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Chemisch-analytische Untersuchung von Arsenkampfstoffen und ihren Metaboliten

Zusammenfassung  Arsenkampfstoffe sind in der Umwelt persistent und kontaminieren bis heute Boden und Grundwasser. In diesem Beitrag werden die chemischen Reaktionen der Arsenkamptstoffe Diphenylarsinchlorid (CLARK I), Phenylarsindichlorid (PFIFFIKUS), Ethylarsindichlorid (DICK) sowie von Chlorvinylarsinverbindungen (LEWISITE) dargestellt. Die M?glichkeiten der chemisch-analytischen Erfassung dieser chemischen Kampfstoffe als Originalsubstanzen und als Thiol-Derivate werden pr?sentiert.      

Influence of delayed metamorphosis on survival and growth of juvenile barnacles Balanus amphitrite

Competent cyprid larvae of the barnacle Balanus amphitrite Darwin were prevented from metamorphosing in the laboratory for 3 or 5 d using three different techniques (holding at low temperature, crowding, and detaining on a silanized surface). We then assessed the effects of prolonging larval life on post-metamorphic growth and survival, in comparison with control individuals that metamorphosed soon after they were competent to do so. Seven experiments were conducted over 2 yr (July 1987 to September 1989). In all experiments (each with six replicates per treatment), postponing larval metamorphosis for 3 or 5 d dramatically depressed postmetamorphic growth rate (P<0.05), although metamorphic success and post-metamorphic survival were not affected (P>0.10). The results suggest that B. amphitrite cyprids deferring their metamorphosis in the field may be less successful in competing for space, at least during the first few weeks of postlarval life.     

Benthic Algal (Periphyton) Growth Rates in Response to Nitrogen and Phosphorus: Parameter Estimation for Water Quality Models

Nitrogen (N) and phosphorus (P) are significant pollutants that can stimulate nuisance blooms of algae. Water quality models (e.g., Water Quality Simulation Program, CE‐QUAL‐R1, CE‐QUAL‐ICM, QUAL2k) are valuable and widely used management tools for algal accrual due to excess nutrients in the presence of other limiting factors. These models utilize the Monod and Droop equations to associate algal growth rate with dissolved nutrient concentration and intracellular nutrient content. Having accurate parameter values is essential to model performance; however, published values for model parameterization are limited, particularly for benthic (periphyton) algae. We conducted a 10‐day mesocosm experiment and measured diatom‐dominated periphyton biomass accrual through time as chlorophyll a (chl a) and ash‐free dry mass (AFDM) in response to additions of N (range 5–11,995 µg nitrate as nitrogen [NO₃‐N]/L) and P (range 0.89–59.51 µg soluble reactive phosphorus/L). Resulting half‐saturation coefficients and growth rates are similar to other published values, but minimum nutrient quotas are higher than those previously reported. Saturation concentration for N ranged from 150 to 2,450 µg NO₃‐N/L based on chl a and from 8.5 to 60 µg NO₃‐N/L when based on AFDM. Similarly, the saturation concentration for P ranged from 12 to 29 µg‐P/L based on chl a, and from 2.5 to 6.1 µg‐P/L based on AFDM. These saturation concentrations provide an upper limit for streams where diatom growth can be expected to respond to nutrient levels and a benchmark for reducing nutrient concentrations to a point where benthic algal growth will be limited.     

NUMERICAL MODELING OF THERMAL STRATIFICATION IN A RESERVOIR WITH LARGE DISCHARGE-TO-VOLUME RATIO1

ABSTRACT: A numerical model study of thermal stratification in a high discharge-to-volume reservoir is described. Predicted temperature profiles are compared with field data for two different years. The model accurately predicts the date of fall turnover, and predicts degree of stratification and depth of the thermocline within about 20% for both years simulated. A parametric study of stratification mechanics for a high flow reservoir indicated that diffusion was the predominant heat transport mechanism in the hypolimnion, while surface effects dominated the epilimnion. Flow effects for the particular case studied, in which all inflows and outflows occur in the epilimnion, did not significantly affect stratification behavior.     

Miniaturisierung des Wachstumshemmtestes mit der Grünalge Desmodesmus subspicatus nach DIN 38412 Teil 33

Background, aim, and scope Biological test systems have been successfully used to analyse and assess the ecotoxicological potentials of sediments and dredged materials. In compliance with the German directive for dredged-material management (HABAB-WSV, BfG 2000) standardised bioassays with organisms of different trophic levels are applied to limnic sediments. The growth-inhibition test with the green alga Desmodesmus subspicatus according to DIN 38412 part 33 is one of three mandatory bioassays (Guidance paper “Ökotoxikologische Baggergutuntersuchungen”, BfG 2007). The laboratories of the German Federal Institute of Hydrology (BfG) conduct this algal test in agreement with the DIN standard in test tubes of 10?ml volume. In the following, this method is called the “conventional method” or “DIN-method”. The research described below was conducted in the BfG in a diploma-thesis aiming to develop a miniaturized algae test procedure that uses microtiter plates, but yields comparable results. Automation and miniaturization should increase the throughput capacity and reduce the time and labour requirements. Materials and methods The growth-inhibition test with the green alga Desmodesmus subspicatus according to DIN standard 38412 part 33 was taken as the starting point for the miniaturization. The testing method in microtiter plates was optimised by systematic examination of the cultivation conditions, coverages of the wells, and settings of the measuring instruments. To verify the results of the miniaturized test procedure, 25 environmental samples (20 pore waters and five single substances) were tested with the conventional and the miniaturized procedure. The results of both test procedures were compared using statistical analyses. Results The comparison of the growth inhibition test results from the microtiter plates with those from the conventional procedure indicated an average deviation of about 20?%-points. In approximately 30?% of the cases, a statistical verification with the Mann-Whitney-U-Test showed agreement of the inhibition values obtained with both methods. A method to express the ecotoxicological potential of a sample is the pT-value (Krebs 1988). The pT-values were determined based on the toxicities obtained using serial dilution. (Krebs 1988). When comparing both methods 10 out of 20 environmental samples had the same pT-value (50?%). In 40?% of the samples, the deviation was one pT-value, in 10?% it was more than one pT-value. Discussion During the optimization of the method, different parameters of the algal growth inhibition test were examined and adapted to the miniaturized system, so that all criteria required after DIN 38412 part 33 should be met. However, the miniaturized test did not reliably achieve these validity criteria, namely the increase in the biomass by a factor of 30 in the controls. This criterion was only fulfilled in two out of 31 test runs. The validation of the miniaturized growth inhibition test on the basis of a statistical comparison with the conventional method showed partially highly significant differences. Overall, significantly different inhibition values were found in about 60?% of the cases. Conclusions Without further adjustments and optimization it is not possible to substitute the conventional method by the miniaturized system. Recommendations and perspectives Further research is required to miniaturize the test procedure and to perform the algae test on microtiter plates. The validity criteria of the DIN standard, such as the increase of biomass production in the controls, should be reliably met. Basically, the aim of miniaturizing the algae test procedure is the increase in throughput capacity and, at the same time, reduced work efforts by automation. However, the test results of the miniaturized method should be comparable to those of the conventional method.