Refinar búsqueda
Resultados 851-860 de 3,189
Phytoremediation of Explosive-Contaminated Soils
2015
Kiiskila, Jeffrey D. | Das, Padmini | Sarkar, Dibyendu | Datta, Rupali
In order to select appropriate plant species for phytoremediation of explosive compounds, phytotoxicity, uptake proficiency, capability of the plant to degrade/transform the compounds, and several environmental factors need to be considered. The environmental factors comprise climatic attributes, soil type, the water environment, root penetration depth, contaminant kinetics, and bioavailability. Out of the plant species that have shown efficient TNT uptake, there are only a few that can do so in a variety of environments, which is imperative in case of contaminants that are widespread, such as TNT and RDX. The two most effective species for TNT uptake reported to date are Eurasian water milfoil, Myriophyllum spicatum and vetiver grass, Chrysopogon zizanioides. For RDX phytoremediation, reed canary grass, fox sedge, and rice have shown promise, although degradation of RDX in the plant tissue is limited. Over the past few decades, a considerable amount of information on phytotoxicity and metabolism of TNT and RDX in plants and microorganisms have been collected, which has led to the identification of potential plant species for use in TNT and RDX phytoremediation, as well as candidate genes for developing effective transgenic plants. Recent research has also revealed promising non-transgenic approaches, such as use of chaotropic agents for enhanced solubilization and uptake of TNT, which could prove to be practical and effective for military sites. Field trials of some of these promising new technologies are necessary for the development of effective, low-cost, and environmentally friendly phytoremediation of explosive-contaminated sites.
Mostrar más [+] Menos [-]Paleo-Perspectives on Potential Future Changes in the Oxidative Capacity of the Atmosphere Due to Climate Change and Anthropogenic Emissions
2015
Alexander, Becky | Mickley, Loretta J.
The oxidizing capacity of the atmosphere, defined as the global mean tropospheric abundance of the hydroxyl radical (OH·), strongly influences air pollution by controlling the lifetimes of gaseous pollutants and the production of particulate matter. Predicting future changes in OH· due to anthropogenic emissions and climate change is of interest to air quality managers, but it is difficult because of multiple competing effects. Models of atmospheric chemistry suggest that these competing effects buffer significant change in OH· in the past and in the near future. However, proxy-based observations for past changes in OH· and other oxidants over the preindustrial-industrial and glacial-interglacial time scales suggest much larger changes than models estimate. Model sensitivity studies show that variability in past and future OH· is highly sensitive to relative emissions of reactive nitrogen and carbon, water vapor, lightning, and stratospheric ozone, implying that one or more of these variables is highly sensitive to climate.
Mostrar más [+] Menos [-]Histopathological indices in sole (Solea solea) and hake (Merluccius merluccius) for implementation of the European Marine Strategy Framework Directive along the Basque continental shelf (SE Bay of Biscay)
2015
Cuevas, Nagore | Zorita, Izaskun | Costa, Pedro M. | Quincoces, Iñaki | Larreta, Joana | Franco, Javier
Sole and hake, together with sediments, were collected during two campaigns along the Basque continental shelf to study the utility of two existing histopathological indices for assessing the biological effects of contaminants to implement the European Marine Strategy Framework Directive. Hepatic and gonadal histopathology were measured, and metal and/or organic contaminants were determined in both liver and sediments. Sediments from the Basque continental shelf were found to be moderately impacted by metals but non-impacted by organic compounds. Metal bioaccumulation and histopathological lesions in liver were higher in sole than in hake, although non-specific and early non-neoplastic toxicopathic lesions were observed in both species. No gross alterations were recorded in gonad. The two histopathological indices applied were highly correlated in both organs but the lack of correlation between sediment contamination levels, bioaccumulation and histopathological indices suggests that other factors, rather than pollution alone, are responsible for the biological effects observed.
Mostrar más [+] Menos [-]Changes in bioaccumulation and translocation patterns between root and leafs of Avicennia schaueriana as adaptive response to different levels of metals in mangrove system
2015
Souza, Iara da C. | Rocha, Lívia D. | Morozesk, Mariana | Bonomo, Marina M. | Arrivabene, Hiulana P. | Duarte, Ian D. | Furlan, Larissa M. | Monferrán, Magdalena V. | Mazik, K. (Krysia) | Elliott, Michael | Matsumoto, Silvia T. | Milanez, Camilla R.D. | Wunderlin, Daniel A. | Fernandes, Marisa N.
Espírito Santo estuaries (Brazil) are impacted by industrial activities, resulting in contamination of water and sediments. This raise questions on biological uptake, storage and consequences of metal contamination to mangrove plants. The goal of this work was evaluating accumulation and translocation of metals from sediment to roots and leaves of Avicennia schaueriana, growing in areas with different degrees of contamination, correlating bioaccumulation with changes in its root anatomy. Highest bioconcentration factors (BCFs) were observed in plants growing in less polluted areas. Conversely, highest translocation factors were found in plants from highest polluted area, evidencing an adaptive response of A. schaueriana to less favourable conditions. Namely, the absorption of metals by roots is diminished when facing highest levels of metals in the environment; alternatively, plants seem to enhance the translocation to diminish the concentration of toxic metals in roots. Root also responded to highly polluted scenarios with modifications of its anatomy.
Mostrar más [+] Menos [-]Temporal variations of heavy metals levels in Perna viridis, on the Chacopata-Bocaripo lagoon axis, Sucre State, Venezuela
2015
Pinto, Rafael | Acosta, Vanessa | Segnini, Mary Isabel | Brito, Leonor | Martínez, Gregorio
Perna viridis was used as biomonitor to assess heavy metal levels in the Chacopata-Bocaripo lagoon axis, Venezuela, during rain and drought seasons. The mussels were weighed and measured. The metal concentrations were determined by atomic absorption spectrophotometry. For rain period, the order of bioavailability was: Cu>Ni>Mn>Co>Cd>Pb, and for drought: Cu>Mn>Ni>Co>Pb>Cd. The concentrations of Ni, Co, Cd and Pb showed significant differences (P<0.05) in both periods. There was higher metal accumulation during drought season, possibly related to upwelling, since it produces an increase in primary productivity, which translates more food into organisms, making metals bioavailable for mussels. Only Cu and Mn showed significant relationships between the size and metal concentration, during drought period, it may be because of the organisms need for these essential metals in different physiological processes.
Mostrar más [+] Menos [-]The NET effect of dispersants — a critical review of testing and modelling of surface oil dispersion
2015
Zeinstra-Helfrich, Marieke | Koops, Wierd | Murk, Albertinka J.
Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and transport of the oil.We aim to identify how natural, chemical and mechanical dispersion could be quantified in oil spill models. For each step in the dispersion process, we review available experimental data in order to identify overall trends and propose an algorithm or calculation method. Additionally, the conditions for successful mechanical and chemical dispersion are defined.Two commonly identified key parameters in surface oil dispersion are: oil properties (viscosity and presence of dispersants) and mixing energy (often wind speed). Strikingly, these parameters play a different role in several of the dispersion sub-processes. This may explain difficulties in simply relating overall dispersion effectiveness to the individual parameters.
Mostrar más [+] Menos [-]Variations in macrobenthic community structures in relation to environmental variables in the Seto Inland Sea, Japan
2015
Nishijima, Wataru | Umehara, Akira | Okuda, Tetsuji | Nakai, Satoshi
A data set of 425 sites investigated by the Ministry of the Environment in 2001–2005 was used to evaluate the current sediment situation and its effect on macrobenthic community structure in the Seto Inland Sea, Japan. Cluster analysis and principle component analysis of sediments using physico-chemical parameters revealed that total organic carbon, mud, sulfide contents, and oxidation–reduction potential were important parameters influencing macrobenthic population size and biodiversity. A total organic carbon of 1mgg−1 interval was highly negatively correlated with two biodiversity indices in the range of 1–20mgg−1. Overall, 42% of total sites were organically enriched with much lower macrobenthic population sizes and biodiversity, while 26% were characterized by sandy sediment with a high population size and high proportion of Arthropoda. Nemertea sp., Glycera sp., Notomastus sp. and Ophiophragmus japonicus were common macrobenthos, while Theora fragilis and Ptychoderidae were typical macrobenthos in organically enriched sediments.
Mostrar más [+] Menos [-]Sharks and people: Insight into the global practices of tourism operators and their attitudes to Shark behaviour
2015
Richards, Kirsty | O’Leary, Bethan C. | Roberts, Callum M. | Ormond, Rupert | Gore, Mauvis | Hawkins, Julie P.
Shark tourism is a popular but controversial activity. We obtained insights into this industry via a global e-mailed questionnaire completed by 45 diving/snorkelling operators who advertised shark experiences (shark operators) and 49 who did not (non-shark operators). 42% of shark operators used an attractant to lure sharks and 93% stated they had a formal code of conduct which 86% enforced “very strictly”. While sharks were reported to normally ignore people, 9 operators had experienced troublesome behaviour from them. Whilst our research corroborates previous studies indicating minimal risk to humans from most shark encounters, a precautionary approach to provisioning is required to avoid potential ecological and societal effects of shark tourism. Codes of conduct should always stipulate acceptable diver behaviour and appropriate diver numbers and shark operators should have a moral responsibility to educate their customers about the need for shark conservation.
Mostrar más [+] Menos [-]Spatial and temporal distribution and risk assessment of polycyclic aromatic hydrocarbons in surface seawater from the Haikou Bay, China
2015
Li, Yuhu | Li, Ping | Ma, Wandong | Song, Qingqing | Zhou, Hailong | Han, Qian | Diao, Xiaoping
Spatial and temporal distributions of 14 polycyclic aromatic hydrocarbons (PAHs) were investigated in surface waters of Haikou Bay, China from October 2013 to September 2014. The total PAHs concentrations ranged from 420.2 to 2539.1ngL−1 with the average value of 1016.3±455.8ngL−1, which were predominated by low molecular weight PAHs (2- and 3-ring PAHs). Moreover, PAHs displayed spatial and temporal variations in the concentration and composition pattern. Source analysis based on isomer ratios indicated that the PAHs mostly originated from petroleum and combustion processes. An eco-toxicological risk assessment showed that the potential risk of individual PAHs had reached moderate to high levels and the total concentrations of PAHs had also reached a relatively high level compared with previous studies. This study offers important information on the pollution levels of 14 PAHs in the surface waters of Haikou Bay and recommends that prevention and control of PAHs pollution should be implemented in the region.
Mostrar más [+] Menos [-]Response of a seagrass fish assemblage to improved wastewater treatment
2015
Ourgaud, M. | Ruitton, S. | Bell, J.D. | Letourneur, Y. | Harmelin, J.G. | Harmelin-Vivien, M.L.
We compared the structure of a seagrass fish assemblage near a sewage outlet before and after improvements to wastewater treatment. To determine whether responses by the fish assemblage were due to changes in water quality or to other factors, comparisons were made with the structure of a fish assemblage from a nearby site unaffected by sewage effluent. Total species richness, density and biomass of fish, decreased at both sites over the 30-year period. An increase in mean trophic level near the sewage outlet following improvements in water quality indicated that wastewater treatment had another important effect. This result is consistent with the reductions in food webs supporting pelagic and benthic fishes that typically accompany decreases in nutrient inputs. Although improvements to wastewater treatment explained much of the variation in the structure of the fish assemblage at PC, our results also suggest that fishing and climate change, at both sites.
Mostrar más [+] Menos [-]