Refine search
Results 1641-1650 of 4,042
A numerical investigation of reactive air pollutant dispersion in urban street canyons with tree planting Full text
2016
Moradpour, Maryam | Afshin, Hossein | Farhanieh, Bijan
Vegetation acts as a momentum and thermal sink, affecting the mixing of species and temperature-dependent constants of reaction rates. Numerical simulations were performed to investigate the effects of vegetation on the dispersion of reactive pollutants using a computational fluid dynamic (CFD) model coupled with NO-NO2-O3 photochemistry. Moreover, characteristics of temperature and flow fields were analyzed for different aspect ratios and leaf area densities. The results showed that flow is reversed in the presence of trees, and it enhances as leaf area density (LAD) increases; additionally, vegetation creates downward and vortex flows. The results also revealed that the dispersion of nitrogen oxides is influenced by the flow patterns; nevertheless, chemical reactions are significant for the dispersion of ozone. In addition, the vegetation is observed to weaken ventilation efficiency of NO and NO2; however, ventilation efficiency of O3 improves in LAD = 0.5 and 1.0. Aspect ratios and leaf area densities are also found to interact with each other; consequently, the optimum LAD is different for each aspect ratio. The larger regions with maximum concentrations of nitrogen oxides at the height of 2 m for aspect ratios of 0.5, 1.0, and 2.0 correspond to LAD = 2.0, 1.5, and 1.0, respectively. Furthermore, vegetation as compared to tree-free environment, mostly leads to a better chemical equilibrium.
Show more [+] Less [-]Investigating ozone high levels and the role of sea breeze on its transport Full text
2016
Monteiro, Alexandra | Gama, Carla | Cândido, Marta | Ribeiro, Isabel | Carvalho, David | Lopes, Myriam
This works intends to investigate the ozone episodes reported in three different monitoring sites distributed along the Central region of Portugal (from the coast to inland direction). Ozone data time series are first analysed according to the legislation thresholds fulfilment (information threshold and target value) and two episodes are selected according to the magnitude and simultaneously exceedances at the three sites. The episodes are then analysed in terms of meteorological data (surface and vertical profiles) obtained with the WRF model and also using backtrajectories obtained with the HYSPLIT model. The integration of both results, together with the ozone and NO2 precursor concentration time series, allowed to conclude about the different origin of ozone in the two episodes. A sea breeze circulation is present in the first episode, inducing the transport of this pollutant and its precursors from the coast to inland (about 30 km), which is verified by the wind patterns and vertical profiles and by the daily profile of O3 measured at the three sites. The second episode studied does not show so clearly this influence.
Show more [+] Less [-]New direction for environmental water management Full text
2016
Tomita, Akio | Nakura, Yoshio | Ishikawa, Takuya
Japan experienced severe environmental problems including water pollution and damages to aquatic organisms and fishery industry through and after the high economic growth period in the 1960s.One of the countermeasures to address these problems was the Total Pollutant Load Control System (TPLCS), which has been implemented with the aim of reducing the total amount of pollutant loads, specifically targeting Chemical Oxygen Demand (COD), total nitrogen and total phosphorus.The TPLCS has significantly improved the quality of the coastal sea water. However, while the accumulated pollutant loads from the past industrialization have still remained, new environmental concerns have arisen. Our new environmental policies are thus to deal with conservation of biological diversity and other related marine environmental issues.Japan has entered a new phase of environmental management, setting the new direction and framework toward a beautiful, bio-diverse, bustling-with-people and bountiful sea.
Show more [+] Less [-]Comparative bioavailability of ammonium, nitrate, nitrite and urea to typically harmful cyanobacterium Microcystis aeruginosa Full text
2016
Li, Jihua | Zhang, Jibiao | Huang, Wei | Kong, Fanlong | Li, Yue | Xi, Min | Zheng, Zheng
Phosphorus is generally considered as the prime limiting nutrient responsible for cyanobacterial blooms. However, recent research is drawing attention to the importance of bioavailable nitrogen (N) in freshwater eutrophication. This study investigated the bioavailability of NO3−-N, NO2−-N, NH4+-N and Urea-N under different concentrations of 1.2, 3.6 and 6.0mgL−1 to Microcystis aeruginosa. Overall, Urea-N ranked the first in promoting M. aeruginosa growth, followed by NO3−-N and NO2−-N. However, the algal growth cultured in NH4+-N was depressed under test N levels. The bioavailability of N to M. aeruginosa was seriously influenced by both N forms and N concentrations (p<0.01). Total N concentrations in Urea-N treatment decreased the fastest, which were corresponding with the μ values of M. aeruginosa. The high enzymic activities of nitrate reductase, nitrite reductase and glutamine synthetase indicated that the decomposition process for urea is effective, which contributed in N assimilation and utilization in M. aeruginosa cells.
Show more [+] Less [-]Bioaccumulation of organochlorine pesticides (OCPs) in the northern fulmar (Fulmarus glacialis) from the Sea of Okhotsk Full text
2016
Tsygankov, Vasiliy Yu | Boyarova, Margarita D. | Lukyanova, Olga N.
Hexachlorocyclohexane (HCH) isomers (α-, β-, and γ-), DDT and its metabolites (DDD and DDE) were detected in five individuals of Northern fulmar Fulmarus glacialis Linnaeus, 1761 from the Sea of Okhotsk. The average amount of HCHs in the organs of fulmars ranged from 608±177ng/g lipids in the total homogenate of the organs to 2093±264ng/g lipids in the feathers with skin. The average range of the amounts of DDTs was from 3606±333ng/g lipids in the feathers with skin to 4076±1624ng/g lipids in the feathers. The bioaccumulation of DDTs by seabirds of the Sea of Okhotsk is approximately equal to that of birds from other regions of the world's oceans, while the HCHs concentration is significantly higher.
Show more [+] Less [-]Effects of emerging contaminants on neurotransmission and biotransformation in marine organisms — An in vitro approach Full text
2016
Luis, Luis G. | Barreto, Ângela | Trindade, Tito | Soares, Amadeu M.V.M. | Oliveira, Miguel
The effects of gold (ionic form and nanoparticles — AuNPs) and pharmaceuticals (carbamazepine and fluoxetine) on enzymes involved in neurotransmission (acetylcholinesterase — AChE) and biotransformation (glutathione S-transferases — GST) were assessed by their incubation with Mytilus galloprovincialis' hemolymph and subcellular fraction of gills, respectively. AuNPs did not alter enzymatic activities unlike ionic gold that inhibited AChE and GST activities at 2.5 and 0.42mg·L−1, respectively. Carbamazepine inhibited AChE activity at 500mg·L−1 and fluoxetine at 1000mg·L−1. GST was inhibited by carbamazepine at 250mg·L−1 and by fluoxetine at 125mg·L−1. Increased AChE activity was found in simultaneous exposures to fluoxetine and bovine serum albumin coated AuNPs (BSA-AuNPs). Concerning GST, in the simultaneous exposures, AuNPs revealed protective effects against carbamazepine (citrate and polyvinylpyrrolidone coated) and fluoxetine (citrate and BSA coated) induced inhibition. However, BSA-AuNPs increased the inhibition caused by carbamazepine. AuNPs demonstrated ability to interfere with other chemicals toxicity justifying further studies.
Show more [+] Less [-]Trace elements in striped dolphins (Stenella coeruleoalba) from the Eastern Mediterranean: A 10-years perspective Full text
2016
Shoham-Frider, Efrat | Goffman, Oz | Harlavan, Yehudit | Kress, Nurit | Morick, Danny | Roditi-Elasar, Mia | Shefer, Edna | Kerem, Dan
Concentrations of Hg, Se, Cd, Cu, Zn, Fe, Mn and As, in kidney, liver, muscle and blubber from 7 specimens of Stenella coeruleoalba, stranded along the Israeli Mediterranean coast (IMC) from 2006 to 2011 (2011-series) were determined and compared to previous data on S. coeruleoalba from the IMC (2001-series). No differences were observed in essential and toxic elements concentrations, between the two series, except for hepatic Mn which was higher in the latter. Hg/Se molar ratios in blubber, kidney and liver increased linearly with log Hg concentrations, while muscle was more heterogenic in this respect. Means (±SD) of hepatic Hg concentrations (134±89 and 181±200mgkg−1, from the 2011 and 2001 series, respectively) were similar to that found in 2007–2009 specimens from Spain, possibly reflecting the relatively high natural background levels of mercury in the Mediterranean Sea.
Show more [+] Less [-]Lead, cadmium and mercury in the blood of the blue-footed booby (Sula nebouxii) from the coast of Sinaloa, Gulf of California, Mexico Full text
2016
Lerma, Miriam | Castillo-Guerrero, José Alfredo | Ruelas-Inzunza, Jorge | Fernández, Guillermo
We used blood samples of the Blue-footed Booby, considering sex (female and male) and age-class (adult and chick) of individuals at different breeding stages during two breeding seasons (2010–2011 and 2011–2012) in Isla El Rancho, Sinaloa, to determine lead, cadmium, and mercury concentrations. Lead and cadmium concentrations were below our detection limit (0.05 and 0.36ppm, respectively). A higher concentration of mercury was found in early stages of breeding, likely related to changes in mercury environmental availability. Mercury concentrations in adults did not relate with their breeding output. Males and adults had higher mercury concentration than females and chicks. We provide information of temporal, sex and age-related variations in the concentrations of mercury in blood of the Blue-footed Booby.
Show more [+] Less [-]Biases and best approaches for assessing debris ingestion in sea turtles, with a case study in the Mediterranean Full text
2016
Casale, Paolo | Freggi, Daniela | Paduano, Valentina | Oliverio, Marco
In a sample of 567 loggerhead turtles (Caretta caretta) from the central Mediterranean, debris occurrence varied according to methods and turtle source, and was up to 80% in pelagic turtles. Frequencies of plastic types, size and color are also reported. These results and a critical review of 49 studies worldwide indicate that: (i) the detected occurrence of plastic (% turtles) is affected by several factors (e.g., necropsy/feces, ecological zone, type and date of finding, captivity period for feces collection), (ii) mixed dataset and opportunistic approaches provide results which are biased , not comparable, and ultimately of questionable value, (iii) only turtles assumed to have had a normal feeding behaviour at the time of capture or death should be considered, (iv) turtle foraging ecology and possible selectivity may undermine the use of turtles as indicator species for monitoring marine litter, as recently proposed for the Mediterranean.
Show more [+] Less [-]Assessment of heavy metal pollution in Red River surface sediments, Vietnam Full text
2016
Nguyẽ̂n, Thị Thu Hiè̂n | Zhang, Weiguo | Li, Zhen | Li, Jie | Ge, Can | Liu, Jinyan | Bai, Xuexin | Feng, Huan | Yu, Lizhong
Surface sediment samples were collected from upstream down to the subaqueous delta of the Red River in Vietnam to assess heavy metal pollution. Sediment Cr and V concentrations are strongly correlated with Al, Fe, Mn and total organic carbon concentrations, as well as particle size, suggesting that these two metals are derived primarily from natural sources and enriched in the fine fraction of sediments. In contrast, Cu, Cd, Pb, Ni and Zn concentrations show weaker correlations with particle size, with very high concentrations observed at several sites in the upper reach of the river, pointing to anthropogenic input as a possible source of these heavy metals. Enrichment factors (EF) of Cu, Cd, Pb, Ni and Zn suggest that heavy metal pollution is present in sediments with significantly high values in the upstream. The data analysis indicates that Cd, Cu and Pb are the dominant pollutants in the Red River, with their concentrations reaching moderate to serious pollution levels.
Show more [+] Less [-]