细化搜索
结果 591-600 的 2,503
Baseline concentrations of faecal sterols and assessment of sewage input into different inlets of Admiralty Bay, King George Island, Antarctica
2014
Martins, César C. | Aguiar, Sabrina N. | Wisnieski, Edna | Ceschim, Liziane M.M. | Figueira, Rubens C.L. | Montone, Rosalinda C.
The Antarctic region is one of the best preserved environments in the world. However, human activities such as the input of sewage result in the alteration of this pristine site. We report baseline values of faecal sterols in Admiralty Bay, Antarctica. Four sediment cores were collected during the 2006/2007 austral summer at the Ezcurra (THP and BAR), Mackelar (REF) and Martel (BTP) inlets. Concentrations of faecal sterols (coprostanol+epicoprostanol) were <0.16μgg−1, suggesting no sewage contamination and probable “biogenic” contributions for these compounds. Baseline values, calculated using the mean concentration of faecal sterols in core layers for THP, BAR, REF and BTP, were 0.04±0.02, 0.03±0.01, 0.07±0.01 and 0.04±0.02μgg−1, respectively. These results established as natural contributions of faecal sterols, suggesting that these markers can be useful indicators of human-derived faecal input and contributing to monitoring programs to prevent anthropogenic impacts.
显示更多 [+] 显示较少 [-]Detoxification of hazardous dust with marine sediment
2014
Wei, Yu-Ling | Lin, Chang-Yuan | Wang, H Paul
Hazardous electric arc furnace dust containing dioxins/furans and heavy metals is blended with harbor sediment, fired at 950–1100°C to prepare lightweight aggregates. Dust addition can lower the sintering temperature by about 100°C, as compared to a typical industrial process. After firing at 950°C and 1050°C, more than 99.85% of dioxins/furans originally present in the dust have been removed and/or destructed in the mix containing a dust/sediment ratio of 50:100. The heavy metals leached from all fired mixes are far below Taiwan EPA legal limits. The particle density of the lightweight aggregates always decreases with increasing firing temperature. Greater addition of the dust results in a considerably lower particle density (mostly <2.0gcm−3) fired at 1050°C and 1100°C. However, firing at temperatures lower than 1050°C produces no successful bloating, leading to a denser particle density (>2.0gcm−3) that is typical of bricks.
显示更多 [+] 显示较少 [-]Chemical profiles of urban fugitive dust over Xi'an in the south margin of the Loess Plateau, China
2014
Zhang, Qian | Shen, Zhenxing | Cao, Junji | Ho, KinFai | Zhang, Renjian | Bie, Zengjun | Chang, Hairu | Liu, Suixin
Urban fugitive dust samples were collected to determine the chemical profiles of fugitive dust over Xi'an. Seventy eight samples were collected and divided into categories of paved road dust, construction dust, cement dust, and soil dust. Eighteen elements, including Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Ba, and Pb, and eight water–soluble inorganic ions, including Na+, Mg2−, Ca2−, NH4−, F−, Cl−, NO3− and SO42−, were measured. The most abundant elements in these urban dust samples were Al, Si, Ca, and Fe. Al, Si, K, and Ti and showed strong positive correlations with each other, indicating they are typical dust trace elements. In contrast, elements of Ca, Zn, As, and Pb had negative correlations to crustal elements. Si/Al, K/Al, Ti/Al, Mn/Al, and Fe/Al ratios varied insignificantly among these four samples types; these ratios are similar to the properties of loess, desert, and Gobi soil dust reported in previous studies. A significantly higher Ca/Al ratio was dominant in the chemical profile of the cement samples. In addition, high Pb/Al and Zn/Al ratios were detected in comparison with those in the Gobi soil, desert soil, and loess soil samples, which indicated that Pb/Al and Zn/Al ratios can be considered as markers of urban dust. To t a l water–soluble ions occupied only a small fraction (<5%) in the urban fugitive soil samples indicating that most of the materials in the fugitive dust were insoluble. Ca2+ and SO42− were the most abundant ions in all samples. Most of the Ca and K in the fugitive soil samples were in insoluble phases, which differ significantly in comparison with combustion sources. A strong correlation was observed between Ca2+ and estimated CO32− levels indicating that most of Ca2+ was in the form of CaCO3 rather than other calcium minerals in Xi’an fugitive dust.
显示更多 [+] 显示较少 [-]Inshore capture-based tuna aquaculture impact on Posidonia oceanica meadows in the eastern part of the Adriatic Sea
2014
Kružić, Petar | Vojvodić, Vjeročka | Bura-Nakić, Elvira
Mapping and monitoring of the seagrass Posidonia oceanica in the eastern (Croatian) part of the Adriatic Sea since 2004 indicates a significant decline in meadow density in an area impacted by inshore capture-based tuna aquaculture. The density and overall condition of P. oceanica meadows impacted by tuna farms near Fulija Islet was compared to two reference sites (Iž Island and Mrtovnjak Islet). The factors with the most significant influence on P. oceanica meadows were found to be the input of organic matter originating from the cages, as well as high epiphyte biomass caused by nutrient enrichment. Significant differences in nutrient concentrations were found between the sites impacted by tuna farms (Fulija Islet) and the control stations. Shoot density of the P. oceanica meadows decreased at the stations in close vicinity to the tuna farm, which suggests that the tuna farm activity strongly affected the surrounding meadows.
显示更多 [+] 显示较少 [-]Simulated distribution and ecotoxicity-based assessment of chemically-dispersed oil in Tokyo Bay
2014
Koyama, Jiro | Imakado, Chie | Uno, Seiichi | Kuroda, Takako | Hara, Shouichi | Majima, Takahiro | Shirota, Hideyuki | Añasco, Nathaniel C.
To assess risks of chemically-dispersed oil to marine organisms, oil concentrations in the water were simulated using a hypothetical spill accident in Tokyo Bay. Simulated oil concentrations were then compared with the short-term no-observed effect concentration (NOEC), 0.01mg/L, obtained through toxicity tests using marine diatoms, amphipod and fish. Area of oil concentrations higher than the NOEC were compared with respect to use and non-use of dispersant. Results of the simulation show relatively faster dispersion near the mouth of the bay compared to its inner sections which is basically related to its stronger water currents. Interestingly, in the inner bay, a large area of chemically-dispersed oil has concentrations higher than the NOEC. It seems emulsifying oil by dispersant increases oil concentrations, which could lead to higher toxicity to aquatic organisms. When stronger winds occur, however, the difference in toxic areas between use and non-use of dispersant is quite small.
显示更多 [+] 显示较少 [-]Effects of salinity on anatomical features and physiology of a semi-mangrove plant Myoporum bontioides
2014
Xu, H.M. | Tam, N.F.Y. | Zan, Q.J. | Bai, M. | Shin, P.K.S. | Vrijmoed, L.L.P. | Cheung, S.G. | Liao, W.B.
The effect of different concentrations of NaCl, 0, 100, 200, 300 and 400mM, on the anatomical features and physiology of Myoporum bontioides was investigated. The photosynthetic rates (Pn) were significantly reduced by salt stress, with the lowest values at 400mM NaCl. The content of malondialdehyde (MDA), proline and soluble sugar, as well as the activities of peroxidase (POD) and catalase (CAT) increased at the beginning, but became similar to the control as the experiment proceeded. The NaCl effect on superoxide dismutase (SOD) was different from the other parameters, with a significant reduction at 400mM NaCl at Day 7. Salt glands were found in both upper and lower epidermis, and the ratios of the thickness of palisade to spongy mesophyll tissues increased with NaCl concentrations. The medullary ray was clearly damaged by NaCl at levels of 200 and 300mM. These results demonstrated that M. bontioides could adapt to a relatively low salinity, and was not a halophilous species.
显示更多 [+] 显示较少 [-]Comparative molecular analysis of bacterial communities inhabiting pristine and polluted with polycyclic aromatic hydrocarbons Black Sea coastal sediments
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.
显示更多 [+] 显示较少 [-]Chemical composition of gas and particle–phase products of OH–initiated oxidation of 1,3,5–trimethylbenzene
2014
Huang, Mingqiang | Hu, Changjin | Guo, Xiaoyong | Gu, Xuejun | Zhao, Weixiong | Wang, Zhenya | Fang, Li | Zhang, Weijun
A laboratory study was performed to investigate the composition of products formed from OH–initiated oxidation of aromatic hydrocarbon 1,3,5–trimethylbenzene. The experiments were conducted by irradiating 1,3,5–trimethylbenzene/CH3ONO/NO/air mixtures in smog chamber. The chemical composition of gas and particle–phase products have been investigated with gas chromatography/mass spectrometry (GC/MS) and the aerosol laser time–of–flight mass spectrometer (ALTOFMS), respectively. Experimental results showed that 3,5–dimethyl benzaldehyde, 2,4,6–trimethylphenol, 2–methyl–4–oxo–2–pentenal and 3,5–dimethyl–2–furanone were the predominant products in both the gas and particle–phases. However, there were some differences between detected gas–phase products and those of particle–phase, for example, oxalic acid, 2–methyl–2–hydroxy–3,4–dioxo–pentanal, and 2,3,5–trimethyl–3–nitro–phenol were only existing in the particle–phase. The possible reaction mechanisms leading to these products are also proposed. Compared to offline methods such as GC–MS measurement, the ALTOFMS detection can analyze real–time the secondary organic aerosol (SOA) successfully and provide more information on the products. Thus, ALTOFMS is a useful tool to reveal the formation and transformation processes of SOA particles in smog chambers.
显示更多 [+] 显示较少 [-]Distribution, sources and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in surface soils of the Yellow River Delta, China
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.
显示更多 [+] 显示较少 [-]Stable isotopes of carbon and nitrogen in the study of organochlorine contaminants in albatrosses and petrels
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.
显示更多 [+] 显示较少 [-]