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Resultados 611-620 de 3,208
An assessment of human influences on sources of polycyclic aromatic hydrocarbons in the estuarine and coastal sediments of China Texto completo
2015
Duan, Xiaoyong | Liu, Jinqing | Zhang, Daolai | Yin, Ping | Li, Yanxia | Li, Xianguo
Sediments collected from the coastal area of China, embracing west coast of Bohai Sea, south coast of Shandong Peninsula, and the Changjiang estuary (listed in order of decreasing north latitude), were analyzed for polycyclic aromatic hydrocarbons (PAHs). ∑PAH (Sixteen US EPA priority PAHs) were 2.7–350.9ng/g. Petroleum residue was the major contributor of PAHs in the coastal sediments of China due to oil leakage from ships and offshore oil fields. The contribution of vehicular emissions in coast of North China was significantly lower than that in the Changjiang Estuary, and the reverse was true for coal combustion. PAH concentrations in the sediment core of the Changjiang estuary steadily increased upward and the variation was primarily due to economic development and severe floods. The impact on PAHs by vehicular emissions (37.2%) and petrogenic sources (45.8%) overwhelmed combustion sources (17.0%).
Mostrar más [+] Menos [-]Evaluation of metals and hydrocarbons in sediments from a tropical tidal flat estuary of Southern Brazil Texto completo
2015
Costa, Eduardo S. | Grilo, Caroline F. | Wolff, George A. | Thompson, Anu | Figueira, Rubens Cesar Lopes | Neto, Renato Rodrigues
Although the Passagem Channel estuary, Espírito Santo State, Brazil, is located in an urbanized and industrialized region, it has a large mangrove system. Here we examined natural and anthropogenic inputs that may influence trace metal (Cd, Cr, Cu, Ni, Sc, Pb and Zn) and hydrocarbon (n-alkane and terpane) deposition in three sediment cores collected in the tidal flat zone of the estuary. The cores were also analyzed for carbonate, grain size and stable isotopic composition (δ13Corg. and δ15Ntotal). Metal enrichment and its association to petroleum hydrocarbons in the surficial sediments of one of the cores, indicate crude oil and derivative inputs, possibly from small vessels and road run-off from local heavy automobile traffic. At the landward sites, the major contributions for metals and hydrocarbons are from natural sources, but in one case, Cu may have been enriched by domestic effluent inputs.
Mostrar más [+] Menos [-]Long-term functional changes in an estuarine fish assemblage Texto completo
2015
Baptista, J. | Martinho, F. | Nyitrai, D. | Pardal, M.A. | Dolbeth, M.
Long-term functional changes in an estuarine fish assemblage Texto completo
2015
Baptista, J. | Martinho, F. | Nyitrai, D. | Pardal, M.A. | Dolbeth, M.
The functional diversity of the fish assemblages of the Mondego estuary was studied for a discontinuous 30-year period (1988–2012). During this time, hydrological changes occurred due to man-induced alterations and weather extremes. These changes led to alterations in the structure and function of the fish community. Species richness and functional richness decreased over time and the fish community started to explore new micro-habitats and food resources. Before severe hydrological changes, the community was dominated by pelagic, detritivorous and species with wider salinity ranges. After, the community became dominated by demersal, benthic, piscivorous and marine species. During a drought, omnivorous became increasingly important, reflecting greater possibilities of using available feeding resources. We have also found an increase in sub-tropical species throughout the years, which might be related to gradual temperature increases at a global scale. This study also confirmed estuaries as extremely important for restocking several commercial species.
Mostrar más [+] Menos [-]Long-term functional changes in an estuarine fish assemblage Texto completo
2015 | 1000
Baptista, J. | Martinho, F. | Nyitrai, D. | Pardal, M. A. | Dolbeth, M.
The functional diversity of the fish assemblages of the Mondego estuary was studied for a discontinuous 30-year period (1988–2012). During this time, hydrological changes occurred due to man-induced alterations and weather extremes. These changes led to alterations in the structure and function of the fish community. Species richness and functional richness decreased over time and the fish community started to explore new micro-habitats and food resources. Before severe hydrological changes, the community was dominated by pelagic, detritivorous and species with wider salinity ranges. After, the community became dominated by demersal, benthic, piscivorous and marine species. During a drought, omnivorous became increasingly important, reflecting greater possibilities of using available feeding resources. We have also found an increase in sub-tropical species throughout the years, which might be related to gradual temperature increases at a global scale. This study also confirmed estuaries as extremely important for restocking several commercial species.
Mostrar más [+] Menos [-]Physical controls of hypoxia in waters adjacent to the Yangtze Estuary: A numerical modeling study Texto completo
2015
Chen, Xiaofeng | Shen, Zhenyao | Li, Yangyang | Yang, Ye
A three-dimensional circulation model (the Environmental Fluid Dynamic Code) was used to examine the role that physical forcing (river discharge, wind speed and direction) plays in controlling hypoxia in waters adjacent to the Yangtze Estuary. The model assumes that the biological consumption of oxygen is constant in both time and space, which allows the role of physical forcing in modulating the oxygen dynamics to be isolated. Despite of the simplicity of this model, the simulation results showed that it can reproduce the observed variability of dissolved oxygen in waters adjacent to the Yangtze Estuary, thereby highlighting the important role of changes in physical forcing in the variation of hypoxia. The scenarios tested revealed appreciable changes in the areal extent of hypoxia as a function of wind speed and wind direction. Interestingly, well-developed hypoxia was insensitive to river discharge.
Mostrar más [+] Menos [-]Sequencing Batch Reactor for Wastewater Treatment: Recent Advances Texto completo
2015
Dutta, Aparna | Sarkar, Sudipta
Sequencing batch reactors (SBRs), due to its operational flexibility and excellent process control possibilities, are being extensively used for the treatment of wastewater which nowadays is fast becoming contaminated with newer and more complex pollutants. It is also possible to include different expanding array of configurations and various operational modifications to meet the effluent limits which are also continuously getting upgraded. This article provides basic description of SBR process along with its functional and physical variants that lead to improved the removal of nutrients and emerging contaminants. The significance of selectors and various recent advancements in the application of SBR has been discussed along with the possibilities held by SBR process in the treatment of wastewater of different origins and composition to produce effluent of reusable quality.
Mostrar más [+] Menos [-]An effective seed protection method for planting Zostera marina (eelgrass) seeds: Implications for their large-scale restoration Texto completo
2015
Zhang, Pei-Dong | Fang, Chao | Liu, Jie | Xu, Qiang | Li, Wen-Tao | Liu, Yan-Shan
We describe an innovative method of planting Zostera marina (eelgrass) seeds in which hessian bags filled with high-silted sediments are used as a seed protecting device. Here, we evaluated the effectiveness of the method through a field seed-sowing experiment over a three year period. The suitable seed planting density required by the seeds of Z. marina in this method was also investigated. In the spring following seed distribution, seedling establishment rate of Z. marina subjected to different seed densities of 200–500seedsbag−1 ranged from 16% to 26%. New eelgrass patches from seed were fully developed and well maintained after 2–3years following distribution. The seed planting density of 400seedsbag−1 may be the most suitable for the establishment of new eelgrass patches. Our results demonstrate that seed-based restoration can be an effective restoration tool and the technique presented should be considered for future large-scale Z. marina restoration projects.
Mostrar más [+] Menos [-]Proteomic analysis of the European flounder Platichthys flesus response to experimental PAH–PCB contamination Texto completo
2015
Galland, Claire | Dupuy, Célie | Loizeau, Véronique | Danion, Morgane | Auffret, Michel | Quiniou, Louis | Laroche, Jean | Pichereau, Vianney
Platichthys flesus is often used as a sentinel species to monitor the estuarine water quality. In this study, we carried out an experimental contamination of fish using a PAHs/PCBs mixture, which was designed to mimic the concentrations found in the Seine estuary (C1) and 10 times these concentrations (C2). We used a proteomic approach to understand the molecular mechanisms implied in the response of P. flesus to these xenobiotics. We showed that 54 proteins were differentially accumulated in one or several conditions, which 34 displayed accumulation factors higher than two. 18 of these proteins were identified by MALDI TOF–TOF mass spectrometry. The results indicated the deregulation of oxidative stress- and glutathione metabolism-(GST, GPx) proteins as well as of several proteins belonging to the betaine demethylation pathway and the methionine cycle (BHMT, SHMT, SAHH), suggesting a role for these different pathways in the P. flesus response to chemical contamination.
Mostrar más [+] Menos [-]Response of benthos to ocean outfall discharges: does a general pattern exist? Texto completo
2015
Puente, A. | Diaz, R.J.
We assessed the effects of 40 ocean outfalls on adjacent macrobenthic invertebrates. Data were obtained from a review of gray and peer-review literature. Different parameters describing the outfall characteristics were compiled (length, maximum depth, treatment level, flow and organic matter mass discharged). Exposure to wave action was represented by significant wave height. The magnitude of the effect was categorized in three impact levels and classified considering different ecological indicators. A theoretical predictive model was formulated in which the lower the organic matter and the higher the energy of the system, the lower the benthic impact. The main conclusion was that the general pattern of the succession of benthic communities brought about by ocean outfalls fits the model of Pearson–Rosenberg but with some deviations i) the probability of a significant impact is much lower, ii) not all the successional stages occur and, iii) the magnitude of the changes are usually lower.
Mostrar más [+] Menos [-]Marine debris ingestion by albatrosses in the southwest Atlantic Ocean Texto completo
2015
Jiménez, Sebastián | Domingo, Andrés | Brazeiro, Alejandro | Defeo, Omar | Phillips, Richard A.
Plastics and other marine debris affect wildlife through entanglement and by ingestion. We assessed the ingestion of marine debris by seven albatross species in the southwest Atlantic by analyzing stomach contents of birds killed in fisheries. Of the 128 specimens examined, including four Diomedea species (n=78) and three Thalassarche species (n=50), 21 (16.4%) contained 1–4 debris items, mainly in the ventriculus. The most common type was plastic fragments. Debris was most frequent in Diomedea species (25.6%) and, particularly, Diomedea sanfordi (38.9%) and very rare in Thalassarche species (2.0%), presumably reflecting differences in foraging behavior or distribution. Frequency of occurrence was significantly higher in male than female Diomedea albatrosses (39.3% vs. 18.0%). Although levels of accumulated debris were relatively low overall, and unlikely to result in gut blockage, associated toxins might nevertheless represent a health risk for Diomedea albatrosses, compounding the negative impact of other human activities on these threatened species.
Mostrar más [+] Menos [-]Human and riverine impacts on the dynamics of biogeochemical parameters in Kwangyang Bay, South Korea revealed by time-series data and multivariate statistics Texto completo
2015
The successful management of sustainable coastal environments that are beneficial to both humans and marine ecosystems requires knowledge about factors that are harmful to such environments. Here, we investigated seawater nutrient and carbon parameters between 2010 and 2012 in Kwangyang Bay, Korea, a coastal environment that has been exposed to intensive anthropogenic activities. The data were analyzed using cluster and factor analysis. We found that the biogeochemical cycles of nutrients and carbon were determined by river discharge into the bay and biological activity. However, the impacts of these factors varied both spatially and seasonally. During the past 10years, nutrient loads from the river and industrial complexes to the bay have decreased. The impacts of this decrease are visible in the phosphate concentration, which has fallen to a third of its initial value. We also examined the potential role of atmospheric nitrogen deposition in nitrogen cycling in the study area.
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