With increasing global plastics production, the amounts of fragmenting, microscopic plastic debris (microplastics, MPs) are anticipated to rise in aquatic environments. The ecological consequences of this pollution are currently unknown. Studies are being conducted at present to assess these risks but many have been shown to be uninformative from a risk assessment perspective due to flawed and environmentally unrealistic experimental designs; the main problem being confounding effects of food dilution due to the use of particle free controls. Natural particles, such as clay are in the microplastic-size range and ubiquitous in the environment. Hence, to counteract and improve on the poor experimental design to test microplastic effects, the aim of the study was to develop a simple, high throughput screening method which accounts for naturally occurring microparticles like suspended clay in mixtures with MP. Lethal and sub lethal effects of MP alone and in mixtures at different ratios were investigated. Single particle exposures revealed a significant and up to a hundred times higher LC50 for clay compared to the plastics. Among the plastics, weathered plastics were four to five times more toxic than the pristine forms. The mixtures indicated interaction effects of all particles and revealed toxic microplastic-specific effects. A mean decrease of 19 % in the protein content across all particle types was observed after 96 h, however, one plastic type showed a higher reduction in the protein content. Testing MPs effects in mixtures with natural particulates is important due to various interaction effects but more comparative studies with environmental relevant concentrations are required in future. / <p>Master thesis is used for further publication.</p> / WEATHER-MIC, irPLAST, MICROPOLL

The thesis presents a two pronged approach for predicting aerodynamics of air- foils/wings in the vicinity of the ground. The first approach is effectively a model for ground effect studies, employing an inexpensive Discrete Vortex Method for the 2D pre- dictions and the well known Numerical lifting line theory for the 3D predictions. The second one pertains to the dynamic ground effect analysis which employs the state of the art moving mesh methodology based time accurate CFD. In that sense, the thesis deals with two ends of spectrum in the ground effect analysis; one, a model to be used in the concept design phase and the other an advanced CFD tool for analysis. The proposed model for ground effect studies is based on the well known Discrete Vortex Method (DVM). An important aspect of this method is that it employs what is referred to as the Generalized Kutta Joukowski Theorem (GKJ), meant for interaction problems with multiple vortices, for predicting the lift (and drag) within a potential flow framework. After ascertaining the correctness of using the GKJ theorem for lift prediction for airfoils in ground effect, a modified DVM is presented as a model for ground effect predictions. As per this model, knowing the free stream lift and drag (either from an ex- periment or from a RANS computation) the aerodynamics of the section in ground effect can be predicted. The model is effectively built by constraining the DVM to produce the reference lift/drag in the free stream. The accuracy of the model, particularly for the more relevant high lift sections used during take-off and landing, is systematically estab- lished for a number of test cases. Knowing the sectional ground effect, the extension to 3D analysis is very simple and this is achieved through the well known Numerical Lifting Line theory. The efficacy of the proposed method for the 3D applications is demonstrated using a high lift wing in ground effect. It is worth noting that the proposed model predicts the lift and drag very accurately, practically at no computational cost as compared to modern RANS based CFD tools requiring over 40 or 50 million volumes at a high computational cost and intense human intervention for generating the grids for every ground clearance. The other aspect of the thesis pertains to what is referred to as the Dynamic Ground Effect. Normally the CFD computations mimic the ground effect experiments in simulat- ing the ground effect. These simulations do not maintain geometric similarity with the actual landing or take-off sequence of the aircrafts and this can only be achieved when the simulations are dynamic. Dynamics is also important in case of combat aircrafts (particularly their naval versions) with an aggressive landing and take-off. The dynamic ground effect simulations also provides a framework for simulating varied gust conditions. This dynamic simulation of the ground effect is accomplished using a novel sinking grid methodology, which allows the grids to sink in the ground as the aircraft approaches the ground along the glide path. These simulations make use of the state of the art, time accurate moving grid methods and therefore can be computationally expensive. Never- theless, the utility of such computations in terms of their ability to produce continuous data has been highlighted in the thesis. In that sense, these dynamic computations will be cheaper as compared to the static simulations to produce data at the same level of resolution.