خيارات البحث
النتائج 171 - 180 من 1,956
Long-term trend of haze pollution and impact of particulate matter in the Yangtze River Delta, China النص الكامل
2013
Cheng, Zhen | Wang, Shuxiao | Jiang, Jingkun | Fu, Qingyan | Chen, Changhong | Xu, Bingye | Yu, Jianqiao | Fu, Xiao | Hao, Jiming
Haze pollution caused by heavy particulate matter (PM) loading brings significant damage in eastern China. Long-term monitoring from 1980 to 2011 and 1-year field measurement in 2011–2012 are used for investigating visibility variation and the impact of PM pollution for the Yangtze River Delta (YRD). It was found that visual range in the YRD endured a sharp reduction from 13.2 km to 10.5 km during 1980–2000. Average mass extinction efficiency (MEE) for inhalable PM (PM10) is 2.25 m2/g in 2001–2011, and extinction coefficient due to PM10 is 207 Mm−1, accounting for 36.2% of total extinction coefficient. MEE of PM2.5 and PM2.5–10 are 4.08 m2/g and 0.58 m2/g, respectively. Extinction coefficient due to PM2.5 and PM2.5–10 is 198 Mm−1 (39.6%) and 20 Mm−1 (4.0%) in 2011–2012. Maximum daily concentration of PM10 and PM2.5 is estimated to be 63 μg/m3 (RH: 73%) and 38 μg/m3 (RH: 70%) to keep visual range above 10 km. Fine particulate matter is the key factor for haze pollution improvement in the YRD area.
اظهر المزيد [+] اقل [-]Influence of different types of nanomaterials on their bioaccumulation in a paddy microcosm: A comparison of TiO2 nanoparticles and nanotubes النص الكامل
2013
Yeo, Min-Kyeong | Nam, Dong-Ha
We investigated the environmental fate and bioaccumulation of TiO2 nanomaterials in a simplified paddy microcosm over a period of 17 days. Two types of TiO2 nanomaterials, nanoparticles (TiO2-NP) and nanotubes (TiO2-NT), were synthesized to have a negative surface charge. Ti concentrations in the environmental media (water, soil), crops (quillworts, water dropworts), and some lower and higher trophic organisms (biofilms, algae, plant-parasitic nematodes, white butterfly larva, mud snail, ricefish) were quantified after exposure periods of 0, 7, and 17 days. The titanium levels of the two nanomaterials were the highest in biofilms during the exposure periods. Bioaccumulation factors indicated that TiO2-NP and TiO2-NT were largely transferred from a prey (e.g., biofilm, water dropwort) to its consumer (e.g., nematodes, mud snail). Considering the potential entries of such TiO2 nanomaterials in organisms, their bioaccumulation throughout the food chain should be regarded with great concern in terms of the overall health of the ecosystem.
اظهر المزيد [+] اقل [-]Isosteric heats of sorption and desorption of phenanthrene in soils and carbonaceous materials النص الكامل
2013
Wang, Guohui | Grathwohl, Peter
Isosteric heats (ΔH) of sorption/desorption of phenanthrene were determined for carbonaceous materials (Pahokee peat, lignite, and high-volatile bituminous coal) and two soils based on reported equilibrium sorption/desorption isotherms at four different temperatures (4, 20, 46 and 77 °C). In addition, ΔH for desorption of native phenanthrene was determined to elucidate the “aging” effect by equilibrating samples with water at six temperatures (20, 40, 53, 61, 73, and 86 °C). Isosteric heats decreased with increasing solute concentration and were in a range of 19–35 kJ mol−1. Values higher than the heat of octanol–water phase transfer for phenanthrene (19 kJ mol−1) imply that both partitioning and adsorption processes are involved for these materials, where the sorptive contributions from both processes were estimated based on the phenanthrene thermodynamic data. Moreover, on the basis of ΔH values of desorption, release of native and spiked phenanthrene from our samples was similar.
اظهر المزيد [+] اقل [-]Quantitative determination of regional contributions to fine and coarse particle mass in urban receptor sites النص الكامل
2013
Kavouras, I.G. | Lianou, M. | Chalbot, M.-C. | Vei, I.C. | Kotronarou, A. | Hoek, G. | Hameri, K. | Harrison, R.M.
In this study, we demonstrate that regression analysis of trajectories residence time estimates the contributions of geographical sectors to fine and coarse particle mass in urban receptor sites. We applied the methodology to coarse and fine particles in Amsterdam, Athens, Birmingham and Helsinki. The sectors with the highest contributions on PM2.5 and PM10–2.5 for Amsterdam and Birmingham were Central/Eastern Europe and the Atlantic Ocean/North Sea, respectively. For Athens, the four sectors within 500 km accounted for the largest fraction of PM2.5. The Mediterranean Sea and North Africa added more than half of PM10–2.5 in Athens. For Helsinki, more than 50% of PM2.5 and PM10–2.5 were from sources outside Finland. This approach may be applied to assess the impact of transport on particle mass levels, identify the spatial patterns of particle sources and generate valuable data to design national and transnational efficient emission control strategies.
اظهر المزيد [+] اقل [-]Dioxin-induced acute cardiac mitochondrial oxidative damage and increased activity of ATP-sensitive potassium channels in Wistar rats النص الكامل
2013
Pereira, Susana P. | Pereira, Gonçalo C. | Pereira, Cláudia V. | Carvalho, Filipa S. | Cordeiro, Marília H. | Mota, Paula C. | Ramalho-Santos, João | Moreno, António J. | Oliveira, Paulo J.
The environmental dioxin 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is classified as a Group 1 human carcinogen and teratogenic agent. We hypothesize that TCDD-induced oxidative stress may also interfere with mitochondrial ATP-sensitive potassium channels (mitoKATP), which are known to regulate and to be regulated by mitochondrial redox state. We investigated the effects of an acute treatment of male Wistar rats with TCDD (50 μg/kg i.p.) and measured the regulation of cardiac mitoKATP. While the function of cardiac mitochondria was slightly depressed, mitoKATP activity was 52% higher in animals treated with TCDD. The same effects were not observed in liver mitochondria isolated from the same animals. Our data also shows that regulation of mitochondrial ROS production by mitoKATP activity is different in both groups. To our knowledge, this is the first report to show that TCDD increases mitoKATP activity in the heart, which may counteract the increased oxidative stress caused by the dioxin during acute exposure.
اظهر المزيد [+] اقل [-]Volatile organic compounds (VOCs) in air from Nisyros Island (Dodecanese Archipelago, Greece): Natural versus anthropogenic sources النص الكامل
2013
Tassi, F. | Capecchiacci, F. | Giannini, L. | Vougioukalakis, G.E. | Vaselli, O.
This study presents the chemical composition of VOCs in air and gas discharges collected at Nisyros Island (Dodecanese Archipelago, Greece). The main goals are i) to discriminate between natural and anthropogenic VOC sources and ii) to evaluate their impact on local air quality. Up to 63 different VOCs were recognized and quantitatively determined in 6 fumaroles and 19 air samples collected in the Lakki caldera, where fumarolic emissions are located, and the outer ring of the island, including the Mandraki village and the main harbor. Air samples from the crater area show significant concentrations of alkanes, alkenes, cyclic, aromatics, and S- and O-bearing heterocycles directly deriving from the hydrothermal system, as well as secondary O-bearing compounds from oxidation of primary VOCs. At Mandraki village, C6H6/Σ(methylated aromatics) and Σ(linear)/Σ(branched) alkanes ratios <1 allow to distinguish an anthropogenic source related to emissions from outlet pipes of touristic and private boats and buses.
اظهر المزيد [+] اقل [-]Fate and movement of selenium from drainage sediments disposed onto soil with and without vegetation النص الكامل
2013
Bañuelos, G.S. | Bitterli, C. | Schulin, R.
Disposal options for salty and selenium-laden agricultural drainage sediments are needed to protect the agricultural ecosystem in Central California. Thus, a 7-year pilot-scale field study evaluated the effects of disposing Se-laden drainage sediment onto soil that was planted with either salado grass (Sporobolus airoides ‘salado’) or cordgrass (Spartina patens ‘Flageo’), or on soil left bare with and without irrigation. Significant decreases in salinity and water-extractable and total soil Se concentrations were observed in all treatments to a depth 30 cm, while water extractable Se and salinity increased most significantly between 30 and 60 cm. Total yields increased over time for both species, while plant Se concentrations were ≈10 and 12 mg kg−1 DM for salado and cordgrass, respectively. The results show that Se and soluble salts disposed of as Se-laden drainage sediment onto light textured soils will significantly migrate to lower depths with or without vegetation.
اظهر المزيد [+] اقل [-]Microbial effects on the release and attenuation of arsenic in the shallow subsurface of a natural geochemical anomaly النص الكامل
2013
Drahota, Petr | Falteisek, Lukáš | Redlich, Aleš | Rohovec, Jan | Matoušek, Tomáš | Čepička, Ivan
Critical factors leading to arsenic release and attenuation from the shallow subsurface were studied with multidisciplinary approach in the natural gold–arsenic geochemical anomaly at Mokrsko (Czech Republic). The results show that microbial reduction promotes arsenic release from Fe(III) (hydr)oxides and Fe(III) arsenates, thereby enhancing dissolved arsenic in the shallow groundwater at average concentration of 7.76 mg/L. In the organic-rich aggregates and wood particles, however, microbial sulfate reduction triggers the formation of realgar deposits, leading to accumulation of As in the distinct organic-rich patches of the shallow subsurface. We conclude that precipitation of realgar in the shallow subsurface of soil/sediment depends on specific and non-trivial combination of water and rock chemistry, microbial community composition and spatial organisation of the subsurface zone, where speciation in saturated environments varied on a centimeter scale from reduced (decomposed wood, H2S and realgar present) to oxidized (goethite and arsenate minerals are present).
اظهر المزيد [+] اقل [-]Variations in exposure to traffic pollution while travelling by different modes in a low density, less congested city النص الكامل
2013
Kingham, Simon | Longley, Ian | Salmond, Jenny | Pattinson, Woodrow | Shrestha, Kreepa
This research assessed the comparative risk associated with exposure to traffic pollution when travelling via different transport modes in Christchurch, New Zealand. Concentrations of PM1, UFPs and CO were monitored on pre-defined routes during the morning and evening commute on people travelling concurrently by car, bus and bicycle. It was found that car drivers were consistently exposed to the highest levels of CO; on-road cyclists were exposed to higher levels of all pollutants than off-road cyclists; car and bus occupants were exposed to higher average levels of UFP than cyclists, and travellers were occasionally exposed to very high levels of pollution for short periods of time. PM10 and PM2.5 were found to be poor indicators of exposure to traffic pollution. Studying Christchurch adds to our understanding as it was a lower density city with limited traffic congestion compared most other cities previously studied.
اظهر المزيد [+] اقل [-]Chemical stabilization of metals and arsenic in contaminated soils using oxides – A review النص الكامل
2013
Komárek, Michael | Vaněk, Aleš | Ettler, Vojtéch
Oxides and their precursors have been extensively studied, either singly or in combination with other amendments promoting sorption, for in situ stabilization of metals and As in contaminated soils. This remediation option aims at reducing the available fraction of metal(loid)s, notably in the root zone, and thus lowering the risks associated with their leaching, ecotoxicity, plant uptake and human exposure. This review summarizes literature data on mechanisms involved in the immobilization process and presents results from laboratory and field experiments, including the subsequent influence on higher plants and aided phytostabilization. Despite the partial successes in the field, recent knowledge highlights the importance of long-term and large-scale field studies evaluating the stability of the oxide-based amendments in the treated soils and their efficiency in the long-term.
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