خيارات البحث
النتائج 461 - 470 من 2,459
Assessment of the abiotic and biotic effects of sodium metabisulphite pulses discharged from desalination plant chemical treatments on seagrass (Cymodocea nodosa) habitats in the Canary Islands
2014
Portillo, E. | Ruiz de la Rosa, M. | Louzara, G. | Ruiz, J.M. | Marín-Guirao, L. | Quesada, J. | González, J.C. | Roque, F. | González, N. | Mendoza, H.
Reverse osmosis membranes at many desalination plants are disinfected by periodic shock treatments with sodium metabisulphite, which have potentially toxic effects to the environment for marine life, although no empirical and experimental evidence for this is yet available. The aim of this study was to characterise for the first time, the physico-chemical modification of the marine environment and its biological effects, caused by hypersaline plumes during these membrane cleaning treatments. The case study was the Maspalomas II desalination plant, located in the south of Gran Canaria (Canary Islands, Spain). Toxicity bioassays were performed on marine species characteristic for the infralittoral soft bottoms influenced by the brine plume (Synodus synodus and Cymodocea nodosa), and revealed a high sensitivity to short-term exposure to low sodium metabisulphite concentrations. The corrective measure of incorporating a diffusion system with Venturi Eductors reduced nearly all the areas of influence, virtually eliminating the impact of the disinfectant.
اظهر المزيد [+] اقل [-]A probabilistic model for accidental cargo oil outflow from product tankers in a ship–ship collision
2014
Goerlandt, Floris | Montewka, Jakub
In risk assessment of maritime transportation, estimation of accidental oil outflow from tankers is important for assessing environmental impacts. However, there typically is limited data concerning the specific structural design and tank arrangement of ships operating in a given area. Moreover, there is uncertainty about the accident scenarios potentially emerging from ship encounters. This paper proposes a Bayesian network (BN) model for reasoning under uncertainty for the assessment of accidental cargo oil outflow in a ship–ship collision where a product tanker is struck. The BN combines a model linking impact scenarios to damage extent with a model for estimating the tank layouts based on limited information regarding the ship. The methodology for constructing the model is presented and output for two accident scenarios is shown. The discussion elaborates on the issue of model validation, both in terms of the BN and in light of the adopted uncertainty/bias-based risk perspective.
اظهر المزيد [+] اقل [-]Occurrence and distribution of antibiotics in the surface sediments of the Yangtze Estuary and nearby coastal areas
2014
Shi, Hao | Yang, Yi | Liu, Min | Yan, Caixia | Yue, Haiying | Zhou, Junliang
The occurrence and distribution of five groups of antibiotics were investigated in the surface sediments of the Yangtze Estuary over four seasons. Four tetracyclines (TCs), sulfaquinoxaline (SQ), enrofloxacin (EFC) and thiamphenicol (TAP) were detected in all the samples, while sulfamerazine (SM) and sulfathiazole (ST) showed the lowest detection frequency. The detection frequencies and antibiotic concentrations were generally higher in January and May, indicating that low flow conditions and low temperature might enhance the persistence of antibiotics in sediment. Antibiotic levels varied with location, with the highest concentrations being observed around river discharges and sewage outfalls. Furthermore, a positive correlation between the concentration of quinolones and TOC revealed the significant role played by TOC. The concentration of quinolones at Wusongkou exceeded the trigger value (0.10mgkg−1) of the Steering Committee of the Veterinary International Committee on Harmonization (VICH), which should be paid attention to in future studies.
اظهر المزيد [+] اقل [-]Essential, trace and toxic element concentrations in the liver of the world’s largest bony fish, the ocean sunfish (Mola mola)
2014
Perrault, Justin R. | Buchweitz, John P. | Lehner, Andreas F.
No studies document essential (calcium, magnesium, phosphorus, potassium, sodium), trace (barium, boron, chromium, cobalt, copper, iron, manganese, molybdenum, selenium, zinc) or toxic element (antimony, arsenic, cadmium, lead, mercury, thallium) concentrations in any members of the family Molidae, including the world’s largest bony fish, the ocean sunfish (Mola mola). Here, we analyzed 21 elements in the liver of one M. mola. These values were compared to liver concentrations in multiple species with spatial and dietary overlap. Concentrations of calcium (3339ppm wet weight) and iron (2311ppm wet weight) were extremely elevated in comparison to a number of other fish species, indicating that calcium and/or iron toxicity may have occurred in this animal. Concentrations of toxic elements were generally low, with the exception of cadmium (3.5ppm). This study represents the first report of essential, trace and toxic elements in this species.
اظهر المزيد [+] اقل [-]Quantifying and modelling the carbon sequestration capacity of seagrass meadows – A critical assessment
2014
Macreadie, P.I. | Baird, M.E. | Trevathan-Tackett, S.M. | Larkum, A.W.D. | Ralph, P.J.
Seagrasses are among the planet’s most effective natural ecosystems for sequestering (capturing and storing) carbon (C); but if degraded, they could leak stored C into the atmosphere and accelerate global warming. Quantifying and modelling the C sequestration capacity is therefore critical for successfully managing seagrass ecosystems to maintain their substantial abatement potential. At present, there is no mechanism to support carbon financing linked to seagrass. For seagrasses to be recognised by the IPCC and the voluntary C market, standard stock assessment methodologies and inventories of seagrass C stocks are required. Developing accurate C budgets for seagrass meadows is indeed complex; we discuss these complexities, and, in addition, we review techniques and methodologies that will aid development of C budgets. We also consider a simple process-based data assimilation model for predicting how seagrasses will respond to future change, accompanied by a practical list of research priorities.
اظهر المزيد [+] اقل [-]Litter survey detects the South Atlantic ‘garbage patch’
2014
Ryan, Peter G.
A distance-based technique was used to assess the distribution and abundance of floating marine debris (>1cm) in the southeast Atlantic Ocean between Cape Town and Tristan da Cunha, crossing the southern edge of the South Atlantic ‘garbage patch’ predicted by surface drift models. Most litter was made of plastic (97%). Detection distances were influenced by the size and buoyancy of litter items. Litter density decreased from coastal waters off Cape Town (>100 itemskm−2) to oceanic waters (<10 itemskm−2), and was consistently higher (6.2±1.3 itemskm−2) from 3 to 8°E than in adjacent oceanic waters (2.7±0.3 itemskm−2) or in the central South Atlantic around Tristan (1.0±0.4 itemskm−2). The area with high litter density had few seaweeds, suggesting that most litter had been drifting for a long time. The results indicate that floating debris is accumulating in the South Atlantic gyre as far south as 34–35°S.
اظهر المزيد [+] اقل [-]Out of sight but not out of mind: Harmful effects of derelict traps in selected U.S. coastal waters
2014
Arthur, Courtney | Sutton-Grier, Ariana E. | Murphy, Peter | Bamford, Holly
There is a paucity of data in the published literature on the ecological and economic impacts of derelict fishing traps (DFTs) in coastal ecosystems. We synthesized results from seven NOAA-funded trap fisheries studies around the United States and determined that DFT-caused losses to habitat and harvestable annual catch are pervasive, persistent, and largely preventable. Based on this synthesis, we identified key gaps to fill in order to better manage and prevent DFTs. We conclude with suggestions for developing a U.S. DFT management strategy including: (1) targeting studies to estimate mortality of fishery stocks, (2) assessing the economic impacts of DFTs on fisheries, (3) collaborating with the fishing industry to develop solutions to ghost fishing, and (4) examining the regional context and challenges resulting in DFTs to find effective policy solutions to manage, reduce, and prevent gear loss.
اظهر المزيد [+] اقل [-]Vertical distribution and source identification of polycyclic aromatic hydrocarbons (PAHs) in southwest of the Caspian Sea: Most petrogenic events during the late Little Ice Age
2014
Varnosfaderany, Mohammad Nemati | Bakhtiari, Alireza Riyahi | Gu, Zhaoyan | Chu, Guoqiang
In this study, 75 samples of two 210Pb-dated cores from the southwest of the Caspian Sea were analysed for 30 compounds of polycyclic aromatic hydrocarbons (PAHs). The TPAH29 flux of the last six centuries ranged from 16.3 to 177.3 and 22.3 to 426.2ngcm−2y−1 in the Rezvanshahr and Anzali core sediments, respectively. Prior to 1840, four distinct maxima in PAH fluxes (61–426.2ngcm−2y−1) with a low weathered petrogenic pattern were found in each of the core sediments. Simultaneity of distinct peaks of PAH fluxes before 1840 and Caspian Sea level high-stands during the Little Ice Age (LIA), revealed the high importance of this phenomenon in washing and transport of land-based oil pollution into the Caspian Sea. An overall increase in some diagnostic ratios (Flu/202, IP/276 and BaA/228), especially after 1940, indicated increase of pyrogenic PAHs as a result of industrial development in the catchment area.
اظهر المزيد [+] اقل [-]Carbonaceous particulate matter characterization in an urban and a rural site in the Philippines
2014
Bautista, Angel T. | Pabroa, Preciosa Corazon B. | Santos, Flora L. | Racho, Joseph Michael D. | Quirit, Leni L.
Concentrations of organic carbon (OC) and elemental carbon (EC) in PM2.5 were measured at an urban (Valenzuela City, Metro Manila) and a rural (Angat, Bulacan) site in the Philippines from September 2011 to August 2012 by thermal–optical reflectance analysis following IMPROVE–A protocol. Results show that OC (8.00μg m−3) and EC (6.63μg m−3) levels in Valenzuela were 2–3 times higher than those in Angat (OC: 4.08μg m−3, EC: 2.29μg m−3). The total carbon contributions (OC+EC) to PM2.5 mass for the urban and rural site were 38.9% and 19.7% respectively. Compared to neighboring countries in Asia, the Philippine sites have intermediate OC concentrations and greatly elevated EC levels. These suggest the presence of highly inefficient combustion sources and highlight the need for the regulation of such emissions. Valenzuela was dominated by OC2, OC3, and EC1 (carbon fractions evolving at 280°C and 480°C in pure He phase and 580°C in He/O2 phase of the analysis, respectively) which points to vehicular, industrial, and cooking sectors as the possible main sources. While generally having lower concentrations and being less EC–dominated, Angat had remarkably higher levels of the EC2 fraction which suggests a unique EC source in the area. Conditional Probability Function (CPF) for Valenzuela OC and EC show similar results pointing towards the 30°, 150°, and 210° direction, indicating common sources for these species. Detailed survey of the surrounding area is needed to ascertain the identities of the sources present in these directions.
اظهر المزيد [+] اقل [-]Levels and neurodevelopmental effects of polycyclic aromatic hydrocarbons in settled house dust of urban dwellings on preschool–aged children in Nanjing, China
2014
Wang, Bing–Ling | Pang, Shu–Tao | Zhang, Xiao–Ling | Li, Xi–Ling | Sun, Yong–Gang | Lu, Xiao–Mei | Zhang, Qi | Zhang, Zheng–Dong
This study investigated levels and possible determinants of polycyclic aromatic hydrocarbons (PAHs) in settled house dust of urban dwellings with preschool–aged children in Nanjing, China. The possible neurodevelopmental effects of house–dust PAHs on the children were also investigated. Settled house dust was collected from 203 urban houses. Fifteen PAHs were measured using an HPLC with a fluorescence detector and wavelength programming. The Child Behavior Checklist and the Gesell Development Inventory were used to evaluate the overall development of the children. PAHs were detected in settled house dust of >90% of houses, where high molecular weight PAHs predominated. Most PAHs with two or three rings were found at significantly higher levels in indoor compared with outdoor dust. PAH isomeric ratios showed that PAHs with four or more rings might be derived from outdoor coal burning sources. Naphthalene was found at lower concentrations in houses with more hours of natural ventilation, while pyrene, chrysene (Chr) and benzo[k]fluoranthene (BkF) were present at higher concentrations in these houses. A higher floor level correlated with lower levels of PAHs, especially those with four or more rings, while older houses had higher PAH levels. Benzo[a]pyrene (BaP) and indeno[1,2,3–cd]pyrene levels were positively associated with most behavioral problem scores. Higher BaP and benzo[g,h,i]perylene levels showed lower Gesell language development quotient (DQs), and higher Chr and BkF were associated with lower Gesell social skill DQs. In conclusion, 15 PAHs are ubiquitous in urban settled house dust, where outdoor coal burning and indoor cooking oil fumes are the two main sources of PAHs in Nanjing, China. Natural ventilation, floor level and residence age potentially influence house dust PAH levels. The potential adverse effect of postnatal exposure to PAHs on the behavior and neurodevelopment of preschool–aged children requires follow up in larger studies.
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