Heavy metal contamination was identified in groundwater monitoring wells surrounding a waste deposit facility at the Rönnskär Cu–Pb–Zn smelter in Skellefteå, northern Sweden. The main objective of this study is to identify the sources of contamination, utilizing element screening analyses and multivariate statistical techniques. A second objective is to determine the usefulness of these techniques in Environmental Forensics investigations of contaminated groundwater at a complex industrial site. Water samples were collected from four groundwater monitoring wells and six waste deposit cells surrounding the contaminated area. Seventy-two elements are statistically examined and the dataset is reduced to the variables representative of the contaminated source material from the smelting process. A three-component model is identified and explains 88% of the total variation in the dataset. Component 1 includes concentrations of Cd, Co, Ni, Rb, Re, and Zn. This component displays a high correlation with two of the deposit cells and their associated groundwater monitoring wells. Component 2 is comprised of Sb, Cu, and Mo. This component displays a correlation between all monitoring wells and deposits likely due to the high mobility of these elements as oxyanions. Component 3 is dominated by As and displays high correlation to three older deposit cells representing a completely different source than for Components 1 and 2. The application of screening analyses and multivariate statistics in this study has achieved a meaningful identification of sources of contamination in the investigated area. It was also shown to be useful as an initial survey aiming to optimize a full-scale monitoring program at the site.

The increasing use of Technology-critical elements (TCEs) in modern technologies is expected to raise their concentrations in soils of many areas, prompting concerns about their mobility and entry into the food chain. This study examines pore water availability and plant uptake of gallium (Ga), thallium (Tl), and the rare earth elements gadolinium (Gd), neodymium (Nd), and ytterbium (Yb). Lettuce (Lactuca sativa) was grown under controlled greenhouse conditions in a native agricultural soil from Sweden, both at the baseline concentrations of the elements and after spiking in a concentration series in which the highest level corresponded to a 40-fold enrichment of the original concentrations. Our findings indicate that Tl poses the greatest risk among the investigated TCEs, as it was readily taken up by lettuce even at moderate concentrations in the soil, with a clear dose-dependent increase in accumulation (Bioconcentration factor, BCF = 0.084–1.5). Gallium demonstrated a low concentration in pore water and limited accumulation in lettuce (BCF = 0.00010–0.00066), suggesting a low immediate concern. However, the Ga uptake increased substantially at the highest contamination level, indicating a potential risk threshold. Relative to Ga and Tl, the REEs demonstrated intermediate levels of both pore water availability and lettuce uptake, although the uptake increased with rising soil concentrations (BCF = 0.0013–0.0071, 0.0013–0.012, and 0.0011–0.0020, for Gd, Nd, and Yb respectively). Notably, Nd was also found to negatively affect seed germination, suggesting a possible risk to crop productivity. Together, our findings highlight the need for targeted risk assessments of specific TCEs, as these elements may increasingly find their way onto our plates through soil-to-plant transfer under potential future soil contamination.

Technology-critical elements (TCEs), essential in emerging technologies, are increasingly finding their way into our environment, raising concerns about their sparsely studied behavior and toxicity. To contribute insights into the toxicological aspects, we employed in vitro bioassays to investigate the possible cytotoxic effects in four representative cell lines (AR-EcoScreen GR-KO-M1, DR-EcoScreen, MCF7AREc32, VM7Luc4E2) and the potential to induce oxidative stress via the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway for a number of these elements. Nine TCEs, three rare-earth elements (REEs: Gd, Nd, Yb) and six less-studied TCEs (LSTCEs: Ga, Ge, In, Ta, Te, Tl), were selected for this study, along with three well-studied traditional metal contaminants (TMCs: As, Cd, Pb) for comparison. Among the 12 studied elements, nine showed signs of inducing cytotoxicity: As, Cd, Ga, Nd, and Te in three out of the four studied cell lines and Gd, Ta, Tl, and Yb in one to two cell lines. Tellurium repeatedly exhibited the highest potency. The TCEs Ga and In, similar to As and Cd, also demonstrated the potential to induce oxidative stress. The results of this study suggest that some TCEs may potentially cause adverse health effects similar to As and Cd, thus prompting further investigations. 

Municipal Solid Waste Incineration (MSWI) plants pose significant environmental concerns, generating solid by-products, namely Fly Ash (FA) and Bottom Ash (BA). These MSWI residues have received attention due to the presence of valuable elements, Potentially Toxic Elements (PTE), and other contaminants. Radionuclide detection is also critical because they can concentrate in incineration ashes to pose a radiological hazard. Therefore, multi-element and radionuclide analysis was performed on BA and FA, including samples from bag filters containing lime (FAL) and soda (FAS) additives collected from two MSWI plants in northern Italy. BA and FA were sampled in 2013, 2020, 2021, and 2022 for a multi-year assessment, including during the COVID-19 pandemic. Our objectives were to evaluate the potential of elemental flows and radiological impact of the two different MSWI plants. The chemical concentration of 70 elements and the activity of 8 radionuclides were determined using sector Field Inductively Coupled Plasma Mass Spectrometry (ICP-SFMS) and alpha and gamma spectrometry, respectively. Regarding major elements (Fe, Al, Mg, Ti, and P), high mean concentrations were found in BA, followed by FAL and FAS. Notably, in BA samples, Fe, Al, Zn, and Cu averaged 47600, 35300, 4100, and 3500 mg kg−1, respectively, and critical raw materials, namely elements of economic importance such as Mg, P, Ti, and Ba, were concentrated at 16100, 6800, 3500, and 1400 mg kg−1, respectively. The annual flows of elements from MSWI residue streams ranged in the order of 103-104 kg a-1 for Fe, Al, Zn, Cu, Mg and Ti, and the sum of Rare Earth Elements (∑REE) was about hundreds of kg per year. Chondrite-normalized patterns of REE and normalized patterns of selected elements over crustal averages helped to evaluate anthropogenic signals, which enabled us to hypothesise elemental sources related to the input MSW. BA and FA showed a higher content of natural radionuclides than artificial ones. In BA, natural radionuclides, 40K and 210Pb, ranged from 666 to 693 Bq kg−1 and 23.3–48.1 Bq kg−1, respectively. In FA, 40K ranged from 308 to 2198 Bq kg−1 and 210Pb from 17.1 to 534 Bq kg−1. Activity concentration index (ACI) results in all-natural radionuclides below the permissible limit (<1). Still, the significant abundance of 210Pb and 40K, coupled with their complex behaviour, calls for new and continuous evaluation of long-term emissions and the radiological hazard related to MSWI systems. 

While vegetable uptake of traditional metal contaminants is a well-studied pathway to human exposure and risk, a paucity of information exists on the uptake of emerging metal contaminants. This study evaluated the uptake of the Technology-critical elements (TCEs) gallium (Ga), germanium (Ge), niobium (Nb), tantalum (Ta), thallium (Tl), and rare earth elements (REEs) into lettuce cultivated in 21 European urban soils. For comparison, the uptake of cadmium (Cd) was also analysed. First, the uptake was predicted by multiplying soil concentrations with previously established bioconcentration factors (BCFs). Subsequently, multiple regression models incorporating geochemical variables as predictors were used to determine whether prediction accuracy could be improved. A "3-predictor model" incorporated soil TCE concentration, pH, and organic matter (OM), and a "7-predictor model" added data on clay content and the soil concentrations of Fe, Al, and Mn as well. With the exception of Cd, Ge, and Tl, the BCF approach provided unsatisfactory predictions (R2 < 0.5), while the 7-predictor models yielded the best predictions, even when accounting for the greater number of predictors. While the most important predictors of uptake varied somewhat between the TCEs, the concentrations of TCEs in the soil generally explained the largest proportion of the variation. The least influential predictors in our dataset were [Mnsoil], [Fesoil], and soil OM. Incorporating geochemical data generally improved the predictions of uptake by lettuce, and these findings underscore the need for more detailed characterisations of the uptake potential of TCEs by food plants and subsequent consequences for human health.

Increased demand for rare earth elements (REE) has resulted in their increased exploitation and the need to better understand their cycling in aquatic environments. Thus far much of the research in boreal areas focused on REE cycling in larger rivers, while relatively little is known regarding their mobilization in smaller headwater streams. Here we used the Krycklan Catchment Study in northern boreal Sweden to investigate how REE are mobilized from diverse boreal headwaters and how their catchment exports are influenced by processes such as weathering, hydrology, and complexation with other solutes. We found that wetland dominated headwaters were source limited and prone to dilution during high discharge, while forested headwaters had considerably higher total REE concentrations and were less affected by discharge fluctuations. Larger downstream catchments showed clear discharge driven seasonal patterns, with high concentrations during spring flood and low concentrations during base flow. While the proportion of mineral soils and water travel time in the catchment were important predictors of REE mobilization, complexation with organic matter appears to play a greater role in higher-order streams with higher pH and a larger contribution from deeper groundwater sources. Overall, we highlight the stark differences between REE cycling in the headwaters and in higher order streams, which can provide important information on the processes that mobilize REE from catchments.

We present isotopic data bearing on the origin of the vent-distal, Lovisa stratiform Zn-Pb sulfide deposit, Bergslagen, Sweden. The age of deposition is constrained by secondary ionisation mass spectrometry (SIMS) U–Pb zircon dating of pumiceous mass flow deposits interbedded with mineralised, fine-grained volcaniclastic strata. Two mass flow deposits in the stratigraphic footwall yield ages of 1892 ± 2 Ma and 1892 ± 5 Ma respectively, whereas a mass flow deposit in the stratigraphic hanging wall yields an age of 1891 ± 3 Ma, constraining the mineralisation to c. 1892 Ma. Positively correlated δ66Zn (-0.299 to + 0.219‰), δ34S (-0.2 to + 4.7‰) and Zn/Cd (122 to 659) in sphalerite suggest mass-dependent, kinetic fractionation during sulfide deposition. Upwards decrease in these parameters and Zn/Pb relative to stratigraphic younging suggest that the hydrothermal system matured over time, whereby later fluid batches reached the depositional site less fractionated. Thermochemical sulfate reduction and cooling of single hydrothermal fluid batches are suggested as sulfide precipitation mechanisms while bacteriogenic sulfate reduction is deemed less likely based on by absence of highly negative δ114Cd (-0.212 to -0.069‰), and δ34S values. Sphalerite and galena Pb isotope compositions indicate leaching of c. 1.91–1.89 Ga felsic volcanic rocks as a principal metal source followed by subsequent, syn-metamorphic addition of radiogenic Pb. Limited syn-metamorphic isotopic homogenisation is suggested by retained systematic variations in different sulfide beds. 

A common, yet poorly evaluated, advice to remove contaminants from urban vegetables is to wash the produce before consumption. This study is based on 63 samples of chard, kale, lettuce and parsley that have grown near a heavily trafficked road in the third largest city in Sweden, with one portion of each sample being analysed without first being washed, and the other portion being subjected to common household washing. Concentrations of 71 elements were analysed by ICP-SFMS after a sample digestion that dissolves both the plant tissues and all potentially adhering particles. The results show that the washing effect, or the fraction removed upon washing, varies significantly between elements: from approximately 0 % for K to 68 % for the ∑REEs. Considering traditional metal contaminants, the efficiency decreased from Pb (on average 56 % lost) to Co (56 %) > Cr (55 %) > As (45 %) > Sb (35 %) > Ni (33 %) > Cu (13 %) > Zn (7 %) > Cd (7 %), and Ba (5 %). A clear negative correlation between the washing effect and the different elements' bioconcentration factors shows that the elements' accessibility for plant uptake is a key controlling factor for the degree to which they are removed upon washing. Based on the average washing efficiencies seen in this study, the average daily intake of Pb would increase by 130 % if vegetables are not washed prior to consumption. For the other contaminant metals this increase corresponds to 126 % (Co), 121 % (Cr), 82 % (As), 55 % (Sb), 50 % (Ni), 16 % (Cu), 8 % (Zn), 7 % (Cd) and 5 % (Ba). The advice to wash vegetables is therefore, for many elements, highly motivated for reducing exposure and health risks. For elements which are only slightly reduced when the vegetables are washed, however, advising should rather focus on reducing levels of contamination in the soil itself.

While urban-grown vegetables could help combat future food insecurity, the elevated levels of toxic metals in urban soils need to be met with measures that minimise transfer to crops. The study firstly examines soil/dust particle inclusion in leafy vegetables and its contribution to vegetable metals (As, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sb, and Zn), using vegetable, soil and dust data from an open-field urban farm in southeastern Sweden. Titanium concentrations were used to assess soil/dust adherence. Results showed that vegetables contained 0.05–1.3 wt% of adhering particles (AP) even after washing. With 0.5 % AP, an adult with an average intake of vegetables could ingest approximately 100mg of particles per day, highlighting leafy vegetables as a major route for soil/dust ingestion. The presence of adhering particles also significantly contributed to the vegetable concentrations of As (9-20%), Co (17-20%), Pb (25-29%), and Cr (33-34%). Secondly, data from an indoor experiment was used to characterise root metal uptake from 20 urban soils from Sweden, Denmark, Spain, the UK, and the Czech Republic. Combining particle adherence and root uptake data, vegetable metal concentrations were calculated for the 20 urban soils to represent hypothetical field scenarios for these. Subsequently, average daily doses were assessed for vegetable consumers (adults and 3-6 year old children), distinguishing between doses from adhering particles and root uptake. Risks were evaluated from hazard quotients (HQs; average daily doses/tolerable intakes). Lead was found to pose the greatest risk, where particle ingestion often resulted in HQs>1 across all assessed scenarios. In summary, since washing was shown to remove only a portion of adhering metal-laden soil/dust particles from leafy vegetation, farmers and urban planners need to consider that measures to limit particle deposition are equally important as cultivating in uncontaminated soil.

Anthropogenic contamination of water resources remains a severe environmental concern on a global scale. Radiogenic and stable isotope measurements (especially for light elements) constitute well-known tools for the identification of pollution sources and thus have considerable potential in prevention and remediation efforts. Recent instrumental and methodological advances have extended the isotope ‘toolbox’ to include a significant number of new stable isotope systems, which in turn resulted in rapid growth of studies using these novel tracers in the field of environmental forensics. Isotopic fractionation, occurring during post-release transformation of contaminants, offers an additional benefit of possibility to study the fate of pollutants in aquatic systems. This review will focus on selected relevant studies in the field and present future trends and development.