Pesticide leaching from agricultural fields to groundwater is an environmentally relevant and highly variable process. In the present paper, leaching scenarios typical in European agriculture are defined. These scenarios consider important sources of pesticide leaching variability, namely site factors, farming practice, and substance properties. The logic-tree method was used to structure these scenarios. For each scenario, leached fractions of pesticide applied in agriculture were calculated with data and models used in the registration process of the European Union (EU). Contributions of all parameters to variability were calculated for 11 pesticides. Substance properties (Koc and DT50,soil) contributed the mostto variability, followed by site, weather, season of application, crop, and macropore flow. The results of the variability assessment may be directly applied in policy making or they may be used in the environmental assessment of pesticides, e.g. with the life-cycle assessment (LCA) method. Several approaches are suggested for howthe variability assessment presented in this paper may be incorporated in LCA. The application of these approaches is illustrated by a case study on atrazine.
The final part density in laser powder bed fusion is influenced by the powder particle size distribution. Too fine powders are not spreadable, and too coarse powders cause porosity. Powder blends, especially bimodal ones, can exhibit higher packing densities and changes in flowability compared to their monomodal constituents. These properties can influence final part density. Therefore, the influence of bimodal powder on final part density was investigated. Two gas atomized 316L (1.4404) powders with a D50 of 20.3 µm and 60.3 µm were blended at weight ratios of 3:1, 1:1, and 1:3, and the original and blended powders were processed. The results show that the final part porosity increases almost linearly with an increasing volume fraction of coarse powder. Furthermore, the final part density is independent of powder bulk density and flowability. Measurements of the top surface show that an increase of part porosity by coarse powder is caused by an increase in melt pool fluctuation, which in turn causes irregular solidified scan tracks. Additionally, the results show that the powder segregation during coating is stronger for the bimodal powder; however, no influence of the segregation on the part density could be found.
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