Clustering and forecasting of dissolved oxygen concentration on a river basin   总被引：1，自引：1，他引：0  

Marco Costa  A. Manuela Gon?alves 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(2):151-163

The aim of this contribution is to combine statistical methodologies to geographically classify homogeneous groups of water quality monitoring sites based on similarities in the temporal dynamics of the dissolved oxygen (DO) concentration, in order to obtain accurate forecasts of this quality variable. Our methodology intends to classify the water quality monitoring sites into spatial homogeneous groups, based on the DO concentration, which has been selected and considered relevant to characterize the water quality. We apply clustering techniques based on Kullback Information, measures that are obtained in the state space modelling process. For each homogeneous group of water quality monitoring sites we model the DO concentration using linear and state space models, which incorporate tendency and seasonality components in different ways. Both approaches are compared by the mean squared error (MSE) of forecasts.  相似文献   

Iron isotope variations in Holocene sediments of the Gotland Deep, Baltic Sea   总被引：5，自引：0，他引：5  

Manuela A. Fehr  Per S. Andersson  Carl-Magnus Mörth 《Geochimica et cosmochimica acta》2008,72(3):807-826

Holocene sediments from the Gotland Deep basin in the Baltic Sea were investigated for their Fe isotopic composition in order to assess the impact of changes in redox conditions and a transition from freshwater to brackish water on the isotope signature of iron. The sediments display variations in δ⁵⁶Fe (differences in the ⁵⁶Fe/⁵⁴Fe ratio relative to the IRMM-14 standard) from −0.27 ± 0.09‰ to +0.21 ± 0.08‰. Samples deposited in a mainly limnic environment with oxygenated bottom water have a mean δ⁵⁶Fe of +0.08 ± 0.13‰, which is identical to the mean Fe isotopic composition of igneous rocks and oxic marine sediments. In contrast, sediments that formed in brackish water under periodically euxinic conditions display significantly lighter Fe isotope signatures with a mean δ⁵⁶Fe of −0.14 ± 0.19‰. Negative correlations of the δ⁵⁶Fe values with the Fe/Al ratio and S content of the samples suggest that the isotopically light Fe in the periodically euxinic samples is associated with reactive Fe enrichments and sulfides. This is supported by analyses of pyrite separates from this unit that have a mean Fe isotopic composition of −1.06 ± 0.20‰ for δ⁵⁶Fe. The supply of additional Fe with a light Fe isotopic signature can be explained with the shelf to basin Fe shuttle model. According to the Fe shuttle model, oxides and benthic ferrous Fe that is derived from dissimilatory iron reduction from shelves is transported and accumulated in euxinic basins. The data furthermore suggest that the euxinic water has a negative dissolved δ⁵⁶Fe value of about −1.4‰ to −0.9‰. If negative Fe isotopic signatures are characteristic for euxinic sediment formation, widespread euxinia in the past might have shifted the Fe isotopic composition of dissolved Fe in the ocean towards more positive δ⁵⁶Fe values.  相似文献   

Effects of long term nutrient and climate variability on subfossil Cladocera in a deep,subalpine lake (Lake Garda,northern Italy)     

Manuela Milan  Christian Bigler  Monica Tolotti  Krystyna Szeroczyńska 《Journal of Paleolimnology》2017,58(3):335-351

Albeit subfossil Cladocera remains are considered as a reliable proxy for tracking historical lake development, they have been scarcely studied in large subalpine lakes south of the Alps. In this study, subfossil Cladocera remains from Lake Garda in northern Italy were analyzed to track the lake’s environmental changes since the Middle Ages. One core was retrieved from the largest sub-basin of Lake Garda (Brenzone, 350 m deep) and two cores were retrieved from the profundal and littoral zone of the smaller lake sub-basin (Bardolino, 80 and 40 m deep, respectively). The species distribution of Cladocera remains in recent sediment layers was similar to that observed in contemporary water samples. The deepest sections of the three cores were characterized by species sensitive to water temperature, which suggest a key role of major climatic events in driving the lake response during the late Holocene. The most evident change in Cladocera assemblages in the studied cores was observed during the 1960s, when planktonic taxa such as Daphnia spp. and Bosmina spp. became dominant at the expense of littoral taxa. Despite the highly coherent general pattern of subfossil Cladocera, the cores showed a set of minor differences, which were attributed to different morphological and hydrological features of the two basins forming Lake Garda. Multivariate analysis revealed a clear relation of Cladocera to climate variability during periods of low lake nutrient levels (i.e. before the 1960s). This provides additional information on past ecological responses of Lake Garda, as contrast previous data from subfossil diatom and pigment analyses did not fully capture effects of climate change during the same period. Since the 1960s shifts in assemblage composition of Cladocera and diatoms were highly coherent, in response to nutrient increase and the following, less pronounced, decrease in nutrient concentrations. During the last five decades, the response of the Cladocera to climate variability appeared to be masked by nutrient change. This work points up the potential of the multi-proxy approach for disentangling the multifaceted biological responses to multiple environmental stressors in large and deep lakes.  相似文献   

Testing the Usability of OpenStreetMap's iD Tool     

Jan Behrens  Corné P. J. M. van Elzakker  Manuela Schmidt 《The Cartographic journal》2013,50(2):177-184

The objective of this study is to investigate the usability of the iD editor of OpenStreetMap (OSM). To this end a usability test with 18 participants has been conducted. The participants were given mapping tasks to complete using iD and observed with the thinking aloud method as well as screen recording and mouse/keyboard logging. Additionally, the test persons were interviewed after each test. The data gathered were analysed with regard to key usability criteria such as learnability, efficiency, error tolerance, and subjective user satisfaction. The outcome of this study is the identification of usability issues from which possible improvements of the tool have been derived. The study shows that iD is an overall usable tool for novice users, but still shows opportunities for improvement especially in terms of learnability and error handling.  相似文献   

Predicting seasonal and hydro-meteorological impact in environmental variables modelling via Kalman filtering   总被引：1，自引：1，他引：0  

A. Manuela Gonçalves  Marco Costa 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(5):1021-1038

This study focuses on the potential improvement of environmental variables modelling by using linear state-space models, as an improvement of the linear regression model, and by incorporating a constructed hydro-meteorological covariate. The Kalman filter predictors allow to obtain accurate predictions of calibration factors for both seasonal and hydro-meteorological components. This methodology can be used to analyze the water quality behaviour by minimizing the effect of the hydrological conditions. This idea is illustrated based on a rather extended data set relative to the River Ave basin (Portugal) that consists mainly of monthly measurements of dissolved oxygen concentration in a network of water quality monitoring sites. The hydro-meteorological factor is constructed for each monitoring site based on monthly precipitation estimates obtained by means of a rain gauge network associated with stochastic interpolation (kriging). A linear state-space model is fitted for each homogeneous group (obtained by clustering techniques) of water monitoring sites. The adjustment of linear state-space models is performed by using distribution-free estimators developed in a separate section.  相似文献   

The hermitage of Cerbaiolo (Tuscany,Italy): stability conditions and geomorphological characterization     

Laura Melelli  Corrado Cencetti  Manuela Cecconi  Luciano Faralli  Alessia Vecchietti  Vincenzo Pane 《Environmental Earth Sciences》2016,75(4):322

  相似文献   

Chemical characterization of sub-micrometer aerosol particles in the tropical Atlantic Ocean: marine and biomass burning influences     

Manuela van Pinxteren  Björn Fiedler  Dominik van Pinxteren  Yoshiteru Iinuma  Arne Körtzinger  Hartmut Herrmann 《Journal of Atmospheric Chemistry》2015,72(2):105-125

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PAOLO: A Polarimeter Add‐On for the LRS Optics at a Nasmyth focus of the TNG     

S. Covino  E. Molinari  P. Bruno  M. Cecconi  P. Conconi  P. D'Avanzo  L. di Fabrizio  D. Fugazza  M. Giarrusso  E. Giro  F. Leone  V. Lorenzi  S. Scuderi 《Astronomische Nachrichten》2014,335(2):117-123

We describe a new polarimetric facility available at the Istituto Nazionale di AstroFisica / Telescopio Nazionale Galileo at La Palma, Canary islands. This facility, PAOLO (Polarimetric Add‐On for the LRS Optics), is located at a Nasmyth focus of an alt‐az telescope and requires a specific modeling in order to remove the time‐ and pointing position‐dependent instrumental polarization. We also describe the opto‐mechanical structure of the instrument and its calibration and present early examples of applications. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves Instruments: Radio Flux Density Variations with Frequency     

V. Krupar  M. Maksimovic  O. Santolik  E. P. Kontar  B. Cecconi  S. Hoang  O. Kruparova  J. Soucek  H. Reid  A. Zaslavsky 《Solar physics》2014,289(8):3121-3135

We have performed a statistical study of 152 Type III radio bursts observed by Solar TErrestrial RElations Observatory (STEREO)/Waves between May 2007 and February 2013. We investigated the flux density between 125 kHz and 16 MHz. Both high- and low-frequency cutoffs were observed in 60 % of events, suggesting an important role of propagation. As already reported by previous authors, we observed that the highest flux density occurs at 1 MHz on both spacecraft. We developed a simplified analytical model of the flux density as a function of radial distance and compared it with the STEREO/Waves data.  相似文献   

Integrated cave drip monitoring for epikarst recharge estimation in a dry Mediterranean area,Sif Cave,Israel     

Nathan A. Sheffer  Moty Cohen  Efrat Morin  Tamir Grodek  Alex Gimburg  Einat Magal  Haim Gvirtzman  Manuela Nied  Daniel Isele  Amos Frumkin 《水文研究》2011,25(18):2837-2845

Understanding recharge mechanisms and controls in karst regions is extremely important for managing water resources because of the dynamic nature of the system. The objective of this study was to evaluate water percolation through epikarst by monitoring water flow into a cave and conducting artificial irrigation and tracer experiments, at Sif Cave in Wadi Sussi, Israel from 2005 through 2007. The research is based on continuous high‐resolution direct measurements of both rainfall and water percolation in the cave chamber collected by three large PVC sheets which integrate drips from three different areas (17, 46, and 52 m²). Barrels equipped with pressure transducers record drip rate and volume for each of the three areas. The combined measured rainfall and cave data enables estimation of recharge into the epikarst and to better understand the relationship of rainfall‐recharge. Three distinct types of flow regimes were identified: (1) ‘Quick flow’ through preferential flow paths (large fractures and conduits); (2) ‘Intermediate flow’ through a secondary crack system; and (3) ‘Slow flow’ through the matrix. A threshold of ～100 mm of rain at the beginning of the rainy season is required to increase soil water content allowing later rainfall events to percolate deeper through the soil and to initiate dripping in the cave. During winter, as the soil water content rises, the lag time between a rain event and cave drip response decreases. Annual recharge (140–160 mm in different areas in the cave) measured represents 30–35% of annual rainfall (460 mm). Copyright © 2011 John Wiley & Sons, Ltd.  相似文献