The influence of precipitate formation on the chemical oxidation of TCE DNAPL with potassium permanganate     

Michael R. West  Gavin P. Grant  Jason I. Gerhard  Bernard H. Kueper 《Advances in water resources》2008

A three-dimensional two-phase flow model is coupled to a non-linear reactive transport model to study the efficacy of potassium permanganate treatment on dense, non-aqueous phase liquid (DNAPL) source removal in porous media. A linear relationship between the soil permeability (k) and concentration of manganese dioxide precipitate ([MnO_2(s)]), k = k_o + S_rind [MnO_2(s)], is utilized to simulate nodal permeability reductions due to precipitate formation. Using published experimental column studies, an S_rind = −5.5 × 10⁻¹⁶ m² L/mg was determined for trichloroethylene (TCE) DNAPL. This S_rind was then applied to treatment simulations on three-dimensional TCE DNAPL source zones comprising either DNAPL at residual saturations, or DNAPL at pooled saturations.  相似文献   

Oil seepage and carbonate formation: A case study from the southern Gulf of Mexico     

Daniel Smrzka  Jennifer Zwicker  David Misch  Christoph Walkner  Susanne Gier  Patrick Monien  Gerhard Bohrmann  Jrn Peckmann 《Sedimentology》2019,66(6):2318-2353

Oil seeps from the southern Gulf of Mexico can be regarded as natural laboratories where the effect of crude oil seepage on chemosynthesis‐based communities and carbonate precipitation can be studied. During R/V Meteor cruise 114 the seep sites UNAM (Universidad Nacional Autónoma de México) Ridge, Mictlan Knoll and Tsanyao Yang Knoll (Bay of Campeche, southern Gulf of Mexico) were investigated and sampled for authigenic carbonate deposits containing large amounts of liquid oil and solid asphalt. The δ¹³C values of individual carbonate phases including: (i) microcrystalline matrix aragonite and calcite; (ii) grey, cryptocrystalline to microcrystalline aragonite; and (iii) clear, fibrous aragonite cement, are between ?30‰ and ?20‰, agreeing with oil as the primary carbon source. Raman spectra reveal that residual heavy oils from all sites are immature and most likely originate from the same reservoir. Geochemical batch modelling using the software code PHREEQC demonstrates how sulphate‐driven oxidation of oil‐derived low‐molecular to high‐molecular weight hydrocarbons affects carbonate saturation state, and shows that the oxidation state of carbon in hydrocarbon compounds and oxidation rates of hydrocarbons control carbonate saturation and precipitation at oil seeps. Phase‐specific trace and rare earth element contents of microcrystalline aragonite and calcite, grey cryptocrystalline aragonite and clear aragonite were determined, revealing enrichment in light rare earth elements for grey aragonite. By comparing trace element patterns of carbonates with those of associated oils, it becomes apparent that liquid hydrocarbons constitute an additional source of trace metals to sedimentary pore waters. This work not only demonstrates that the microbial degradation of oil at seeps may result in the precipitation of carbonate minerals, it also elucidates that trace metal inventories of seep carbonates archive diagnostic elemental patterns, which can be assigned to the presence of heavy hydrocarbons in interstitial pore waters.  相似文献   

Nitrogen transformation processes in the Elbe River: Distinguishing between assimilation and denitrification by means of stable isotope ratios in nitrate   总被引：3，自引：0，他引：3  

Barbara Deutsch  Maren Voss  Helmut Fischer 《Aquatic Sciences - Research Across Boundaries》2009,71(2):228-237

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Risk-adjusted approaches for planning sustainable agricultural development   总被引：1，自引：1，他引：0  

Günther Fischer  Tatiana Ermolieva  Yuri Ermoliev  Laixiang Sun 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(4):441-450

In this paper we show that explicit treatment of risks and uncertainties in agricultural production planning may considerably alter strategies for achieving robust outcomes with regard to sustainable agricultural developments. We discuss production planning models under uncertainties and risks that may assist in planning location-specific production expansion within environmental and health risk indicators and constraints. The proposed approaches are illustrated with the example of spatially explicit livestock production allocation in China to 2030.  相似文献   

Determination of the Tin Stable Isotopic Composition in Tin‐bearing Metals and Minerals by MC‐ICP‐MS          下载免费PDF全文

Gerhard Brügmann  Daniel Berger  Ernst Pernicka 《Geostandards and Geoanalytical Research》2017,41(3):437-448

This study uses MC‐ICP‐MS for the precise analysis of the stable tin isotopic composition in ore minerals of tin (cassiterite, stannite), tin metal and tin bronze. The ultimate goal is to determine the provenance of tin in ancient metal objects. We document the isotope compositions of reference materials and compare the precision of different isotope ratios and the accuracy of different procedures of mass fractionation correction. These data represent a base with which isotopic data of future studies can be directly compared. The isotopic composition of cassiterite and stannite can be determined after reduction to tin metal and bronze, respectively. Both metals readily dissolve in HCl, but while the solutions of tin metal can be directly measured, the bronze solutions must be purified with an anion exchanger. The correction of the mass bias is best performed with an internal Sb standard and an empirical regression method. A series of Sn isotope determinations on commercially available mono‐element Sn solutions as well as reference bronze materials and tin minerals show fractionations ranging from about ?0.09‰ to 0.05‰/amu. The combined analytical uncertainty (2s) was determined by replicate dissolutions of reference materials of bronze (BAM 211, IARM‐91D) and averages at about 0.005‰/amu.  相似文献   

Diversity,composition and host-species relationships of epiphytic orchids and ferns in two forests in Nepal   总被引：1，自引：0，他引：1  

Yagya P. Adhikari  Anton Fischer  Hagen S. Fischer  Maan B. Rokaya  Prakash Bhattarai  Axel Gruppe 《山地科学学报》2017,14(6):1065-1075

Epiphytic plant species are an important part of biological diversity. It is therefore essential to understand the distribution pattern and the factors influencing such patterns. The present study is aimed at observing the patterns of species richness, abundances and species composition of epiphytic orchids and ferns in two subtropical forests in Nepal. We also studied the relationship of host plants (Schima wallichii and Quercus lanata) and epiphyte species. Data were collected in Naudhara community forest (CF) and the national forest (NF) in Shivapuri Nagarjun National Park. The data were analyzed using univariate and multivariate tests. In total, we recorded 41 species of epiphytes (33 orchid and 8 fern species). Orchid species abundance is significantly higher in CF compared to NF. Orchid species richness and abundance increased with increasing southern aspect whereas it decreased with increasing canopy cover, and fern species richness increased with host bark roughness. Orchid abundance was positively correlated with increasing bark pH, stem size, tree age and tree height and negatively correlated with increasing steepness of the area. Likewise, fern abundances were high in places with high canopy cover, trees that were tall and big, but decreased with increasing altitude and southern aspect. The composition of the orchid and fern species was affected by altitude, aspect, canopy cover, DBH, number of forks and forest management types. We showed that the diversity of orchid and fern epiphytes is influenced by host characteristics as well as host types. The most important pre-requisite for a high epiphyte biodiversity is the presence of old respectively tall trees, independent of the recent protection status. This means: (i) for protection, e.g. in the frame of the national park declaration, such areas should be used which host such old tall trees; and (ii) also in managed forests and even in intensively used landscapes epiphytes can be protected by letting a certain number of trees be and by giving them space to grow old and tall.  相似文献   

Seabirds and floating plastic debris     

Cadée GC 《Marine pollution bulletin》2002,44(11):1294-1295

80% of floating plastic debris freshly washed ashore on a Dutch coast showed peckmarks made by birds at sea. They either mistake these debris for cuttlebones or simply test all floating objects. Ingestion of plastic is deleterious for marine organisms. It is urgent to set measures to plastic litter production.  相似文献   

Incorporation and leaching of heavy metals in clay annealed with Pb, Cu and V     

Volker Karius  Petra Bruhns  Kay Hamer  Reinhard X. Fischer 《Environmental Geology》2001,41(3-4):297-304

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CELIAS - Charge, Element and Isotope Analysis System for SOHO   总被引：1，自引：0，他引：1  

D. Hovestadt  M. Hilchenbach  A. Bürgi  B. Klecker  P. Laeverenz  M. Scholer  H. Grünwaldt  W. I. Axford  S. Livi  E. Marsch  B. Wilken  H. P. Winterhoff  F. M. Ipavich  P. Bedini  M. A. Coplan  A. B. Galvin  G. Gloeckler  P. Bochsler  H. Balsiger  J. Fischer  J. Geiss  R. Kallenbach  P. Wurz  K. -U. Reiche  F. Gliem  D. L. Judge  H. S. Ogawa  K. C. Hsieh  E. Möbius  M. A. Lee  G. G. Managadze  M. I. Verigin  M. Neugebauer 《Solar physics》1995,162(1-2):441-481

The CELIAS experiment on SOHO is designed to measure the mass, ionic charge and energy of the low and high speed solar wind, of suprathermal ions, and of low energy flare particles. Through analysis of the elemental and isotopic abundances, the ionic charge state, and the velocity distributions of ions originating in the solar atmosphere, the investigation focuses on the plasma processes on various temporal and spatial scales in the solar chromosphere, transition zone, and corona. CELIAS includes 3 mass- and charge-discriminating sensors based on the time-of-flight technique: CTOF for the elemental, charge and velocity distribution of the solar wind, MTOF for the elemental and isotopic composition of the solar wind, and STOF for the mass, charge and energy distribution of suprathermal ions. The instrument will provide detailed in situ diagnostics of the solar wind and of accelerated particles, which will complement the optical and spectroscopic investigations of the solar atmosphere on SOHO. CELIAS also contains a Solar Extreme Ultraviolet Monitor, SEM, which continously measures the EUV flux in a wide band of 17 – 70 nm, and a narrow band around the 30.4 nm He II line.Principal-InvestigatorPrincipal-Investigator for data phase  相似文献   

Hail frequency in the Pretoria — Witwatersrand area during 1962 to 1972     

Gerhard Held 《Pure and Applied Geophysics》1974,112(5):765-776

Summary Hail observations were made in the Transvaal, South Africa, during the decade 1962 to 1972. The hail-reporting network covered an area of 2800 km² with Pretoria in the northeast and the also densely-populated Witwatersrand in the south. A panel of about 800 voluntary observers contributed 10 560 hail reports during this period. Isopleths of hail frequency within the network were plotted. The pattern was strikingly similar to the isohyetal map. More rain and hail occurred in the urban areas than elsewhere and there was a relationship to topography. Pretoria received less hail than the Witwatersrand, a ridge about 300 m higher than Pretoria.  相似文献