خيارات البحث
النتائج 681 - 690 من 3,208
Distributions, sources and ecological risk assessment of arsenic and mercury in the surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea النص الكامل
2015
Zhuang, Wen | Gao, Xuelu
The spatial distributions of As and Hg in riverine and marine surface sediments of the coastal southwestern Laizhou Bay were obtained, and multiple indices and guidelines were applied to assess their contamination and ecological risks. The As concentrations in riverine sediments were close to those in marine sediments, and on the whole the dominant proportion of As was identified to be from natural sources. The Hg concentrations in riverine sediments were much higher than those in marine sediments, so river transportation was likely the main way of Hg into the southwestern Laizhou Bay. In respect of As, the sediment quality was fine according to the risk assessment methods used; in contrast, Hg presented an extremely contaminated status with a very high ecological risk in some riverine sediments, while most of the marine sediments were relatively much less polluted by Hg and under a lower ecological risk from it.
اظهر المزيد [+] اقل [-]Impaired gamete production and viability in Atlantic croaker collected throughout the 20,000km2 hypoxic region in the northern Gulf of Mexico النص الكامل
2015
Thomas, Peter | Rahman, Md Saydur | Picha, Matthew E. | Tan, Wenxian
The long-term impacts of recent marked increases in the incidence and extent of hypoxia (dissolved oxygen <2mg/L) in coastal regions worldwide on fisheries and ecosystems are unknown. Reproductive impairment was investigated in Atlantic croaker collected in 2010 from the extensive coastal hypoxic region in the northern Gulf of Mexico. Potential fecundity was significantly lower in croaker collected throughout the ~20,000km2 hypoxic region than in croaker from normoxic sites. In vitro bioassays of gamete viability showed reductions in oocyte maturation and sperm motility in croaker collected from the hypoxic sites in response to reproductive hormones which were accompanied by decreases in gonadal levels of membrane progestin receptor alpha, the receptor regulating these processes. The finding that environmental hypoxia exposure reduces oocyte viability in addition to decreasing oocyte production in croaker suggests that fecundity estimates need to be adjusted to account for the decrease in oocyte maturation.
اظهر المزيد [+] اقل [-]Integrated environmental mapping and monitoring, a methodological approach to optimise knowledge gathering and sampling strategy النص الكامل
2015
Nilssen, Ingunn | Ødegård, Øyvind | Sørensen, Asgeir J. | Johnsen, Geir | Moline, Mark A. | Berge, Jørgen
New technology has led to new opportunities for a holistic environmental monitoring approach adjusted to purpose and object of interest. The proposed integrated environmental mapping and monitoring (IEMM) concept, presented in this paper, describes the different steps in such a system from mission of survey to selection of parameters, sensors, sensor platforms, data collection, data storage, analysis and to data interpretation for reliable decision making. The system is generic; it can be used by authorities, industry and academia and is useful for planning- and operational phases. In the planning process the systematic approach is also ideal to identify areas with gap of knowledge. The critical stages of the concept is discussed and exemplified by two case studies, one environmental mapping and one monitoring case. As an operational system, the IEMM concept can contribute to an optimised integrated environmental mapping and monitoring for knowledge generation as basis for decision making.
اظهر المزيد [+] اقل [-]Simulation of scenarios of oil droplet formation from the Deepwater Horizon blowout النص الكامل
2015
Zhao, Lin | Boufadel, Michel C. | Adams, Eric | Socolofsky, Scott A. | King, Thomas | Lee, Kenneth | Nedwed, Timothy
Knowledge of the droplet size distribution (DSD) from the Deepwater Horizon (DWH) blowout is an important step in predicting the fate and transport of the released oil. Due to the absence of measurements of the DSD from the DWH incident, we considered herein hypothetical scenarios of releases that explore the realistic parameter space using a thoroughly calibrated DSD model, VDROP-J, and we attempted to provide bounds on the range of droplet sizes from the DWH blowout within 200m of the wellhead. The scenarios include conditions without and with the presence of dispersants, different dispersant treatment efficiencies, live oil and dead oil properties, and varying oil flow rate, gas flow rate, and orifice diameter. The results, especially for dispersant-treated oil, are very different from recent modeling studies in the literature.
اظهر المزيد [+] اقل [-]Laboratory tests for the phytoextraction of heavy metals from polluted harbor sediments using aquatic plants النص الكامل
2015
Mânzatu, Carmen | Nagy, Boldizsár | Ceccarini, Alessio | Iannelli, Renato | Giannarelli, Stefania | Majdik, Cornelia
The aim of this study was to investigate the concentrations and pollution levels of heavy metals, organochlorine pesticides, and polycyclic aromatic hydrocarbons in marine sediments from the Leghorn Harbor (Italy) on the Mediterranean Sea. The phytoextraction capacity of three aquatic plants Salvinia natans, Vallisneria spiralis, and Cabomba aquatica was also tested in the removal of lead and copper, present in high concentration in these sediments. The average detectable concentrations of metals accumulated by the plants in the studied area were as follows: >3.328±0.032mg/kg dry weight (DW) of Pb and 2.641±0.014mg/kg DW of Cu for S. natans, >3.107±0.034g/kg DW for V. spiralis, and >2.400±0.029mg/kg DW for C. aquatica. The occurrence of pesticides was also analyzed in the sediment sample by gas chromatography coupled with mass spectrometry (GC/MS).Due to its metal and organic compound accumulation patterns, S. natans is a potential candidate in phytoextraction strategies.
اظهر المزيد [+] اقل [-]Seasonal effect on biomarkers of exposure to petroleum hydrocarbons in fish from Kuwait's marine area النص الكامل
2015
Beg, M.U. | Al-Subiai, S.N. | Al-Jandal, N. | Butt, S.A. | Beg, K.R. | Al-Husaini, M.
The aquatic biota of the Arabian Gulf deals with exposure to chronic oil pollution, several constituents of which cause induction of Cytochrome P450 1A that serves as a biomarker of AhR ligand exposure. In this study, fluorescent aromatic compounds (FACs) in bile and 7-ethoxyresorufin-o-deethylase (EROD) catalytic activity were determined as a measure of exposure biomarkers in two fish species, yellow fin seabream (Acanthopagrus latus) and tonguesole (Cynoglossus arel) captured from Kuwait Bay and outside the Bay area. FACs in fish bile determined by using fixed-wavelength fluorescence (FF) showed high fluorescence ratios between FF290/335 and FF380/430 indicating predominant exposure to low molecular weight, naphthalene-rich petroleum products (375±91.0pgml−1). Exposures to benzo(a)pyrene-type high-molecular weight polycyclic aromatic hydrocarbons (PAHs) originating from burnt fuel were also present in appreciable concentration in the bile. The ratio of petrogenic to pyrogenic hydrocarbon was twofold higher in winter compared to summer months in both species. Seasonal effect on EROD was significant in tonguesole in Auha site (P<0.05); whereas seabream resisted seasonal change. Tonguesole is considered to be a suitable bioindicator of oil pollution in Kuwait Bay area.
اظهر المزيد [+] اقل [-]Comparative assessment of water quality parameters of mariculture for fish production in Hong Kong Waters النص الكامل
2015
Leung, H.M. | Leung, S.K.S. | Au, C.K. | Cheung, K.C. | Wong, Y.K. | Leung, A.O.W. | Yung, K.K.L.
The objective of the study is to evaluate the effect of fish cultivation on water quality in fish culture zone (FCZ) and analysed by Principle Component Analysis (PCA). 120 surface water samples were collected from Hong Kong Waters (60 samples in Victoria Harbour and another 60 in Ma Wan FCZ). Significant difference was found in dissolved oxygen (MW: 59.6%; VH: 81.3%), and Escherichia coli (MW: 465CFU/100ml; VH: 162.5CFU/100ml). Three principle components are responsible for water quality variations in the studying sites. The first component included E. coli (0.625) and dissolved oxygen (0.701). The second included E. coli (0.387) and ammonical-nitrogen (0.571). The third included E. coli (0.194) and ammonical-nitrogen (0.287). This framework provides information to assess the relative contribution of eco-aquaculture to nutrient loads and the subsequent risk of eutrophication. To conclude, a rigorous monitoring of water quality is necessary to assess point and nonpoint source pollution. Besides, appropriate remediation techniques should be used to combat water pollution and achieve sustainability.
اظهر المزيد [+] اقل [-]Enhancing the efficacy of electrolytic chlorination for ballast water treatment by adding carbon dioxide النص الكامل
2015
Cha, Hyung-Gon | Seo, Min-Ho | Lee, Heon-Young | Lee, Ji-Hyun | Lee, Dong-Sup | Shin, Kyoungsoon | Choi, Keun-Hyung
We examined the synergistic effects of CO2 injection on electro-chlorination in disinfection of plankton and bacteria in simulated ballast water. Chlorination was performed at dosages of 4 and 6ppm with and without CO2 injection on electro-chlorination. Testing was performed in both seawater and brackish water quality as defined by IMO G8 guidelines. CO2 injection notably decreased from the control the number of Artemia franciscana, a brine shrimp, surviving during a 5-day post-treatment incubation (1.8 and 2.3 log10 reduction in seawater and brackish water, respectively at 6ppm TRO+CO2) compared with water electro-chlorinated only (1.2 and 1.3 log10 reduction in seawater and brackish water, respectively at 6ppm TRO). The phytoplankton Tetraselmis suecica, was completely disinfected with no live cell found at >4ppm TRO with and without CO2 addition. The effects of CO2 addition on heterotrophic bacterial growth was not different from electro-chlorination only. Total residual oxidant concentration (TRO) more rapidly declined in electro-chlorination of both marine and brackish waters compared to chlorine+CO2 treated waters, with significantly higher amount of TRO being left in waters treated with the CO2 addition. Total concentration of trihalomethanes (THMs) and haloacetic acids (HAAs) measured at day 0 in brackish water test were found to be 2- to 3-fold higher in 6ppm TRO+CO2-treated water than in 6ppm TRO treated water. The addition of CO2 to electro-chlorination may improve the efficiency of this sterilizing treatment of ballast water, yet the increased production of some disinfection byproducts needs further study.
اظهر المزيد [+] اقل [-]Particulate matter sources and long-term trends in a small New Zealand city النص الكامل
2015
Ancelet, Travis | Davy, P. K. (Perry K.) | Trompetter, William J.
Particulate matter samples (PM10 and PM2.5) in downtown Nelson, New Zealand were collected from 2006 to 2012. These samples were used to investigate sources of PM10 and PM2.5, and to evaluate long-term trends in PM10 and BC concentrations. Five PM10 and PM2.5 sources were identified using positive matrix factorization: biomass combustion, motor vehicles, secondary sulfate, marine aerosol and soil. Overall, biomass combustion was the dominant contributor to PM10 (48%) and PM2.5 (77%) mass. The biomass combustion factor profile featured arsenic, suggesting that locals were burning copper chrome arsenate-treated timber, an activity that appears to occur throughout New Zealand.Trend analyses on PM10 and black carbon concentrations revealed that both were decreasing year-on-year, at an average rate of 0.5 μg m−3 per year and 100 ng m−3 per year, respectively. This study provides important information for Nelson City Council, who are responsible for managing air quality in Nelson, to effectively manage air quality. This study also shows that relatively simple mitigation measures can instigate decreases in PM and BC concentrations.
اظهر المزيد [+] اقل [-]Tempting long-memory in the historic surface ozone concentrations at Athens, Greece النص الكامل
2015
Varotsos, Costas | Tzanis, Chris | Efstathiou, Maria | Deligiorgi, Despina
The intrinsic features of the temporal evolution of the air pollution are of crucial importance for its reliable modeling. In this regard, Varotsos et al. (2012) suggested that the surface ozone fluctuations at Athens since 1900, exhibit long-range dependence (long-memory), despite its present-day doubling. We herewith establish the long-memory in surface ozone concentrations that assumed in Varotsos et al. (2012), by employing recent analytical tools.
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