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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Seasonal variation of Polycyclic Aromatic Hydrocarbons in the Atmosphere in Kaohsiung Coast

Zeng, Kun-Yan 27 August 2008 (has links)
A high-volume air sampler (PS-1) was used to measure the concentrations of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of Kaohsiung coast, PAHs diagnostic ratios,Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) were employed to determine the potential sources of PAHs. The results show that the lowest concentrations of PAHs occurred in May (2.62 ngm-3), while the highest occurred in December (36.4 ngm-3). The nighttime concentrations of PAHs are higher than daytime with average night / day ratio of 1.65. The PAHs was more distributed in gas phase with proportions between 64.1 to 93.7 %. The 2, 3-Ring PAHs were mostly present in the gaseous phase (96.2 and 96.5 % respectively), 4-Ring also present dominantly in the gaseous phase (73.0 %), 5-Ring present mostly in the particle phase (80.2 %), 6, 7-Ring PAHs were mostly present in particulate phase (97.4 and 97.7 % respectively). During the Ghost Festiva and Asian dust storm events, atmospheric concentrations of PAHs and PAHs/TSP ratios were both found increased. It is found that gaseous and particulate PAHs correlate negatively with ambient temperature(r=-0.62, -0.57). Results from analyses of diagnostic ratios, HCA and PCA, the major sources of pollution include gasoline, diesel exhaust and industrial emission.
2

Factors affecting atmospheric Polycyclic Aromatic¡@Hydrocarbons in Kaohsiung coast by GMDH

Chiou, Guo-Yang 18 August 2010 (has links)
Coastal atmospheric concentrations of polycyclic aromatic hydrocarbons (PAHs) were measured at top of a building on campus of the National Sun Yat-sen University of Kaohsiung. Concentrations of 52 PAH compounds were analyzed in both gaseous and particulate phases in air samples collected from May 2008 through April 2009. PAHs diagnostic, Hierarchical Analysis (HCA) and Principal Component Analysis (PCA) were employed to determine the potential sources of PAHs. The Group Method of Data Handling (GMDH) was applied to relate atmospheric PAH concentration to air quality variables like SO2 and O3, as well as meteorological conditions like precipitation and temperature. During the sampling period the mean of total PAH concentrations was 14.2 ng/m3. Over all, PAH concentrations in winter were higher than summer, with the lowest concentrations of PAHs occurred in June (2.22 ng/m3), while the highest occurred in January (32.4 ng/m3). The night-time concentrations of PAHs are higher than daytime. The 2, 3-ring PAHs were mostly present in the gaseous phase, 4-ring were dominant in the gaseous phase, while 5, 6, 7-ring PAHs were mostly present in the particulate phase. During the Ghost festival and Asian dust storm events, atmospheric concentrations of PAHs and PAHs/TSP ratios were both found increased. Meteorological conditions, such as temperature and relative humidity, may strongly affect PAH concentrations, the gaseous and particulate PAHs correlate significantly with SO2, NOx, and PM10. Result from analyses of diagnostic rations, HCA and PCA, indicates the major sources of PAHs include gasoline and diesel exhaust. By using GMDH, a reasonable appraisal index was obtained for the pattern forecast potency with the meteorological and air quality variables. The GMDH algorithm obtained during 2008~2009 was tested in predictions and compared with what measured in 2007~2008.
3

Physicochemical Characteristics and Source Allocation of Asian Dusts Sampled in Penghu Islands

Liu, Yi-chi 25 August 2008 (has links)
In recent years, the Asian dust storms occurred frequently. It was estimated that approximately eight hundred million metric tons of Asian dusts transported to the atmosphere yearly. During the dust storm period, Asian dusts not only induce poor air quality, but also reduce atmospheric visibility and influence human health. In order to investigate the physicochemical characteristics and source allocation of Asian dusts, this study collect the Asian dusts in the Pescadores Islands during the years of 2002~2006. In addition, this study collected top soils in three regions of Inner Mongolia and resuspended the soil samples in a resuspension chamber to analyze their chemical composition. Moreover, this study applied enrichment factor analysis (EF) and grey relational analysis to allocate the potential sources of Asian dusts and compare them with the transportation routes obtained from backward trajectory. During Asian dust storm periods, the concentration of atmospheric particulate matter (PM10) in the Pescadores Islands increased significantly, probably is 3~6 times of PM10 during non-dust storm periods. Among them, coarse particles (PM2.5-10) particularly rose from 10~30 £gg/m3 to 80~130 £gg/m3 and the size distribution changed from bi-modal distribution to single modal distribution of coarse particles during Asian dust storm periods. This study further analyzed the chemical composition of Asian dusts, including water-soluble ionic species, carbon contents, and metallic contents. For fine particles (PM2.5), the order of water-soluble ionic species was SO42- > NH4+ > NO3- > Cl- > Ca2+ > Na+ > K+ > Mg2+ > F-. For coarse particles (PM2.5-10), the order of water-soluble ionic species was Cl- > SO42- > NO3- > Na+ > Ca2+ > NH4+ > Mg2+ > K+ > F-. The carbon contents distributes mainly in fine particles. The major contents of both fine and coarse particles were crustal elements (i.e. Al, Fe, Na, Mg, K, Ca, and Sr). In addition to the analysis of physicochemical characteristics of Asian dusts, this study applied HYSPLIT MODEL to figure out their transportation routes by backward trajectory. According to the backward trajectories, this study compartmentalized Asian dusts storm transportation routes into three categories: Eastward Transportation and Retraced (ETR), Southeasterly Transportation and Circumrotated (STC), and Straight Southeasterly Transportation (SST). Analyzing the spatial and temporary background variables to investigate the influence of transportation routes on Asian dusts¡¦ physicochemical characteristic. This study revealed that the physicochemical characteristics were very similar for same category of Asian dust storms, which can be used to allocate the source regions of Asian dust storms. This study resuspended the soil samples collected in Inner Mongolia inside a resuspension chamber and collected the suspended particles (PM2.5, PM2.5-10) for chemical analysis. Chemical analysis results indicated that the fingerprints of chemical composition for different regions were similar but still distinguishable, which can be used to identify the source areas of Asian dusts. This study further compare and correlate the Asian dusts collected at the Pescadores Islands during Asian dust storm periods with the soils collected in Inner Mongolia chemically by enrichment factor and grey relational analysis. This study further compared the source allocation of Asian dust storms obtained from enrichment factor, grey relational analysis, and backward trajectory and found the results of these three methods were quite similar. For enrichment factor analysis, 88% of similarity was obtained by using two separate reference elements (Al and Fe). The similarity of backward trajectory and grey relational analysis reached as high as 83%. Moreover, the backward trajectory and enrichment factor were similar up to 75%, while the grey relational analysis and enrichment factor were similar up to 69%. Overall, two out of three aforementioned methods can effectively allocate the source regions of Asian dusts by 94%, while all three methods can successfully allocate the source regions of Asian dusts by 56%. Comparison of three aforementioned methods showed that they can be applied to allocate the source regions of Asian dusts.
4

Analyses of Common Elements and Oxides in the Paleosols of the Bahamas and of the Northern Mariana Islands

Ersek, Vasile 07 August 2004 (has links)
Paleosols from the Bahamas and the Northern Mariana Islands (CNMI) are closely related to past atmospheric circulation and dust load. In the Bahamas the sources of insoluble residue (IR) must be allogenic because the islands consist of almost pure carbonates. The Al2O3:TiO2 ratio was used to establish the provenance of the IR of the paleosols. Comparisons of this ratio from Bahamian paleosols, North African dust, Lesser Antilles ash and North American loess reveal that the African dust is the major contributor to the IR, with a potential minor volcanic input from the Lesser Antilles. The contribution of the North American loess to the IR was not determined because of geochemical similarities with the North African dust. The study of two outcrops in Eleuthera indicate that paleosols can act as aquicludes. The Bahamian samples were collected on a roughly north-south transect in order to establish the climatic influence on paleosol properties. Even though there is a marked climatic gradient in the Bahamas, the paleosol geochemistry shows no trend that could be related to paleoclimate. While previous studies indicated that the source of insoluble residues in the soils of CNMI is carbonate dissolution, the present study shows that atmospheric deposition of ash from the Mariana arc and dust from the Asian continent may play a significant role in paleosol formation.

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