488 
Archives of Environmental Contamination and Toxicology (2022) 82:481—492 
South Combined- a 
LEF M2MAD TIF M2MAD TIF 
Table 3 Ranges of calculated 
local enrichment factors (LEFs) 
along with their respective 
tühreshold values estimated 
by the M2MAD and TIF 
approaches of each TCE in the 
two different regions (North 
and South) as well as threshold 
values for the combined dataset. 
All threshold values are given 
in mg kg”! apart from In, Tb, 
Ho, and Ta where threshold 
values are given in ug kg”! and 
therefore set in italic 
North 
LEF M2MAD TIF 
Sc 
21.7 
0.6-1.4 34.2 
0.8-1.6 25 
0.9-2.0 25 
0.8-1.9 15.3 
0.6-2.3 265 
0.7-1.0 413.9 
0.6-1.2 82 
0.7-1.3 10.7 
0.7-1.3 38 
0.8-1.4 79 
0.8-1.4 1.83 
0.8-1.3 3.3 
0.8-1.5 1240 
0.8-1.5 7.7 
0.8-1.5 1450 
0.7-1.5 40 
0.8-1.7 510 
0.8-1.7 3.2 
0.7-1.5 500 
07-20 1400 
22.3 
Ga 
Ge 
Nb 
In 
La 
17.8 18.5 18.9 19.8 
0.8-1.3 29.8 31.0 a2 34.8 
0.9-1.5 20 24 20 24 
0.8-1.5 22 2.2 24 2.4 
0.6—1.7 16.8 19.4 16.1 17.1 
0.8-1.6 158 168 232 
0.8-1.5 54.3 56.4 51.5 
0.7-1.5 112 100 
0.7-1.5 13.9 12.6 
0.7-1.5 47 
0.7-1.5 
9.8-1.3 
3.8-1.4 
.8-1.3 
J.8-1.3 
28-13 
2.8-1.3 
530 0.7-1.4 
3.3 0.7-1.5 
520 0.8-1.4 
1400 0.7185 
241 
47 
114 91 
13.9 11.5 
"0 42 
9.9 8,8 9.2 
‘95 1.79 1.92 
3.7 8.3 8.6 
1230 1250 1270 
70 7.2 7,5 
‘300 1400 1430 
9 4.2 
510 530 560 
1 3.1 3.4 
540 520 530 
1400 1300 1400 
Ce 
Pr 
Nd 
Sm 
Eu 
Gd 
Tb 
Dy 
Ho 
er 
Tm 
Yb 
Lu 
Ta 
TCE mass fractions in the North Sea (cf. Table 2) appear to 
fit well with the already observed ranges and the respective 
crustal abundances (UCC). However, the minimum mass 
fractions of the TCEs in the North Sea are often higher than 
the respective sediment literature values for coastal sedi- 
ments. Given the respective crustal abundances of TCEs, 
especially In and some REESs seem to exceed these abun- 
dances. Nevertheless, under consideration of the respective 
uncertainties and due to the circumstance that the observed 
maximum values only occur temporally, it may be assumed 
that they are not significantly higher than the given UCC 
values. Thus, significant anthropogenic inputs of TCEs are 
relatively unlikely. 
Comparing the two observed regions (North and South), 
there are only minor differences in the observed TCE mass 
fractions. However, for many of the TCEs (Ga, Ge, Nb, In, Eu, 
Gd, Dy, Ho, Yb, and Ta) mass fractions of the North region 
are elevated. This may be due to the partly different geological 
characteristics (e.g., net sedimentation and grain size distribu- 
tion) of the sediments in these two regions of the North Sea 
(Ducrotoy et al. 2000; Federal Maritime and Hydrographic 
Agency (BSH) 2016). 
Calculation of Local Enrichment Factors of TCEs in North 
Sea Sediments 
To better evaluate the TCE load of the observed regions, local 
enrichment factors (LEF) were calculated for each element 
with Sc as reference element as the REESs, in general, appeared 
to be anthropogenically unaffected (cf. PAAS-normalized plots 
in supplemental information Fig. A.1). 
Following the enrichment factor (EF) thresholds defined 
oy Birch (2017), Table 3 gives an overview of the calculated 
LEFS of each TCE (Birch 2017). For all observed stations, 
at any time little to no pollution (LEF< 1.5) occurred. Only 
the LEFSs of Ga, Ge, Nb, In, and Ta show elevated LEFSs of 
.5 to 2.5, thus indicating the possibility of slightly polluted 
sediments. Additionally, it becomes evident that LEFSs for both 
‚egions do not differ within their observed ranges. Potential 
anthropogenic influences, such as the construction and com- 
missioning of offshore wind turbines, could be indicated by 
slightly enriched In LEFs (Kirchgeorg et al. 2018; Reese et al. 
2020). Nevertheless, other possible sources of pollution, such 
as the Elbe or the deposition of diluted H,SO,, are not consid- 
ered to be significant input sources for TCEs into the German 
Bight. 
A Springer