خيارات البحث
النتائج 1111 - 1120 من 4,309
Community-wide patterns of plastic ingestion in seabirds breeding at French Frigate Shoals, Northwestern Hawaiian Islands النص الكامل
2017
Rapp, Dan C. | Youngren, Sarah M. | Hartzell, Paula | David Hyrenbach, K.
Between 2006 and 2013, we salvaged and necropsied 362 seabird specimens from Tern Island, French Frigate Shoals, Northwestern Hawaiian Islands. Plastic ingestion occurred in 11 of the 16 species sampled (68.75%), representing four orders, seven families, and five foraging guilds: four plunge-divers, two albatrosses, two nocturnal-foraging petrels, two tuna-birds, and one frigatebird. Moreover, we documented the first instance of ingestion in a previously unstudied species: the Brown Booby. Plastic prevalence (percent occurrence) ranged from 0% to 100%, with no significant differences across foraging guilds. However, occurrence was significantly higher in chicks versus adult conspecifics in the Black-footed Albatross, one of the three species where multiple age classes were sampled. While seabirds ingested a variety of plastic (foam, line, sheets), fragments were the most common and numerous type. In albatrosses and storm-petrels, the plastic occurrence in the two stomach chambers (the proventriculus and the ventriculus) was not significantly different.
اظهر المزيد [+] اقل [-]Assessing the seawater quality of a coastal city using fecal indicators and environmental variables (eastern Aegean Sea) النص الكامل
2017
Kacar, Asli | Omuzbuken, Burcu
The presence of fecal bacteria in seawater is one of the most important bio-indicator parameters of fecal pollution. In this study, the Bay of İzmir (in the eastern Aegean Sea), which is a critical area because of its relationship with marine transportation and industrial and commercial activities, was evaluated for its microbiological and physicochemical parameters through a monitoring program. The data were obtained from seasonally assembled surface seawater samples from 2015 to 2017 at 23 sampling stations. Bacteriological investigations were performed by membrane filtration technique. During the monitoring period, for stations at the inner and middle-outer part, it was found that the inner part is exposed to more number of fecal coliforms (8.8×102cfu/100mL) and fecal streptococci (1.1×103cfu/100mL). The monitoring analysis performed in this study showed that there was negative correlation between physicochemical parameters and the level of fecal bacteria, but no significance was recorded by the Pearson correlation test. Fecal contamination parameters should be routinely monitored for improving the environmental conditions of coastal cities.
اظهر المزيد [+] اقل [-]Coral morphology and sedimentation النص الكامل
2017
Duckworth, Alan | Giofre, Natalie | Jones, Ross
The sediment rejection ability of 8 coral species of 5 families and 3 morphologies were assessed in a series of short term exposure tests over a sedimentation range of 0.5–40mgcm−2d−1 and one longer term exposure test of 235mgcm−2. Sediment accumulation rates on live corals and dead (enamel-covered) skeletons varied between morphologies, with branching species often more adept at self-cleaning. Flow rates (0–17cms−1) significantly affected sediment-shedding ability as did differences in particle sizes, with coarse silt rejected faster than fine silt, but only at very high (235mgcm−2) deposition rates. Siliciclastic sediment was rejected faster than carbonate sediments and smothering for many days by mms of low organic content carbonate sediment resulted in bleaching, but no mortality. The findings are discussed with respect to turbidity generated in natural and dredging-related resuspension events and in the context for impact prediction for dredging projects.
اظهر المزيد [+] اقل [-]Tidal fluctuations influence E. coli concentrations in urban estuaries النص الكامل
2017
Jovanović, Dušan | Coleman, Rhys | Deletic, A. (Ana) | McCarthy, David T.
This study investigated the influence of water level and velocity on Escherichia coli levels over multiple tidal cycles in an urban microtidal estuary in Melbourne, Australia. Over 3,500 E. coli samples and high resolution water level and velocity measurements from two locations within the estuary were used for the analysis. E. coli negatively correlated with water level in the upper estuary which was proposed to be linked to increased resuspension of estuarine sediments during low tide. No relationship was found in the lower estuary, likely due to wet weather inputs dwarfing subtler tidal-related processes. Removal of wet weather data enabled significant relationships to emerge in the lower estuary: 1) positive with water level (when a 9-h shift applied corresponding to the phase shift between water levels and velocities) and; 2) positive with velocity (no shift applied). This supports a link between increased E. coli levels and tidal-related resuspension.
اظهر المزيد [+] اقل [-]Using a multi-biomarker approach to assess the effects of pollution on sand flathead (Platycephalus bassensis) from Port Phillip Bay, Victoria, Australia النص الكامل
2017
Fu, Dingkun | Bridle, Andrew | Leef, Melanie | Gagnon, Marthe Monique | Hassell, Kathryn L. | Nowak, Barbara F.
Hepatic gene expression and liver histology were examined in sand flathead (Platycephalus bassensis) from six locations in Port Phillip Bay, Victoria, Australia. Four sets of genes including thyroid-related genes (D1, D2, TTR, TRα and TRβ), metal metabolism-related genes (MT, MTF1, TF, Ferritin and FPN1), apoptosis-related genes (Diablo/SMAC1, Diablo/SMAC2 and CYP1A) and an endoplasmic reticulum stress biomarker gene (GRP78) were examined in female flathead using qRT-PCR. TRβ and Diablo/SMAC1 gene expression was significantly up-regulated in fish from all polluted sites compared to those from a reference site. The transcripts of TRα and FPN1 were significantly higher in flathead from Corio Bay, while the hepatic mRNA of TTR and GRP78 were significantly lower in those fish. Positive correlations were observed between Diablo/SMAC1 and CYP1A, D2 and TRβ, TRα and TRβ. This study demonstrates that application of pathway-based biomarker genes and histopathology can provide comprehensive information on the impact of environmental pollutants on fish.
اظهر المزيد [+] اقل [-]Phospholipid fatty acid (PLFA) analysis for profiling microbial communities in offshore produced water النص الكامل
2017
Fan, Fuqiang | Zhang, Baiyu | Morrill, Penny L.
A method based on phospholipid fatty acid (PLFA) analysis for profiling microbial communities in offshore produced water was optimized. The operation parameters affecting final PLFA profiling performance from the solid phase extraction (SPE) purification and fatty acid methyl esters (FAMEs) yielding process were investigated. Under the selected conditions, 92.9%, 96.3% and 92.8% of the spiked phospholipid standards C16:1 (cis-9) PC, C18:1 (cis-9) PC, and C19:0 PC were recovered, respectively, using 10mL methanol as elution solvent on a non-commercial SPE column. Over 90% of spiked C19:0 PC was recovered before sample transesterification. Four parameters including alkaline reagent, volume of acid for neutralization, time and temperature for FAMEs derivatization were examined. Gas Chromatography-Mass Spectrometry (GC-MS) was used to analyze FAMEs and the method linearities, recoveries of 29 FAMEs during transesterification, detection limits, relative standard deviations were presented. The results provided valuable information for biological reservoir souring control.
اظهر المزيد [+] اقل [-]Multi-criteria decision-making on assessment of proposed tidal barrage schemes in terms of environmental impacts النص الكامل
2017
Wu, Yunna | Xu, Chuanbo | Ke, Yiming | Chen, Kaifeng | Xu, Hu
For tidal range power plants to be sustainable, the environmental impacts caused by the implement of various tidal barrage schemes must be assessed before construction. However, several problems exist in the current researches: firstly, evaluation criteria of the tidal barrage schemes environmental impact assessment (EIA) are not adequate; secondly, uncertainty of criteria information fails to be processed properly; thirdly, correlation among criteria is unreasonably measured. Hence the contributions of this paper are as follows: firstly, an evaluation criteria system is established from three dimensions of hydrodynamic, biological and morphological aspects. Secondly, cloud model is applied to describe the uncertainty of criteria information. Thirdly, Choquet integral with respect to λ-fuzzy measure is introduced to measure the correlation among criteria. On the above bases, a multi-criteria decision-making decision framework for tidal barrage scheme EIA is established to select the optimal scheme. Finally, a case study demonstrates the effectiveness of the proposed framework.
اظهر المزيد [+] اقل [-]Fate of microplastics and mesoplastics carried by surface currents and wind waves: A numerical model approach in the Sea of Japan النص الكامل
2017
Iwasaki, Shinsuke | Isobe, Atsuhiko | Kako, Shin'ichiro | Uchida, Keiichi | Tokai, Tadashi
A numerical model was established to reproduce the oceanic transport processes of microplastics and mesoplastics in the Sea of Japan. A particle tracking model, where surface ocean currents were given by a combination of a reanalysis ocean current product and Stokes drift computed separately by a wave model, simulated particle movement. The model results corresponded with the field survey. Modeled results indicated the micro- and mesoplastics are moved northeastward by the Tsushima Current. Subsequently, Stokes drift selectively moves mesoplastics during winter toward the Japanese coast, resulting in increased contributions of mesoplastics south of 39°N. Additionally, Stokes drift also transports micro- and mesoplastics out to the sea area south of the subpolar front where the northeastward Tsushima Current carries them into the open ocean via the Tsugaru and Soya straits. Average transit time of modeled particles in the Sea of Japan is drastically reduced when including Stokes drift in the model.
اظهر المزيد [+] اقل [-]Polycyclic aromatic hydrocarbons in the Yellow River estuary: Levels, sources and toxic potency assessment النص الكامل
2017
Li, Jing | Li, Fadong
This paper presents a systematic but preliminary study on the levels, sources and risk of exposure to polycyclic aromatic hydrocarbons (PAHs) in the Yellow River estuary by examining 16 priority PAHs listed by the U.S. EPA in four main environmental media (soil, surface water, groundwater and sediment). The concentration of individual PAHs in each medium in the study area was compared with the reported PAH values in China and abroad and to related environmental quality standards. The pollution levels of PAHs were found to be moderate in the soil and sediment, and low in the surface water and groundwater. Wood, coal combustion and petroleum inputs are the main PAH sources in soil and sediment, while petroleum inputs and petroleum combustion are the main PAH sources in surface water and groundwater. This indicates that PAH input caused by the high-speed inflow of external water over a long time has made a definite contribution to the occurrence of PAHs in surface water and groundwater in the study area. Furthermore, the mean value of the sum of the Excess Lifetime Cancer Risk (∑ELCR) exposure to PAHs in all media exceeded the generally acceptable risk level of 1.0E−06 recommended by the USEPA for carcinogenic chemicals, and the relative proportion contributed by DBA to the ∑ELCR was the greatest.
اظهر المزيد [+] اقل [-]Study of continuous air pollution in winter over Wuhan based on ground-based and satellite observations النص الكامل
2017
A comprehensive research was conducted to analyze the formation and characteristics of continuous air pollution during winter in Wuhan, China, based on ground and satellite joint observation. The effect of meteorological conditions, the source of pollutants and the optical properties of aerosols were investigated. The pressure and the accumulation of pollutants were the two main causes of continuous haze formation. The continuous cold high-pressure system, accompanied by a stable inversion layer, limited the contaminants below the height of 700 m on 15–23 January. The height of the boundary layer was below 1 000 m, based on the lidar observation. Meteorological condition contributes to the accumulation of pollutants. Then, dust transport and local anthropogenic pollutant emissions promoted the accumulation of pollutants, resulting in continuous haze pollution. Different from the heavy pollution (the 24 h-average PM2.5 is more than 200.0 μgm−3) over the Beijing-Tianjin-Hebei region, the contaminants in the Wuhan area were mainly primary pollutants, including airborne dust and anthropogenic pollutants. Moreover, a photochemical reaction was observed. However, the extent of secondary pollution formation was not high during haze pollution. Result in the particle size distribution confirmed the process of dust transport. Fine-mode and coarse-mode particles sometimes appear in the haze pollution in winter. According to the satellite data, the AOD maintained a large level of approximately 0.8 during the pollution. The aerosol extinction ability was relatively strong during the pollution period, whether aerosol is absorbed or a scattering effect dominated. In this study, the formation process of haze pollution revealed which can be used to validate air-quality models over the Wuhan region and can also provide guidance for government for the prevention work of haze pollution over Central China.
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