A high volume sampling system for isotope determination of volatile halocarbons and hydrocarbons

The isotopic composition of volatile organic compounds (VOCs) can provide valuable information on their sources and fate not deducible from mixing ratios alone. In particular the reported carbon stable isotope ratios of chloromethane and bromomethane from different sources cover a δ13C-range of almost 100‰ making isotope ratios a very promising tool for studying the biogeochemistry of these compounds. So far, the determination of the isotopic composition of C1 and C2 halocarbons others than chloromethane is hampered by their low mixing ratios. In order to determine the carbon isotopic composition of C1 and C2 halocarbons with mixing ratios as low as 1 pptv (i) a field suitable cryogenic high volume sampling system and (ii) a chromatographic set up for processing these samples have been developed and validated. The sampling system was tested at two different sampling sites, an urban and a coastal location in Northern Germany. The average δ13C-values for bromomethane at the urban site were −42.9 ± 1.1‰ and agreed well with previously published results. But at the coastal site bromomethane was substantially enriched in 13C by almost 10‰. Less pronounced differences were observed for chlorodifluoromethane, 1,1,1-trichloroethane and chloromethane. We suggest that these differences are related to the turnover of these compounds in ocean surface waters. Furthermore we report first carbon isotope ratios for iodomethane (−40.4‰ to −79.8‰), bromoform (−13.8‰ to 22.9‰), and other halocarbons

Data for: Strategically placed landscape fuel treatments decrease fire severity and promote recovery in the northern Sierra Nevada

These data files contain 1) field measurements, and 2) FARSITE model output used in the paper "Strategically placed landscape fuel treatments decrease fire severity and promote recovery in the northern Sierra Nevada.&quot

Data for: Strategically placed landscape fuel treatments decrease fire severity and promote recovery in the northern Sierra Nevada

These data files contain 1) field measurements, and 2) FARSITE model output used in the paper "Strategically placed landscape fuel treatments decrease fire severity and promote recovery in the northern Sierra Nevada."THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

HALOGEN SUBSTITUTION AT PHOSPHORUS IN PHOSPHAALKENES AND PHOSPHASILENES VERSUS BIS(METHYLENE)PHOSPHORANES - A QUANTUM-CHEMICAL EVALUATION OF BONDING PROPERTIES

Schoeller W, STRUTWOLF J, TUBBESING U, BEGEMANN C. HALOGEN SUBSTITUTION AT PHOSPHORUS IN PHOSPHAALKENES AND PHOSPHASILENES VERSUS BIS(METHYLENE)PHOSPHORANES - A QUANTUM-CHEMICAL EVALUATION OF BONDING PROPERTIES. JOURNAL OF PHYSICAL CHEMISTRY. 1995;99(8):2329-2334.The bonding properties of/at phosphorus-halogen substituted (F, Cl, Br, I) phosphaalkenes and -silenes were explored with ab initio calculations with effective core potential (ECP(d)) optimizing the geometries at the RHF and CISD levels. Compared with the parent compounds HP=CH2 the PC bond is slightly shrunk, indicating the formation of an ion pair X(-)PCH(2)(+). This is substantiated by an analysis of the natural atomic orbital populations. They evidence a strong shift of electron density from phosphorus toward the electronegative halogen atom in the a-space, with negligible pi-mesomeric interaction of the lone pair at the halogen with the PC sc-bond. A similar but slightly less affirmed situation results for the P-halogen substituted phosphasilenes as well as for the bis(methylene)phosphoranes. Furthermore, for the latter the halogen substitution enforces a Jahn-Teller distortion, causing symmetry reduction from C-2v to C-2 symmetry. d-orbital participation at phosphorus does not play any role in bonding

Model reactions and natural occurrence of furans from hypersaline environments

Volatile organic compounds like furan and its derivatives are important for atmospheric properties and reactions. In this work the known abiotic formation of furan from catechol under Fenton-like conditions with Fe3+ sulfate was revised by the use of a bispidine Fe2+ complex as a model compound for iron with well-known characteristics. While total yields were comparable to those with the Fe3+ salt, the bispidine Fe2+ complex is a better catalyst as the turnover numbers of the active iron species were higher. Additionally, the role of iron and pH is discussed in relation to furan formation from model compounds and in natural sediment and water samples collected from the Dead Sea and several salt lakes in Western Australia. Various alkylated furans and even traces of halogenated furans (3-chlorofuran and 3-bromofuran) were found in some Australian samples. 3-chlorofuran was found in three sediments and four water samples, whereas 3-bromofuran was detected in three water samples. Further, the emission of furans is compared to the abundance of several possible precursors such as isoprene and aromatic hydrocarbons as well as to the related thiophenes. It is deduced that the emissions of volatile organic compounds such as furans contribute to the formation of ultra-fine particles in the vicinity of salt lakes and are important for the local climate

Cation and anion stabilities of low-coordinated π-bonded phosphorus systems. An ab initio quantum chemical investigation

Schoeller W, Tubbesing U, Begeman C, Strutwolf J. Cation and anion stabilities of low-coordinated π-bonded phosphorus systems. An ab initio quantum chemical investigation. In: Phosphorus, Sulfur, and Silicon and the Related Elements. Phosphorus, Sulfur, and Silicon and the Related Elements. Vol 109. GORDON BREACH SCI PUBL LTD; 1996: 101-104.Quantum chemical calculations at RHF/6-3 1+g(d,p) with electron correlation (MP4SDTQ) corrections are reported on (a) a relative scale of model cations and anions derived from low-coordinated pi-bonded phosphorus, (b) on band structure calculations (tight-binding approximation:) of the P-iodine iminophosphane and (c) on lithiation to (unsolvated) corresponding structures derived from the anionic species

Anatrichosoma sp. in the footpads of a cat: Diagnosis and pathology of Namibian case

Anatrichosoma species are an unusual group of zoonotic trichuroid nematodes. Due to limited knowledge of their life cycle and diagnostic challenges, anatrichosomiasis has been reported only 3 times in domestic animals. A short-haired cat from central Windhoek, Namibia, presented with ulceration, swelling, and sepsis on all four paws, a severe generalized lymphadenopathy and considerable invasive eosinophilia. Histological analysis revealed epidermal hyperplasia, with severe serocellular crusting on the skin surface. One specimen revealed a series of thick-walled eggs within nematode segments with a few sections containing eggs with bioperculate appearance which is compatible with the Aphasmid group of nematodes, more specifically, the genus Anatrichosoma. Ivermectin treatment completely cleared the condition. This is the first report of Anatrichosoma sp. in the Republic of Namibia, identified from a unique location in the capital, Windhoek.Peer reviewedEntomology and Plant Patholog