Archives of Environmental Contamination and Toxicology (2022) 82:481-492 
TCEs in sediment digests (Klein et al. 2021). The ICP-MS/ 
MS system consists of an Agilent 8800 ICP-MS/MS (Agi- 
lent 8800, Agilent Technologies, Tokyo, Japan) coupled to 
an ESI SC-4 DX FAST autosampler (Elemental Scientific, 
Omaha, Nebraska, USA) equipped with an ultra-low pen- 
etration air (ULPA) filtration unit (Elemental Scientific, 
Omaha, Nebraska, USA). For each measurement, the instru- 
ment was optimized on a daily basis using a tune solution 
containing Li, Co, Y, Ce, and T1 (10 ug L7'!). Optimal tuning 
and instrument parameters can be found in the supplemental 
information Table A.4. An external calibration, covering a 
concentration range from 0.1 ug L7! to 100 ug L7! for all 
analytes, was used to allow quantification of each element. 
Each solution for instrument tuning and quantification was 
prepared from custom-made multielement standards (Inor- 
ganic Ventures, Christiansburg, USA) on a daily basis. A 
solution containing 10 ug L7! of Ir and Rh was dosed online 
to the sample solutions to allow for drift correction. To mon- 
itor potential carryover effects, wash blanks of 2% (w/w) 
HNO, were measured after each sample triplicate. 
Data Processing and Calculations 
Multielement data were pre-processed using MassHunter 
version 4.4 (Agilent Technologies, Tokyo, Japan) in com- 
bination with a custom-written Excel® spreadsheet. This 
spreadsheet was used to calculate limits of detection (LOD) 
(3x SD) as well as the limits of quantification (LOQ) 
(10x SD) of the method using procedural blanks (n=6) 
(MacDougall and Crummett 1980). Furthermore, combined 
uncertainties (U, k=2) for each sample and reference mate- 
rial were calculated using a simplified Kragten approach 
following Reese et al. (2019) (Kragten 1994; Reese et al. 
2019). The measurement precision of the samples and the 
reproducibility of multiple digests were taken into account. 
The significant number of digits is given according to 
GUM and EURACHEM guidelines, whereby the highest 
uncertainty of all measured samples determines the sig- 
nificant number of digits to be presented with the values 
(Magnusson et al. 2015; Ellison and Williams 2012). 
Calculation of Local Enrichment Factors 
and Preliminary Reference Thresholds 
For evaluation and estimation of the TCE load in North Sea 
sediments, both local enrichment factors (LEF) and prelimi- 
nary reference thresholds were determined. Calculation of 
LEF is carried out according to Matys Grygar and Popelka 
(2016). The natural mass fraction (Xp) of a target element 
X is determined by an empirical function of a suitable refer- 
ence element (in this case Sc, f(Sc)). The LEF is then calcu- 
lated according to the following formula for the respective 
485 
elements (Matys Grygar et al. 2014; Matys Grygar and 
Popelka 2016). 
X 
LEFx = — with Xcpr = F(Sc) 
XGBE 
A list showing the respective function for each TCE for 
the calculation of Xp using Sc as reference element as well 
as the coefficient of determination (CD) of the chosen function 
can be found in the supplemental information Table A.5. 
The preliminary reference thresholds are calculated fol- 
lowing Reimann et al. (2018) using the M2MAD and TIF 
approach. According to Reimann et al. (2018), these two 
estimates for threshold values are calculated as follows: 
M2MAD = 10° 
where b = median(log 9 (X) + 2*MAD(log 9 (X) 
and MAD = 1.48 median (x; — median (X;)) 
TIF = Q3 + 1.5 IQR 
X; represents the mass fractions of the respective TCE and 
Q3 is the 3rd quartile of the dataset while IQR is the inter- 
quartile range (Q3 —- Q1) (Reimann et al. 2018). 
Results and Discussion 
Mass Fractions of TCEs in North Sea Sediments 
For this study, the < 20 um grain size fraction of 50 sedi- 
ment samples was analyzed. Sampling locations were 
either located close to the southern coast of Heligoland or 
further offshore in the North Sea. 
Despite the comparatively small geographical area, the 
North Sea is a very unique and dynamic marine ecosys- 
tem with very different geological characteristics, which is 
partly due to intensive sediment movements in the coastal 
area, either by anthropogenic sediment relocation or by 
natural currents (Ducrotoy et al. 2000; Federal Maritime 
and Hydrographic Agency (BSH) 2016). The investigated 
part of the North Sea is considered to be anthropogenically 
affected, which becomes particularly evident within long- 
:erm monitoring data (Federal Maritime and Hydrographic 
Agency (BSH) 2016). Mass fractions of legacy pollutants 
like Zn, Pb, and Hg often exceed background and even 
low effect threshold values (NOAA effect range low). In 
many cases, elevated mass fractions are observed near 
‘he coast, which indicates possible discharges by rivers or 
other near-shore anthropogenic sources (Federal Maritime 
2 Springer