Effect of Preozonation on the Formation of Chlorinated Disinfection By‐products for River Ruhr     

Y.‐W. Ko  G. Abbt‐Braun  F. H. Frimmel 《洁净——土壤、空气、水》2000,28(5):256-261

The purpose of the study is to gain a better understanding about the formation of THM (trihalomethanes), HAA (haloacetic acids), and AOX (adsorbable organic halogen) in river water (river Ruhr, Essen) through a chlorination kinetics approach. The effect of chlorination time and preozonation on the formation of THM, HAA, and AOX substances was studied. Preozonation can reduce the chlorine demand and the precursors for AOX and THM. THM generation was reduced further, when the ozone dosage consumed increased from 3.5 to 12.5 mg in the 1.4 L reaction vessel. AOX and TCAA (trichloroacetic acid) concentrations also decreased dramatically when 3.5 mg of ozone had reacted with the river water, but a higher dose of ozone did not further reduce AOX and TCAA formations. Besides, the characteristics of organic matter in raw water, ozonated water, and preozonated/chlorinated water was investigated. The results suggest the formation of low‐molecular‐weight acids with low UV absorbance when high‐molecular refractive matter is oxidized.  相似文献   

The tectonic evolution of the Southern Alps, New Zealand: insights from fully thermally coupled dynamical modelling   总被引：1，自引：0，他引：1  

Geoffrey E. Batt  & Jean Braun 《Geophysical Journal International》1999,136(2):403-420

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Influence of forest and shrub canopies on precipitation partitioning and isotopic signatures          下载免费PDF全文

Chris Soulsby  Hannah Braun  Matthias Sprenger  Markus Weiler  Doerthe Tetzlaff 《水文研究》2017,31(24):4282-4296

Over a 4‐month summer period, we monitored how forest (Pinus sylvestris ) and heather moorland (Calluna spp. and Erica spp.) vegetation canopies altered the volume and isotopic composition of net precipitation (NP) in a southern boreal landscape in northern Scotland. During that summer period, interception losses were relatively high and higher under forests compared to moorland (46% of gross rainfall [GR] compared with 35%, respectively). Throughfall (TF) volumes exhibited marked spatial variability in forests, depending upon local canopy density, but were more evenly distributed under heather moorland. In the forest stands, stemflow was a relatively small canopy flow path accounting for only 0.9–1.6% of NP and only substantial in larger events. Overall, the isotopic composition of NP was not markedly affected by canopy interactions; temporal variation of stable water isotopes in TF closely corresponded to that of GR with differences of TF‐GR being ?0.52‰ for δ²H and ?0.14‰ for δ¹⁸O for forests and 0.29‰ for δ²H and ?0.04‰ for δ¹⁸O for heather moorland. These differences were close to, or within, analytical precision of isotope determination, though the greater differences under forest were statistically significant. Evidence for evaporative fractionation was generally restricted to low rainfall volumes in low intensity events, though at times, subtle effects of liquid–vapour moisture exchange and/or selective transmission though canopies were evident. Fractionation and other effects were more evident in stemflow but only marked in smaller events. The study confirmed earlier work that increased forest cover in the Scottish Highlands will likely cause an increase in interception and green water fluxes at the expenses of blue water fluxes to streams. However, the low‐energy, humid environment means that isotopic changes during such interactions will only have a minor overall effect on the isotopic composition of NP.  相似文献   

Helioseismic imaging of sunspots at their antipodes     

Charles Lindsey  Douglas C. Braun 《Solar physics》1990,126(1):101-115

Recent work by Braun, Duvall, and LaBonte has shown that sunspots absorb helioseismic waves. We propose that sunspot absorption causes a seismic deficit that should be imaged at the antipode of the sunspot. If these images are observable, it should be possible to produce seismic maps of magnetic regions on the far side of the Sun. This possibility opens a broad range of synoptic and diagnostic applications. Diagnostic applications would include lifetimes of higher-frequency modes, and possibly rotation of the solar interior and detection of subsurface magnetic structure. We outline elements of the theory of seismic imaging and consider some applications. We propose the extention of acoustic holography to solar interior diagnostics in the context of antipodal imaging.Now at the Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, U.S.A.  相似文献   

Counting statistics of f −β fluctuations: a new method for analysis of earthquake data     

H. R. Bittner  P. Tosi  C. Braun  M. Meesmann  K. -D. Kniffki 《International Journal of Earth Sciences》1996,85(1):110-115

In a variety of biological and physical phenomena, temporal fluctuations are found, which are not explainable as consequences of statistically independent random events. If these fluctuations are characterized by a power spectrum density S(f) decaying as f ^– at low frequencies, this behaviour is called 1/f noise.Counting statistics applied to earthquake activity data leads to three time scales with different characteristics, represented by the exponent : at interval lengths less than 1 h, the shocks are randomly distributed as in a Poisson process. For medium time intervals (1 day to 3 months), the exponent 1 + is larger (1.4 for M ₀=3), but approaches unity for higher threshold magnitudes M ₀. In longer time ranges the exponent assumes values near 1.55, however, with increasing statistical variation at higher M ₀, due to lower counts.The temporal sequence is different from white noise; thus, it might be fruitful to apply neural network algorithms, because this method allows predictions in some other cases with similar characteristics.  相似文献   

Numerical modelling of landscape evolution on geological time-scales: a parameter analysis and comparison with the south-eastern highlands of Australia     

Peter van der Beek  & Jean Braun 《Basin Research》1998,10(1):49-68

Surface-process models (SPMs) have the potential to become an important tool in predicting sediment flux to basins, but currently suffer from a lack of quantitative understanding of their controlling parameters, as well as difficulties in identifying landscape properties that can be used to test model predictions. We attempt to constrain the parameter values that enter a SPM by comparing predictions of landscape form (as expressed by hypsometric and fractal measures) and process rates obtained for different parameter sets with observations from the south-eastern Australian highlands, a rifted margin mountain belt that has remained tectonically stable during Cenozoic times. We map the hypsometry and fractal characteristics of south-eastern Australia and find that the roughness amplitude (G) correlates well with local relief, whereas the hypsometric integral (H ) correlates slightly better with elevation than with relief. The fractal dimension (D) does not correlate with any other morphometric measure and varies randomly throughout the region. Variograms generally show three kinds of scaling behaviour of topography with increasing wavelength, with topography only being truly self-affine at wavelengths between ～1 and 10 km. From a review of the available data on long-term denudation rates in south-eastern Australia, we infer that these have been 1–10 m Myr^?1, and average escarpment retreat rates 0.2–1.0 km Myr^?1, throughout the Cenozoic. Model predictions, using a SPM that includes hillslope diffusion and long-range fluvial transport, suggest that landscape form evolves with time; after an initial phase where D, G and relief increase, all morphometric measures decrease with increasing denudation. The behaviour of GandH in the models is qualitatively compatible with the observations; D, however, varies predictably in the models, in contrast with its random behaviour in the real world. The observed present-day morphology of SE Australia does not impose quantitative constraints on parameter values. The fractal analyses do impose general conditions of relative parameter values that have to be met in order to create ‘realistic’ topographies. They also suggest that there is no theoretical basis for including hillslope diffusion in SPMs with a spatial resolution coarser than 1 km. A comparison of the observed denudation and retreat rates with model predictions places order-of-magnitude constraints on parameter values. Thus, data pertaining to landscape evolution are much more valuable than static present-day topography data for calibrating SPMs.  相似文献   

A pollution history of Chesapeake Bay     

Edward D. Goldberg  Vern Hodge  Minoru Koide  John Griffin  Eric Gamble  Owen P. Bricker  Gerry Matisoff  George R. Holdren  Ruth Braun 《Geochimica et cosmochimica acta》1978,42(9):1413-1425

Present day anthropogenic fluxes of some heavy metals to central Chesapeake Bay appear to be intermediate to those of the southern California coastal region and those of Narragansett Bay. The natural fluxes, however, are in general higher. On the bases of Pb-210 and Pu-239 + 240 geochronologies and of the time changes in interstitial water compositions, there is a mixing of the upper 30 or so centimeters of the sediments in the mid-Chesapeake Bay area through bioturbation by burrowing mollusks and polychaetes. Coal, coke and charcoal levels reach one percent or more by dry weight in the deposits, primarily as a consequence of coal mining operations.  相似文献   

The structure and evolution of a slow deflagration front propagating into a degenerate star     

A. Braun  R. Yahel 《Astrophysics and Space Science》1979,63(1):57-78

The structure and evolution of a slow reaction front propagation into a cool, hydrogen rich shell above an inert core has been studied. It has been found that, during the evolution of the front, the total radiative luminosity drops from 10⁴ L to 10^–4 L in a time scale of the order of 10⁹ yr. The burned up fraction of the fuel is found to be less than 1%.  相似文献   

Observations concerning the relationship between the quiet-time ring current and electron temperatures at trough latitudes     

William J. Burke  Hans J. Braun  J.W. Münch  Rita C. Sagalyn 《Planetary and Space Science》1979,27(9):1175-1185

The relationship between the simultaneously observed positions of the maximum omnidirectional flux of the quiet-time ring current positive ions (Λ_φ) and the maximum electron temperature Λ_T in the trough is studied in the midnight sector of the topside ionosphere. Λ_φ maps to the inner edge of the plasma sheet where ring current fluxes change from nearly isotropic to trapped. At altitudes near 2500 km, the electron temperature at trough latitudes were always sharply peaked. Although Λ_φ varied with the level of geomagnetic activity, (Λ_φ ? Λ_T) did not. These observations support the hypothesis that the quiet-time ring current is the source of elevated electron temperatures found near the plasmapause. Below 1300 km, peaked electron temperature distributions in the trough were not consistent features of the data. It is shown that (Λ_φ ? Λ_T) increased with decreasing altitude. The possible influences of a westward component to the convective electric field and ionospheric refraction of ion cyclotron waves are discussed.  相似文献   

Limnologische Untersuchungen an einigen Seen im Amazonasgebiet     

Rudolf Braun 《Aquatic Sciences - Research Across Boundaries》1952,14(1):1-128

Ohne Zusammenfassung  相似文献