Impact and Implications of Melting on the Preservation of Trace Elements in High-Alpine Snow and Glacier Ice

Cold high-Alpine glaciers are invaluable archives of past climate and atmospheric composition. Especially trace element records from high-Alpine ice cores and snow pits contain comprehensive information about paleo atmospheric changes. Monitoring past environmental pollution is particularly important for Europe, one of the world’s most densely populated and most highly industrialized regions. Trace element records from different high-Alpine sites revealed that human activities have significantly impacted the composition of the atmosphere during the last 150 years. Unanswered questions still remain. For instance, the onset of European anthropogenic impact on the atmosphere, such as the impact from the earliest metal production in Western Europe interfering with natural background levels of trace elements from mineral dust deposition, has not been identified yet. Due to the current global climate warming, particularly pronounced for mountain regions such as the European Alps, many glaciers even at high altitudes are increasingly in danger to significantly suffer from melting. Apart from severe socioeconomic impacts caused by glacial melting, as Alpine glaciers are the major fresh water resource in Europe, meltwater percolation has been shown to substantially alter the information stored in these environmental archives. To further use trace element records as paleo atmospheric archives to investigate the open research questions, the influence of melting on the preservation of trace elements in snow and ice needs to be thoroughly understood. Only little and ambiguous information is available on meltwater-induced relocation of trace elements so far. The behavior of atmospheric impurities during meltwater percolation is assumed to be strongly dependent on their location in the ice microstructure. This spatial distribution of impurities at a grain scale is likely to be determined by rearrangement processes during snow metamorphism. However, information on the micro scale distribution of trace elements in Alpine snow and glacier ice and on the corresponding role of snow metamorphism is not yet available. In this thesis, part of the interdisciplinary “Microscale Distribution of Impurities in Snow and Glacier Ice (MiSo)” project, the behavior of trace elements during melting of high-Alpine snow and glacier ice was extensively investigated to assess their potential as reconstruction proxies in melt-affected ice core and snow pit records. Particular attention was dedicated to understand the underlying causes and mechanisms leading to the observed trace element behavior during melting, including the spatial distribution of trace elements in high-Alpine glacier ice and rearrangement processes during snow metamorphism. To examine the impact of melting on the preservation of trace elements of natural and anthropogenic origin, a 50 m segment of an ice core from upper Grenzgletscher, Switzerland, was analyzed for 35 trace elements using discrete inductively coupled plasma mass spectrometry. This segment included a 16 m section affected by meltwater percolation in the firn part. A fractionation depending on water solubility and location at the grain scale was observed. Ba, Ca, Cd, Co, Mg, Mn, Na, Ni, Sr, and Zn revealed significant concentration depletion, while Ag, Al, Bi, Cu, Cs, Fe, Li, Mo, Pb, Rb, Sb, Th, Tl, U, V, W, Zr, and the rare-earth elements (Ce, Eu, La, Nd, Pr, Sc, Sm, Yb) were well preserved. Trace elements likely to originate from insoluble minerals were found to be mostly preserved, even though typically enriched on grain surfaces. Immobility with meltwater percolation is a result of their insolubility in water. Trace elements linked to water-soluble particles revealed a variable meltwater-mobility. While trace elements occurring in ultra-low concentrations tend to be preserved due to incorporation into the ice lattice, abundant trace elements are prone to meltwater-induced relocation due to exceeded solubility limits in ice and consequent segregation to grain surfaces. The size of the corresponding ions was found to have a negligible effect. For ice cores from high-Alpine sites partially affected by melting, records of Ag, Al, Bi, Cu, Cs, Fe, Li, Mo, Pb, Rb, Sb, Th, Tl, U, V, W, Zr, and the rare-earth elements are proposed to be still applicable as robust environmental proxies. In collaboration with the Swiss Snow and Avalanche Research Institute, the impact of melting on the preservation of trace elements in snow was studied by conducting an extensive snow pit campaign at the Weissfluhjoch test site, Switzerland, with regular sampling from January to June 2017, to monitor the behavior of trace elements during melting of the snow pack. Comparison of snow pit profiles representing dry (insignificant occurrence of melting) and wet conditions (snow pack heavily soaked with meltwater) revealed a preferential loss of certain trace elements depending on their presumed microscopic location and their water solubility. The obtained elution behavior matched the findings from the upper Grenzgletscher ice core. Variable mobility was observed for trace elements originating from water-soluble particles, where low abundant trace elements were preferably retained. Concentration-independent preservation was visible for water-insoluble trace elements, owing to their meltwater immobility. Precipitation at the two 180 km distant high-Alpine sites upper Grenzgletscher andWeissfluhjoch is characteristic for Central European atmospheric aerosol composition. As the large majority of investigated trace elements revealed a consistent behavior with meltwater percolation at those two sites, the proposed applicability of trace elements as reconstruction proxies in melt-affected ice core and snow pit records is therefore most likely representative for the entire Alpine region. The redistribution of six major ions (ammonium, calcium, chloride, fluoride, sodium, sulfate) and 35 trace elements during artificial and natural snow metamorphism was extensively investigated in another collaboration with the Swiss Snow and Avalanche Research Institute. For this, artificial and natural snow samples were exposed to a controlled temperature gradient of 40 K m−1 in the laboratory for up to 90 days. Simultaneously, the distribution of the same atmospheric impurities was studied in samples taken from different depths of the snow pack at the Weissfluhjoch test site, each corresponding to a distinct exposure time of a natural temperature gradient. Initial snow structures, monitored by X-ray micro-tomography, and impurity distribution, determined by elution experiments, varied strongly between the different snow samples. However, with progressing snow metamorphism, snow structures became similar and ions exhibiting a high solubility in ice (ammonium, fluoride, chloride) were gradually buried in the ice interiors, whereas calcium, sodium, and sulfate were enriched at ice crystal surfaces. The redistribution of atmospheric impurities during snow metamorphism was shown to be strongly dependent on the temperature gradient, the exposure time, and the chemical composition. The observed preferred incorporation of certain species into the ice interior during snow metamorphism is correlated with their persistence during meltwater percolation. The elution experiments allowed investigation of water-soluble major ions only, whereas results for the trace elements could not be interpreted due to non-quantitative dissolubility of trace elements in the deployed eluent (ultra-pure water). An analytical method for the direct in situ analysis of trace elements at a submillimeter resolution in high-Alpine glacier ice was developed in collaboration with the Institute of Geochemistry and Petrology at ETH Zurich. This method is based on laser ablation inductively coupled plasma mass spectrometry. The development process comprised the construction and the consistent further development of a cooled sample holder, featuring an automatic coolant leakage detection system and compatibility to a commercially available laser ablation system, as well as choice of the optimal cooling medium, customization of the pre-existing laser ablation hardware and software, and the development of additional equipment for both sample preparation and handling. In addition to this, a measurement procedure for high-Alpine glacier ice was established, involving the determination of appropriate laser ablation parameters and setting up a procedure for signal intensity quantification. The availability of an internal standard in ice was evaluated and an approach to prepare matrix-matched ice standards from multi-element standard solutions for external calibration was established. The acidity of the multi-element solutions and the storage time of the ice standard after preparation were found to have the most significant impact on the calibration. Preliminary measurements of high-Alpine glacier ice samples from upper Grenzgletscher demonstrated that samples exhibiting an overwhelming mineral dust abundance do not provide evidence for a linkage between micro-scale distribution of trace elements and the grain boundary network. Such a dispersion of atmospheric contaminants in the ice matrix has also very recently been reported for layers with high impurity enrichment in deep ice from Antarctica and Greenland. Future work should involve in situ analysis of high-Alpine glacier ice exhibiting ultra-low levels of trace elements to minimize the influence of dust particles on the fractionation of trace elements at a grain scale and to further directly corroborate the indirect assessment of trace element location in the firn part of the ice core from upper Grenzgletscher. This requires further background suppression of the developed micro analytical method. The proposed applicability of trace elements as reconstruction proxies in melt-affected high-Alpine ice core and snow pit records should be reviewed for other regions with a different overall trace element composition, as high-mountain glaciers worldwide are increasingly affected by melting. For instance, the presence of water-insoluble trace elements, less prone to meltwater-induced relocation, is favored in glacier ice where higher mineral dust content prevails. Additionally, the impact of melting on the preservation of other reconstruction proxies, such as mercury or black carbon, should be investigated to possibly expand the set of rather “meltwater-persistent” proxies

Quantitative and qualitative characteristics of hospital waste in the city of Behshahr-2016

Background: Recently, the rapid increase in quantity and type of waste has resulted to environmental pollution and health hazards which serve as a major challenge to humans. The level of this waste can be so high that dangerous chemicals and biological contaminants can be found in ordinary household waste. Major sources of waste in every city are mostly from care/health centers. Hence, this study aims to investigate the quantitative and qualitative waste taken from hospitals in the city. Methods: In this cross-sectional study, four city hospitals were examined in the city. For this purpose, a questionnaire was designed for quantitative analysis method and weighing scales based on the Ministry of Health questionnaire. Data were analyzed using SPSS software and for statistical analyses, Excel and Graph Pad Prism 5 were used. Results: According to findings, the total amount of hospital waste comprising infectious waste, sharp and pharmaceutical chemicals were related to Imam Khomeini hospital with values of 44 220 012 and 10 kg per day respectively, with 220 kg per day of general waste related to same hospital. Hence, the total weight of waste produced per capita, for infectious waste, general waste, chemical waste, and sharp - machinery were 2.35 ± 0.25, 0.39 ± 0.075, 1.25 ± 0.66, 0.05 ± 0.028 and 0.021 ± 0.015 kg per day per bed respectively. Conclusion: The data should be more focused on waste management and frequent orientation to hospitalized patients. This evaluation indicates the poor management of hospital wastes in view of collection, separation, infectious waste care, temporary storage station and on-time transmission and health disposal. Keywords: Hospital, Medical, Infectious, Solid wastes, Characteristics, Behshahr, Ira

ACHORD: communication-aware multi-robot coordination with intermittent connectivity

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksCommunication is an important capability for multi-robot exploration because (1) inter-robot communication (comms) improves coverage efficiency and (2) robot-to-base comms improves situational awareness. Exploring comms-restricted (e.g., subterranean) environments requires a multi-robot system to tolerate and anticipate intermittent connectivity, and to carefully consider comms requirements, otherwise mission-critical data may be lost. In this paper, we describe and analyze ACHORD (Autonomous & Collaborative High-Bandwidth Operations with Radio Droppables), a multi-layer networking solution which tightly co-designs the network architecture and high-level decision-making for improved comms. ACHORD provides bandwidth prioritization and timely and reliable data transfer despite intermittent connectivity. Furthermore, it exposes low-layer networking metrics to the application layer to enable robots to autonomously monitor, map, and extend the network via droppable radios, as well as restore connectivity to improve collaborative exploration. We evaluate our solution with respect to the comms performance in several challenging underground environments including the DARPA SubT Finals competition environment. Our findings support the use of data stratification and flow control to improve bandwidth-usage.Peer ReviewedPostprint (author's final draft

Modeling and Control of a Superimposed Steering System

A superimposed steering system is the combination of a conventional steering system with an electric motor which is used to alter the steering angle imposed by the driver. The potential benefits are increased agility, automatic compensation for lateral wind forces and decreased braking distance (in combination with an electronic stability program). In this thesis we implement a model and a controller for a superimposed steering system thus achieving the first of these potential benefits. The vehicle model is based on the single-track or bicycle model. Unlike most other publications, the motor model in this thesis goes down to the level of the electrical dynamics of the motor. The model is divided into three main modules (vehicle module, steering module and friction module) as well as several submodules to ensure easy adaptability. The overall control objective consists of increasing vehicle agility by achieving a variable ratio between the steering wheel angle and the actual road wheel angle as a function vehicle velocity. We divide the controller into a torque and a current controller. The actual controller is derived in three steps starting from an analog torque controller as well as an analog current controller then moving to a digital torque controller. In doing so we use the model matching, feedback linearization and state feedback control techniques. The model and the controller are evaluated using the parameters of a small truck and different road scenarios. Finally, the Validation Square technique is applied to assess the validity of the results.M.S.Committee Chair: Taylor, David G.; Committee Member: Egerstedt, Magnus; Committee Member: Heck-Ferri, Bonnie S