خيارات البحث
النتائج 831 - 840 من 2,512
Total and organic mercury concentrations in the muscles of Pacific albacore (Thunnus alalunga) and bigeye tuna (Thunnus obesus) النص الكامل
2014
Chen, Chiee-Young | Lai, Chien-Cheng | Chen, Kuo-Shu | Xu, Jianzhong | Hung, Chin-Chang | Chen, Meng-Hsien
Muscles of 115 North Pacific albacore (ALB, Thunnus alalunga) and 75 Pacific bigeye tuna (BET, Thunnus obesus), collected from 2001 to 2006, were analyzed. No ALB, but 13 large BET had organic mercury (OHg) concentrations exceeding 1μgg−1 wet weight. For both ALB and BET, total mercury (THg) and OHg concentrations were significantly and positively correlated with fork length (FL) and body weight. The muscle Hg bioaccumulation rates of BET were higher than those of ALB, particularly in the adult fish. Moreover, the lines had crossover points among the two species that imply the young BET (FL<110cm) contains lower muscle Hg concentrations than ALB of the same size. The suggested weekly dietary intake of ALB and small-BET meats is 340g, and of BET meat it is 150g for a 60-kg person based on the provisional tolerable weekly intake (PTWI) of methylmercury set by the WHO.
اظهر المزيد [+] اقل [-]Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in surface soils of the Yellow River Delta, China النص الكامل
2014
Yuan, Hongming | Li, Tiegang | Ding, Xigui | Zhao, Guangming | Ye, Siyuan
PAH concentrations of 61 surface soil samples collected from the Yellow River Delta (YRD), China were measured to determine occurrence levels, sources, and potential toxicological significance of PAHs. The total concentrations of ∑PAHs ranged from 27 to 753ng/g d.w., with a mean of 118±132ng/g. The highest concentrations was found in the mid-southern part of the YRD (753ng/g), which was associated with the oil exploration. The ratios indicated that the PAHs throughout the YRD were mostly of pyrogenic origin; while various sites in mid-southern part in the region were derived mainly from the petrogenic sources. Multivariate statistical analyses supported that the PAHs in surface soils of the YRD were principally from the coal and biomass combustion, petroleum spills, and/or vehicular emissions. The toxic assessment suggested that the PAHs in soils were at low potential of ecotoxicological contamination level for the YRD.
اظهر المزيد [+] اقل [-]Stable isotopes of carbon and nitrogen in the study of organochlorine contaminants in albatrosses and petrels النص الكامل
2014
Colabuono, Fernanda I. | Barquete, Viviane | Taniguchi, Satie | Ryan, Peter G. | Montone, Rosalinda C.
Carbon and nitrogen stable isotopes in albatrosses and petrels collected off southern Brazil were compared with concentrations of organochlorine contaminants (OCs). δ13C and δ15N values, as well as OCs concentrations, exhibited a high degree of variability among individuals and overlap among species. δ13C values reflected latitudinal differences among species, with lower values found in Wandering and Tristan Albatrosses and higher values found in Black-browed and Atlantic Yellow-nosed Albatrosses and White-chinned Petrels. Some relationships were found between OCs and stable isotopes, but in general a partial ‘uncoupling’ was observed between OCs concentrations and stable isotopes ratios (especially for δ15N). δ13C and δ15N values in Procellariiformes tissues during the non-breeding season appear to be a better indicator of foraging habitats than of trophic relationships, which may partially explain the high degree of variability between concentrations of OCs and stable isotopes ratios in birds with a diversified diet and wide foraging range.
اظهر المزيد [+] اقل [-]Satellite-observed variability of phytoplankton size classes associated with a cold eddy in the South China Sea النص الكامل
2014
Lin, Junfang | Cao, Wenxi | Wang, Guifen | Hu, Shuibo
Ocean-color remote sensing has been used as a tool to detect phytoplankton size classes (PSCs). In this study, a three-component model of PSC was reparameterized using seven years of pigment measurements acquired in the South China Sea (SCS). The model was then used to infer PSC in a cyclonic eddy which was observed west of Luzon Island from SeaWiFS chlorophyll-a (chla) and sea-surface height anomaly (SSHA) products. Enhanced productivity and a shift in the PSC were observed, which were likely due to upwelling of nutrient-rich water into the euphotic zone. The supply of nutrients promoted the growth of larger cells (micro- and nanoplankton), and the PSC shifted to greater sizes. However, the picoplankton were still important and contributed ∼48% to total chla concentration. In addition, PSC time series revealed a lag period of about three weeks between maximum eddy intensity and maximum chlorophyll, which may have been related to phytoplankton growth rate and duration of eddy intensity.
اظهر المزيد [+] اقل [-]Analysis of water quality and circulation of four recreational Miami beaches through the use of Lagrangian Coherent Structures النص الكامل
2014
Fiorentino, L.A. | Olascoaga, M.J. | Reniers, A.
Four popular, recreational beaches in Miami, FL are Hobie Beach, Virginia Key Beach, Crandon Park Beach, and Bill Baggs Cape Florida State Park. While all of the beaches are within a few miles of each other in Biscayne Bay, they have greatly differing water qualities, as determined by the testing for fecal indicator bacteria performed by the Florida Department of Health. Using the geodesic theory of transport barriers, we identify Lagrangian Coherent Structures (LCSs) in each area. We show how these material curves, which shape circulation and mixing patterns, can be used to explain the incongruous states of the water at beaches that should be comparable. The LCSs are computed using a hydrodynamic model and verified through field experimentation at each beach.
اظهر المزيد [+] اقل [-]Comparative molecular analysis of bacterial communities inhabiting pristine and polluted with polycyclic aromatic hydrocarbons Black Sea coastal sediments النص الكامل
2014
Todorova, Nadezhda H. | Mironova, Roumyana S. | Karamfilov, Ventzislav K.
Molecular analysis was applied to characterize bacterial community structure in sediment samples collected from pristine site and oil-polluted Black Sea harbor. Amplified Ribosomal DNA Restriction Analysis (ARDRA) revealed a high similarity in the restriction patterns of both samples thus not demonstrating the effect of the pollutant on the structure of the bacterial communities. Constructed 16S rRNA gene libraries gave more detailed assessment of members. Results showed that α- and γ-Proteobacteria were dominant in the oil polluted site, whereas the pristine site was characterized by prevalence of Actinobacteria. The biodegradative potential of the adapted bacterial community in the oil-polluted sediments was demonstrated by the presence of the aromatic ring hydroxylating dioxygenase genes.
اظهر المزيد [+] اقل [-]Organic and metal contamination in marine surface sediments of Guánica Bay, Puerto Rico النص الكامل
2014
Whitall, David | Mason, Andrew | Pait, Anthony | Brune, Lia | Fulton, Michael | Wirth, Ed | Vandiver, Lisa
Land based sources of pollution have the potential to adversely impact valuable coral reef ecosystems. In Guánica Bay (Puerto Rico) sediment samples collected and analyzed in 2009 demonstrate unusually high concentrations of total chlordane, total PCBs, nickel and chromium. A variety of other contaminants (total DDT, total PAHs, As, Cu, Hg, and Zn) were also at levels which may indicate sediment toxicity. With the exception of chromium, all of these contaminants were detected in coral tissues (Porites astreoides), although it is unclear at what level these contaminants affect coral health. PCBs and chlordane are environmentally persistent and likely represent legacy pollution from historical uses in close geographic proximity to the Bay. We hypothesize that the high nickel and chromium levels are due to a combination of naturally high Ni and Cr in rock and soils in the watershed, and enhanced (human driven) erosional rates.
اظهر المزيد [+] اقل [-]Coastal surface sediment quality assessment in Leizhou Peninsula (South China Sea) based on SEM–AVS analysis النص الكامل
2014
Li, Feng | Lin, Jin-qin | Liang, Yan-yan | Gan, Hua-yang | Zeng, Xiang-yun | Duan, Zhi-peng | Liang, Kai | Liu, Xing | Huo, Zhen-hai | Wu, Chang-hua
Surface sediments from the coastal area of the Leizhou Peninsula in the South China Sea were collected and analyzed and the potential ecological risks in the area were assessed based on acid-volatile sulfide (AVS) model. The AVS levels are between 0.109 and 55.6μmolg−1, with the average at 4.45μmolg−1. The high AVS-concentration zones include the aquaculture areas of Liusha Bay and the densely populated areas of Zhanjiang Bay. The simultaneously extracted metals (SEM) range from 0.026μmolg−1 to 8.61μmolg–1, with the average at 0.843μmolg–1. Most of high SEM-concentration stations were located in ports or aquaculture zones. Most of the coastal surface sediments of the Leizhou Peninsula (90%) had no adverse biological effects according to the criterion proposed by USEPA (2005); while adverse effects were uncertain in some stations (8%); even in 2 stations (2%) adverse biological effects may be expected.
اظهر المزيد [+] اقل [-]Possible change in distribution of seaweed, Sargassum horneri, in northeast Asia under A2 scenario of global warming and consequent effect on some fish النص الكامل
2014
Komatsu, Teruhisa | Fukuda, Masahiro | Mikami, Atsuko | Mizuno, Shizuha | Kantachumpoo, Attachai | Tanoue, Hideaki | Kawamiya, Michio
Global warming effects on seaweed beds are already perceptible. Their geographical distributions greatly depend on water temperatures. To predict future geographical distributions of brown alga, Sargassum horneri, forming large beds in the northwestern Pacific, we referred to future monthly surface water temperatures at about 1.1° of longitude and 0.6° of latitude in February and August in 2050 and 2100 simulated by 12 organizations under an A2 scenario of global warming. The southern limit of S. horneri distribution is expected to keep moving northward such that it may broadly disappear from Honshu Island, the Chinese coast, and Korean Peninsula in 2100, when tropical Sargassum species such as Sargassum tenuifolium may not completely replace S. horneri. Thus, their forests in 2100 do not substitute those of S. horneri in 2000. Fishes using the beds and seaweed rafts consisting of S. horneri in East China Sea suffer these disappearances.
اظهر المزيد [+] اقل [-]Surfactants in the sea-surface microlayer and atmospheric aerosol around the southern region of Peninsular Malaysia النص الكامل
2014
This study was conducted to determine the composition of surfactants in the sea-surface microlayer (SML) and atmospheric aerosol around the southern region of the Peninsular Malaysia. Surfactants in samples taken from the SML and atmospheric aerosol were determined using a colorimetric method, as either methylene blue active substances (MBAS) or disulphine blue active substances (DBAS). Principal component analysis with multiple linear regressions (PCA–MLR), using the anion and major element composition of the aerosol samples, was used to determine possible sources of surfactants in atmospheric aerosol. The results showed that the concentrations of surfactants in the SML and atmospheric aerosol were dominated by anionic surfactants and that surfactants in aerosol were not directly correlated (p>0.05) with surfactants in the SML. Further PCA–MLR from anion and major element concentrations showed that combustion of fossil fuel and sea spray were the major contributors to surfactants in aerosol in the study area.
اظهر المزيد [+] اقل [-]