خيارات البحث
النتائج 471 - 480 من 2,512
Analysis of total column ozone in Peninsular Malaysia retrieved from SCIAMACHY النص الكامل
2014
Tan, Kok Chooi | Lim, Hwee San | Mat Jafri, Mohd Zubir
Due to lack of observational studies on greenhouse gases in Malaysia, most studies in this field were carried out based on ground station data. These studies did not utilize satellite data from the equatorial area. Satellite remote sensing is one of the most effective approaches for greenhouse gas distribution monitoring on a global scale. As such, satellite remote sensing exhibits a very high spatial and temporal resolution. Variations of ozone concentrations in Peninsular Malaysia were observed and investigated by means of data retrieved from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY). The aim of this study was to determine the monthly and seasonal ozone concentrations in Peninsular Malaysia from January 2003 to December 2009. We utilized total column ozone at level 2 of the WFMD version 1.0. A spatial resolution value of 1°×1.25° was used. Analysis indicated that the five selected sites exhibited strong seasonal atmospheric ozone concentration variations. These variations resulted from the significant differences between the northeast monsoon (NEM) and the southwest monsoon (SWM). As the NEM prevails, cold air breaks out from Siberia and spreads to the equatorial region in the form of northeasterly cold surge winds. These winds manifest in low–level anticyclones over Southeast Asia. Inversely, the air masses from the southwest contribute to long–range air pollution. During SWM, the transport of atmospheric ozone by wind is associated with biomass burning in Sumatra, Indonesia. HYSPLIT was also utilized to identify the air pollutant transport between NEM and SWM toward Peninsular Malaysia. Comparisons were made between the ozone data from five sites in 2009. Data were retrieved from SCIAMACHY and the Atmospheric Infrared Sounder (AIRS). The relative difference average of the ozone data measured by SCIAMACHY and AIRS was approximately 6%.
اظهر المزيد [+] اقل [-]The traffic linked urban ambient air superfine and ultrafine PM1 mass concentration, contents of pro–oxidant chemicals, and their seasonal drifts in Lucknow, India النص الكامل
2014
Verma, Mukesh Kumar | Singh Chauhan, Lalit Kumar | Sultana, Sarwat | Kumar, Sushil
The anthropogenic PM2.5 in ambient air is implicated in the increased health risks and morbidities of urban subjects. However in the literature, there is a limited information on mass concentrations and size segregated chemical profile of ultrafine and superfine PM1 fractions of traffic linked urban ambient air. The size, and the adsorbed chemicals, and response to seasonal change in this submicron range of particles have seldom been studied so far. We have looked into these aspects in urban ambient air of Lucknow Uttar Pradesh India. A 10–stage MOUDI cascade impactor sampled the superfine (PM0.56, PM0.32, PM0.18) and ultrafine particles (PM0.1, PM0.056) distributed in traffic linked ambient air. We studied their morphology, mass concentrations, the adsorbed metal contents and organic chemical moieties using TEM, gravimetric analyses, AAS, and FTIR spectroscopy. A change in their contents and profile with season was also examined. Results revealed spherical and fractal shapes of PM0.1, 50nm–2μm size range of PM0.56 fractions, and 10–100nm size range of constituent spherules. Gravimetric analyses disclosed mass concentrations and multifold increases in their levels in winter. Cr, Cd, Ni, Pb and transition element Cu, Fe were found to be present in the studied particles. The presence of aliphatic and aromatic hydrocarbons with hydroxyl, carbonyl, and ketone groups were also found and displayed changes in their levels with season. Presence of organonitrate compounds indicated the role of submicron and nanosize particulates in secondary aerosol formation also. Results are important for epidemiological studies and public policy on superfine and ultrafine particulate matter in urban ambient air for identification of toxicity risk or health hazard, air quality monitoring and regulation.
اظهر المزيد [+] اقل [-]Quantifying and modelling the carbon sequestration capacity of seagrass meadows – A critical assessment النص الكامل
2014
Macreadie, P.I. | Baird, M.E. | Trevathan-Tackett, S.M. | Larkum, A.W.D. | Ralph, P.J.
Seagrasses are among the planet’s most effective natural ecosystems for sequestering (capturing and storing) carbon (C); but if degraded, they could leak stored C into the atmosphere and accelerate global warming. Quantifying and modelling the C sequestration capacity is therefore critical for successfully managing seagrass ecosystems to maintain their substantial abatement potential. At present, there is no mechanism to support carbon financing linked to seagrass. For seagrasses to be recognised by the IPCC and the voluntary C market, standard stock assessment methodologies and inventories of seagrass C stocks are required. Developing accurate C budgets for seagrass meadows is indeed complex; we discuss these complexities, and, in addition, we review techniques and methodologies that will aid development of C budgets. We also consider a simple process-based data assimilation model for predicting how seagrasses will respond to future change, accompanied by a practical list of research priorities.
اظهر المزيد [+] اقل [-]The application of histo-cytopathological biomarkers in the mud crab Scylla serrata (Forskal) to assess heavy metal toxicity in Pulicat Lake, Chennai النص الكامل
2014
Arockia Vasanthi, Lourduraj | Muruganandam, Azhagu | Revathi, Peranandam | Baskar, Balakrishnan | Jayapriyan, Kodhilmozhian | Baburajendran, Ramaswamy | Munuswamy, Natesan
The concentrations of heavy metals and their associated structural deformities in the gills, muscles and hepatopancreas of Scylla serrata from Pulicat Lake were determined and compared with crabs live along Kovalam coast. The concentrations of metals were high in the hepatopancreas and gills of crab from Pulicat Lake, whereas, low in crab from the Kovalam coast. Data were visualized using a principal component analysis (PCA). Significant differences were found for all variables at the plot scale; however, the overall variation was relatively low for muscle tissues in both stations. The structural deformities observed in the gills, hepatopancreas and muscle was due to metal toxicity, and the degree of damage was correlated with the elevated metal concentration. The results showed significant metal accumulation and histo-cytological lesions in the crabs from Pulicat Lake. The results suggest that these biomarkers are useful for assessing the impact of metal pollution in the coastal environments.
اظهر المزيد [+] اقل [-]Seasonal distribution of ultraphytoplankton and heterotrophic prokaryotes in relation to abiotic variables on the north coast of Sfax after restoration النص الكامل
2014
Rekik, Amira | Denis, Michel | Dugenne, Mathilde | Barani, Aude | Maalej, Sami | Ayadi, Habib
The Taparura project was set up to restore the north Sfax coast (Tunisia) by shutting down the northern phosphate plant responsible for chronic pollution and uncontrolled phosphogypsum dumping. The restoration effect on coastal ultraphytoplankton (<10μm) and heterotrophic prokaryotes was investigated using conventional flow cytometry over four successive seasons during 2009–2010. Cell concentrations were generally higher than values reported for the open sea, both in the western and eastern Mediterranean basins. One striking point was that chl a concentration on the north Sfax coast was unchanged after restoration but was still one order of magnitude higher than in the Gulf of Gabès. Restoration of pH, following the shutdown of the phosphate processing plants on the north coast, appeared to reach normal levels for seawater during the study, whereas seawater acidification persisted on the south coast where plants are still in operation. The largest ultraphytoplankton biomass was from an unknown cell group, whose identity and role needs to be established.
اظهر المزيد [+] اقل [-]Human health risk of polycyclic aromatic hydrocarbons from consumption of blood cockle and exposure to contaminated sediments and water along the Klang Strait, Malaysia النص الكامل
2014
Tavakoly Sany, Seyedeh Belin | Hashim, Rosli | Rezayi, Majid | Salleh, Aishah | Rahman, M. Azizur (Mohammad Azizur) | Safari, Omid | Sasekumar, A.
The concentration of carcinogenic poly aromatic hydrocarbons (c-PAHs) present in water and sediment of Klang Strait as well as in the edible tissue of blood cockle (Anadara granosa) was investigated.The human health risk of c-PAHs was assessed in accordance with the standards of the United States Environmental Protection Agency (US EPA). The cancer risks of c-PAHs to human are expected to occur through the consumption of blood cockles or via gastrointestinal exposure to polluted sediments and water in Kalng Strait. The non-carcinogenic risks that are associated with multiple pathways based on ingestion rate and contact rates with water were higher than the US EPA safe level at almost all stations, but the non-carcinogenic risks for eating blood cockle was below the level of US EPA concern. A high correlation between concentrations of c-PAHs in different matrices showed that the bioaccumulation of c-PAHs by blood cockles could be regarded as a potential health hazard for the consumers.
اظهر المزيد [+] اقل [-]Driving factors behind the distribution of dinocyst composition and abundance in surface sediments in a western Mediterranean coastal lagoon: Report from a high resolution mapping study النص الكامل
2014
Fertouna-Bellakhal, Mouna | Dhib, Amel | Béjaoui, Béchir | Turki, Souad | Aleya, Lotfi
Species composition and abundance of dinocysts in relation to environmental factors were studied at 123 stations of surface sediment in Bizerte Lagoon. Forty-eight dinocyst types were identified, mainly dominated by Brigantidinium simplex, Votadinum spinosum, Alexandrium pseudogonyaulax, Alexandrium catenella, and Lingulodinum machaerophorum along with many round brown cysts and spiny round brown cysts. Cysts ranged from 1276 to 20126cystsg−1dry weight sediment. Significant differences in cyst distribution pattern were recorded among the zones, with a higher cyst abundance occurring in the lagoon’s inner areas. Redundancy analyses showed two distinct associations of dinocysts according to location and environmental variables. Ballast water discharges are potential introducers of non-indigenous species, especially harmful ones such as A. catenella and Polysphaeridium zoharyi, with currents playing a pivotal role in cyst distribution. Findings concerning harmful cyst species indicate potential seedbeds for initiation of future blooms and outbreaks of potentially toxic species in the lagoon.
اظهر المزيد [+] اقل [-]Characterizing metal levels and their speciation in intertidal sediments along Mumbai coast, India النص الكامل
2014
Fernandes, Lina L. | Nayak, G.N.
The present study investigated the concentration, distribution and speciation of metals (Fe, Mn, Cu, Pb, Co, Zn and Cr) in sediments of Mumbai region. Pearson’s correlation matrix and cluster analyses showed good association of metals with grain size and organic matter. Factor analysis applied to the speciation data helped to identify the role of different sediment fractions in metal retention. The environmental risks of metals, evaluated by sediment quality guidelines, revealed some contamination in the region. However, the Individual and Global Contamination Factors and the Risk Assessment Code, suggested low risk to the aquatic environment, except of Mn in the creek sediments.
اظهر المزيد [+] اقل [-]Protected areas in the Atlantic facing the hazards of micro-plastic pollution: First diagnosis of three islands in the Canary Current النص الكامل
2014
Baztan, Juan | Carrasco, Ana | Chouinard, Omer | Cleaud, Muriel | Gabaldon, Jesús E. | Huck, Thierry | Jaffrès, Lionel | Jorgensen, Bethany | Miguelez, Aquilino | Paillard, Christine | Vanderlinden, Jean-Paul
Coastal zones and the biosphere as a whole show signs of cumulative degradation due to the use and disposal of plastics. To better understand the manifestation of plastic pollution in the Atlantic Ocean, we partnered with local communities to determine the concentrations of micro-plastics in 125 beaches on three islands in the Canary Current: Lanzarote, La Graciosa, and Fuerteventura. We found that, in spite of being located in highly-protected natural areas, all beaches in our study area are exceedingly vulnerable to micro-plastic pollution, with pollution levels reaching concentrations greater than 100g of plastic in 1l of sediment. This paper contributes to ongoing efforts to develop solutions to plastic pollution by addressing the questions: (i) Where does this pollution come from?; (ii) How much plastic pollution is in the world’s oceans and coastal zones?; (iii) What are the consequences for the biosphere?; and (iv) What are possible solutions?
اظهر المزيد [+] اقل [-]Analysis of daily average PM10 predictions by generalized linear models in Brno, Czech Republic النص الكامل
2014
Huebnerova, Zuzana | Michalek, Jaroslav
Ambient air quality assessment and management plays an important role in the current European Union policy. Among others, air pollution by PM10 is being monitored. A previous analysis of PM10 aimed at identifying factors affecting air pollution in stations in the City of Brno using available observed meteorological variables. However, the studied model cannot be used for predicting the level of PM10 pollution because the included meteorological variables are not available exactly at the time when the prediction is requested. In that case, we should base the predictions on available predicted variables, namely on temperature, wind direction, wind speed, and cloud cover. A comparison of obtained predictions with the observed values of PM10 during a testing period allows us to evaluate a loss of prediction quality when the predicted covariates are used instead of the observed ones. The presented analysis based on test of symmetry and test of homogeneity of the marginal distribution of two–way contingency tables shows that the loss of prediction quality by employing the predicted meteorological variables is non–significant in the studied case. This observation suggests that the model with predicted meteorological variables can be employed in environmental management processes.
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