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11.
José Antonio Rodríguez Martín Nikos Nanos José Carlos Miranda Gregoria Carbonell Luis Gil 《Die Naturwissenschaften》2013,100(8):739-747
Mercury (Hg) is a toxic element that is emitted to the atmosphere by both human activities and natural processes. Volcanic emissions are considered a natural source of mercury in the environment. In some cases, tree ring records taken close to volcanoes and their relation to volcanic activity over time are contradictory. In 1949, the Hoyo Negro volcano (La Palma-Canary Islands) produced significant pyroclastic flows that damaged the nearby stand of Pinus canariensis. Recently, 60 years after the eruption, we assessed mercury concentrations in the stem of a pine which survived volcano formation, located at a distance of 50 m from the crater. We show that Hg content in a wound caused by pyroclastic impacts (22.3 μg kg?1) is an order of magnitude higher than the Hg concentrations measured in the xylem before and after the eruption (2.3 μg kg?1). Thus, mercury emissions originating from the eruption remained only as a mark—in pyroclastic wounds—and can be considered a sporadic and very high mercury input that did not affect the overall Hg input in the xylem. In addition, mercury contents recorded in the phloem (9.5 μg kg?1) and bark (6.0 μg kg?1) suggest that mercury shifts towards non-living tissues of the pine, an aspect that can be related to detoxification in volcanism-adapted species. 相似文献
12.
Currently, a large number of companies consider recycling of materials as an opportunity to maximize profits and to reduce the environmental impact generated by these materials after they are disposed. However, there is also a strong constraint on the use of recycled materials mainly due to the lack of technical/scientific information, which would relate their physical properties to their recycling cycle. This information should be used in the initial phase of the product design to serve as reference for the simulation of a project to point out the physical properties obtained from recycling the Projected material (Pm). Thus, it would be possible to foresee some recycling strategy to keep the good characteristics of recycled materials by encouraging their use, regardless of the product to be designed.Therefore, the Recycling Cycle of Materials (RCM) is a tool that provides scientific/technical support in the selection of materials. It uses the information related to the physical properties of the Pm as a parameter for product design after five recycling cycles. For the case study, this tool has been applied to obtain the basic material of ABS/PC blend. Subsequently, this blend was evaluated using DSC, FTIR, traction and impact methods to obtain delimiting data for the definition of the mechanical properties resulting from the application of RCM. 相似文献
13.
Mapping the Spatial Variability of Plant Diversity in a Tropical Forest: Comparison of Spatial Interpolation Methods 总被引:4,自引:0,他引:4
Hernandez-Stefanoni JL Ponce-Hernandez R 《Environmental monitoring and assessment》2006,117(1-3):307-334
Knowledge of the spatial distribution of plant species is essential to conservation and forest managers in order to identify
high priority areas such as vulnerable species and habitats, and designate areas for reserves, refuges and other protected
areas. A reliable map of the diversity of plant species over the landscape is an invaluable tool for such purposes. In this
study, the number of species, the exponent Shannon and the reciprocal Simpson indices, calculated from 141 quadrat sites sampled
in a tropical forest were used to compare the performance of several spatial interpolation techniques used to prepare a map
of plant diversity, starting from sample (point) data over the landscape. Means of mapped classes, inverse distance functions,
kriging and co-kriging, both, applied over the entire studied landscape and also applied within vegetation classes, were the
procedures compared. Significant differences in plant diversity indices between classes demonstrated the usefulness of boundaries
between vegetation types, mapped through satellite image classification, in stratifying the variability of plant diversity
over the landscape. These mapped classes, improved the accuracy of the interpolation methods when they were used as prior
information for stratification of the area. Spatial interpolation by co-kriging performed among the poorest interpolators
due to the poor correlation between the plant diversity variables and vegetation indices computed by remote sensing and used
as covariables. This indicated that the latter are not suitable covariates of plant diversity indices. Finally, a within-class
kriging interpolator yielded the most accurate estimates of plant diversity values. This interpolator not only provided the
most accurate estimates by accounting for the indices' intra-class variability, but also provided additional useful interpretations
of the structure of spatial variability of diversity values through the interpretation of their semi-variograms. This additional
role was found very useful in aiding decisions in conservation planning. 相似文献
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Lauren Withycombe Keeler Arnim Wiek Daniel J. Lang Makoto Yokohari John van Breda Lennart Olsson Barry Ness Jordi Morato Jordi Segalàs Pim Martens Luis A. Bojórquez-Tapia James Evans 《Sustainability Science》2016,11(5):749-762
A promising approach for addressing sustainability problems is to recognize the unique conditions of a particular place, such as problem features and solution capabilities, and adopt and adapt solutions developed at other places around the world. Therefore, research and teaching in international networks becomes critical, as it allows for accelerating learning by sharing problem understandings, successful solutions, and important contextual considerations. This article identifies eight distinct types of research and teaching collaborations in international networks that can support such accelerated learning. The four research types are, with increasing intensity of collaboration: (1) solution adoption; (2) solution consultation; (3) joint research on different problems; and (4) joint research on similar problems. The four teaching types are, with increasing intensity of collaboration: (1) adopted course; (2) course with visiting faculty; (3) joint course with traveling faculty; and (4) joint course with traveling students. The typology is illustrated by extending existing research and teaching projects on urban sustainability in the International Network of Programs in Sustainability, with partner universities from Europe, North America, Asia, and Africa. The article concludes with challenges and strategies for extending individual projects into collaborations in international networks. 相似文献
18.
Luis Carlos Belalcazar Oliver Fuhrer Minh Dung Ho Erika Zarate Alain Clappier 《Atmospheric environment (Oxford, England : 1994)》2009,43(36):5830-5837
Road traffic emissions, one of the largest source categories in megacity inventories, are highly uncertain. It is essential to develop methodologies to reduce these uncertainties to manage air quality more effectively. In this paper, we propose a methodology to estimate road traffic emission factors (EFs) from a tracer experiment and from roadside pollutants measurements. We emitted continuously during about 300 non-consecutive hours a passive tracer from a finite line source placed on one site of an urban street. At the same time, we measured continuously the resulting tracer concentrations at the other side of the street with a portable on-line gas chromatograph. We used n-propane contained in commercial liquid petroleum gas (LPG) as a passive tracer. Propane offers several advantages to traditional tracers (SF6, N2O, CFCs): low price, easily available, non-reactive, negligible global warming potential, and easy to detect with commercial on-line gas chromatographs.The tracer experiment was carried out from January to March 2007 in a busy street of Ho Chi Minh City (Vietnam). Traffic volume, weather information and pollutant concentrations were also measured at the measurement site. We used the results of the tracer experiment to calculate the dilution factors and afterwards we used these dilution factors, the traffic counts and the pollutant concentrations to estimate the EFs. The proposed method assumes that the finite emission line represents the emission produced by traffic in the full area of the street and therefore there is an error associated to this assumption. We use the Computational Fluids Dynamics (CFD) model MISKAM to calculate this error and to correct the HCMC EFs. EFs for 15 volatile organic compounds (VOCs) and NO are reported here. A comparison with available studies reveals that most of the EFs estimated here are within the range of EFs reported in other studies. 相似文献
19.
Twenty four hours diel cycles of arsenic speciation in Acid Mine Drainage (AMD) due to photooxidation have been reported for the first time. AMD samples were taken during 48 h (31st March and 1st April, 2005) at 6 h intervals from the effluent of a massive abandoned polymetallic sulphide mine of the Iberian Pyrite Belt (Sw Spain). Samples were preserved in situ using cationic exchange prior to analysis by coupled high performance liquid chromatography, hydride generation and atomic fluorescence spectrometry (HPLC-HG-AFS) for arsenic speciation. The results indicated the presence of inorganic arsenic species with daily means of 262mugl(-1) for As(V) and 107 microg l(-1) for As(III). No marked diel trend was observed for As(V). However, a marked diel trend was observed for As(III) in the two studied days, with maximum concentrations during nighttime (141-143 microg l(-1)) and minimum concentrations at daytime (72-77 microg l(-1)). This difference in concentration during daytime and nighttime is ca. 100%. A similar diel cycle was observed for iron. An explanation for the arsenic diel cycles observed is the light induced photooxidation of As(III) and the elimination of As(V) due to its adsorption onto Fe precipitates during the daytime. Furthermore, the diel changes in arsenic speciation emphasize the importance of designing suitable sampling strategies in AMD systems. 相似文献
20.
Silva FA Neves RC Quintero-Pinto LG Padilha CC Jorge SM Barros MM Pezzato LE Padilha PM 《Chemosphere》2007,68(8):1542-1547
This paper presents a simple, fast and sensitive method to determine selenium in samples of feces and of fish feed by graphite furnace atomic absorption spectrometry (GFAAS) through the direct introduction of slurries of the samples into the spectrometer's graphite tube. The limits of detection (LOD) and quantification (LOQ) calculated for 20 readings of the blank of the standard slurries (0.50% m/v of feces or feed devoid of selenium) were 0.31 microg l(-1) and 1.03 microg l(-1), respectively, for the standard feces slurries and 0.35 microg l(-1) and 1.16 microg l(-1), respectively, for the standard feed slurries. The proposed method was applied in studies of bioavailability of selenium in different fish feeds and the results proved consistent with that obtained from samples mineralized by acid digestion using the microwave oven. 相似文献