Уточнить поиск
Результаты 811-820 из 3,189
Assessing the mineral dust from North Africa over Portugal region using BSC–DREAM8b model
2015
Alexandra, Monteiro | Ana Patricia, Fernandes | Carla, Gama | Carlos, Borrego | Oxana, Tchepel
Over the last decade, air pollution has become a major problem in Portugal mainly due to the high concentrations of particulate matter in the atmosphere, which surpassed the daily limit values. An abundant type of natural atmospheric aerosol is related with the suspension and long–range transport of mineral dust from North Africa deserts. The main objective of this work was to assess the mineral dust over Portugal, namely in what concerns both long–term period (one year) and episode peaks. The BSC–DREAM8b v1.0 model was applied for the entire year of 2011 and the modeled surface concentrations were explored. The annual mean of the simulated dust has a magnitude of 2–6μg m–3. The monthly average analysis highlights the largest mineral dust average values in April and May (about 4μg m–3 higher than the other months). The influence of the transport of mineral dust from North Africa to Portugal is limited on time scale, since in 50% of the time this contribution is below 0.2μg m–3. Only when high percentiles are analyzed the dust surface concentrations over Portugal become relevant (>3μg m–3; with peak contribution around 10–25μg m–3). To characterize the strongest episodes of dust, a group of days with modeled surface daily concentrations above 5μg m–3 was selected, and data were extracted for 7 sites, spatially distributed along Portugal. A cluster analysis of the air parcels back trajectories that arrive at each site was performed in order to identify the mean flow patterns associated to each mineral dust episode. The prevalence of the flow regimes coming from North Africa during the episode days was different for the studied sites, with high frequency (above 70%) at south sites. This work contributes to the characterization and assessment of the dust episodes that affect Portugal, on a yearly basis and based on a modeling approach.
Показать больше [+] Меньше [-]Daily variations in pathogenic bacterial populations in a monsoon influenced tropical environment
2015
Khandeparker, Lidita | Anil, Arga Chandrashekar | Naik, Sneha D. | Gaonkar, Chetan C.
Changing climatic conditions have influenced the monsoon pattern in recent years. Variations in bacterial population in one such tropical environment were observed everyday over two years and point out intra and inter annual changes driven by the intensity of rainfall. Vibrio spp. were abundant during the monsoon and so were faecal coliforms. Vibrio alginolyticus were negatively influenced by nitrate, whereas, silicate and rainfall positively influenced Vibrio parahaemolyticus numbers. It is also known that pathogenic bacteria are associated with the plankton. Changes in the abundance of plankton, which are governed mainly by environmental changes, could be responsible for variation in pathogenic bacterial abundance during monsoon, other than the land runoff due to precipitation and influx of fresh water.
Показать больше [+] Меньше [-]Characterization and evolution of the sediments of a Mediterranean coastal lagoon located next to a former mining area
2015
García, Gregorio | Muñoz-Vera, Ana
Coastal lagoons are ecosystems that are relatively enclosed water bodies under the influence of both the terrestrial and the marine environment, being vulnerable to human impacts. Human activities, such as mining extraction, are significant anthropogenic coastal stressors that can negatively affect ecosystems and communities. In light of the above, the objective of this research is to examine the influence of metal mining activities on the composition of sediments of a Mediterranean coastal lagoon, named Mar Menor. This paper presents a comprehensive characterization for grain size, mineralogy, geochemistry and organic matter of sediments of this coastal lagoon, investigating their variation along space and time. Sedimentation dynamics are ruling clearly the grain size predominant in each area of the Mar Menor coastal lagoon, determining the existence of entrainment, transport and sedimentation areas. For minerals, elements and organic matter, sedimentation dynamics are also determining their distribution.
Показать больше [+] Меньше [-]Eutrophication effects on phytoplankton size-fractioned biomass and production at a tropical estuary
2015
Guenther, Mariana | Araújo, Moacyr | Flores-Montes, Manuel | Gonzalez-Rodriguez, Eliane | Neumann-Leitão, Sigrid
Size-fractioned phytoplankton (pico, nano and microplankton) biomass and production were estimated throughout a year at Recife harbor (NE Brazil), a shallow well mixed tropical hypereutrophic estuary with short residence times but restricted water renewal. Intense loads of P-PO4 (maximum 14μM) resulted in low N:P ratios (around 2:1), high phytoplankton biomass (B=7.1–72μgchl-aL−1), production (PP=10–2657μgCL−1h−1) and photosynthetic efficiency (PB=0.5–45μgCμgchl-a−1), but no oxygen depletion (average O2 saturation: 109.6%). Nanoplankton dominated phytoplankton biomass (66%) but micro- and nanoplankton performed equivalent primary production rates (47% each). Production-biomass models indicate an export of the exceeding microplankton biomass during most of the year, possibly through grazing. The intense and constant nutrient and organic matter loading at Recife harbor is thus supporting the high microplankton productivity that is not accumulating on the system nor contributing to oxygen depletion, but supporting the whole system’s trophic web.
Показать больше [+] Меньше [-]Baseline concentration of 210Po and 210Pb in Sargassum from the northern Gulf
2015
Uddin, S. | Aba, A. | Bebhehani, M.
This baseline study highlights the 210Po and 210Pb concentration in two species of the benthic macroalgae Sargassum from northern Gulf, also known as the ROPME Sea Area (RSA). Within the marine environment, 210Po is initially absorbed from water and concentrated by phytoplankton and macroalgae, and this concentrated 210Po can then readily be passed along to the higher trophic level of the marine food web. The 210Po concentration measured in Sargassum boveanum (22.5–25.6Bqkg−1) was higher than that in Sargassum oligocystum (20.2–22.5Bqkg−1), but is not statistically significant (p>0.064), where as the difference between 210Pb concentrations in Sargassum boveanum (15.3–16.8Bqkg−1) and Sargassum oligocystum (18.4–22.0Bqkg−1) was statistically significant (p>0.019). The measured concentration factor for 210Po in Sargassum in the northern Gulf varied between 0.55 and 1.2×104, values higher to the IAEA recommended value of 1×103. The 210Po enrichment is observed in both the species of Sargassum,210Po/210Pb ratio was >1 at all the stations for all the samples.
Показать больше [+] Меньше [-]Scallop larvae hatcheries as source of bacteria carrying genes encoding for non-enzymatic phenicol resistance
2015
Miranda, Claudio D. | Rojas, Rodrigo | Geisse, Julieta | Romero S., Jaime | González-Rocha, Gerardo
The main aim of the study was to evaluate the role of scallop hatcheries as source of the floR and cmlA genes. A number of 133 and 121 florfenicol-resistant strains were isolated from scallop larval cultures prior to their transfer to seawater and from effluent samples from 2 commercial hatcheries and identified by 16S rRNA gene sequence analysis, observing a predominance of the Pseudomonas, Pseudoalteromonas and Halomonas genera and exhibiting an important incidence of co-resistance to streptomycin, oxytetracycline and co-trimoxazole. A high percentage of strains from both hatcheries carried the floR gene (68.4% and 89.3% of strains), whereas a lower carriage of the cmlA gene was detected (27.1% and 54.5% of strains). The high prevalence of floR-carrying bacteria in reared scallop larvae and hatchery effluents contributes to enrich the marine resistome in marine environments, prompting the need of a continuous surveillance of these genes in the mariculture environments.
Показать больше [+] Меньше [-]Detection of water quality parameters in Hangzhou Bay using a portable laser fluorometer
2015
Chen, Peng | Pan, Delu | Mao, Zhihua | Tao, Bangyi
A field, light-weight laser fluorometer based on the method of laser induced fluorescence was developed for water quality monitoring. The basic instrument configuration uses a high pulse repetition frequency microchip laser, a confocal reflective fluorescent probe and a broadband hyperspectral micro spectrometer; it weights only about 1.7kg. Simultaneous estimates of three important water quality parameters, namely, chlorophyll a (chl-a), colored dissolved organic matter (CDOM), and total suspended matter (TSM) measured by the laser fluorometer were observed to agree well with those measured by traditional methods (0.27–0.84μgL−3 chl-a, R2=0.88; 0.104–0.295m−1 CDOM absorption, R2=0.90; and 59.8–994.9mgL−3 TSM, R2=0.86) in Hangzhou Bay water. Subsequently, distribution and characteristics of CDOM and chl-a laser fluorescence in Hangzhou Bay were analyzed, which will enhance our understanding of biogeochemical processes in this complex estuarine system at high-resolution, high-frequency and long-term scale.
Показать больше [+] Меньше [-]Source apportionment analysis of airborne VOCs using positive matrix factorization in industrial and urban areas in Thailand
2015
Saeaw, Neungrothai | Thepanondh, Sarawut
Airborne volatile organic compounds (VOCs) concentration data from monitoring stations in industrial and urban (Bangkok) area of Thailand were analyzed using Positive Matrix Factorization (PMF) to identify and elaborate on their source profiles. Analyzed data were obtained from those measured from January 2009 to December 2013 in the study area. The PMF was performed to estimate the contribution of specific source types to ambient concentrations. The most suitable number of factors for a dataset in this study was found to be eleven factors for compositions and characteristics of VOCs. Emission sources of VOCs in industrial area were classified into three to five groups based on their contribution. In industrial area, 42 to 57% of total VOC concentrations were contributed from mobile sources. Contribution to total VOCs concentration from industrial processes and household chemical usage were about 15 to 44% and 3 to 10%, respectively. Moreover, some species of VOCs particularly the ozone depleting substances such as Freon 11, Freon 114 and carbon tetrachloride were found as background concentration in ambient air. As for Bangkok, it was found that most of total VOC concentrations were contributed from mobile source emissions.
Показать больше [+] Меньше [-]Participation in ICZM initiatives: Critical aspects and lessons learnt from the Mediterranean and Black Sea experiences
2015
Soriani, Stefano | Buono, Fabrizia | Tonino, Marco | Camuffo, Monica
Public participation is recognized as a necessary tool to ensure a successful implementation of Integrated Coastal Zone Management (ICZM) strategies and plans. This paper, based on the experiences carried out in the Mediterranean and in the Black Sea within the EU FP7 project PEGASO, presents some critical aspects and lessons learnt regarding participation in ICZM projects. The research shows that data availability, the complexity of data interpretation, an inadequate legal and cultural framework and the difficulties in promoting integration of all the components of coastal management within short term projects are all elements that if not properly considered since the beginning of the participatory process may hinder public participation effectiveness. Moreover the definition of the spatial scale of coastal phenomenon as well as the discrepancy between the local scale of coastal governance and the complex multi-scale nature of coastal systems remain highly critical aspects to be addressed.
Показать больше [+] Меньше [-]Sulphur-cycling bacteria and ciliated protozoans in a Beggiatoaceae mat covering organically enriched sediments beneath a salmon farm in a southern Chilean fjord
2015
Aranda, Carlos P. | Valenzuela, Cristian | Matamala, Yessica | Godoy, Félix A. | Aranda, Nicol
The colourless mat covering organically enriched sediments underlying an intensive salmon farm in Estero Pichicolo, southern Chile, was surveyed by combined 454 PyroTag and conventional Sanger sequencing of 16S/18S ribosomal RNA genes for Bacteria and Eukarya. The mat was dominated by the sulphide-oxidizing bacteria (SOB) Candidatus Isobeggiatoa, Candidatus Parabeggiatoa and Arcobacter. By order of their abundances, sulphate-reducing bacteria (SRB) were represented by diverse deltaproteobacterial Desulfobacteraceae, but also within Desulfobulbaceae, Desulfuromonadaceae and Desulfovibrionaceae. The eukaryotic PyroTags were dominated by polychaetes, copepods and nematodes, however, ciliated protozoans were highly abundant in microscopy observations, and were represented by the genera Condylostoma, Loxophyllum and Peritromus. Finally, the abundant Sulfurimonas/Sulfurovum also suggest the occurrence of zero-valence sulphur oxidation, probably derived from Beggiatoaceae as a result of bacteriovorus infaunal activity or generated as free S0 by the Arcobacter bacteria. The survey suggests an intense and complex sulphur cycle within the surface of salmon-farm impacted sediments.
Показать больше [+] Меньше [-]