Gaschromatographische Bestimmung von polychlorierten Biphenylen in Wasser nach Headspace-Festphasenmikroextraktion

Gas-chromatographic Determination of Polychlorinated Biphenyls in Water after Headspace Solid-phase Microextraction Headspace-analytical techniques are usually applied to the determination of easily volatile substances in water, whereas semivolatiles are generally isolated by liquid-liquid or solid-phase extraction. In the present paper, a method is presented for isolating high boiling polychlorinated biphenyls (PCB) using headspace solid-phase microextraction at elevated temperature. In spite of their low vapor pressure, the analytes are adsorbed very efficiently on a poly-dimethylsiloxane-coated fiber. Thus, in combination with GC/ECD, a very simple and sensitive solventless determination of PCB is accomplished. Using the simplest possible standard conditions, limits of determination in the lowest nanogram-per-liter range are achieved. Further increased sensitivity down to the ppq (parts per quadrillion) range is possible by stirring and increasing the sample volume and adsorption time. Moderate matrix effects have been observed in some surface and groundwaters.     

Ein kompetitiver Immunoassay zur Bestimmung des Herbizids Fluazifop in Trink- und Grundwasser

A Competitive Immunoassay for the Determination of the Herbicide Fluazifop in Drinking Water and Groundwater A competitive solid-phase enzyme immunoassay using rabbit polyclonal antibodies was developed for the detection of the herbicide fluazifop [(RS)-2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy]propionic acid] in drinking water and groundwater. Present regulatory limits for drinking water in Germany were taken as the critical level. The carrier protein was bovine serum albumin; horseradish peroxidase was used as marker enzyme with 3,3′,5,5′-tetramethylbenzidine as substrate. A high concentration of high-affinity antibodies in the serum, optimization of test conditions (antibody and enzyme tracer concentration, incubation time etc.), and very low cross reactivities to substances of similar structures led to a highly sensitive and specific ELISA with a detection limit below 0.1 μg/L for fluazifop as free acid. On testing the suitability of the assay's use as a screening test with one hundred drinking-water samples, the three samples which had been spiked in the laboratory were recognized as positive with respect to their fluazifop content. Confirmation by gas chromatography-mass spectrometry showed the test results of two other samples to be false positive. False negative results did not appear. The concentration was in the detection limit region of 0.1 μg/L.     

A reexamination of the valley wind system in the Alpine Inn Valley with numerical simulations

Summary This paper presents idealized numerical simulations of the valley wind circulation in the Alpine Inn Valley, which are compared with existing data and are used to improve our dynamical understanding of the valley wind. The simulations have been performed with the Penn State/NCAR mesoscale model MM5. They use a high-resolution realistic topography but idealized large-scale conditions without any synoptic forcing to focus on the thermally induced valley wind system. The comparison with the available observations shows that this simplified set-up is sufficient to reproduce the essential features of the valley wind.The results show that the tributaries of the Inn Valley have a considerable impact on the along-valley mass fluxes associated with the valley wind circulation. The upvalley mass flux is found to increase where tributaries enter the Inn Valley from the north, that is, from the direction where the Alpine foreland is located. On the other hand, the upvalley mass flux is reduced at the junctions with southern tributaries because part of the upvalley flow is deflected into these tributaries. For the downvalley flow, the situation is essentially reversed, but the influence of the valley geometry on the flow structure is larger than for the upvalley flow. The most important feature is a lateral valley contraction near the valley exit into the Alpine foreland. It reduces the downvalley mass flux at low levels, so that the wind maximum in the interior of the valley is shifted to a fairly large distance from the ground. North of the valley contraction, however, the downvalley flow strongly accelerates and forms a pronounced low-level jet. A dynamical analysis indicates that this acceleration can be interpreted as a transition from subcritical to supercritical hydraulic flow. Another interesting feature is that the low-level jet maintains its structure for several tenths of kilometres into the Alpine foreland. This appears to be related to the fact that the lateral wind shear on the flanks of the jet is associated with a strong dipole of potential vorticity (PV). Due to the conservation properties of the PV, the downstream advection of the PV dipole leads to the formation of a band-like feature that decays fairly slowly.     

Mitigating the Effects of Climate Change on the Water Resources of the Columbia River Basin

The potential effects of climate change on the hydrology and water resources of the Columbia River Basin (CRB) were evaluated using simulations from the U.S. Department of Energy and National Center for Atmospheric Research Parallel Climate Model (DOE/NCAR PCM). This study focuses on three climate projections for the 21st century based on a `business as usual' (BAU) global emissions scenario, evaluated with respect to a control climate scenario based on static 1995 emissions. Time-varying monthly PCM temperature and precipitation changes were statistically downscaled and temporally disaggregated to produce daily forcings that drove a macro-scale hydrologic simulation model of the Columbia River basin at 1/4-degree spatial resolution. For comparison with the direct statistical downscaling approach, a dynamical downscaling approach using a regional climate model (RCM) was also used to derive hydrologic model forcings for 20-year subsets from the PCM control climate (1995–2015) scenario and from the three BAU climate(2040–2060) projections. The statistically downscaled PCM scenario results were assessed for three analysis periods (denoted Periods 1–3: 2010–2039,2040–2069, 2070–2098) in which changes in annual average temperature were +0.5,+1.3 and +2.1 °C, respectively, while critical winter season precipitation changes were –3, +5 and +1 percent. For RCM, the predicted temperature change for the 2040–2060 period was +1.2 °C and the average winter precipitation change was –3 percent, relative to the RCM controlclimate. Due to the modest changes in winter precipitation, temperature changes dominated the simulated hydrologic effects by reducing winter snow accumulation, thus shifting summer streamflow to the winter. The hydrologic changes caused increased competition for reservoir storage between firm hydropower and instream flow targets developed pursuant to the Endangered Species Act listing of Columbia River salmonids. We examined several alternative reservoir operating policies designed to mitigate reservoir system performance losses. In general, the combination of earlier reservoir refill with greater storage allocations for instream flow targets mitigated some of the negative impacts to flow, but only with significant losses in firm hydropower production (ranging from –9 percent in Period1 to –35 percent for RCM). Simulated hydropower revenue changes were lessthan 5 percent for all scenarios, however, primarily due to small changes inannual runoff.     

Estimation of Site Effects in Beijing City

— For the realistic modeling of the seismic ground motion in lateral heterogeneous anelastic media, the database of 3-D geophysical structures for Beijing City has been built up to model the seismic ground motion in the City, caused by the 1976 Tangshan and the 1998 Zhangbei earthquakes. The hybrid method, which combines the modal summation and the finite-difference algorithms, is used in the simulation. The modeling of the seismic ground motion, for both the Tangshan and the Zhangbei earthquakes, shows that the thick Quaternary sedimentary cover amplifies the peak values and increases the duration of the seismic ground motion in the northwestern part of the City. Therefore the thickness of the Quaternary sediments in Beijing City is the key factor controling the local ground effects. Four zones are defined on the base of the different thickness of the Quaternary sediments. The response spectra for each zone are computed, indicating that peak spectral values as high as 0.1 g are compatible with past seismicity and can be well exceeded if an event similar to the 1697 Sanhe-Pinggu occurs.     

Statistical Detection and Characterization of a Deviation from the Gutenberg-Richter Distribution above Magnitude 8

— We present a quantitative statistical test for the presence of a crossover c₀ in the Gutenberg-Richter distribution of earthquake seismic moments, separating the usual power-law regime for seismic moments less than c₀ from another faster decaying regime beyond c₀. Our method is based on the transformation of the ordered sample of seismic moments into a series with uniform distribution under condition of no crossover. A simulation method allows us to estimate the statistical significance of the null hypothesis H₀ of an absence of crossover (c₀=infinity). When H₀ is rejected, we estimate the crossover c₀ using two different competing models for the second regime beyond c₀ and the simulation method. For the catalog obtained by aggregating 14 subduction zones of the Circum-Pacific Seismic Belt, our estimate of the crossover point is log(c₀)=28.14 ± 0.40 (c₀ in dyne-cm), corresponding to a crossover magnitude m_W=8.1 ± 0.3. For separate subduction zones, the corresponding estimates are substantially more uncertain, so that the null hypothesis of an identical crossover for all subduction zones cannot be rejected. Such a large value of the crossover magnitude makes it difficult to associate it directly with a seismogenic thickness as proposed by many different authors. Our measure of c₀ may substantiate the concept that the localization of strong shear deformation could propagate significantly in the lower crust and upper mantle, thus increasing the effective size beyond which one should expect a change of regime.