Impact of intensive fish farming on methane emission in a tropical hydropower reservoir     

Marcelo Gomes da Silva  Ana Paula Packer  Fernanda G. Sampaio  Luciano Marani  Ericka V. C. Mariano  Ricardo A. A. Pazianotto  Willian J. Ferreira  Plínio C. Alvalá 《Climatic change》2018,150(3-4):195-210

Fisheries and aquaculture are important sources of food for hundreds of millions of people around the world. World fish production is projected to increase by 15% in the next 10 years, reaching around 200 million tonnes per year. The main driver of this increase will be based on fish farming management in developing countries. In Brazil, fish farming is increasing due to the climate conditions and large supply of water resources, with the production system based on Nile tilapia (Oreochromis niloticus) farming in reservoirs. Inland waters like reservoirs are a natural source of methane (CH₄) to the atmosphere. However, knowledge of the impact from intensive fish production in net cages on CH₄ fluxes is not well known. This paper presents in situ measurements of CH₄ fluxes and dissolved CH₄ (DM) in the Furnas Hydroelectric Reservoir in order to evaluate the impact of fish farming on methane emissions. Measurements were taken in a control area without fish production and three areas with fish farming. The overall mean of diffusive methane flux (DMF) (5.9?±?4.5 mg CH₄ m^?2 day^?1) was significantly lower when compared to the overall mean of bubble methane flux (BMF) (552.9?±?1003.9 mg CH₄ m^?2 day^?1). The DMF and DM were significantly higher in the two areas with fish farming, whereas the BMF was not significantly different. The DMF and DM were correlated to depth and chlorophyll-a. However, the low production of BMF did not allow the comparison with the limnological parameters measured. This case study shows that CH₄ emissions are influenced more by reservoir characteristics than fish production. Further investigation is necessary to assess the impact of fish farming on the greenhouse gas emissions.  相似文献   

Region-based classification of PolSAR data using radial basis kernel functions with stochastic distances     

Rogério G. Negri  Alejandro C. Frery  Wagner B. Silva  Tatiana S. G. Mendes  Luciano V. Dutra 《International Journal of Digital Earth》2019,12(6):699-719

Region-based classification of PolSAR data can be effectively performed by seeking for the assignment that minimizes a distance between prototypes and segments. Silva et al. [“Classification of segments in PolSAR imagery by minimum stochastic distances between wishart distributions.” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 6 (3): 1263–1273] used stochastic distances between complex multivariate Wishart models which, differently from other measures, are computationally tractable. In this work we assess the robustness of such approach with respect to errors in the training stage, and propose an extension that alleviates such problems. We introduce robustness in the process by incorporating a combination of radial basis kernel functions and stochastic distances with Support Vector Machines (SVM). We consider several stochastic distances between Wishart: Bhatacharyya, Kullback-Leibler, Chi-Square, Rényi, and Hellinger. We perform two case studies with PolSAR images, both simulated and from actual sensors, and different classification scenarios to compare the performance of Minimum Distance and SVM classification frameworks. With this, we model the situation of imperfect training samples. We show that SVM with the proposed kernel functions achieves better performance with respect to Minimum Distance, at the expense of more computational resources and the need of parameter tuning. Code and data are provided for reproducibility.  相似文献   

Examining deforestation and agropasture dynamics along the Brazilian TransAmazon Highway using multitemporal Landsat imagery     

Guiying Li  Emilio Moran  Miquéias Freitas Calvi  Luciano Vieira Dutra  Mateus Batistella 《地理信息系统科学与遥感》2019,56(2):161-183

This research aims to understand the difference of major land-cover change results caused in various time periods and to examine the impacts of human-induced factors on land-cover changes along the TransAmazon Highway region. The Landsat Thematic Mapper and Operational Land Imager data from 2011, 2014, and 2017 and our previous land-cover classification results in 1991, 2000, and 2008 were used to examine land-cover dynamics. A classification system consisting of five land-cover classes – primary forest (PF), secondary forest (SF), agropasture (AP), urban area, and water – were chosen. The hierarchical-based classification method was used to generate land-cover classification results, and the post-classification comparison approach was used to produce detailed “from-to” conversions for each detection period. The emphasis was on deforestation of PF, dynamic change of SF and AP, and urbanization over time. The impacts of human-induced factors such as population and economic conditions on urban expansion, AP expansion, and deforestation were examined. This research indicated that selection of a suitable time period was critical for effectively detecting land-cover changes; that is, too long time period (i.e., 9 years) cannot accurately capture some land-cover changes such as the AP and SF in this research. Although deforestation – the conversion from PF to SF and AP – accounted for a large proportion of land-cover changes, the changes between SF and AP became more important than PF conversion, and required a short time period (i.e., 3 years here) for effectively reflecting their dynamics. Human-induced factors play important roles in deforestation, dynamic changes between AP and SF, and urbanization.  相似文献   

Gravity field and interior of Rhea from Cassini data analysis   总被引：1，自引：0，他引：1  

Luciano Iess  Nicole J. Rappaport  Jonathan Lunine  Sami W. Asmar  Francesco Zingoni 《Icarus》2007,190(2):585-593

The Cassini spacecraft encountered Rhea on November 26, 2005. Analysis of the Doppler data acquired at and around closest approach yields the mass of Rhea and the quadrupole moments of its gravity field with unprecedented accuracy. We obtained which corresponds to a density of . Our results for J₂ and C₂₂ are (7.947±0.892)×¹⁰⁻⁴ and (2.3526±0.0476)×¹⁰⁻⁴, respectively. These values are consistent with hydrostatic equilibrium. From the value of C₂₂, we infer the non-dimensional moment of inertia C/MR²=0.3721±0.0036. Our models of Rhea's interior based on the gravity data favor an almost undifferentiated satellite. A discontinuity between a core and a mantle is possible but not required by the data. Models with a constant silicate mass fraction throughout the body cannot account for the determined quadrupole coefficients. The data exclude fully differentiated models in which the core would be composed of unhydrated silicates and the mantle would be composed of pure ice. If the mantle contains 10% in mass of silicates, the core extends to 630 km in radius and has a silicate mass fraction of 40%. A continuous model in which the silicates are more concentrated toward the center of the body than in the outer layers is allowed by the gravity data but excluded by thermal evolution considerations. The one model that fits the gravity data and is self-consistent when energy transport and ice melting are qualitatively considered is an “almost undifferentiated” Rhea, in which a very large uniform core is surrounded by a relatively thin ice shell containing no rock at all.  相似文献   

Preface for the thematic issue “Early Warning of Landslides”     

Kyoji Sassa  Luciano Picarelli 《Landslides》2010,7(3):217-217

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Relativistic simulations of the phase-transition-induced collapse of neutron stars     

Ernazar B. Abdikamalov  Harald Dimmelmeier  Luciano Rezzolla  John C. Miller 《Monthly notices of the Royal Astronomical Society》2009,392(1):52-76

An increase in the central density of a neutron star may trigger a phase transition from hadronic matter to deconfined quark matter in the core, causing it to collapse to a more compact hybrid star configuration. We present a study of this, building on previous work by Lin et al.. We follow them in considering a supersonic phase transition and using a simplified equation of state, but our calculations are general relativistic (using 2D simulations in the conformally flat approximation) as compared with their 3D Newtonian treatment. We also improved the treatment of the initial phase transformation, avoiding the introduction of artificial convection. As before, we find that the emitted gravitational wave spectrum is dominated by the fundamental quasi-radial and quadrupolar pulsation modes but the strain amplitudes are much smaller than suggested previously, which is disappointing for the detection prospects. However, we see significantly smaller damping and observe a non-linear mode resonance which substantially enhances the emission in some cases. We explain the damping mechanisms operating, giving a different view from the previous work. Finally, we discuss the detectability of the gravitational waves, showing that the signal-to-noise ratio for current or second generation interferometers could be high enough to detect such events in our Galaxy, although third generation detectors would be needed to observe them out to the Virgo cluster, which would be necessary for having a reasonable event rate.  相似文献   

Beyond ideal MHD: towards a more realistic modelling of relativistic astrophysical plasmas     

Carlos Palenzuela  Luis Lehner  Oscar Reula  Luciano Rezzolla 《Monthly notices of the Royal Astronomical Society》2009,394(4):1727-1740

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Effects of non-stoichiometry on the spinel structure at high pressure: Implications for Earth’s mantle mineralogy     

Fabrizio Nestola  Joseph R. Smyth  Luciano Secco  Marco Bruno  Alberto Dal Negro 《Geochimica et cosmochimica acta》2009,73(2):489-3427

A non-stoichiometric sample of spinel with composition ^T(Mg_0.4Al_0.6)^M(Al_1.8□_0.2)O₄ was investigated by single-crystal X-ray diffraction in situ up to about 8.7 GPa using a diamond anvil cell. The P(V) data were fitted using a third-order Birch-Murnaghan equation of state and the unit-cell volume V₀, the bulk modulus K_T0 and its first pressure derivative K′ were refined simultaneously providing the following coefficients: V₀ = 510.34(6) Å³, K_T0 = 171(2) GPa, K′ = 7.3(6). This K_T0 value represents the lowest ever found for spinel crystal structures. Comparing our data with a stoichiometric and natural MgAl₂O₄ (pure composition) we observe a decrease in K_T0 by about 11.5% and a strong increase in K′ by about 33%. These results demonstrate how an excess of Al accompanied by the formation of significant cation vacancies at octahedral site strongly affects the thermodynamic properties of spinel structure. If we consider that the estimated mantle composition is characterized by 3-5% of Al₂O₃ this could imply an Mg/Al substitution with possible formation of cation vacancies. The results of our study indicate that geodynamic models should take into account the potential effect of Mg/Al substitution on the incompressibility of the main mantle-forming minerals (olivine, wadsleyite, ringwoodite, Mg-perovskite).  相似文献   

Accurate hypocentre locations in the Middle-Durance Fault Zone, South-Eastern France     

Sebastiano Imposa  Jean-Pierre Fourno  Rosario Raffaele  Antonio Scaltrito  Luciano Scarfi 《Central European Journal of Geosciences》2009,1(4):416-423

A one-dimensional velocity model and station corrections for the Middle-Durance fault zone (south-eastern France) were computed by inverting P-wave arrival times recorded on a local seismic network of 8 stations. A total of 93 local events with a minimum of 6 P-phases, RMS 0.4 s and a maximum gap of 220° were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn from our findings. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of south-eastern France.  相似文献   

Chemical composition of wet and dry atmospheric depositions in an urban environment: local,regional and long-range influences     

Luciano Morselli  Elena Bernardi  Ivano Vassura  Fabrizio Passarini  Enrico Tesini 《Journal of Atmospheric Chemistry》2008,59(3):151-170

The results of a 8 year survey of wet and dry depositions collected in Bologna (Northern Italy) are presented and discussed: monthly fluxes of the main ions (hydrogen, sodium, potassium, calcium, magnesium, ammoniacal and nitrate nitrogen, sulphate and chloride) have been registered and statistically discussed. The trend of hydrogen ion, whose largest correlation in the global deposition was found with sulphate, is clearly downwards, with peaks mainly in winter months. By means of a data factor analysis, three main sources to explain the variability of the deposition chemistry were recognized: an anthropogenic contribution (particularly represented by NO₃ ⁻, SO₄ ²⁻, H⁺), the sea spray (Na⁺, Cl⁻ and, to a lesser extent, K⁺ and Mg²⁺) and a terrigenous fraction, particularly characterized by higher Ca²⁺ concentration; however, some concentration peaks of this ion have been found in association with some episodes of Saharan dust transportation.  相似文献