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07-4-13 EST最新文章和摘要
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Temperature and Wavelength Dependence of Nitrite Photolysis in Frozen and Aqueous Solutions Liang Chu and Cort Anastasio* Atmosphere Science Program, Department of Land, Air, and Water Resources, University of California, One Shields Avenue, Davis, California 95616-8627 Received for review November 15, 2006 Revised manuscript received March 5, 2007 Accepted March 9, 2007 Abstract: While the photolysis of nitrite is an important source of hydroxyl radical (OH) in some natural waters, its wavelength and temperature dependence have not been fully described in solution. In addition, there are no studies of this reaction on ice, although there is evidence of nitrite production in snow. To address these gaps, we have measured the wavelength and temperature dependence of the quantum yields of OH from the photolysis of frozen and aqueous NO2-. From our solution and ice results, we derive a master equation that describes the OH quantum yield from NO2- photolysis as a function of both temperature (240-295 K) and illumination wavelength (302-390 nm): (N OH)T, = (y0 + a/(1 + exp(( - c)/b)))exp(((e + f)/R) × (1/295 - 1/T)) where y0 = 0.0204 ± 0.0010, a = 0.0506 ± 0.0022, b = 11.2 ± 1.2, c = 332 ± 1, e = 20.5 ± 3.2, f = 7553 ± 1204, uncertainties represent 1 standard error, T is the temperature (K), R is the gas constant (8.314 J mol-1 K-1), and is the wavelength (nm). Using these results we predict the pseudo-steady-state concentrations of nitrite on sunlit polar snow grains and compare the relative importance of the photolysis of nitrite, nitrate, and hydrogen peroxide as sources of snow-grain OH. -------------------------------------------------------------------------------- Importance of Structural Makeup of Biopolymers for Organic Contaminant Sorption Xilong Wang and Baoshan Xing* Department of Plant, Soil, and Insect Sciences, University of Massachusetts, Amherst, Massachusetts 01003 Received for review October 27, 2006 Revised manuscript received March 2, 2007 Accepted March 16, 2007 Abstract: Sorption of pyrene, phenanthrene, naphthalene, and 1-naphthol by original (lignin, chitin, and cellulose) and coated biopolymers was examined. Organic carbon normalized distribution coefficients (Koc) of all compounds by the original biopolymers followed the order lignin > chitin > cellulose, in line with the order of their hydrophobicity. Hydrophobicity of structurally similar organic compounds is the main factor determining their ability to occupy sorption sites in biopolymers. Specific interactions (e.g., H-bonding) between 1-naphthol and chitin or cellulose increased its ability to occupy sorption sites. Lignin coating resulted in an increased Koc for phenanthrene (13.6 times for chitin and 6.9 times for cellulose) and 1-naphthol (6.0 times for chitin and 3.7 times for cellulose) relative to the acetone-treated chitin and cellulose. Also, these coated biopolymers had increased isotherm nonlinearity, due to the newly formed condensed domains. An increase in phenanthrene and 1-naphthol sorption by lignin-coated biopolymers as compared to chitin and cellulose was contributed by the newly created high-energy sites in condensed domains and coated lignin. Results of this study highlight the importance of the structural makeup of biopolymers in controlling the sorption of hydrophobic organic compounds. -------------------------------------------------------------------------------- Atmospheric Outflow of Anthropogenic Semivolatile Organic Compounds from East Asia in Spring 2004 Toby Primbs, Staci Simonich,* David Schmedding, Glenn Wilson, Dan Jaffe, Akinori Takami, Shungo Kato, Shiro Hatakeyama, and Yoshizumi Kajii Departments of Chemistry and Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, University of Washington-Bothell, Bothell, Washington, Atmospheric Environmental Division, National Institute of Environmental Studies, Tsukuba, Japan, and Applied Chemistry, Faculty of Engineering, Tokyo Metropolitan University, Tokyo, Japan Received for review September 21, 2006 Revised manuscript received March 7, 2007 Accepted March 8, 2007 Abstract: To estimate the emissions of anthropogenic semivolatile organic compounds (SOCs) from East Asia and to identify unique SOC molecular markers in Asian air masses, high-volume air samples were collected on the island of Okinawa, Japan between 22 March and 2 May 2004. Contributions from different source regions (China, Japan, the Koreas, Russia, and ocean/local) were estimated by use of source region impact factors (SRIFs). Elevated concentrations of hexachlorobenzene (HCB), hexachlorcyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and particulate-phase polycyclic aromatic hydrocarbons (PAHs) were attributed to air masses from China. A large proportion of the variation in the current-use pesticides, gas-phase PAHs, and polychlorinated biphenyl (PCB) concentrations was explained by meteorology. Chlordanes showed a technical mixture profile and similar concentrations regardless of source region. / HCH and trans/cis chlordane ratios did not vary significantly with different source regions and had regional averages of 2.5 ± 1.0 and 1.2 ± 0.3, respectively. Particulate-phase PAH concentrations were significantly correlated (p value < 0.05) with other incomplete combustion byproduct concentrations, including elemental mercury (Hg0), CO, NOx*, black carbon, submicrometer aerosols, and SO2. By use of measured PAH, CO, and black carbon concentrations and estimated CO and black carbon emission inventories, the emission of six carcinogenic particulate-phase PAHs was estimated to be 1518-4179 metric tons/year for Asia and 778-1728 metric tons/year for China, respectively. These results confirm that East Asian outflow contains significant emissions of carcinogenic particulate-phase PAHs. -------------------------------------------------------------------------------- Uncertainty-Accounting Environmental Policy and Management of Water Systems Christian Baresel* and Georgia Destouni Department of Land and Water Resources Engineering, Royal Institute of Technology (KTH), Brinellvägen 32, 100 44 Stockholm, Sweden, and Department of Physical Geography and Quaternary Geology, Stockholm University, Svante Arrhenius väg 8C, 106 91 Stockholm, Sweden Received for review June 26, 2006 Revised manuscript received February 28, 2007 Accepted March 5, 2007 Abstract: Environmental policies for water quality and ecosystem management do not commonly require explicit stochastic accounts of uncertainty and risk associated with the quantification and prediction of waterborne pollutant loads and abatement effects. In this study, we formulate and investigate a possible environmental policy that does require an explicit stochastic uncertainty account. We compare both the environmental and economic resource allocation performance of such an uncertainty-accounting environmental policy with that of deterministic, risk-prone and risk-averse environmental policies under a range of different hypothetical, yet still possible, scenarios. The comparison indicates that a stochastic uncertainty-accounting policy may perform better than deterministic policies over a range of different scenarios. Even in the absence of reliable site-specific data, reported literature values appear to be useful for such a stochastic account of uncertainty. -------------------------------------------------------------------------------- |
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