细化搜索
结果 741-750 的 1,955
Factors driving the seasonal distribution of planktonic and epiphytic ciliates in a eutrophicated Mediterranean Lagoon 全文
2013
Dhib, Amel | Brahim, Mounir Ben | Ziadi, Boutheina | Akrout, Fourat | Turki, Souad | Aleya, Lotfi
We studied the distribution of planktonic and epiphytic ciliates coupled with environmental factors and microalgae abundance at five stations in Ghar El Melh Lagoon (Tunisia). Planktonic ciliates were monitored for a year and epiphytic ciliates were sampled during summer 2011 in concordance with the proliferation of the seagrass Ruppia cirrhosa. Ciliate assemblage was largely dominated by Spirotrichea followed respectively by Tintinnida of and Strombidiida. No significant difference was found in the distribution of ciliate species among the stations. Redundancy analysis indicates that abiotic factors (temperature and nutriments) have a significant effect on the dynamics of certain ciliates. For epiphytic ciliates, 4 species were identified: Tintinnopsis campanula, Aspidisca sp., Strombidium acutum and Amphorides amphora. Based on PERMANOVA analyses, ciliates exhibit significant correlations among months and stations. According to ACP, epiphyte distribution follows roughly those of R. cirrhosa and pH. Significant correlations were found between harmful dinoflagellates and both planktonic and epiphytic ciliates.
显示更多 [+] 显示较少 [-]The influence of demersal trawl fishing gears on the resuspension of dinoflagellate cysts 全文
2013
Brown, Lyndsay | Bresnan, E. (Eileen) | Summerbell, Keith | O’Neill, Finbarr Gerard
To investigate the influence of towed demersal fishing gears on dinoflagellate cyst resuspension, towing trials with four gear components were carried out at three sites of differing sediment type in the Moray Firth, Scotland. Samples of sediment plumes were collected using plankton nets mounted on a towed sledge. Diversity of resuspended dinoflagellate cysts was similar at all sites and included Protoperidinium and Gonyaulax spp., Proroceratium reticulatum and unidentified ‘round brown’ cysts. Cyst concentrations per gram of resuspended sediment varied by gear component and sediment particle size distribution. Gear components with lower hydrodynamic drag generated wakes with smaller shear stresses, mobilising fewer larger sand particles, giving larger concentrations of cysts. Muddy sediments contained higher cyst concentrations which declined with increasing grain size. This study has shown that fishing gear and sediment type can influence the redistribution of dinoflagellate cysts and highlights the importance this may have in relation to dinoflagellate blooms.
显示更多 [+] 显示较少 [-]A ten–year source apportionment study of ambient fine particulate matter in San Jose, California 全文
2013
Wang, Yungang | Hopke, Philip K.
Fine particulate matter (PM2.5) composition data from the Speciation Trends Network (STN) site in San Jose, CA, were analyzed by positive matrix factorization (PMF) using U.S. Environmental Protection Agency (EPA) PMF version 5.0. These data were 24–h average mass concentrations and compositions obtained from samples taken every third day from October 2002 to February 2012. The eight identified sources include secondary sulfate, secondary nitrate, fresh sea salt, aged sea salt, diesel emission, road salt, gasoline vehicles, and wood combustion. The contributions to PM2.5 of these eight sources were 13.1%, 20.0%, 5.5%, 7.8%, 9.4%, 5.1%, 14.8, and 24.3%, respectively. The Ni–related industrial source, which was detected in previous PMF analysis, was not identified in our study and a sharp decrease in Ni concentrations was observed after the end of 2004. The contribution of road dust source decreased significantly after 2004 (Mann–Whitney test, p<0.01), which is probably the result of the city wide enhanced street sweeping programs starting in 2005. A 40% reduction in the wood combustion PM2.5 contribution between winter 2008 and winter 2009 was found. This decrease could be attributed to the San Francisco Bay Area Air Quality Management District (BAAQMD) wood burning rule implemented in July 2008. In the future, the effectiveness and benefits of the wood burning rule could be evaluated using the multi–wavelength aethalometer delta–c method.
显示更多 [+] 显示较少 [-]Photosynthetically active radiation loss in the atmosphere in North China 全文
2013
Bai, Jianhui
Based on an understanding of energy, empirical formulas of hourly PAR (photosynthetically active radiation) under all sky conditions in North China were introduced and applied. An interesting and important phenomenon of the absorption of “water vapor factor” in 400–700 nm was studied and its real mechanism can be explained by the energy consumption of the substances (gas, liquid, solid–phase) through OH radicals during chemical and photochemical reactions. The PAR at the top of the atmosphere was estimated with good agreement. PAR losses in the atmosphere associated with “photochemical factor” and other materials in North China are spatial and seasonal dependence; their “annual” averages were 15.33 and 309.30 W m–2 in North China, respectively. The energy loss related to the “photochemical factor” should be considered in all kinds of basic processes in the atmosphere and model studies, including radiation transmission, photochemistry, air motion, and climate.
显示更多 [+] 显示较少 [-]Carbonaceous aerosols in a wood burning community in rural New Zealand 全文
2013
Ancelet, Travis | Davy, P. K. (Perry K.) | Trompetter, William J. | Markwitz, A. (Andreas) | Weatherburn, David C.
Particulate matter (PM) in Masterton, New Zealand, a rural community with a population of 20 000, was studied during the winter to gain an understanding of the carbonaceous species and their influence on PM concentrations. The average PM10 concentration during the winter was 21.0±14.8 µg m–3, of which 64% was PM2.5. PM2.5 concentrations were found to be the main cause of elevated PM10 concentrations, and were responsible for exceedances of the New Zealand National Environmental Standard for PM10. Carbonaceous species were 47 and 77% of the total PM10 and PM2.5, respectively. Organic carbon (OC) concentrations were always higher than elemental carbon (EC) concentrations. OC and EC concentrations showed excellent correlation with PM2.5 concentrations, suggesting that combustion processes were the dominant source of PM. Stable isotope analysis yielded δ13C values ranging from –24.9 to –27.6‰, which is indicative of wood combustion. Analysis of particle–phase PAHs by thermal desorption GC/MS yielded an average total PAH concentration of 38.9±25.9ng m–3, accounting for 0.3% of the PM2.5. Analysis of all of the results revealed that residential wood burning for domestic heating was the main source of PM pollution in Masterton. The results of this study suggest that a PM10 standard alone, particularly in areas where wood combustion is common, may not be providing an adequate level of protection for the exposed population.
显示更多 [+] 显示较少 [-]Correlation between atmospheric deposition of Cd, Hg and Pb and their concentrations in mosses specified for ecological land classes covering Europe 全文
2013
Schröder, Winfried | Pesch, Roland | Hertel, Anne | Schonrock, Simon | Harmens, Harry | Mills, Gina | Ilyin, Ilia
Referring to Europe as a whole and to single European countries, previous studies have shown that heavy metal concentrations in mosses (1) are primarily determined by atmospheric deposition of heavy metals; (2) are country and element–specific; and (3) agree well with respect to element–specific spatial patterns and temporal trends of atmospheric deposition of heavy metals. This paper investigates correlations between the concentrations of cadmium, lead and mercury in atmospheric deposition and mosses within the units of an ecological land classification of Europe. To this end, measurements from the 2005/2006 European moss survey and modeled atmospheric deposition in the previous three years were intersected with a map on ecologically defined land classes of Europe. Then, the minimum numbers of sampling sites required within the ecological land classes were computed. Considering spatial auto–correlations, subsequently the correlations between the concentrations of heavy metals in mosses and corresponding deposition were calculated and mapped for each of those ecological land classes containing moss sampling sites. It was concluded that the numbers of sampling sites within Europe and most participating countries as well as within most of the ecological land classes are sufficient for estimating the mean of measurements for the above mentioned three spatial levels within 20% of its true value with 95% confidence. Spatial patterns of correlations between the atmospheric deposition and bioaccumulation were shown to vary by element and ecologically defined land classes.
显示更多 [+] 显示较少 [-]Influence of an intensive agricultural drainage basin on the seasonal distribution of organic pollutants in seawater from a Mediterranean coastal lagoon (Mar Menor, SE Spain) 全文
2013
Moreno-González, R. | Campillo, J.A. | León, V.M.
The seasonal distribution of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, organochlorine pesticides, organophosphorus pesticides, triazines and other organic pollutants in surface seawater from the Mar Menor lagoon (SE Spain) was characterized from spring 2009 to winter 2010 by stir bar sorptive extraction and thermal desorption followed by capillary gas chromatography coupled to mass spectrometry (SBSE–GC–MS). The most ubiquitous pollutants were chlorpyrifos, chlortal-dimethyl, terbuthylazine, naphthalene and propyzamide throughout the year. Insecticides and herbicides were predominant in summer and spring, and fungicides were more abundant in autumn and winter. Chlorpyrifos was predominant in autumn and spring; herbicides (propyzamide, terbuthylazine and terbuthylazine-desethyl) in autumn and fungicides (flutolanil, boscalid, cyprodinil) in autumn and winter. The highest concentrations for the majority of pollutants were detected in autumn as consequence of air and surface/ground water inputs, and above all of desorption from terrigenous materials deposited in sediments by two intense flash flood events (September 2009).
显示更多 [+] 显示较少 [-]Kinetics and equilibrium models for the sorption of tributyltin to nZnO, activated carbon and nZnO/activated carbon composite in artificial seawater 全文
2013
Ayanda, Olushola S. | Fatoki, Olalekan S. | Adekola, Folahan A. | Ximba, Bhekumusa J.
The removal of tributyltin (TBT) from artificial seawater using nZnO, activated carbon and nZnO/activated carbon composite was systematically studied. The equilibrium and kinetics of adsorption were investigated in a batch adsorption system. Equilibrium adsorption data were analyzed using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models. Pseudo first- and second-order, Elovich, fractional power and intraparticle diffusion models were applied to test the kinetic data. Thermodynamic parameters such as ΔG°, ΔS° and ΔH° were also calculated to understand the mechanisms of adsorption. Optimal conditions for the adsorption of TBT from artificial seawater were then applied to TBT removal from natural seawater. A higher removal efficiency of TBT (>99%) was obtained for the nZnO/activated carbon composite material and for activated carbon but not for nZnO.
显示更多 [+] 显示较少 [-]Impacts of marine debris on wild animals in the coastal area of Korea 全文
2013
Hong, Sunwook | Lee, Jongmyoung | Jang, Yong Chang | Kim, Yŏng-jun | Kim, Hee Jong | Han, Donguk | Hong, Sang Hee | Kang, Daeseok | Shim, Won Joon
Over the last decade, marine debris has become a major factor affecting the coastal ecosystem of Korea. This study compiled information regarding how marine debris impacts wildlife in Korea. Cases of marine debris impacting wildlife were collected from experts of various fields and from local participants through an open access website from February 2010 to March 2012. A total of 21 species were affected by marine debris: 18 species of birds, 2 species of mammals, and 1 species of crustacean. Five threatened or protected species were identified: black-faced spoonbill, finless porpoise, water deer, whooper swan, and greater painted snipe. Recreational fishing gears were the types of debris that most frequently impacted wildlife, especially birds. Black tailed gulls were the most vulnerable species to recreational fishing hooks and lines. Although it was preliminary, this study revealed that recreational fishing activities should be prioritized when managing marine debris in Korea.
显示更多 [+] 显示较少 [-]An integrative method for the evaluation, monitoring, and comparison of seagrass habitat structure 全文
2013
Irving, Andrew D. | Tanner, Jason E. | Gaylard, Sam G.
An integrative method for the evaluation, monitoring, and comparison of seagrass habitat structure 全文
2013
Irving, Andrew D. | Tanner, Jason E. | Gaylard, Sam G.
Assessing environmental condition is essential for the management of coasts and their resources, but better management decisions occur when large databases are simplified into more manageable units of information. Here we present the habitat structure index (HSI), which enables rapid assessment and direct comparison of seagrass habitat structure using scores of 0 (poor) to 100 (excellent) based on integrating five habitat variables: area, continuity, proximity, percentage cover, and species identity. Acquiring data to calculate the HSI can be done in situ or from video recordings, and requires relatively simple methodology of belt transects, estimating percentage cover, and basic taxonomy. Spatiotemporal comparisons can usefully identify locations and periods of seagrass habitat change, potentially providing an early warning indicator of habitat damage and decline in environmental quality. Overall, the integrative approach of the HSI represents a step toward simplifying the exchange of environmental information among researchers, coastal managers, and governing bodies.
显示更多 [+] 显示较少 [-]An integrative method for the evaluation, monitoring, and comparison of seagrass habitat structure 全文
2013
Irving, A. | Tanner, J. | Gaylard, S.
Abstract not available | Andrew D. Irving, Jason E. Tanner, Sam G. Gaylard
显示更多 [+] 显示较少 [-]