خيارات البحث
النتائج 1661 - 1670 من 4,307
Capability of Paraguaçu estuary (Todos os Santos Bay, Brazil) to form oil–SPM aggregates (OSA) and their ecotoxicological effects on pelagic and benthic organisms النص الكامل
2017
For experiments concerning the formation of oil–suspended particulate matter (SPM) aggregates (OSA), oil and sediment samples were collected from Campos Basin and six stations of Paraguaçu estuary, Todos os Santos Bay, Brazil, respectively. The sediments samples were analyzed for organic matter determined by the EMBRAPA method, nitrogen determined by the Kjeldahl method, and phosphorus determined by the method described by Aspila. The oil trapped in OSA was extracted following the method described by Moreira. The experiment showed a relationship between the amount of organic matter and OSA formation and consequently the dispersion of the studied oil. On the basis of the buoyancy of OSA and the ecotoxicological effects on pelagic and benthic community, the priority areas for application of remediation techniques are Cachoeira, Maragogipe, and Salinas da Margarida because of the large amount of oil that accumulated at the bottom of the experiment flask (5.85%, 27.95%, and 38,98%; 4.2%, 17.66%, and 32.64%; and 11.82%, 8.07%, and 10.91% respectively).
اظهر المزيد [+] اقل [-]Geochemical markers of sedimentary organic matter in Todos os Santos Bay, Bahia – Brazil. Indicators of sources and preservation النص الكامل
2017
de Souza, José Roberto Bispo | do Rosário Zucchi, Maria | Costa, Alexandre Barreto | de Azevedo, Antonio Expedito Gomes | Spano, Saulo
Natural stable isotopes, such as carbon (C) and nitrogen (N), are modern tools to assess geochemical processes. C and N in organic matter can carry fingerprints of their hydrologic flows and sedimentary processes, including any anthropogenic modification on the natural system. This study focuses on the determination of aliphatic and polycyclic aromatic hydrocarbons and isotopic ratio in the sediment of Todos os Santos Bay (TSB). The isotopic results of the total organic matter indicate varied contribution marine and terrigenous. Typical rates of PAHs mainly indicate a pyrogenic source and mixture between pyrogenic and petrogenic sources. Typical ratios for the n-alkanes indicate the presence of petroleum hydrocarbons. The isotopic composition of n-alkanes suggests a mixture of sources, with the possible contribution of petrogenic.
اظهر المزيد [+] اقل [-]Use of moss biomonitors for turbulent transport coefficient estimation for industrial emissions النص الكامل
2017
Ryzhakova, Nadezhda K. | Borisenko, Alexei L. | Babicheva, Valentina O.
The important mechanism transporting substances in the surface layer of the atmosphere is turbulent diffusion. The intensity of turbulent transport is characterized by the turbulent diffusion coefficient. Calculation is a difficult task without a unique characterization. Distinguished turbulent models of atmospheric flow have been developed for particular atmospheric states and simple landscapes. These restrictions complicate the use of such models when assessing the distribution of industrial emissions in the atmosphere. The aims of the present work are to (i) develop a semi-empirical method for estimating the turbulent diffusion coefficient of the emissions of large industries, and (ii) study the turbulence intensity dependence of fundamental factors: the wind speed and landscape. The method relies on the distribution function of the concentration of contaminants measured along any direction of the altitude of a point source. Epiphytic mosses (Pylaisia polyantha, Sanionia uncinata) were used with an exposure time of 3 years. The chemical contents of the mosses were determined by neutron activation analysis and atomic emissive spectrometry. It is shown that in the territories of the coal-fired thermal power station and aluminum plant, the average values of the turbulent transport coefficient at heights above 1 m are k1¯=0.15 m2/s and k1¯=0.02 m2/s respectively. High turbulence within the location of the thermal power station is explained by obstacles of various heights and a higher wind speed. The proposed method is useful for the estimation and forecast of the spatial distribution of emissions from large industries and for determining the zones of their influence.
اظهر المزيد [+] اقل [-]Distinguishing globally-driven changes from regional- and local-scale impacts: The case for long-term and broad-scale studies of recovery from pollution النص الكامل
2017
Hawkins, S.J. | Evans, A.J. | Mieszkowska, N. | Adams, L.C. | Bray, S. | Burrows, M.T. | Firth, L.B. | Genner, M.J. | Leung, K.M.Y. | Moore, P.J. | Pack, K. | Schuster, H. | Sims, D.W. | Whittington, M. | Southward, E.C.
Marine ecosystems are subject to anthropogenic change at global, regional and local scales. Global drivers interact with regional- and local-scale impacts of both a chronic and acute nature. Natural fluctuations and those driven by climate change need to be understood to diagnose local- and regional-scale impacts, and to inform assessments of recovery. Three case studies are used to illustrate the need for long-term studies: (i) separation of the influence of fishing pressure from climate change on bottom fish in the English Channel; (ii) recovery of rocky shore assemblages from the Torrey Canyon oil spill in the southwest of England; (iii) interaction of climate change and chronic Tributyltin pollution affecting recovery of rocky shore populations following the Torrey Canyon oil spill. We emphasize that “baselines” or “reference states” are better viewed as envelopes that are dependent on the time window of observation. Recommendations are made for adaptive management in a rapidly changing world.
اظهر المزيد [+] اقل [-]In situ, high-resolution DGT measurements of dissolved sulfide, iron and phosphorus in sediments of the East China Sea: Insights into phosphorus mobilization and microbial iron reduction النص الكامل
2017
Ma, Wei-Wei | Zhu, Mao-Xu | Yang, Gui-Peng | Li, Tie
Dissolved sulfide, iron (Fe), and phosphorus (P) concentrations in sediments of the East China Sea were simultaneously measured in situ by diffusive gradients in thin films (DGT) technique. The results, by combination with solid-phase Fe speciation, were used to characterize the interplays of Fe, S and P. Diverse distributions of dissolved sulfide among the sites are attributable to highly dynamic diagenetic regimes and varying availability of labile organic carbon (OC). The DGT technique provided high-resolution evidence for coexistence of microbial iron reduction (MIR) and sulfate reduction in localized zones, and for Fe-coupled P mobilization. Measured Fe2+/P ratios suggest that Fe2+ reoxidatiion at the oxic zones can serve as an efficient scavenger of P. Empirical estimation indicates that MIR plays an important role in anaerobic OC mineralization in the sediments, which is a combined result of low availability of labile OC, high reactive Fe content, and unsteady diagenetic regimes.
اظهر المزيد [+] اقل [-]Taiwanese marine microbenthic algal communities remain similar yet chlorophyll a concentrations rise in mesocosms with elevated CO2 and temperature النص الكامل
2017
Tew, K.S. | Siao, Y.J. | Liu, P.J. | Lo, W.T. | Meng, P.J.
The effects of increasing CO2 concentrations and temperature on microalgal assemblages were examined in Taiwan using mesocosms that simulate coral reef ecosystem. We assessed changes in abundance and diversity of benthic algae grown at 25°C and 28°C, under ambient (~400μatm) and at high CO2 conditions (800–1000μatm). Total alkalinity, pCO2, and the aragonite saturation state, were all significantly different between control and high CO2 treatments in both temperature treatments. Chl a concentration increased significantly in CO2-treated groups at 25°C, but benthic microalgal abundance was not significantly different. The number of microalgal species and the microalgal community structure did not differ between control and CO2-treated groups at both temperatures. Our results suggest that increasing CO2 may boost benthic microalgal primary productivity if sufficient nutrients are available, although site-specific responses are difficult to predict.
اظهر المزيد [+] اقل [-]Benthic Foraminifera as bio-indicators of anthropogenic impacts in coastal environments: Acqua dei Corsari area case study (Palermo, Italy) النص الكامل
2017
Musco, Marianna | Cuttitta, Angela | Bicchi, Erica | Quinci, Enza Maria | Sprovieri, Mario | Tranchida, Giorgio | Giaramita, Luigi | Traina, Anna | Salvagio Manta, Daniela | Gherardi, Serena | Mercurio, Pietro | Siragusa, Angelo | Mazzola, Salvatore
This study investigates living benthic foraminiferal assemblages as bio-indicators of anthropogenic activities in a coastal area within the Gulf of Palermo (Sicily, Italy), affected by industrial and urban activities, and evaluates the environmental quality through the calibration of a Tolerant Species index (%TSstd).Sediments from 6 stations were sampled along a bathymetric transect from the coast to offshore. Sediment grain size, TOC, major, minor and trace elements and polycyclic aromatic hydrocarbons (PAHs) were compared to benthic foraminiferal assemblages and species at each station.Diversity and density of benthic foraminiferal assemblages were not affected by the presence of pollutants, while tolerant species increased with organic (TOC and PAHs) or chemical (As and Pb) concentrations. Moreover, the calibration of the %TSstd formula to >125μm foraminiferal assemblage, gives a detailed description of environmental quality along the transect, representing a good and sensitive tool to evaluate marine coastal environment.
اظهر المزيد [+] اقل [-]Cryptosporidium species from common edible bivalves in Manila Bay, Philippines النص الكامل
2017
Pagoso, Edison Jay A. | Rivera, Windell L.
Manila Bay is one of the major propagation sites of edible bivalves in the Philippines. Studies have shown that bivalves might be contaminated with human pathogens like the protozoan parasite Cryptosporidium, one of the major causes of gastroenteritis in the world. In this study, Cryptosporidium from four species of edible bivalves were isolated using a combination of sucrose flotation and immunomagnetic separation. Using direct fluorescent antibody test, Cryptosporidium oocysts were found in 67 out of 144 samples collected. DNA sequence analysis of the 18S rRNA gene of the isolates detected C. parvum and C. hominis (major causes of human cryptosporidiosis) and C. meleagridis (causes infection in avian species). Analysis of the 60kDa glycoprotein gene further confirmed the genotypes of the Cryptosporidium isolates. This study is the first to provide baseline information on Cryptosporidium contamination of Manila Bay where bivalves are commonly cultured.
اظهر المزيد [+] اقل [-]Tools for evaluating environmental performance at Brazilian public ports: Analysis and proposal النص الكامل
2017
Roos, Erica Caetano | Kliemann Neto, Francisco José
The port sector critically needs improved management techniques to evaluate its environmental performance. In the present study, we conducted an exploratory research to understand the metrics used in the Brazilian public ports to assess their environmental performance. We considered two state agencies and two port authorities of southern Brazil. As preliminary results, we found that economic factors are excluded in the tools for measuring environmental performance. A system of indicators to address this shortcoming was then proposed, but it could not be applied because of data deficiencies. Thus, the system was divided into two parts: a simplified system with 7 indicators (measuring costs related to criteria were measured only technically) and an advanced system with 5 indicators (approaching costs were currently difficult to measure). Thus, the proposed indicators can be applied by port authorities to facilitate decision-making related to environmental management. As suggestions for further work, we propose research that includes more ports, both public and private, to provide an overview at the national level.
اظهر المزيد [+] اقل [-]Shipping noise in a dynamic sea: a case study of grey seals in the Celtic Sea النص الكامل
2017
Chen, F. | Shapiro, G.I. | Bennett, K.A. | Ingram, S.N. | Thompson, D. | Vincent, C. | Russell, D.J.F. | Embling, C.B.
Shipping noise is a threat to marine wildlife. Grey seals are benthic foragers, and thus experience acoustic noise throughout the water column, which makes them a good model species for a case study of the potential impacts of shipping noise. We used ship track data from the Celtic Sea, seal track data and a coupled ocean-acoustic modelling system to assess the noise exposure of grey seals along their tracks. It was found that the animals experience step changes in sound levels up to ~20dB at a frequency of 125Hz, and ~10dB on average over 10–1000Hz when they dive through the thermocline, particularly during summer. Our results showed large seasonal differences in the noise level experienced by the seals. These results reveal the actual noise exposure by the animals and could help in marine spatial planning.
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