patterns of sediment deposition during the study period. Additional model experiments indicate that, for a borrow pit of a set volume, creating deep, longitudinally‐shorter borrow pits significantly increased infilling rates relative to elongated pits. Study results provide insight into the resilience of alluvial river channels after a disturbance and the sustainability of sand mining as a sediment source for coastal restoration. Copyright © 2015 John Wiley & Sons, Ltd.     

A Biogeochemical View of Estuarine Eutrophication: Seasonal and Spatial Trends and Correlations in the Delaware Estuary

The Delaware River and Bay Estuary is one of the major urbanized estuaries of the world. The 100-km long tidal river portion of the estuary suffered from major summer hypoxia in the past due to municipal and industrial inputs in the urban region; the estuary has seen remarkable water quality improvements from recent municipal sewage treatment upgrades. However, the estuary still has extremely high nutrient loading, which appears to not have much adverse impact. Since the biogeochemistry of the estuary has been relatively similar for the past two decades, our multiple year research database is used in this review paper to address broad spatial and seasonal patterns of conditions in the tidal river and 120 km long saline bay. Dissolved oxygen concentrations show impact from allochthonous urban inputs and meteorological forcing as well as biological influences. Nutrient concentrations, although high, do not stimulate excessive algal biomass due to light and multiple nutrient element limitations. Since the bay does not have strong persistent summer stratification, there is little potential for bottom water hypoxia. Elevated chlorophyll concentrations do not exert much influence on light attenuation since resuspended bottom inorganic sediments dominate the turbidity. Dissolved inorganic carbon and dissolved and particulate organic carbon distributions show significant variability from watershed inputs and lesser impact from urban inputs and biological processes. Ratios of dissolved and particulate carbon, nitrogen, and phosphorus help to understand watershed and urban inputs as well as autochthonous biological influences. Owing to the relatively simple geometry of the system and localized anthropogenic inputs as well as a broad spatial and seasonal database, it is possible to develop these biogeochemical trends and correlations for the Delaware Estuary. We suggest that this biogeochemical perspective allows a revised evaluation of estuarine eutrophication that should have generic value for understanding other estuarine and coastal waters.     

Guidelines for the good practice of surface wave analysis: a product of the InterPACIFIC project

Surface wave methods gained in the past decades a primary role in many seismic projects. Specifically, they are often used to retrieve a 1D shear wave velocity model or to estimate the V_S,30 at a site. The complexity of the interpretation process and the variety of possible approaches to surface wave analysis make it very hard to set a fixed standard to assure quality and reliability of the results. The present guidelines provide practical information on the acquisition and analysis of surface wave data by giving some basic principles and specific suggestions related to the most common situations. They are primarily targeted to non-expert users approaching surface wave testing, but can be useful to specialists in the field as a general reference. The guidelines are based on the experience gained within the InterPACIFIC project and on the expertise of the participants in acquisition and analysis of surface wave data.