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M. Rocío Fernández San Juan Carolina B. Albornoz Karen Larsen Roberto Najle 《Environmental Earth Sciences》2018,77(11):404
Contamination with heavy metals in surface and groundwater is a threat to human health and ecosystems. Due to this, the need arises to remediate water polluted through ecological and profitable technologies, such as phytoremediation. The objective of the work was to evaluate the concentration of lead (Pb) and zinc (Zn) in the floating macrophytes Limnobium laevigatum and Ludwigia peploides, after being exposed to contaminated water experimentally. In this way to be able to determine if these plants have mechanisms that allow them to accumulate the metals in the roots and to perform the translocation of these to different vegetative organs, L. laevigatum and L. peploides were placed in solutions contaminated with Pb ([Pb]?=?5 mg/l) and Zn ([Zn]?=?20 mg/l). The concentrations of metals in water, root and leaf samples were evaluated as a function of time (0, 1, 2 and 4 days). The determination of the metals was performed by the atomic absorption spectrophotometry technique. After 4 days of exposure to Pb and Zn, the plants showed high metal removal efficiencies of water, more to 70% in all cases. Pb was accumulated fundamentally by roots, while Zn was accumulated more in the leaves. In addition, the bioconcentration and translocation factors for each metal were calculated. 相似文献
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Giacomo Grassi Roberto Pilli Jo House Sandro Federici Werner A. Kurz 《Carbon balance and management》2018,13(1):8
Background
The credibility and effectiveness of country climate targets under the Paris Agreement requires that, in all greenhouse gas (GHG) sectors, the accounted mitigation outcomes reflect genuine deviations from the type and magnitude of activities generating emissions in the base year or baseline. This is challenging for the forestry sector, as the future net emissions can change irrespective of actual management activities, because of age-related stand dynamics resulting from past management and natural disturbances. The solution implemented under the Kyoto Protocol (2013–2020) was accounting mitigation as deviation from a projected (forward-looking) “forest reference level”, which considered the age-related dynamics but also allowed including the assumed future implementation of approved policies. This caused controversies, as unverifiable counterfactual scenarios with inflated future harvest could lead to credits where no change in management has actually occurred, or conversely, failing to reflect in the accounts a policy-driven increase in net emissions. Instead, here we describe an approach to set reference levels based on the projected continuation of documented historical forest management practice, i.e. reflecting age-related dynamics but not the future impact of policies. We illustrate a possible method to implement this approach at the level of the European Union (EU) using the Carbon Budget Model.Results
Using EU country data, we show that forest sinks between 2013 and 2016 were greater than that assumed in the 2013–2020 EU reference level under the Kyoto Protocol, which would lead to credits of 110–120 Mt CO2/year (capped at 70–80 Mt CO2/year, equivalent to 1.3% of 1990 EU total emissions). By modelling the continuation of management practice documented historically (2000–2009), we show that these credits are mostly due to the inclusion in the reference levels of policy-assumed harvest increases that never materialized. With our proposed approach, harvest is expected to increase (12% in 2030 at EU-level, relative to 2000–2009), but more slowly than in current forest reference levels, and only because of age-related dynamics, i.e. increased growing stocks in maturing forests.Conclusions
Our science-based approach, compatible with the EU post-2020 climate legislation, helps to ensure that only genuine deviations from the continuation of historically documented forest management practices are accounted toward climate targets, therefore enhancing the consistency and comparability across GHG sectors. It provides flexibility for countries to increase harvest in future reference levels when justified by age-related dynamics. It offers a policy-neutral solution to the polarized debate on forest accounting (especially on bioenergy) and supports the credibility of forest sector mitigation under the Paris Agreement.46.
Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8 m long) was recovered from a water depth of 7 m, while the second core (SK19, 5.8 m long) was recovered close to the present‐day shoreline (water depth of 2 m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Naked‐eye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have under‐saturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9 cal. ka BP) eruptions of Somma‐Vesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4 cal. ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2 cal. ka BP), Agnano Monte Spina (ca. 4.5 cal. ka BP) and Agnano Pomici Principali (ca. 12.3 cal. ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight 14C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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The growing concern for health‐related problems deriving from pollutants leaching is driving national and international administrations to support the development of tools for evaluating the effects of alternate management scenarios and identifying vulnerable areas. Cropping systems models are powerful tools for evaluating leachates under different environmental, social, and management conditions. As percolating water is the transport vehicle for pollutants transport in soil, a reliable evaluation of water balance models is a fundamental prerequisite for investigating pesticides and nitrate fate. As specific approaches for the evaluation of multi‐layer evolution of state variables are missing, we propose a fuzzy‐based, integrated indicator (ISWC: 0, best; 1, worst) for a comprehensive evaluation of soil water content (SWC) simulations. We aggregated error metrics with others quantifying the homogeneity of errors across different soil layers, the capability of models to reproduce complex dynamics function of both time and soil depth, and model complexity. We tested ISWC on a sample dataset where the models CropSyst and CERES‐Wheat were used to simulate SWC for winter wheat systems. ISWC revealed that, in the explored conditions, the global assessment of the two models' performances allowed identification of CropSyst as the best (average ISWC = 0·441, with a value of 0·537 obtained by CERES‐Wheat), although each model prevailed for some of the metrics. CropSyst presented the highest accuracy (average agreement module = 0·400), whereas CERES‐Wheat's accuracy was slightly worse, although achieved with a simplified modelling approach (average Akaike Information Criterion = − 230·44), thereby favouring large‐area applicability. The non‐univocal scores achieved by the models for the different metrics support the use of multi‐metric evaluation approaches for quantifying the different aspects of water balance model performances. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Roberto Villa Verde 《地震工程与结构动力学》1991,20(3):223-241
Presented herein are the results of a study carried out to investigate the prevalent factors that contributed to the collapse of the upper floors of a large number of buildings during the earthquake of September 19, 1985, in Mexico City. The study involves the review of the available data from such collapses, the identification of common characteristics among the buildings that suffered such type of collapse, the design of a typical 10-storey reinforced concrete frame structure according to the 1976 Mexico City building code, and the non-linear analysis of one of its frames under one of the accelerograms from the earthquake. It is found that in many cases the upper floor collapses might have occurred because the large accelerations and long duration of the earthquake induced in the failed buildings the formation of plastic hinges at their upper columns, and because these plastic hinges in turn induced the lateral instability of the affected storeys and the ones above them. It is also found that in some structures this failure mechanism can occur after plastic hinges are formed in most of their beams, and that it may result from the consequent elongation of their natural periods, their response in a second or third mode and in resonance with the ground motion that excites them, and their vibration in a mode not considered to be the predominant one in their design. 相似文献
50.
Roberto Villaverde 《地震工程与结构动力学》1985,13(1):33-42
It is shown that two of the damping ratios of certain systems composed of a building and a small attachment in resonance are given by the average of the damping ratios of the two independent components. Based on this fact and the fact that the seismic response of a building can always be reduced by increasing its damping, it is demonstrated that the attachment of a small heavily-damped system in resonance can increase the damping of a building and reduce thus its response to earthquake excitations. Numerical solutions are presented to confirm the demonstration, and recommendations are given to calculate the parameters of such systems. 相似文献