خيارات البحث
النتائج 1081 - 1090 من 4,044
The value of offshore field experiments in oil spill technology development for Norwegian waters النص الكامل
2016
Faksness, Liv-Guri | Brandvik, Per Johan | Daling, Per S. | Singsaas, Ivar | Sørstrøm, Stein Erik
The blowout on the Ekofisk field in the North Sea in 1977 initiated R&D efforts in Norway focusing on improving oil spill contingency in general and more specifically on weathering processes and modeling drift and spreading of oil spills. Since 1978, approximately 40 experimental oil spills have been performed under controlled conditions in open and ice covered waters in Norway. The importance of these experimental oil spills for understanding oil spill behavior, development of oil spill and response models, and response technologies are discussed here. The large progress within oil spill R&D in Norway since the Ekofisk blowout has been possible through a combination of laboratory testing, basin studies, and experimental oil spills. However, it is the authors' recommendation that experimental oil spills still play an important role as a final validation for the extensive R&D presently going on in Norway, e.g. deep-water releases of oil and gas.
اظهر المزيد [+] اقل [-]Determination of the concentrations of alternative antifouling agents on the Korean coast النص الكامل
2016
Lee, Seongeon | Lee, Yong-Woo
Since the ban on tributyltin (TBT) in 2008, dozens of alternative antifouling agents have been used instead. Unfortunately, these alternative antifouling agents contain diverse toxic components, which have contaminated the coasts. From 2006 to 2013, the concentration of chlorothalonil, dichlofluanid, and Irgarol 1051 were monitored continuously, and their mean concentrations increased due to the increase in maritime cargo and consequent increase in the incoming and outgoing ships in harbors. An analysis of the sampling points according to harbor type showed that the contamination was more severe in fishing and big harbors, where there are more incoming and outgoing ships. A correlation analysis indicated a high correlation between chlorothalonil and dichlofluanid. Unlike Irgarol 1051, which is only used as an antifouling agent, the other two substances are used as agricultural chemicals as well, which could explain the high correlation. This study suggests that these alternative antifouling agents should be tracked continuously.
اظهر المزيد [+] اقل [-]Inferring sources of polycyclic aromatic hydrocarbons (PAHs) in sediments from the western Taiwan Strait through end-member mixing analysis النص الكامل
2016
Li, Tao | Sun, Guihua | Ma, Shengzhong | Liang, Kai | Yang, Chupeng | Li, Bo | Luo, Weidong
Concentration, spatial distribution, composition and sources of polycyclic aromatic hydrocarbons (PAHs) were investigated based on measurements of 16 PAH compounds in surface sediments of the western Taiwan Strait. Total PAH concentrations ranged from 2.41 to 218.54ngg−1. Cluster analysis identified three site clusters representing the northern, central and southern regions. Sedimentary PAHs mainly originated from a mixture of pyrolytic and petrogenic in the north, from pyrolytic in the central, and from petrogenic in the south. An end-member mixing model was performed using PAH compound data to estimate mixing proportions for unknown end-members (i.e., extreme-value sample points) proposed by principal component analysis (PCA). The results showed that the analyzed samples can be expressed as mixtures of three end-members, and the mixing of different end-members was strongly related to the transport pathway controlled by two currents, which alternately prevail in the Taiwan Strait during different seasons.
اظهر المزيد [+] اقل [-]A reduced form model for ozone based on two decades of CMAQ simulations for the continental United States النص الكامل
2016
Porter, P Steven | Rao, S.T. | Hogrefe, Christian | Mathur, Rohit
A Reduced Form Model (RFM) is a mathematical relationship between the inputs and outputs of an air quality model, permitting estimation of additional modeling without costly new regional-scale simulations. A 21-year Community Multiscale Air Quality (CMAQ) simulation for the continental United States provided the basis for the RFM developed in this study. Predictors included the principal component scores (PCS) of emissions and meteorological variables, while the predictand was the monthly mean of daily maximum 8-h CMAQ ozone for the ozone season at each model grid. The PCS form an orthogonal basis for RFM inputs. A few PCS incorporate most of the variability of emissions and meteorology, thereby reducing the dimensionality of the source-receptor problem. Stochastic kriging was used to estimate the model.The RFM was used to separate the effects of emissions and meteorology on ozone concentrations. By running the RFM with emissions constant (ozone dependent on meteorology), or constant meteorology (ozone dependent on emissions). Years with ozone-conducive meteorology were identified, and meteorological variables best explaining meteorology-dependent ozone were identified. Meteorology accounted for 19%–55% of ozone variability in the eastern US, and 39%–92% in the western US. Temporal trends estimated for original CMAQ ozone data and emission-dependent ozone were mostly negative, but the confidence intervals for emission-dependent ozone are much narrower. Emission-driven changes in monthly mean ozone levels for the period 2000–2010 ranged from 6.4 to 10.9 ppb for the eastern US and from 1.4 to 2.5 ppb for the western US.
اظهر المزيد [+] اقل [-]Difference analysis of the relationship between household per capita income, per capita expenditure and per capita CO2 emissions in China: 1997–2014 النص الكامل
2016
Dong, Yiman | Zhao, Tao
Driven by the buoyancy of economy and continuous improvement of people's living standards, residential sector has gradually become the second largest CO2 emissions source in China. Reducing the fast rising rate of CO2 emissions in this sector is essential for realizing the target of carbon emission mitigation in China. The researches on the driving factors of residential CO2 emissions have attracted scholars' attention recently, yet few studies can interpret the causality relationship between household per capita income-expenditure-CO2 emissions at national and regional levels. Based on econometric techniques and a panel data set, this paper presents an investigation of the causality relationship, which combines household per capita income, per capita expenditure and per capita CO2 emissions (hereafter referred to as PI, PE, and CE, respectively) on a national level and within three regions (namely, eastern, central, and western regions of China) from 1997 to 2014. Urban and rural areas are considered as well. The empirical results manifest a varied causality relationship in different regions. For example, PI and PE correspond to CE in eastern rural area, but this phenomenon does not occur in central rural area. In addition, urban and rural differences are displayed. There is no causality between PI and PE in western urban area, while a bidirectional causal relationship emerges in PI and PE for western rural area. Finally, this study proposes some policy implications to decrease the increase rate of household CO2 emissions in China.
اظهر المزيد [+] اقل [-]Microbial colonization and degradation of polyethylene and biodegradable plastic bags in temperate fine-grained organic-rich marine sediments النص الكامل
2016
Nauendorf, Alice | Krause, Stephan | Bigalke, Nikolaus K. | Gorb, Elena V. | Gorb, Stanislav | Haeckel, Matthias | Wahl, Martin | Treude, Tina
To date, the longevity of plastic litter at the sea floor is poorly constrained. The present study compares colonization and biodegradation of plastic bags by aerobic and anaerobic benthic microbes in temperate fine-grained organic-rich marine sediments. Samples of polyethylene and biodegradable plastic carrier bags were incubated in natural oxic and anoxic sediments from Eckernförde Bay (Western Baltic Sea) for 98days. Analyses included (1) microbial colonization rates on the bags, (2) examination of the surface structure, wettability, and chemistry, and (3) mass loss of the samples during incubation. On average, biodegradable plastic bags were colonized five times higher by aerobic and eight times higher by anaerobic microbes than polyethylene bags. Both types of bags showed no sign of biodegradation during this study. Therefore, marine sediment in temperate coastal zones may represent a long-term sink for plastic litter and also supposedly compostable material.
اظهر المزيد [+] اقل [-]Variation in the composition of corals, fishes, sponges, echinoderms, ascidians, molluscs, foraminifera and macroalgae across a pronounced in-to-offshore environmental gradient in the Jakarta Bay–Thousand Islands coral reef complex النص الكامل
2016
Cleary, D.F.R. | Polónia, A.R.M. | Renema, W. | Hoeksema, B.W. | Rachello-Dolmen, P.G. | Moolenbeek, R.G. | Budiyanto, A. | Yahmantoro, | Tuti, Y. | Giyanto, | Draisma, S.G.A. | Prud'homme van Reine, W.F. | Hariyanto, R. | Gittenberger, A. | Rikoh, M.S. | de Voogd, N.J.
Substrate cover, water quality parameters and assemblages of corals, fishes, sponges, echinoderms, ascidians, molluscs, benthic foraminifera and macroalgae were sampled across a pronounced environmental gradient in the Jakarta Bay–Thousand Islands reef complex. Inshore sites mainly consisted of sand, rubble and turf algae with elevated temperature, dissolved oxygen, pH and chlorophyll concentrations and depauperate assemblages of all taxa. Live coral cover was very low inshore and mainly consisted of sparse massive coral heads and a few encrusting species. Faunal assemblages were more speciose and compositionally distinct mid- and offshore compared to inshore. There were, however, small-scale differences among taxa. Certain midshore sites, for example, housed assemblages resembling those typical of the inshore environment but this differed depending on the taxon. Substrate, water quality and spatial variables together explained from 31% (molluscs) to 72% (foraminifera) of the variation in composition. In general, satellite-derived parameters outperformed locally measured parameters.
اظهر المزيد [+] اقل [-]Oil-suspended particulate material aggregates as a tool in preventing potential ecotoxicological impacts in the São Paulo river, Todos os Santos Bay, Bahia, Brazil: Influence of salinity and suspended particulate material النص الكامل
2016
Miranda, Lorena S. | Moreira, Ícaro T.A. | Oliveira, Olívia M.C. | Santos, Carlito P. | Pinheiro, Samires M.M. | Oliveira, Lua M.L. | Martins, Adriele B.O. | Filho, Milton S.C.
Recent studies have revealed the occurrence of a natural process of interaction between oil droplets and suspended particulate material, resulting in the formation of aggregates which are dispersed in the water column, known as oil-suspended particulate material aggregates (OSAs). The experiments aimed to investigate the contribution of OSAS in indicating where most likely is the oil sedimentation in the São Paulo river, Todos os Santos Bay, Brazil, in order to predict possible ecotoxicological risks caused by oil spills. The results showed that salinity and MPS concentration interfere on the formation of aggregates. In addition, the point 3 was nominated as the most vulnerable area to the potential ecotoxicological impacts of oil spills and should be treated as a priority area for the application of preventive and mitigating techniques.
اظهر المزيد [+] اقل [-]Functional diversity of fish communities in two tropical estuaries subjected to anthropogenic disturbance النص الكامل
2016
Dolbeth, M. | Vendel, A.L. | Pessanha, A. | Patrício, J.
The functional diversity of fish communities was studied along the salinity gradient of two estuaries in Northeast Brazil subjected to different anthropogenic pressures, to gain a better understanding of the response of fish communities to disturbance. We evaluated functional complementarity indices, redundancy and analysed functional composition through functional groups based on combinations of different traits. The fish communities in both estuaries share similar functions performed by few functional groups. The upstream areas had generally lower taxonomic, functional diversity and lower redundancy, suggesting greater vulnerability to impacts caused by human activities. Biomass was slightly more evenly distributed among functional groups in the less disturbed estuary, but total biomass and redundancy were lower in comparison to the urbanized estuary. The present findings lend strength to the notion that the less disturbed estuary may be more susceptible to anthropogenic impacts, underscoring the need for more effective conservation measures directed at this estuary.
اظهر المزيد [+] اقل [-]Synthetic fibers in atmospheric fallout: A source of microplastics in the environment? النص الكامل
2016
Dris, Rachid | Gasperi, Johnny | Saad, Mohamed | Mirande, Cécile | Tassin, Bruno
Sources, pathways and reservoirs of microplastics, plastic particles smaller than 5mm, remain poorly documented in an urban context. While some studies pointed out wastewater treatment plants as a potential pathway of microplastics, none have focused on the atmospheric compartment. In this work, the atmospheric fallout of microplastics was investigated in two different urban and sub-urban sites. Microplastics were collected continuously with a stainless steel funnel. Samples were then filtered and observed with a stereomicroscope. Fibers accounted for almost all the microplastics collected. An atmospheric fallout between 2 and 355particles/m2/day was highlighted. Registered fluxes were systematically higher at the urban than at the sub-urban site. Chemical characterization allowed to estimate at 29% the proportion of these fibers being all synthetic (made with petrochemicals), or a mixture of natural and synthetic material. Extrapolation using weight and volume estimates of the collected fibers, allowed a rough estimation showing that between 3 and 10 tons of fibers are deposited by atmospheric fallout at the scale of the Parisian agglomeration every year (2500km2). These results could serve the scientific community working on the different sources of microplastic in both continental and marine environments.
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