Ozon in Waldökosystemen aus atmosphärenchemischer und pflanzenphysiologischer Sicht

The trend of rising ozone concentrations in forest ecosystems and the phytotoxicity of ozone demand a realistic risk assessment according to an internationally accepted and flux-based quality standard. Ozone fluxes within the canopy are influenced by chemical gas-phase reactions with nitrogen oxide and biogenic hydrocarbons and by surface deposition processes. Therefore, a differentiation of the ozone flux within the canopy is needed between stomatal uptake and other transport pathways. The Eddy Covariance technique is the method of choice for the determination of trace gas fluxes relevant for ozone chemistry. This method is also used for stomatal conductance measurements based on evapotranspiration fluxes and for emission measurements of biogenic hydrocarbons by PTR-MS. Although considerably research efforts were directed to canopy measurements in recent years, the underlying processes are not fully understood yet. Thus, major differences occur in the ratios of stomatal ozone uptake, non-stomatal deposition and gas-phase chemistry between different studies. Furthermore, the vertical concentration gradients within the canopy measured at several forest sites are rather inconsistent and the existing deposition models do rarely account for chemical transformation and detoxification processes. Only a simultaneous measurement of all photochemically relevant trace gases, plant physiological parameters at different sites and forest species over entire vegetation periods, and model parameterization according to the measurement results from the experimental sites will contribute to the clarification of the canopy processes and will ensure realistic risk assessments.     

Elevated alpha-fetoprotein and human chorionic gonadotropin as a marker for placental trisomy 16 in the second trimester?

In a series of 2961 consecutive cases with second-trimester biochemical triple screening for Down's syndrome and neural tube defect (NTD), ten (0.3 per cent) showed an apparent increased risk for both conditions. Three cases had chromosomal abnormalities, namely trisomy 16 confined to the placenta. Since placental trisomy 16 as well as cases with increased alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) are associated with (intrauterine growth retardation (IUGR), oligohydramnios, and fetal demise, at least some cases with this atypical biochemical profile could be explained by this chromosomal abnormality. From our results we recommend that in cases with increased risk for both Down's syndrome and NTD, fetal karyotyping should preferably be done on a placental biopsy, especially when ultrasound in the absence of anomalies demonstrates early IUGR.     

On-line real-time measurements at incineration plants: PAHs and a PCDD/F surrogate compound at stationary combustion conditions and during transient emission puffs

Laser mass spectrometry has been applied for on-line monitoring of traces of aromatic compounds from flue gas of incineration plants. The experiments have been carried out at two sampling sites in an industrial hazardous-waste incinerator. With laser mass spectrometry resonance-enhanced multiphoton ionization (REMPI) with time-of-flight mass spectrometry (TOFMS) (REMPI-TOFMS), using the group selective multi-component monitoring approach, aromatic compounds are selectively ionized from the complex flue-gas matrix. In this case, the result of an REMPI-TOFMS on-line measurement is a distinct pattern of aromatic compounds. These patterns are dependent on: (i) the point of measurement, (ii) the incineration plant, (iii) the temperature, and (iv) the fuel. This contribution focuses on the fuel dependence of the pattern. The most transient behavior can be observed when containers filled with hazardous waste are burnt, leading to puffs. Real-time monitoring results of puffs are given. Furthermore, as an approach towards on-line monitoring of the TEQ (PCDD/F toxicity equivalent), REMPI-TOFMS on-line analysis results of chlorobenzene are presented.     

Die Sch?rfung des Ausbildungsprofils der Geo?kologie

Ohne Zusammenfassung     

Complex national sampling design for long-term monitoring of protected dry grasslands in Switzerland

We describe a probabilistic sampling design of circular permanent plots for the long-term monitoring of protected dry grasslands in Switzerland. The population under study is defined by the perimeter of a national inventory. The monitoring focus is on the species composition of the protected grassland vegetation and derived conservation values. Efficient trend estimations are required for the whole country and for some predefined target groups (six biogeographical regions and eleven vegetation types). The target groups are equally important regardless of their size. Consequently, intensified sampling of the less frequent groups is essential for sample efficiency. The prior information needed to draw a targeted sample is obtained from the sampling frame and external databases. The logistics and generalized delineation of the target population may pose further problems. Thus, investments in fieldwork and travel time should be well balanced by selecting a cluster sample. Second, any access problems in the field and non-target units in the sample should be compensated for by selecting reserve plots as they otherwise may considerably reduce the effective sample size. Finally, the design has to be flexible as the sampling frame may change over time and sampling intensity might have to be adjusted to redefined budgets or requirements. Likewise, the variables and biological items of interest may change. To fulfil all these constraints and to optimally use the available prior information, we propose a multi-stage self-weighted unequal probability sampling design. The design uses modern techniques such as: balanced sampling, spreading, stratified balancing, calibration, unequal probability sampling and power allocation. This sampling design meets the numerous requirements of this study and provides a very efficient estimator.