4186 
and Hydrographic Agency (BSH) 2009; Federal Maritime 
and Hydrographic Agency (BSH) 2016). 
Additionally, the southern area of Heligoland is anthro- 
pogenically influenced by the relocation of sediment from 
the Hamburg harbor, but also by the input loads of the Elbe 
River. Until 2011 6.5 million tons of harbor sediments were 
relocated near to the sampling position HPAE3 (Federal 
Maritime and Hydrographic Agency (BSH) 2016; Ham- 
burg Port Authority (HPA) 2021) (cf. Fig. 1). Therefore, 
anthropogenic inputs of TCESs via the river Elbe will most 
likely be measurable at this geographic location. For the 
other region, comparatively lower loads are to be expected. 
Nevertheless, diluted H,„SO, acid from the titanium oxide 
production containing various heavy metal impurities was 
deposited in this region until 1989, which may represent 
a further potential environmental pollution source (Federal 
Maritime and Hydrographic Agency (BSH) 2016; Pickaver 
1982). Furthermore, it is suspected that the TCE load in 
sediments may rise within the next years or decades as dif- 
ferent offshore wind farms were built in this region since 
2012 (Federal Maritime and Hydrographic Agency (BSH) 
2020; Kirchgeorg et al. 2018; Ramirez et al. 2021; Reese 
et al. 2020). Hereafter, the temporal variations of the TCEs 
(Ga, Ge, Nb, In, REESs, and Ta) are described and compared 
with values from the literature. Detailed information on 
measured TCE mass fractions for all stations can be found 
in the supplemental information Table A. 6. 
Gallium 
Figure 2a shows the Ga mass fractions of the regions 
“North” and “South” over the observed time (2010-2020). 
For both regions, it can be seen that mass fractions show 
similar ranges between 14.0 mg kg"!+1.0 mg kg”! and 
23 mg kg"! +5 mg kg”!. Furthermore, it becomes evident 
that the variability of Ga mass fractions over time appears 
to be relatively small. The boxplots in Fig. 3a represent 
all measured Ga mass fractions of the time series at the 
given stations. These boxplots indicate that station URST1 
shows the highest variability over the ten years ranging 
from 15 mg kg”! +1 mg kg”! to 23 mg kg”! +5 mg kg”!. 
All other stations show Ga mass fractions ranging 
between 14 and 20 mg kg”. Overall, a median value of 
17 mg kg”! +1 ug kg7!can be derived for both regions. 
Germanium 
The Ge mass fraction ranges between 1.2+0.2 mg kg”! 
and 2.3 mg kg"! +0.6 mg kg”! for all samples. Figure 2b 
shows only minor variability in Ge mass fractions for both 
regions over time. Referring to the boxplots in Fig. 3b, it 
is evident that stations of the North region feature slightly 
Archives of Environmental Contamination and Toxicology (2022) 82:481-492 
higher mass fractions compared to the South region 
(medianyon = 1.8 ug kg7!; medians. un = 1.5 ug kg7'). Fur- 
thermore, stations KS11 and HPAE3 (South region) feature 
the highest variability over the observed time frame. 
Niobium 
Nb mass fractions of the North region range from 
11.0 ug kg”! +0.8 ug kg”! to 15.4 ug kg”! +1.7 ug kg”, 
whereas the South region shows a range from 
3 ug kg”! +6 ug kg”! to 18.2 ug kg”! +1.3 ug kg7'. Mass 
fractions of Nb show no significant changes over time in 
:he North region. In contrast, the stations in the South 
‚egion like KS11 show some variation between the years 
2010 and 2014 (cf. Fig. 2c), thus resulting in a range of 
Nb mass fractions between 8 mg kg”! +6 mg kg”! and 
18.2 mg kg”! +1.3 mg kg”! for this region. However, 
considering the respective uncertainties, these vari- 
abilities do not appear to be significant. Notwithstand- 
ing the region, boxplots in Fig. 3c show that all stations 
have similar variability and median mass fractions around 
12.0 mg kg”! + 1.0 mg kg”). 
Indium 
In mass fractions of the North region range from 
73 ug kg”! +4 ug kg”! to 237 ug kg”! +13 ug kg”', whereas 
the South region shows a range from 88 ug kg"! +7 ug kg”! 
to 170 ug kg”! + 15 ug kg”!. Figure 2d shows In mass frac- 
tions of the two regions over time. It can be seen that the 
In mass fractions of stations within the North region vary 
noticeably from each other, but remain rather stable over the 
considered period of 10 years, whereas the stations of the 
South region are more homogeneous over time. This fact can 
also be seen in Fig. 3d. It becomes evident that station Ti7 
shows the highest In mass fractions while Ti17 and Ti9 lay 
within the range of the South region. 
Rare Earth Elements 
All mass fractions of the rare earth elements (REEs) show 
similar to identical trends over the observed time. Therefore, 
only La is discussed in detail as a representative for all other 
REES (cf. Table 1). 
As displayed in Fig. 2e, the North region features La 
mass fractions ranging from 18.7 mg kg7!+3.7 mg kg”! 
to 41.9 mg kg7"!+6.1 mg kg”'. Station KS11 of the 
South region shows decreasing mass fractions in the 
years from 2010 to 2014 (58.9 mg kg”! +1.6 mg kg”! to 
31.7 mg kg”! +1.3 mg kg”'). After 2014, the mass fractions 
of station KS11 follow the course of the remaining two sta- 
tions (HPAE3 and KS8) with La mass fractions between 
2 Spring