Nonequilibrium sorption of nonionic organic chemicals in soils: experiments and modeling

In der vorliegenden Arbeit wird die Sorptionskinetik organischer Chemikalien in Boeden untersucht. An hysteretischen Sorptions/Desorptionsdaten des herbizids Chlortoluron in zwei Boeden werden mit Hilfe eines kinetischen Sorptionsmodells Sorptionsparameter bestimmt. Eine anschliessende Vorhersage von Isothermen bei geandertem Boden/Loesungsverhaeltnis sowie von Ratenstudien zeigt dass die Sorption von Chlortoluron durch das Modell gut beschrieben wird. Eine Vorhersage bei vorher getrockneten Boeden ist dagegen unmoeglich. ursache ist eine durch Trocknung des Bodens hervorgerufene Strukturaenderung, die kurzfristig nicht reversibel ist. Anschliessend werden zwei weitere Schuetteltechniken untersucht. In einer Technik wird sukzessiv herbizidhaltige Loesung ersetzt. bei der anderen Methode wird Desorption durch wiederholte Verduennung mit herbizidfreier Loesung erreicht. Beide Isothermen zeigen eine Art Hysterese die aber durch das Modell erfolgreich vorhergesagt werden kann. Um das Modell auch fuer andere Boden/Substanz-Kombinationen zu verifizieren, werden Literaturdaten modelliert. Alle Daten zeigen einen nichtidealen Verlauf der bisher nicht erklaert werden konnte. Abschliessend wird eine in einer frueheren Studie (Dimethylphthalat, zwei Boeden) beschriebene Inkonsistenz, der getrennt an Schuettel- und Saeulenexperimenten ermittelten Sorptionsparameter untersucht. Es wird gezeigt das die Vorhersage der Saeulendaten anhand der aus Batchdaten ermittelten Sorptionsparametern erfolgreich durchfuehrbar ist. Weitere Untersuchungen zeigen, dass die vorher beschriebene Inkonsistenz auf die Modellsensitivitaet gegenueber dem schwer messbaren 'Tailing' der Saeulendaten zurueckzufuehren ist. (orig.)The primary objective of this theses is to investigate the sorption kinetics of organic chemicals in soil. Hysteretic or nonsingular sorption/desorption isotherms of chlortoluron in two soils are utilized to estimate sorption parameters of a two-stage model. these parameters are used to (a) predict rate studies and (b) predict sorption/desorption isotherms at different solution to soil ratios in both soils. Although successful for both cases prediction of data measured with soil samples initially air-dried fails. It is shown that changes within soil organic matter due to drying may be responsible for the deviating behavior. Then two additional batch techniques are investigated. In one technique part of the supernatant is replaced by solute containing solution while in the other technique desorption is induced by successive dilution of the supernatant with time. Again the model predicts both nonideal isotherms successfully. The model is further used to model literature data where nonideality phenomena were unexplained. Finally, an apparent inconsistency between simethylphthalate batch and column experiments in two soils is resolved. In an earlier investigation it was found that the sorption parameters obtained by fitting the model to data obtained with both techniques were inconsistent. Here the two-stage model is used to estimate sorption parameters by fitting the model to batch data. With the estimated set of parameters, the model is able to predict column data adequately. It is then shown that the contrasting earlier findings are most likely caused by the models sensitivity to undetected tailing of nonequilibrium breakthrough curves. (orig.)SIGLEAvailable from: http://opus.tu-bs.de/opus/volltexte/2000/148 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Characteristics of Patients with Breathlessness Results of the German Hospice and Palliative Care Evaluation

Background Breathlessness is a common and distressing symptom in patients with advanced life-limiting disease. The aim of this study was to describe demographical and clinical characteristics of patients with breathlessness in Germany. Methods We conducted a secondary analysis of hospice and palliative care inpatient data from 2006 to 2008. The Hospice and Palliative Care Evaluation (HOPE) is an annual prospective German survey, that includes a validated 16-item symptom-and-problem checklist (severity score 0 - 3). Characteristics of patients with or without breathlessness were compared in a pure descriptive manner. Interpretation of given p-values takes the error inflation due to multiple testing into account. Results Breathlessness was recorded in 2860/5320 (53.8%) patients (mean age 67.2 years (SD 12.4), 51.4% female, 93.6% malignant disease (female/male lung cancer 15.7/29.5%, breast cancer 20.3/0.3 %, colon 10.3/8.7%). Breathless patients compared with those without breathless ness had a significantly worse functional status (ECOG 3 - 4: 78.4% vs. 70.8 %, p < 0.001), suffered from a larger number (11.1 vs. 9.5, p < 0.001) of symptoms and the symptoms were of higher intensity (except confusion). Breathless patients had a higher risk to die during inpatient stay (43.5% vs. 32.4 %, p < 0.001). Conclusion Based on this large sample of hospice and palliative care inpatients, breathlessness is associated with a high symptom burden and shortened survival. Breathless patients need more attention in health care

Pesticide sorption and desorption by lignin described by an intraparticle diffusion model

Lignin was used as a model compound for soil organic matter to gain insight into the mechanisms that control the kinetics of pesticide sorption and desorption. Hydrolytic lignin was immobilized in a matrix of alginate gel, and sorption−desorption experiments were undertaken with isoproturon. Sorption increased with time and was close to equilibrium after 14 days. Desorption was measured after sorption for different time intervals and for a number of successive desorption steps of different lengths. The results showed strong differences between the sorption and desorption isotherms. The ratio of sorbed to dissolved pesticide approached and even exceeded the equilibrium ratio, depending on the number of desorption steps and the length of each equilibration period. A numerical diffusion model was developed to describe radial diffusion into the lignin particles in combination with Freundlich sorption inside the particles. Key model parameters were adjusted to fit the sorption data, and the same parameters were then used to predict stepwise desorption. Desorption was well described by the model, which suggests that sorption and desorption were driven by the same mechanism and occurred at the same rate. The observed difference between the sorption and desorption isotherms could be fully explained by the nonattainment of equilibrium due to slow diffusion into and out of the lignin particles