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RISS 인기검색어
- 검색키워드
- 저자 : James A. Mulholland (검색결과 4 건)
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Characterization of PM<sub>2.5</sub>-bound polycyclic aromatic hydrocarbons in Atlanta
Li, Zheng,Sjodin, Andreas,Porter, Erin N.,Patterson Jr., Donald G.,Needham Jr., Larry L.,Lee Jr., Sangil,Russell Jr., Armistead G.,Mulholland Jr., James A. Elsevier 2009 Atmospheric environment Vol.43 No.5
<P><B>Abstract</B></P><P>Twenty-four hour PM<SUB>2.5</SUB> samples from a rural site, an urban site, and a suburban site (next to a major highway) in the metropolitan Atlanta area in December 2003 and June 2004 were analyzed for 19 polycyclic aromatic hydrocarbons (PAH). Extraction of the air samples was conducted using an accelerated solvent extraction method followed by isotope dilution gas chromatography/mass spectrometry determination. Distinct seasonal variations were observed in total PAH concentration (i.e. significantly higher concentrations in December than in June). Mean concentrations for total particulate PAHs in December were 3.16, 4.13, and 3.40ngm<SUP>−3</SUP> for the urban, suburban and rural sites, respectively, compared with 0.60, 0.74, and 0.24ngm<SUP>−3</SUP> in June. Overall, the suburban site, which is impacted by a nearby major highway, had higher PAH concentration than did the urban site. Total PAH concentrations were found to be well correlated with PM<SUB>2.5</SUB>, organic carbon (OC), and elemental carbon (EC) in both months (<I>r</I><SUP>2</SUP>=0.36–0.78, <I>p</I><0.05), although the slopes from the two months were different. PAHs represented on average 0.006% of total PM<SUB>2.5</SUB> mass and 0.017% of OC in June, compared with 0.033% of total PM<SUB>2.5</SUB> and 0.14% of OC in December. Total PAH concentrations were also correlated with potassium ion (<I>r</I><SUP>2</SUP>=0.39, <I>p</I>=0.014) in December, but not in June, suggesting that in winter biomass burning can potentially be an important source for particulate PAH. Retene was found at a higher median air concentration at the rural site than at the urban and suburban sites—unlike the rest of the PAHs, which were found at lower levels at the rural site. Retene also had a larger seasonal difference and had the weakest correlation with the rest of the PAHs measured, suggesting that retene, in particular, might be associated with biomass burning.</P>
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Homologue Patterns of Polychlorinated Naphthalenes (PCNs) formed via Chlorination in Thermal Process
( Jae Yong Ryu ),( Do Hyong Kim ),( James A Mulholland ),( Seong Ho Jang ),( Chang Yong Choi ),( Jong Bum Kim ) 한국환경과학회 2012 한국환경과학회지 Vol.21 No.8
The chlorination pattern of naphthalene vapor when passed through a 1 cm particle bed of 0.5% (mass) copper (II) chloride (CuCl2) mixed with silicon dioxide (SiO2) was studied. Gas streams consisting of 92% (molar) N2, 8% O2 and 0.1% naphthalene vapor were introduced to an isothermal flow reactor containing the CuCl2/SiO2 particle bed. Chlorination of naphthalene was studied from 100 to 400˚C at a gas velocity of 2.7 cm/s. Mono through hexachlorinated naphthalene congeners were observed at 250˚C whereas a broader distribution of polychlorinated naphthalenes (PCNs) including hepta and octachlorinated naphthalenes was observed at 300˚C. PCN production was peak at 250˚C with 3.07% (molar) yield, and monochloronaphthalene (MCN) congeners were the major products at two different temperatures. In order to assess the effect of a residence time on naphthalene chlorination, an experiment was also conducted at 300˚C with a gas velocity of 0.32 cm/s. The degree of naphthalene chlorination increased as a gas velocity decreased.
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Thermal Formation of Polycyclic Aromatic Hydrocarbons from Cyclopentadiene (CPD)
Do Hyong Kim,Jeong Kwon Kim,Seong Ho Jang,James A. Mulholland,Jae Yong Ryu 대한환경공학회 2007 Environmental Engineering Research Vol.12 No.5
Polycyclic aromatic hydrocarbon growth from cyclopentadiene (CPD) pyrolysis was investigated using a laminar flow reactor operating in a temperature range of 600 to 950℃. Major products from CPD pyrolysis are benzene, indene and naphthalene. Formation of observed products from CPD is explained as follows. Addition of the cyclopentadienyl radical to a CPD π-bond produces a resonance-stabilized radical, which further reacts by one of three unimolecular channels: intramolecular addition, C-H bond β-scission, or C-C bond β-scission. The intramolecular addition pathway produces a 7-norbornenyl radical, which then decomposes to indene. Decomposition by C-H bond β-scission produces a biaryl intermediate, which then undergoes a ring fusion sequence that has been proposed for dihydrofulvalene-to-naphthalene conversion. In this study, we propose C-C bond β-scission pathway as an alternative reaction channel to naphthalene from CPD. As preliminary computational analysis, Parametric Method 3 (PM3) molecular calculation suggests that intramolecular addition to form indene is favored at low temperatures and C-C bond β-scission leading to naphthalene is predominant at high temperatures.
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