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Resultados 491-500 de 1,309
Preparation of low water-sorption lightweight aggregates from harbor sediment added with waste glass
2011
Wei, Yu-Ling | Lin, Chang-Yuan | Ko, Kuan-Wei | Wang, H Paul
A harbor sediment is successfully recycled at 1150°C as low water-absorption lightweight aggregate via addition of waste glass powder. Sodium content in the waste glass is responsible for the formation of low-viscosity viscous phases during firing process to encapsulate the gases generated for bloating pellet samples. Water sorption capacity of the lightweight products can be considerably reduced from 5.6% to 1.5% with the addition of waste glass powder. Low water-absorption property of lightweight products is beneficial for preparing lightweight concrete because the water required for curing the cement would not be seized by lightweight aggregate filler, thus preventing the failure of long-term concrete strength.
Mostrar más [+] Menos [-]Polycyclic aromatic hydrocarbons in surface sediments of the East China Sea and their relationship with carbonaceous materials
2011
Hung, Chin-Chang | Gong, Gwo-Ching | Ko, Fung-Chi | Lee, Hung-Jen | Chen, Hung-Yu | Wu, Jian-Ming | Hsu, Min-Lan | Peng, Sen-Chueh | Nan, Fan-Hua | Santschi, Peter H.
This study measured concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments in the East China Sea (ECS) to investigate possible sources and fate of PAHs. Total concentration of PAHs in the sediments of the ECS ranged from 22 to 244ngg⁻¹, with the highest levels in the coastal area and outer shelf. The observed PAH results showed elevated levels in both inner and outer shelf areas, a finding that is different from predictions by an ocean circulation model, suggesting that terrestrial sources are important for PAH contaminations in the ECS, while sediment resuspension, tidal changes and lateral transport may be important in affecting the distribution of PAHs in the outer shelf. The distribution of PAHs in the surface sediments of the ECS is similar to the distribution of carbonaceous materials (e.g., particulate organic carbon and black carbon), suggesting that carbonaceous materials may strongly affect the distribution of PAHs.
Mostrar más [+] Menos [-]Organochlorine pesticides (OCPs) in soils and sediments, southeast China: A case study in Xinghua Bay
2011
Zhang, Jiaquan | Qi, Shihua | Xing, Xinli | Tan, Lingzhi | Gong, Xiangyi | Zhang, Yuan | Zhang, Junpeng
This study evaluated the contamination status and distribution of organochlorine pesticides (OCPs) between Xinghua Bay and adjacent watersheds in Putian region, southeast China. Twenty-five surface soil samples and two sediment cores were collected from two watersheds and the Xinghua Bay, respectively. Results showed that the concentrations of OCPs in samples of the Mulan River Watershed (MRW), the Qiulu River Watershed (QRW), the inner bay core (IBC) and the open bay core (OBC) were in the range of 4.96–38.20ng/g, 4.62–22.80ng/g, 1.84–80.46ng/g and 1.87–23.43ng/g, respectively. The mean concentration of OCPs was in an order: IBC>MRW>QRW>OBC. The higher concentration of OCPs in recent periods may suggest that a certain amount of OCPs were still input to this area.
Mostrar más [+] Menos [-]Dioxin-like compounds in sediments from the Daliao River Estuary of Bohai Sea: Distribution and their influencing factors
2011
Zhao, Xiaofeng. | Zhang, Haijun | Fan, Jingfeng | Guan, Daoming | Zhao, Huade | Ni, Yuwen | Li, Yun | Chen, Jiping
The concentrations, compositional profiles, and potential ecological risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in sediments of the Daliao River Estuary were investigated. Total concentrations of PCDD/Fs, PCBs, and PCNs were in the range of 11.3–133.2ng/kg dry weight (dw), 1 971–37 632ng/kg dw and 33.1–284.4ng/kg dw, respectively. The total TEQ values varied from 0.37 to 4.08ng/kg dw, with the dominant contributions by PCDD/Fs, then by PCBs and PCNs. The spatial distributions of PCDD/Fs, PCBs and PCNs in the river estuary were much related to hydrodynamic conditions. The risk of contamination to the deeper sea was increased in the flood seasons. Moreover, our data confirmed that both organic matter in sediments and molecular properties of dioxin-like compounds were the factors which strongly influenced the partition behavior of these dioxin-like compounds between sediments and water phase in the estuarine zone.
Mostrar más [+] Menos [-]Status of macrobenthic community of Manifa–Tanajib Bay System of Saudi Arabia based on a once-off sampling event
2011
Joydas, T.V. | Krishnakumar, P.K. | Qurban, Mohammad A. | Ali, Said M. | Al-Suwailem, Abdulaziz | Al-Abdulkader, Khaled
Shallow water bays located in the western Arabian Gulf experience harsh environmental conditions. Some of these bays, including Manifa–Tanajib Bay System (MTBS), were also exposed to the 1991 oil pollution event. This study investigates the status of the macrobenthos in MTBS during 2006. This bay system is characterized by very shallow inner bays with elevated salinity and temperature compared to the rest of the bay area. As a result mainly of the hyper salinity, the inner bay communities are distinct from the outer bay communities. Overall, fairly high species richness with several rare species was observed. High Shannon–Wiener diversity values and ABC plots indicated the healthy status of the polychaete communities, while BOPA index indicated slightly polluted status in 20% of the stations. The oil sensitive amphipods were not completely re-colonized in 20% of the stations, even after 15years of recovery from the 1991 oil spill.
Mostrar más [+] Menos [-]Mercury in blood and eggs of the sea turtle Lepidochelys olivacea from a nesting colony in Oaxaca, Mexico
2011
Páez-Osuna, F. | Calderón-Campuzano, M.F. | Soto-Jiménez, M.F. | Ruelas-Inzunza, J.
Mercury concentrations were assessed in the sea turtle Lepidochelys olivacea from a nesting colony of Oaxaca, Mexico; 25 female turtles were sampled, a total of 250 eggs were collected during the season 2005–2006. Higher concentrations were found in yolk fraction, while in blood and albumen mean levels were below of 0.0010μgg⁻¹ dry wt. On the basis of one nesting season, the maternal transfer of Hg via eggs-laying was estimated in 2.0±1.1%. According to international norms, the health of this population and its habitats is acceptable for Hg and corresponds to baseline levels of a nearly pristine environment.
Mostrar más [+] Menos [-]Inter- and intra-annual patterns of Ulva prolifera green tides in the Yellow Sea during 2007–2009, their origin and relationship to the expansion of coastal seaweed aquaculture in China
2011
Keesing, John K. | Liu, Dongyan | Fearns, Peter | García, Rodrigo
The large green-tide events that occurred in the Yellow Sea in 2008 (3489km²) and 2009 (4994km²) are shown to be novel events preceded only once by a much smaller event in 2007 (82km²). The blooms originated in the coastal area of Jiangsu province and spread north-east towards the Shandong Peninsula. The blooms grew at different rates and mesoscale variability in surface winds explained the differences in the spatial and temporal patterns of blooms in 2008 and 2009. The 2009 bloom was tracked to its origin immediately offshore of extensive intertidal flats between Yancheng and Nantong where recent rapid expansion of Porphyra aquaculture has occurred. We review published hypotheses which have been advanced to explain the occurrence of blooms and in light of our findings, we conclude that the accumulation and disposal of waste Ulva prolifera from Porphyra aquaculture rafts is the most likely cause of the blooms.
Mostrar más [+] Menos [-]Polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in harbor sediments from Sea Lots, Port-of-Spain, Trinidad and Tobago
2011
Mohammed, Azad | Peterman, Paul | Echols, Kathy | Feltz, Kevin | Tegerdine, George | Manoo, Anton | Maraj, Dexter | Agard, John | Orazio, Carl
Concentrations of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were determined in nearshore marine surficial sediments from three locations in Trinidad. Sediments were sampled at Sea Lots on the west coast, in south Port-of-Spain Harbor, south of Sea Lots at Caroni Lagoon National Park, and on Trinidad’s east coast at Manzanilla. Total PCB concentrations in Sea Lots sediments ranged from 62 to 601ng/g (dry weight {dw}), which was higher than at Caroni and Manzanilla, 13 and 8ng/g dw, respectively. Total OCP concentrations at Sea Lots were ranged from 44.5 to 145ng/g dw, compared with 13.1 and 23.8n/g (dw), for Caroni and Manzanilla respectively. The concentrations of PCBs and of some OCPs in sediments from Sea Lots were above the Canadian interim sediment quality guidelines. To date, this data is the first report on the levels of PCBs and other organochlorine compounds from Trinidad and Tobago.
Mostrar más [+] Menos [-]An ecotoxicological approach for the Boka Kotorska Bay (south-eastern Adriatic Sea): First evaluation of lysosomal responses and metallothionein induction in mussels
2011
Da Ros, L. | Moschino, V. | Macic, V. | Schintu, M.
Mytilus galloprovincialis was used as a biomonitoring organism in Boka Kotorska Bay, a coastal transitional ecosystem in south-western Montenegro. Native mussels were collected in June 2008 at four sites thought to be differently impacted. Biological effects were investigated analysing both generic and specific biomarkers at cellular level (metallothionein content, lysosomal membrane stability, lipofuscin and neutral lipid accumulation, lysosomal structural changes). Trace element levels in mussels were quite low, only Cu and Zn exhibiting slight increases in the two sampling sites of Tivat Bay, the first one in front of a small working dockyard and the other in the water area of a former Naval dockyard. Mussels collected from these sites exhibited the highest values in neutral lipid and lysosomal volume density and the lowest neutral red retention times. Metallothionein content was always low, reflecting the minor body burden of the trace elements and suggesting a non-relevant environmental induction.
Mostrar más [+] Menos [-]The toxicity and oxidative stress of TiO₂ nanoparticles in marine abalone (Haliotis diversicolor supertexta)
2011
Zhu, Xiaoshan | Zhou, Jin | Cai, Zhonghua
The increasing use of nanotechnology highlights the need to understand and clarify the environmental impacts of nanomaterials. In this study, the acute toxicity and oxidative stress of titanium dioxide nanoparticles (nTiO₂) in mature marine abalone (Haliotis diversicolor supertexta) were assessed. No acute effect was found in any of the treatment groups with nTiO₂ concentration gradients ranging from 0.1 to 10mg/L. However, the activity of an antioxidant enzyme superoxide dismutase (SOD) significantly increased in the group that was exposed to 1.0mg/L nTiO₂. The content of a non-enzymatic antioxidant, glutathione (GSH), significantly decreased in the groups with an nTiO₂ concentration ⩾1.0mg/L. The level of lipid peroxidation (LPO) was found to increase as the nTiO₂ dose increased. Furthermore, NO was produced in excess in abalone. These results demonstrated that, although nTiO₂ is not acutely toxic to abalone, it does exert oxidative stress on abalone.
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