خيارات البحث
النتائج 1351 - 1360 من 4,309
Spatial and seasonal trends of polychlorinated dioxins, furans and dioxin-like polychlorinated biphenyls in air using passive and active samplers and inhalation risk assessment النص الكامل
2017
Francisco, Ana Paula | Nardocci, Adelaide Cássia | Tominaga, Maria Yumiko | da Silva, Camila Rodrigues | Assunção, João Vicente de
Thirty-five and eleven air samples were collected using, respectively, active samplers (filter + PUF) and passive samplers (PUF disks), over two consecutive four-month periods (spring and autumn-winter), in urban, urban/industrial, and rural (background) sites in São Paulo, Brazil. All the samples were extracted with toluene:acetone (9:1) in a Soxhlet apparatus, and the extracts were then purified. Analysis for polychlorinated dioxins and furans (PCDD/Fs) and for dioxin-like polychlorinated biphenyls (dl-PCBs) were made by High Resolution Gas Chromatography/High Resolution Mass Spectrometry (HRGC-HRMS). Human exposure risk was evaluated using inhalation risk assessment. Results showed: (1) there are statistical differences for PCDD/F concentrations in air between periods 1 and 2 (p = 0.03), whereas dl-PCB levels were not statistically different (p = 0.52); (2) PCDD/F and dl-PCB air levels were in the following order: urban/industrial > urban > rural for both active and passive samples; (3) PCDD/F and dl-PCB concentrations ranged from 7.76 to 453 fg TEQ/m³ in active air samples, and from 6.11 to 469 fg TEQ/m³ in passive air samples; (4) sampling rates for PCDD/Fs by the two approaches used showed considerable differences; (5) average daily intake by inhalation ranged from 18.1 to 55.6 fg TEQ/kg day, respectively, for adults and children, representing 1.8–5.6% of the lower range of the Tolerable Daily Intake recommended by the World Health Organization. Based on these results, the inhalation risk for PCDD/Fs and dl-PCBs, for local São Paulo residents, should be considered low.
اظهر المزيد [+] اقل [-]Perfluorocarbon emissions from electrolytic reduction of rare earth metals in fluoride/oxide system النص الكامل
2017
Lizhi, Zhang | Xiufeng, Wang | Bin, Gong
Perfluorocarbons (PFC) are important greenhouse gas. In the aluminum electrolysis industry, PFC emission had been valued. The electrolytic reduction of rare earth metals in fluoride/oxide system with carbon anode and tungsten cathode also has PFC emission. But the PFC emission in rare earth metals industry received less attention. The PFC emissions during the electrolysis were studied by tracking the change of CF4 concentration in the flue gas of neodymium electrolysis and dysprosium-iron alloy electrolysis. The results showed that there were continuous CF4 overflows in the electrolysis process. The CF4 was outburst when anode effect occurred. The anode effect was always accompanied with the low electrolysis temperature. In addition, because of the electrolytic dysprosium-iron alloy requires higher cell voltage, the PFC emissions are higher than rare earth electrolysis. In general, PFC emissions from rare earth metal electrolysis are quite same as the aluminum electrolysis industry.
اظهر المزيد [+] اقل [-]Phosphorus effects on radial oxygen loss, root porosity and iron plaque in two mangrove seedlings under cadmium stress النص الكامل
2017
Dai, Minyue | Liu, Jingchun | Liu, Wenwen | Lu, Haoliang | Jia, Hui | Hong, Hualong | Yan, Chongling
Phosphorus is an indispensable element for plants, but its role in alleviating the cadmium toxicity of mangrove seedlings is poorly documented. In this study, mangrove seedlings were grown in hydroponics and exposed to various Cd and P treatments. Data suggested that the inhibitory effect of Cd on the rate of radial oxygen loss and root porosity was alleviated by P. A. marina had a higher rate of ROL and POR, indicating that it had a stronger adaptability to anaerobic environment. K. obovata induced a higher Fe concentration in iron plaque under co-application of Cd and P, which may relate to higher biomass. Furthermore, P increased Cd concentration in iron plaque, implying that iron plaque can be an obstacle to prevent Cd entering into the plant, but most Cd was still distributed in its roots. These findings highlight a novel mechanism of Cd detoxification with P addition in mangrove seedlings.
اظهر المزيد [+] اقل [-]Bioturbation transports secondary microplastics to deeper layers in soft marine sediments of the northern Baltic Sea النص الكامل
2017
Näkki, Pinja | Setälä, Outi | Lehtiniemi, Maiju
Microplastics (MPs) are observed to be present on the seafloor ranging from coastal areas to deep seas. Because bioturbation alters the distribution of natural particles on inhabited soft bottoms, a mesocosm experiment with common benthic invertebrates was conducted to study their effect on the distribution of secondary MPs (different-sized pieces of fishing line<1mm). During the study period of three weeks, the benthic community increased MP concentration in the depth of 1.7–5.1cm in the sediment. The experiment revealed a clear vertical gradient in MP distribution with their abundance being highest in the uppermost parts of the sediment and decreasing with depth. The Baltic clam Macoma balthica was the only study animal that ingested MPs. This study highlights the need to further examine the vertical distribution of MPs in natural sediments to reliably assess their abundance on the seafloor as well as their potential impacts on benthic communities.
اظهر المزيد [+] اقل [-]Aliphatic and polycyclic aromatic hydrocarbons in surface sediments collected from mangroves with different levels of urbanization in southern Brazil النص الكامل
2017
Assunção, Maíra Algarve | Frena, Morgana | Santos, Ana Paula Stein | dos Santos Madureira, Luiz Augusto
Three mangroves located in southern Brazil, Carijós (CA), Rio Tavares (RT) and Itacorubi (ITA), with distinct anthropogenic influences, were assessed with regard to the presence of aliphatic and polycyclic aromatic hydrocarbons (PAH). In this study, the n-alkane concentrations ranged from 1.9μg g−1 (CA) to 55.6μg g−1 (ITA) (dry weight). The carbon preference index (CPI) ranged from 2.1 to 7.9 and values for the terrestrial/aquatic ratio (TAR) were >1. Thus, both indexes indicated the predominance of sediment of terrestrial origin, mainly comprised of higher plants. Concentrations of total PAH ranged from 6.8ng g−1 (RT) to 437.3ng g−1 (ITA). The PAH isomeric ratios indicated that these compounds originated mainly from pyrogenic sources. Nevertheless, levels of n-alkanes in the three mangroves were relatively low and they are considered typical of uncontaminated surface sediments, while the level of contamination with PAH was classified as low to moderate.
اظهر المزيد [+] اقل [-]Evaluation on island ecological vulnerability and its spatial heterogeneity النص الكامل
2017
Ji, Yuan | Shi, Honghua | Wang, Yuanyuan | Guo, Zhen | Wang, Enkang
The evaluation on island ecological vulnerability (IEV) can help reveal the comprehensive characteristics of the island ecosystem and provide reference for controlling human activities on islands. An IEV evaluation model which reflects the land–sea dual features, natural and anthropogenic attributes, and spatial heterogeneity of the island ecosystem was established, and the southern islands of Miaodao Archipelago in North China were taken as the study area. The IEV, its spatial heterogeneity, and its sensitivities to the evaluation elements were analyzed. Results indicated that the IEV was in status of mild vulnerability in the archipelago scale, and population pressure, ecosystem productivity, environmental quality, landscape pattern, and economic development were the sensitive elements. The IEV showed significant spatial heterogeneities both in land and surrounding waters sub-ecosystems. Construction scale control, optimization of development allocation, improvement of exploitation methods, and reasonable ecological construction are important measures to control the IEV.
اظهر المزيد [+] اقل [-]Quantifying the particulate matter accumulation on leaf surfaces of urban plants in Beijing, China النص الكامل
2017
Shi, Junna | Zhang, Gang | An, Hailong | Yin, Weilun | Xia, Xinli
Particulate matter is potentially harmful to human health but green tree species act as air filters to adhere these particulates. The elemental composition, number density, and size fractions of particles on leaf surfaces of 14 urban green from Xizhimen overpass and the Olympic Forest Park in Beijing, China were examined by scanning electron microscopy and X-ray energy dispersive spectrometry. Particles that accumulated on leaves were comprised mainly of C, O, Si, Ca, Fe, and Pb. The number density of particles was 50,961.5 mm−2, and 52.9% and 25% of the particles were submicron (<1 μm) and fine (<2.5 μm), respectively. The densities and size fractions of the particles deposited on the adaxial and abaxial side of leaves were significantly different, and 24% of the particles were deposited on the abaxial side of leaves. The densities of the particles in four size fractions differed significantly among the species at the two sampling sites. Salix matsudana, Euonymus japonicus, Magnolia denudate, Sophora japonica, Amygdalus persica, and Salix babylonica efficiently captured all particle sizes on their leaf surfaces. S. matsudana, E. japonicus, M. denudate, S. japonica, Fraxinus chinensis, and Ginkgo biloba efficiently captured submicron and fine particles, which can have serious effects on human health. These differences among species provide more insight into the sink capacity of green tree species, and the efficiencies of plant species for trapping particulates can be used to guide urban tree planning and decrease air pollution.
اظهر المزيد [+] اقل [-]Benchmark dynamics in the environmental performance of ports النص الكامل
2017
Puig, Martí | Michail, Antonis | Wooldridge, Chris | Darbra, Rosa Mari
This paper analyses the 2016 environmental benchmark performance of the port sector, based on a wide representation of EcoPorts members. This is the fifth time that this study has been conducted as an initiative of the European Sea Ports Organisation (ESPO). The data and results are derived from the Self-Diagnosis Method (SDM), a concise checklist against which port managers can self-assess the environmental management of their port in relation to the performance of the EcoPorts membership. The SDM tool was developed in the framework of the ECOPORTS project (2002–2005) and it is managed by ESPO. A total number of 91 ports from 20 different European Maritime States contributed to this evaluation. The main results are that air quality remains as the top environmental priority of the respondent ports, followed by energy consumption and noise.In terms of environmental management, the study confirms that key components are commonly implemented in the majority of European ports. 94% of contributing ports have a designated environmental manager, 92% own an environmental policy and 82% implement an environmental monitoring program. Waste is identified as the most monitored issue in ports (80%), followed by energy consumption (73%) and water quality (70%).
اظهر المزيد [+] اقل [-]Trichodesmium blooms and warm-core ocean surface features in the Arabian Sea and the Bay of Bengal النص الكامل
2017
Jyothibabu, R. | Karnan, C. | Jagadeesan, L. | Arunpandi, N. | Pandiarajan, R.S. | Muraleedharan, K.R. | Balachandran, K.K.
Trichodesmium is a bloom-forming, diazotrophic, non-heterocystous cyanobacteria widely distributed in the warmer oceans, and their bloom is considered a ‘biological indication’ of stratification and nitrogen limitation in the ocean surface layer. In the first part of this paper, based on the retrospective analyses of the ocean surface mesoscale features associated with 59 Trichodesmium bloom incidences recorded in the past, 32 from the Arabian Sea and the Bay of Bengal, and 27 from the rest of the world, we have showed that warm-core features have an inducing effect on bloom formation. In the second part, we have considered the environmental preferences of Trichodesmium bloom based on laboratory and field studies across the globe, and proposed a view about how warm-core features could provide an inducing pre-requisite condition for the bloom formation in the Arabian Sea and the Bay of Bengal. Proposed that the subsurface waters of warm-core features maintain more likely chances for the conducive nutrient and light conditions required for the triggering of the blooms.
اظهر المزيد [+] اقل [-]Microplastics in gut contents of coastal freshwater fish from Río de la Plata estuary النص الكامل
2017
Pazos, Rocío S. | Maiztegui, Tomás | Colautti, Darío C. | Paracampo, Ariel H. | Gómez, Nora
The presence of microplastics (MPs) in gut contents of coastal freshwater fish of the Rio de la Plata estuary was studied. Samples were taken in six sites where 87 fish belonging to 11 species and four feeding habits were captured. Presence of MPs was verified in the 100% of fish. The fibres represented the 96% of MPs found. The number of MPs in gut contents was significantly higher close to sewage discharge. There was not found relationship between number of MPs and fish length, weight or feeding habit. The spatial differences in mean number of MPs in fish observed in this study, suggest that environmental availability of MPs could be of great importance to explain the differences found among sampling sites analysed. This work represents the first study about the interaction between MPs and aquatic organisms in this important estuarine ecosystem of South America.
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