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In the Valongo Belt, with an extension of about 90 km, located very close to Porto, northern Portugal, dozens of ore deposits of various metallic minerals and coal were exploited in the 19th and 20th centuries. One of the metals most intensely exploited was antimony, with or without associated gold mineralization. This research intends to verify the extent of the current environmental legacy of ancient antimony mining. A typical old mine was selected. The main objectives were to verify whether the environmental legacy still manifests today, how natural processes contributed to an environmental dispersion of the mining footprint and whether the environmental legacy was absorbed by developments in a new landscape modified by anthropic activities. The topography of the area was captured using a Light Detection and Ranging (LIDAR) based drone system. The regional background was characterized by the geo-referenced chemical analysis of 157 soil samples, collected in a 35 × 35 m grid. The former mining area was characterized by 58 supplementary samples. The mining area is distinct from the background by higher antimony and zinc levels, constituting two distinct populations, as confirmed by statistical tests. In the samples collected in the industrial zone, six elements were considered contaminants: As, Cu, Mo, Sb, Sn and Zn. The concentrations of these elements were statistically examined using multivariate statistical analyses (principal component analysis and correspondence analysis). The main conclusions are: (a) the mining heritage area is discernible from the highly mineralized background; (b) in the mining zone, it is possible to distinguish the processing industrial area from the waste rock storage; (c) the natural processes of environmental dispersion were of little relevance; (d) the environmental legacy was smoothed and mostly incorporated into the new post-industrial landscape created by anthropic activities. Full article

Wearable sensors to monitor vital health are becoming increasingly popular both in our daily lives and in medical diagnostics. The human body being a huge source of thermal energy makes it interesting to harvest this energy to power such wearables. Thermoelectric devices are capable of converting the abundantly available body heat into useful electrical energy using the Seebeck effect. However, high thermal resistance between the skin and the device leads to low-temperature gradients (2–10 K), making it difficult to generate useful power by this device. This study focuses on the design optimization of the micro-thermoelectric generator for such low-temperature applications and investigates the role of structural geometries in enhancing the overall power output. Electroplated p-type bismuth antimony telluride (BiSbTe) and n-type copper telluride (CuTe) materials’ properties are used in this study. All the simulations and design optimizations were completed following microfabrication constraints along with realistic temperature gradient scenarios. A series of structural optimizations were performed including the thermoelectric pillar geometries, interconnect contact material layers and fill factor of the overall device. The optimized structural design of the micro-thermoelectric device footprint of 4.5 × 3.5 mm², with 240 thermoelectric leg pairs, showcased a maximum power output of 0.796 mW and 3.18 mW when subjected to the low-temperature gradient of 5 K and 10 K, respectively. These output power values have high potential to pave the way of realizing future wearable devices. Full article

There is a lack of prescribed databases and approaches in place for performing comparable Life Cycle Assessments (LCAs) of smartphones and other electronic devices in a coherent manner. Hence there is a need within certain eco-rating initiatives for simplified, yet still precise enough, approaches that are expert independent. Here, five independently published Full LCAs (FLCA) of smartphones—and a metal content declaration of a tablet—are analyzed and compared with the simplified LCA method (Open Eco Rating LCA, OLCA) used by the open eco rating (OER) sustainability assessment. OLCA is described in detail. The comparisons use the same characterization factors that are used for climate change and abiotic resource depletion (ARD) midpoint impact categories. The tablet is only analyzed for the ARD indicator (ARDI). The results show that the difference between the FLCAs and the OLCA is up to 20% for the Global Warming Potential indicator (GWPI). The difference is explained by significantly different emission intensities used in FLCAs and OLCA, especially for integrated circuit and screen production. The life cycle use of metals relevant for ARDI is identified in one of the FLCAs of mobile phones, and used in OLCA and compared with the corresponding FLCA ARDI score. The total FLCA ARDI score is 67% (2.0 vs. 1.2 grams Sb—eq.) and 32% (4.98 vs. 3.76 grams Sb—eq.) higher than OLCA ARDI for the mobile phone and the tablet, respectively. The reason is that OLCA only captures a few of the most relevant metals (gold, silver, tin, indium, and tantalum) for the ARDI. However, cobalt—and to some degree copper and lithium—are significant gaps in the OLCA. The conclusion is that OLCA is an efficient and fair approach for LCAs that are focused on the GWPI of smartphones as the divergence to FLCA can easily be explained. However, the circular footprint formulae, renewable electricity options, and ARD characterization indices for cobalt, copper and lithium should be added to OLCA for further precision. The next step is to compare the Product Environmental Footprint (PEF) FLCA method with OLCA for GWPI and ARDI evaluations of new smartphones. Moreover, the effect of adding more midpoint or single score indicators could be tested in OLCA. Full article