482 
Archives of Environmental Contamination and Toxicology (2022) 82:481-492 
Graphical Abstract 
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The assessment of metals and metalloids in the environment 
is of great concern for many legislators to ensure a good 
environmental status. Especially for marine environments, 
legal directives regulate the maximum values of pollutants in 
aquatic systems (e.g., Water Framework Directive 2000/60/ 
EC, Marine Strategy Framework Directive 2008/56/EG). 
Moreover, transboundary committees urge actions for the 
protection of the good environmental status, e.g., stated in 
the sustainable development goals (SDGs) of the United 
Nations or the Oslo-Paris-Convention (OSPAR). However, 
besides the continuously monitored legacy pollutants (e.g., 
Ni, Cu, Zn, Cd, Hg, Pb), new potential contaminants like 
the so-called technology-critical elements (TCEs) (including 
Ga, Ge, Nb, In, REEs and Ta) may play an important role in 
the near future (Filella and Rodriguez-Murillo 2017; Filella 
and Rodushkin 2018; Klein et al. 2021; Nuss and Blengini 
2018; Reese et al. 2020). 
Even though heavy metals like Cu and Zn show exten- 
sively higher annual production amounts (e.g., in 2017 
Cu: 2.0 10’ t/a vs. Nb: 6.7 10* t/a), TCEs are considered 
emerging contaminants as they have similar pathways into 
the environment (Kelly et al. 2005). Especially given that 
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many TCEs still have highly disrupted circular economies, 
in part due to low recycling rates, their impact on the envi- 
ronment may be of greater concern than other heavy metals 
‘Barth et al. 2000; Bu-Olayan and Thomas 2020; Grandell 
et al. 2016; Hagelüken 2014; Kaya 2019; Ray et al. 2020; 
Romero-Freire et al. 2019). However, the assessment of 
TCESs is still challenging as on one hand only little is known 
about possible (eco)toxicological effects of these elements, 
and on the other hand, little information on specific envi- 
ronmental background values for most of the TCEs are 
available. 
The ecotoxicological evaluation of environmental sam- 
ples such as sediments is challenging. In addition to the 
mass fractions of possible pollutants, knowledge of other 
parameters such as pH, grain size, or biogeochemical pro- 
cesses in the respective regions is required. Hence, geo- 
chemical thresholds are often used as a basis for (legally 
sinding) limit values of different pollutants and to allocate 
elevated concentrations (Reimann et al. 2018). Therefore, 
there is a high demand for data on background thresholds 
or background reference values of TCEs in environmental 
research (LuGic et al. 2021). In order to determine geological 
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