Pliocene–Holocene Alkali-Basaltoid Volcanism of the Tsushima Basin of the Sea of Japan: New Geochemical and Geodynamic Data     

Emelyanova  T. A.  Lelikov  E. P.  Pugachev  A. A. 《Oceanology》2020,60(2):236-247

Oceanology - Abstract—The paper contains original data on the rock-forming and rare element compositions in the Pliocene–Holocene alkaline basaltoids of the Tsushima Basin Sea of Japan,...  相似文献   

Prediction of the calcium carbonate budget in a sedimentary basin: A “source-to-sink” approach applied to Great Salt Lake,Utah, USA     

Anthony Bouton  Emmanuelle Vennin  Philippe Amiotte-Suchet  Christophe Thomazo  Jean-Pierre Sizun  Aurélien Virgone  Eric C. Gaucher  Pieter T. Visscher 《Basin Research》2020,32(5):1005-1034

Most source-to-sink studies typically focus on the dynamics of clastic sediments and consider erosion, transport and deposition of sediment particles as the sole contributors. Although often neglected, dissolved solids produced by weathering processes contribute significantly in the sedimentary dynamics of basins, supporting chemical and/or biological precipitation. Calcium ions are usually a major dissolved constituent of water drained through the watershed and may facilitate the precipitation of calcium carbonate when supersaturating conditions are reached. The high mobility of Ca²⁺ ions may cause outflow from an open system and consequently loss. In contrast, in closed basins, all dissolved (i.e. non-volatile) inputs converge at the lowest point of the basin. The endoreic Great Salt Lake basin constitutes an excellent natural laboratory to study the dynamics of calcium on a basin scale, from the erosion and transport through the watershed to the sink, including sedimentation in lake's waterbody. The current investigation focused on the Holocene epoch. Despite successive lake level fluctuations (amplitude around 10 m), the average water level seems to have not been affected by any significant long-term change (i.e. no increasing or decreasing trend, but fairly stable across the Holocene). Weathering of calcium-rich minerals in the watershed mobilizes Ca²⁺ ions that are transported by surface streams and subsurface flow to the Great Salt Lake (GSL). Monitoring data of these flows was corrected for recent anthropogenic activity (river management) and combined with direct precipitation (i.e. rain and snow) and atmospheric dust income into the lake, allowing estimating the amount of calcium delivered to the GSL. These values were then extrapolated through the Holocene period and compared to the estimated amount of calcium stored in GSL water column, porewater and sediments (using hydrochemical, mapping, coring and petrophysical estimates). The similar estimate of calcium delivered (4.88 Gt) and calcium stored (3.94 Gt) is consistent with the premise of the source-to-sink approach: a mass balance between eroded and transported compounds and the sinks. The amount of calcium deposited in the basin can therefore be predicted indirectly from the different inputs, which can be assessed with more confidence. When monitoring is unavailable (e.g. in the fossil record), the geodynamic context, the average lithology of the watershed and the bioclimatic classification of an endoreic basin are alternative properties that may be used to estimate the inputs. We show that this approach is sufficiently accurate to predict the amount of calcium captured in a basin and can be extended to the whole fossil record and inform on the storage of calcium.  相似文献   

GPS navigation data bit decoding error during strong equatorial scintillation     

Dongyang Xu  Y. T. Jade Morton 《GPS Solutions》2018,22(4):110

Strong equatorial scintillation is often characterized by simultaneous fast phase changes and deep amplitude fading. The combined effect poses a challenge for GNSS receiver carrier tracking performance. One of the consequences of the strong scintillation is increased navigation message data bit decoding error. Understanding the rate of the data bit decoding error under equatorial scintillation is essential for high accuracy and high integrity applications. We present the statistical relationship between the data bit decoding error occurrences and the intensity of amplitude scintillation based on the processing of intermediate frequency GPS scintillation data collected on Ascension Island in March 2013. A third-order phase lock loop (PLL) is implemented to process the data and to access the data bit error typically expected in conventional receivers. A Kalman filter-based PLL is also used to process the same data to demonstrate that the data bit decoding error can be reduced through advanced carrier tracking designs.  相似文献   

On the accuracy of the GPS L2 observable for ionospheric monitoring     

Anthony M. McCaffrey  P. T. Jayachandran  Richard B. Langley  Jean-Marie Sleewaegen 《GPS Solutions》2018,22(1):23

The introduction of the unencrypted global positioning system (GPS) L2 civil (L2C) signal has the potential to improve measurements made with the L2 frequency, an important observable in GPS-based ionospheric research and monitoring. Recent work has shown significant differences between the legacy L2P(Y) and L2C-derived total electron content rate of change index (ROTI). This difference is observed between L2P(Y) and L2C-derived ROTI with certain receiver models and between zero-baseline receiver pairs. We discuss the likely cause for these differences: L1-aided tracking used to track both the L2P(Y) and L2C signals. We also present L2C data that are confirmed to be from tracking independent of L1. Using the ionospheric-free linear combination, we show that the independently tracked carrier phase dynamics are significantly more accurate than the L1-aided observables. This result is confirmed by comparing the behavior of the L2C and L2P(Y) carrier phase observables upon a sudden antenna rotation.  相似文献   

GIS professional development for teachers: lessons learned from high-needs schools     

Jerry T. Mitchell  George Roy  Stephannie Fritch  Brandy Wood 《制图学和地理信息科学》2018,45(4):292-304

University faculty partners from the Departments of Geography and Instruction and Teacher Education at a large, public university collaborated with K-12 teachers and the leadership of a rural school district in order to investigate the crosscutting content of science, mathematics, and geography through the integration of web-based GIS technologies. The project explored the critical connections among technology, pedagogy, and content with a particular emphasis on developing technology-enhanced, inquiry-based lessons in which the teachers and their students used GIS technologies to analyze, visualize, and present data in real-world contexts. The findings highlight the importance of well-structured professional development that builds community, integrates diverse content and pedagogical expertise, provides feedback and coaching, and is of sufficient duration to effect change.  相似文献   

A novel approach to leveraging social media for rapid flood mapping: a case study of the 2015 South Carolina floods     

Zhenlong Li  Cuizhen Wang  Christopher T. Emrich  Diansheng Guo 《制图学和地理信息科学》2018,45(2):97-110

Rapid flood mapping is critical for local authorities and emergency responders to identify areas in need of immediate attention. However, traditional data collection practices such as remote sensing and field surveying often fail to offer timely information during or right after a flooding event. Social media such as Twitter have emerged as a new data source for disaster management and flood mapping. Using the 2015 South Carolina floods as the study case, this paper introduces a novel approach to mapping the flood in near real time by leveraging Twitter data in geospatial processes. Specifically, in this study, we first analyzed the spatiotemporal patterns of flood-related tweets using quantitative methods to better understand how Twitter activity is related to flood phenomena. Then, a kernel-based flood mapping model was developed to map the flooding possibility for the study area based on the water height points derived from tweets and stream gauges. The identified patterns of Twitter activity were used to assign the weights of flood model parameters. The feasibility and accuracy of the model was evaluated by comparing the model output with official inundation maps. Results show that the proposed approach could provide a consistent and comparable estimation of the flood situation in near real time, which is essential for improving the situational awareness during a flooding event to support decision-making.  相似文献   

IAG Newsletter     

Gyula Tóth 《Journal of Geodesy》2018,92(4):453-456

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Gradient-Based Turbulence Estimates from Multicopter Profiles in the Arctic Stable Boundary Layer     

Greene  Brian R.  Kral  Stephan T.  Chilson  Phillip B.  Reuder  Joachim 《Boundary-Layer Meteorology》2022,183(3):321-353

Boundary-Layer Meteorology - We explore the potential of a new method for the estimation of profiles of turbulence statistics in the stable boundary layer (SBL). By applying gradient-based scaling...  相似文献   

Changing depositional environment and factors controlling the growth of mudflat in a tropical estuary,west coast of India     

G. N. Nayak  S. P. Volvoikar  T. Hoskatta 《Environmental Earth Sciences》2018,77(21):741

Mudflats and associated mangroves are most important ecosystems of tropical coastal regions. Mangroves play a very important role in maintaining the environmental balance; thus in addition to mangrove reforestation and restoration, afforestation has also been practiced. We studied distribution of sediment components (sand, silt, clay) organic carbon (OC), heavy metals (Fe, Mn, Cu, Zn, Cr and Co) and pH in six cores collected from one of the largest mudflats of Mandovi estuary, west coast of India. The temporal distribution patterns of these proxies suggested that past changes in tidal energy conditions, fresh water inflow and anthropogenic activities over the last few decades, together helped in development of a middle tidal flat in this estuary. In cores collected from the mangroves, trapping and deposition of finer particles and organic matter were enhanced by a complex aerial mangrove root system in recent years. Mangroves were, therefore, suggested to enhance the buildup of mudflats in Mandovi estuary. Cores collected from mudflats also exhibited higher deposition of finer particles and organic matter (except MF2) in recent years, suggesting maturity and greater stability of the entire mudflat in recent years. Middle tidal flats (mudflats) of Mandovi estuary may, therefore, prove to be suitable substrates for mangrove proliferation in the near future. Finer sediments deposited mainly from mining activities in recent years exhibited lower pH and higher metal content. Organisms dwelling in these recently deposited sediments are, therefore, at higher risk of bioaccumulation and metal toxicity.  相似文献   

Ecotoxicological evaluation of dredged sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro State,Brazil) using bioassays with earthworms and collembolans     

Mariana Vezzone  Ricardo Cesar  Helena Polivanov  Aline Serrano  Danielle Siqueira  Leticia Abreu  Miriam Bianchi  Maria Elizabeth Correia  Zuleica Castilhos  Tácio de Campos 《Environmental Earth Sciences》2018,77(21):743

The toxicity and metal bioavailability were studied in dredged sediments from Rodrigo de Freitas Lagoon (Rio de Janeiro, RJ, Brazil) using acute and avoidance tests with Eisenia andrei, and reproduction tests with Folsomia candida. The sediment was mixed with an artificial soil, and two natural soils (ferralsol and chernosol—representative Brazilian tropical soils) to obtain the following doses: 1, 3, 6, 12, 18, 24 and 30%. Total metal concentrations were determined in the sediment to support the interpretation of ecotoxicological data. Metal concentrations in the mixtures were in agreement with the threshold limits established by Brazilian law. However, significant avoidance responses were found on doses ≥?3% and were the most sensitive endpoint. Earthworm mortality found in artificial soil mixtures (LC50?=?3.9) suggests higher toxicity levels than those obtained in ferralsol (LC50?=?7.6%) and chernosol (11.0%) treatments. Earthworm mortality, avoidance responses and collembolan reproduction levels found in ferralsol mixtures (LC50?=?9.2; avoidance EC50?=?2.3%; reproduction EC50?=?2.8%) were higher compared to chernosol treatments (LC50?=?11.0%; avoidance EC50?=?4.3%; reproduction EC50?=?4.9%). The reduction of toxicity levels in chernosol mixtures is probably due to the abundance of expansive clay minerals in chernosols with capacity of adsorbing metals and other xenobiotic substances from soil pore water, decreasing metal bioavailability. Finally, threshold limits defined by Brazilian legislation for soil quality and land disposal of dredged sediments are not sufficient to prevent noxious effects on soil fauna and should be complemented with a preliminary ecotoxicological evaluation.  相似文献