Predicting Soil Influence on the Performance of Metal Detectors: Magnetic Properties of Tropical Soils

Mine detection and clearance are costly and time-consuming procedures necessary to benefit the communities these weapons affect. A complication surrounding mine detection is the influence of the soil on landmine detection, but little research has been done on the subject. This article discusses how soil can affect mine detectors and research plans to improve mine-detection efficiency

Nonequilibrium Sorption of Nonionic Organic Chemicals in Soils: Experiments and Modeling

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 dimethylphthalate 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.In der vorliegenden Arbeit wird die Sorptionskinetik organischer Chemikalien in Böden untersucht. An hysteretischen Sorptions/Desorptionsdaten des Herbizids Chlortoluron in zwei Böden werden mit Hilfe eines kinetischen Sorptionsmodells Sorptionsparameter bestimmt. Eine anschließende Vorhersage von Isothermen bei geändertem Boden/Lösungsverhältnis sowie von Ratenstudien zeigt daß die Sorption von Chlortoluron durch das Modell gut beschrieben wird. Eine Vorhersage bei vorher getrockneten Böden ist dagegen unmöglich. Ursache ist eine durch Trocknung des Bodens hervorgerufene Strukturänderung, die kurzfristig nicht reversibel ist. Anschließend werden zwei weitere Schütteltechniken untersucht. In einer Technik wird sukzessiv herbizidhaltige Lösung ersetzt. Bei der anderen Methode wird Desorption durch wiederholte Verdünnung mit herbizidfreier Lösung erreicht. Beide Isothermen zeigen eine Art Hysterese die aber durch das Modell erfolgreich vorhergesagt werden kann. Um das Modell auch für andere Boden/Substanz-Kombinationen zu verifizieren, werden Literaturdaten modelliert. Alle Daten zeigen einen nichtidealen Verlauf der bisher nicht erklärt werden konnte. Abschließend wird eine in einer früheren Studie (Dimethylphthalat, zwei Böden) beschriebene Inkonsistenz, der getrennt an Schüttel- und Säulenexperimenten ermittelten Sorptionsparameter untersucht. Es wird gezeigt das die Vorhersage der Säulendaten anhand der aus Batchdaten ermittelten Sorptionsparametern erfolgreich durchführbar ist. Weitere Untersuchungen zeigen, daß die vorher beschriebene Inkonsistenz auf die Modellsensitivität gegenüber dem schwer meßbaren 'Tailing' der Säulendaten zurückzuführen ist

Development of a UAV-Based Gamma Spectrometry System for Natural Radionuclides and Field Tests at Central Asian Uranium Legacy Sites

Uranium mining and processing had been widespread in Central Asia since the mid-1940s. However, with the establishment of the newly independent states in the 1990s, many of the former uranium mining and processing facilities and their associated wastes (dumps and tailings) were abandoned and have since posed a threat to the environment. The fact that the sites were left behind without proper remediation for a long time has led to the uncontrolled spread of radioactive and toxic contaminants in the environment due to landslides or flooding. Knowledge of the exact location of some waste facilities was lost as a result of social disruptions during the 1990s. In order to assess radiological risks and plan and implement adequate, sustainable, and environmental remediation measures, the radiological situation at the uranium legacy sites must be repeatedly mapped with the best possible accuracy in terms of both sensitivity and spatial resolution. In this paper, we present the experimental use of an unmanned aerial vehicle (UAV) equipped with gamma spectrometry systems as a novel tool for mapping, assessing, and monitoring radioactivity at sites affected by uranium mining and processing and other activities related to enhanced natural radioactivity. Special emphasis is put on the practical conditions of using UAV-based gamma spectrometry in an international context focusing on low- and medium-income countries. Challenges and opportunities of this technology are discussed, and its reliability and robustness under field conditions are critically reviewed. The most promising future application of the technology appears to be the radiological monitoring, institutional control, and quality assurance of legacy sites during and after environmental remediation. One-off administrative and logistical challenges of the technology are outweighed by the significant amount of time and cost saved once a UAV-based gamma spectrometry survey system is set up