Degradation of trihalomethanes and choramines by UV and VUV irradiation

Disinfection byproducts (DBPs) generated from the chlorination of natural organic matter (NOM) represent a source of concern related to drinking water quality. Vacuum-ultraviolet (VUV \u3c200 \u3enm), irradiation can be an efficient advanced oxidation process (AOP), has been documented to inactivate pathogens as well as remove micropollutants in drinking water. To compare the effects of VUV and UVC irradiation, four trihalomethanes (THMs) and three chloramines, chloroform (CHCl3), dichlorobromomethane (CHBrCl2), dibromochloromethane (CHBr2Cl), bromoform (CHBr3), monochloramine (NH2Cl), dichloramine (NHCl2) and trichloramine (NCl3), were prepared and analyzed for their degradation reaction rate constant under UVC, VUV/UVC, UVC/Cl2, VUV/UVC/Cl2 processes. A mini-fluidic VUV/UVC photoreaction system (MVPS) was connected directly to a membrane introduction mass spectrometry (MIMS) for many of these experiments to quickly quantify volatile DBPs dynamic behavior. VUV-UVC absorption spectra (180-300 nm) were measured four THMs. THMs and chloramines were found to be degraded faster by VUV irradiation than by UV irradiation. CHBr3 and NCl3 were the fastest degraded compound among THMs and chloramines, respectively. In addition, degradation of total THM as well as trihalomethane formation potential (THMFP) generated from the chlorination of humic acid in the presence of bromide with UVC or VUV irradiation were examined; therefore, specific THM species were also quantified and summarized. Finally, 77% reduction in THMFP was observed in VUV/UVC/Cl2 process and 82% reduction in total THMs was observed in VUV/UVC process

Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico

Zucheng Wang is with the Department of Geography, Northeast Normal University, Changchun, China. -- Zucheng Wang and Zhanfei Liu are with the Marine Science Institute, The University of Texas at Austin, Port Aransas, TX, USA. -- Kehui Xu is with the Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA, USA – and – the Coastal Studies Institute, Louisiana State University, Baton Rouge, LA, USA. -- Lawrence M Mayer is with the School of Marine Sciences, University of Maine, Walpole, ME, USA. -- Zulin Zhang is with The James Hutton Institute, Aberdeen, UK. -- Alexander S. Kolker is with Louisiana Universities Marine Consortium, Chauvin, LA, USA. -- Wei Wu is with the Department of Coastal Sciences, Gulf Coast Research Laboratory, The University of Southern Mississippi, Ocean Springs, MS, USA.Background: Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5 cm) of the northern Gulf of Mexico. Results: PAH concentrations in this region ranged from 100 to 856 ng g−1, with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5–6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments. Conclusion: PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels.Marine [email protected]

Direct Determination of Electron-Phonon Coupling Matrix Element in a Correlated System

High-resolution electron energy loss spectroscopy measurements have been carried out on an optimally doped cuprate Bi2Sr2CaCu2O8+{\delta}. The momentum-dependent linewidth and the dispersion of an A1 optical phonon are obtained. Based on these data as well as the detailed knowledge of the electronic structure from angle-resolved photoemission spectroscopy, we develop a scheme to determine the full structure of electron-phonon coupling for a specific phonon mode, thus providing a general method for directly resolving the EPC matrix element in systems with anisotropic electronic structures