Tracing anthropogenic Technology Critical Elements using Environmental Forensics : Case studies at Kallholmsfjärden and the Bothnian Bay, northern Sweden

Abstract: The rapidly changing landscape of today's technology industry has increased the number of electronic products being discarded. Society is always on the hunt for the latest product and newest technological advancement, thereby creating a constant influx of older model products into fast-growing waste streams. These products often contain a variety of metals, some of which are in high demand for their importance in technological applications but are in relatively short supply. These technology critical elements (TCE) are often insufficiently researched, and their natural abundance and behavior in environmental systems can be poorly understood or not known. This lack of comprehension creates a difficulty in tracing sources of their dissemination into the environment and an inadequacy in understanding the potential effects on environmental habitats. This thesis is an environmental forensics approach to tracing anthropogenically induced Cd and TCEs in sediments and groundwater in Kallholmsfjärdin, Northern Sweden. This area has been heavily industrialized since the early 1930s by Boliden Mineral AB's Cu-Pb-Zn smelter at Rönnskär. Process operations related to sulfide ore smelting, processing secondary scrap metals, and end-of-life electronics are all investigated. This thesis further attempts to identify anthropogenically induced changes to element mobility and influences on sediments in the Bothnian Bay's deeper basins.Paper-I was dedicated to tracing heavy metal contamination in groundwater monitoring wells around Rönnskär's waste deposit area. Sources of contamination were identified using multi-element screening analysis and multivariate statistical techniques such as principal component analysis and cluster analysis. Three sources of contamination were ultimately identified in the area. Principle component analysis was suggested to be a suitable method for the initial surveys prior to a full-scale monitoring program. However, to obtain more detailed information on specific element mobility and source identification, reactive-transport modeling and/or isotope analysis should be used.Paper-II explored the potential of Ta and Nb to serve as tracers for sediment contamination related to the processing of end-of-life electronics at Rönnskär. This paper further investigates changes in mobility related to anthropogenic activity and the possible transport into the Bothnian Bay. Two sediment cores were taken in Kallholm Bay and in the Bothnian Bays deeper basins. Sediments were analyzed using ICP-SFMS and ICP-OES. Identification of fractionated phases was analyzed through a 5-step sequential extraction procedure. The Nb/Ta ratio decreased from 14.5 to 1.7 due to an enrichment of Ta likely resulting from the processing of Ta-capacitor bearing electronics. An anthropogenic influence was also noticed in the partitioning of Ta with an increase in the hydrous ferric oxides (HFOs) and organic matter. This behavior was suggested to be a mechanism of the increase in the mobility of Ta into the Bothnian Bay. However, no increase in Bothnian Bay sediments was seen. Paper-III expanded on these results by investigating the remaining TCEs, including the REEs using the same sediments and methods. Several elements were found to increase in the sediments related to sulfide ore smelting (Ge, Te, Tl, and Re) and secondary scrap metal and end-of-life electronic processing (Ta and W). Gallium, Nb, and the REEs showed no influence from anthropogenic activity. Changes in mobility was observed due to anthropogenic influence for Ge, Tl, and Ta. Only Te showed an increase in the deeper Bothnian Bay sediments.