1 Plant concentration data

1.1 Step 1: Results of reference materials

Reference materials were randomly incorporated into the routine samples to monitor analytical accuracy, precision, and any potential drift or offsets between batches. This approach also helped identify other types of analytical artifacts.

The reference materials used in this process were UPDEEP_SPRU_BARK_DRY, UPDEEP_SPRU_NEED_DRY, and UPDEEP_SPRU_TWIG_DRY. These materials were developed in-house as reference samples representing the three primary types of materials. While they do not adhere to international reference material standards, they have undergone multiple analyses by external laboratories to establish reliable reference values.

Additionally, the international reference material CLV-2 had been used.

1.1.1 Reference values of the reference materials

Below are the results for the reference values of these three reference materials:

Table 1.1: Number of above detection limit values for the preanalysed standard reference material (SRM) samples. The SRM samples are described and data is provided by Middleton et al. (2020). These preanalysed SRM analysis were made of dry-milled material with 2F method provided by Actlabs. The values were used as reference values in the x-charts.
Element UPDEEP_SPRU_BARK_DRY UPDEEP_SPRU_NEED_DRY UPDEEP_SPRU_TWIG_DRY
Ag 0 0 0
As 10 10 10
B 10 10 10
Ba 10 10 10
Be 0 0 0
Bi 10 0 1
Ca 10 10 10
Cd 10 10 10
Ce 10 10 10
Co 10 10 10
Cr 10 10 10
Cs 10 10 10
Cu 10 10 10
Dy 10 10 10
Er 10 10 10
Eu 10 10 10
Fe 10 10 10
Ga 10 10 10
Gd 10 10 10
Ge 10 1 9
Hf 8 0 5
Hg 10 0 0
Ho 10 10 10
In 0 0 0
K 10 10 10
La 10 10 10
Li 0 0 0
Lu 0 3 2
Mg 10 10 10
Mn 10 10 10
Mo 10 10 10
Na 10 10 10
Nb 10 10 10
Nd 10 10 10
Ni 10 10 10
Pb 10 7 10
Pd 0 0 0
Pr 10 10 10
Pt 0 0 0
Rb 10 10 10
Re 0 0 0
Sb 10 0 10
Sc 0 0 0
Se 8 4 7
Sm 10 10 10
Sn 1 0 0
Sr 10 10 10
Ta 10 10 10
Tb 10 6 10
Te 5 2 2
Th 10 10 10
Ti 10 10 10
Tl 10 10 10
Tm 0 0 0
U 10 10 10
V 10 10 10
W 1 1 1
Y 10 10 10
Yb 10 10 10
Zn 10 10 10
Zr 10 10 10

1.1.2 Measurement results of the reference materials

The aforementioned reference materials were randomly added to the sample set as supplementary samples within the larger batch of routine samples. Because of their random inclusion, both the sequence and order of the samples varied, as did the total number of measurements taken.

Table 1.2: Number of different SRM samples analysed with the routine samples. The UpDeep reference samples (Norway spruce needles, twigs and bark) are descibed by Middleton et al. (2020) and the CVL-2 (Black spruce) by Dalton and Dunn (1987).
ParentSampleID N
UPDEEP_SPRU_NEED_DRY 16
UPDEEP_SPRU_BARK_DRY 15
CLV-2 19
UPDEEP_SPRU_TWIG_DRY 16

The results of the measurements of the reference samples provide the following:

Table 1.3: Mean, madian, relative standard deviation (RSD) and relative mean absolute deviation (RMAD) of the four SRMs analysed with the routine samples.
Element CLV-2_Mean CLV-2_Median CLV-2_RSD CLV-2_RMAD UPDEEP_SPRU_BARK_DRY_Mean UPDEEP_SPRU_BARK_DRY_Median UPDEEP_SPRU_BARK_DRY_RSD UPDEEP_SPRU_BARK_DRY_RMAD UPDEEP_SPRU_NEED_DRY_Mean UPDEEP_SPRU_NEED_DRY_Median UPDEEP_SPRU_NEED_DRY_RSD UPDEEP_SPRU_NEED_DRY_RMAD UPDEEP_SPRU_TWIG_DRY_Mean UPDEEP_SPRU_TWIG_DRY_Median UPDEEP_SPRU_TWIG_DRY_RSD UPDEEP_SPRU_TWIG_DRY_RMAD
Ag 1.7e+01 1.7e+01 20 10 8.8e+00 8.6e+00 13 10 2.6e+00 2.9e+00 46 37 1.1e+01 1.2e+01 14 17
Al 1.1e+02 1.1e+02 13 11 9.3e+01 9.2e+01 6 6 7.6e+01 7.3e+01 15 6 9.4e+01 9.1e+01 14 11
As 3.4e+02 3.4e+02 15 17 3.0e+02 2.9e+02 11 13 1.0e+02 9.7e+01 18 17 5.2e+02 5.2e+02 8 6
Au 8.6e-01 5.2e-01 145 79 1.9e-01 1.5e-01 73 84 2.3e-01 2.5e-01 69 74 9.0e-01 2.1e-01 193 105
B 3.1e+01 4.2e+01 49 47 2.1e+00 1.9e+00 50 5 3.1e+00 2.8e+00 48 12 4.2e+00 2.6e+00 61 8
Ba 2.3e+04 2.3e+04 8 8 1.2e+05 1.2e+05 4 4 4.1e+04 4.1e+04 4 5 6.7e+04 6.6e+04 5 5
Be 4.7e+00 4.2e+00 50 33 1.5e+00 1.6e+00 46 52 4.6e+00 4.4e+00 27 28 1.3e+00 1.4e+00 36 30
Bi 9.8e+00 9.2e+00 21 19 8.9e+00 8.8e+00 16 18 3.3e+00 2.9e+00 77 38 4.1e+00 3.8e+00 52 56
Ca 7.5e+03 7.7e+03 8 5 1.0e+04 1.0e+04 8 10 5.4e+03 5.5e+03 7 7 4.0e+03 4.1e+03 6 4
Cd 1.3e+01 1.3e+01 23 15 1.3e+02 1.3e+02 7 6 1.4e+01 1.4e+01 14 11 4.2e+01 4.2e+01 8 10
Ce 2.3e+02 2.2e+02 10 9 7.6e+01 7.5e+01 10 6 1.7e+01 1.7e+01 8 11 7.7e+01 7.6e+01 12 12
Co 6.7e+01 7.0e+01 13 9 1.3e+02 1.3e+02 8 10 8.2e+01 8.1e+01 8 8 2.4e+02 2.3e+02 11 7
Cr 3.9e+02 3.8e+02 10 7 1.4e+02 1.4e+02 7 8 6.1e+01 4.9e+01 103 18 3.0e+02 3.0e+02 11 12
Cs 1.8e+01 1.7e+01 20 18 3.7e+01 3.7e+01 13 5 7.0e+01 6.9e+01 13 18 8.2e+01 8.2e+01 7 7
Cu 2.0e+03 1.9e+03 13 7 5.1e+03 5.1e+03 2 2 1.4e+03 1.4e+03 5 5 5.9e+03 5.8e+03 4 3
Dy 1.4e+01 1.4e+01 12 11 4.7e+00 4.8e+00 18 24 3.2e+00 3.2e+00 19 15 5.2e+00 5.3e+00 16 11
Er 6.4e+00 6.5e+00 15 17 2.5e+00 2.6e+00 21 23 1.7e+00 1.8e+00 27 13 2.8e+00 2.8e+00 22 22
Eu 4.2e+00 3.6e+00 37 44 1.7e+01 1.8e+01 23 4 6.0e+00 6.3e+00 25 10 8.1e+00 9.6e+00 48 33
Fe 2.6e+02 2.5e+02 9 7 9.2e+01 9.4e+01 6 7 4.0e+01 4.0e+01 6 8 1.2e+02 1.2e+02 4 5
Ga 5.3e+01 3.2e+01 53 37 6.6e+00 6.7e+00 61 75 6.7e+01 6.9e+01 26 14 1.6e+01 1.5e+01 31 16
Gd 1.0e+01 9.8e+00 12 12 5.4e+00 5.1e+00 24 25 2.5e+00 2.3e+00 25 17 5.3e+00 5.1e+00 20 21
Ge 2.8e+00 2.7e+00 41 36 2.9e+00 3.0e+00 29 26 5.3e+00 5.4e+00 30 15 1.3e+01 1.7e+01 64 15
Hf 3.4e+00 2.6e+00 86 31 9.0e-01 8.0e-01 41 45 3.1e-01 2.3e-01 90 68 1.2e+00 1.1e+00 29 24
Hg 2.8e+01 2.9e+01 14 14 1.7e+02 1.7e+02 5 5 2.8e+01 2.8e+01 10 6 2.5e+01 2.5e+01 8 9
Ho 2.6e+00 2.6e+00 8 5 1.1e+00 1.1e+00 19 20 7.9e-01 8.4e-01 22 16 1.0e+00 1.0e+00 19 19
In 4.7e-01 4.2e-01 45 56 3.8e-01 3.4e-01 65 101 1.7e-01 1.4e-01 80 69 2.4e-01 1.9e-01 97 80
K 3.7e+03 3.8e+03 9 4 9.0e+02 8.9e+02 7 7 4.0e+03 3.9e+03 7 8 3.8e+03 3.8e+03 4 2
La 1.2e+02 1.1e+02 12 8 6.4e+01 6.5e+01 8 5 2.3e+01 2.3e+01 7 6 6.4e+01 6.5e+01 7 7
Li 1.8e+02 1.7e+02 20 15 1.0e+01 1.0e+01 27 12 1.9e+01 1.9e+01 13 10 3.3e+01 3.4e+01 13 13
Lu 4.9e-01 4.4e-01 39 43 2.6e-01 1.9e-01 79 44 1.2e-01 1.1e-01 66 62 2.9e-01 1.9e-01 105 37
Mg 8.2e+02 8.6e+02 12 5 2.2e+02 2.3e+02 13 20 8.2e+02 8.2e+02 10 12 9.0e+02 9.0e+02 9 9
Mn 1.7e+06 1.8e+06 9 7 3.8e+05 3.8e+05 4 4 1.1e+06 1.1e+06 3 2 5.4e+05 5.4e+05 4 2
Mo 7.1e+01 7.1e+01 15 14 1.4e+01 1.3e+01 28 19 3.1e+01 3.1e+01 16 11 3.0e+01 2.9e+01 17 8
Na 7.4e+00 7.2e+00 33 38 7.6e+01 7.8e+01 7 8 3.0e+01 3.1e+01 8 8 4.9e+01 5.0e+01 8 4
Nb 9.7e+00 1.2e+01 54 76 3.6e+00 3.2e+00 40 19 8.6e-01 8.4e-01 39 11 6.2e+00 4.0e+00 62 18
Nd 9.7e+01 1.0e+02 13 11 3.7e+01 3.6e+01 12 15 1.4e+01 1.4e+01 16 14 4.4e+01 4.3e+01 16 19
Ni 5.2e+02 5.0e+02 25 11 7.5e+02 7.5e+02 9 8 6.6e+02 6.9e+02 11 9 2.3e+03 2.2e+03 18 3
P 8.8e+02 9.1e+02 9 6 1.8e+02 1.8e+02 10 10 1.4e+03 1.5e+03 8 7 1.1e+03 1.1e+03 7 4
Pb 1.1e+03 1.1e+03 10 7 1.2e+03 1.2e+03 6 7 6.9e+01 6.8e+01 17 9 4.6e+02 4.5e+02 12 7
Pd 2.3e+00 1.5e+00 94 138 6.4e+00 6.6e+00 29 18 4.5e+00 4.8e+00 29 12 3.5e+00 4.4e+00 66 37
Pr 2.5e+01 2.5e+01 12 11 9.8e+00 9.7e+00 11 16 3.6e+00 3.6e+00 10 12 1.1e+01 1.1e+01 16 17
Pt 1.2e-01 3.9e-02 146 136 1.7e-01 2.0e-01 74 99 2.0e-01 1.1e-01 80 116 1.8e-01 1.8e-01 65 75
Rb 2.9e+03 3.0e+03 7 4 4.2e+03 4.2e+03 3 4 1.0e+04 1.0e+04 5 3 1.2e+04 1.2e+04 3 3
Re 2.6e+01 2.6e+01 6 3 4.4e-02 3.5e-02 67 100 3.6e-02 2.1e-02 99 120 3.1e-02 2.3e-02 77 96
Sb 3.9e+01 3.4e+01 39 36 2.6e+01 2.4e+01 37 20 6.5e+00 5.5e+00 67 25 2.9e+01 2.1e+01 59 22
Se 3.5e+02 3.9e+02 50 37 3.7e+01 2.8e+01 99 117 3.3e+01 1.9e+01 100 131 6.1e+01 5.1e+01 86 130
Sm 1.8e+01 1.8e+01 17 9 7.0e+00 7.0e+00 14 13 2.9e+00 2.6e+00 33 36 8.0e+00 8.5e+00 23 16
Sn 7.4e+01 5.1e+01 139 33 1.7e+01 1.6e+01 29 28 4.3e+00 2.9e+00 97 80 1.2e+01 1.3e+01 64 68
Sr 1.7e+04 1.7e+04 8 6 2.7e+04 2.7e+04 3 3 1.9e+04 1.9e+04 3 3 2.1e+04 2.1e+04 6 3
Ta 5.6e-01 4.8e-01 72 69 1.6e+00 1.6e+00 45 51 9.0e-01 4.9e-01 144 101 1.7e+00 1.4e+00 53 23
Tb 2.6e+00 2.6e+00 15 18 1.1e+00 1.0e+00 25 18 5.9e-01 5.8e-01 24 31 1.0e+00 9.8e-01 20 17
Te 1.1e+01 7.6e+00 91 101 8.2e+00 6.0e+00 61 30 5.8e+00 5.9e+00 16 22 4.5e+00 4.8e+00 37 32
Th 4.5e+01 4.4e+01 15 21 6.0e+00 5.7e+00 25 12 1.9e+00 1.5e+00 86 44 6.2e+00 5.8e+00 24 26
Ti 2.3e+03 2.3e+03 19 15 3.1e+03 3.0e+03 12 16 8.9e+02 8.2e+02 23 15 4.1e+03 4.1e+03 15 9
Tl 1.4e+01 1.5e+01 21 22 1.6e+01 1.6e+01 12 6 3.1e+01 3.0e+01 11 6 3.8e+01 3.7e+01 17 16
Tm 6.7e-01 8.0e-01 40 41 1.6e-01 1.6e-01 31 35 1.1e-01 9.7e-02 48 48 2.4e-01 1.8e-01 58 45
U 2.9e+03 3.1e+03 15 11 2.3e+00 2.4e+00 20 17 5.2e-01 4.1e-01 93 56 2.3e+00 2.3e+00 18 25
V 3.0e+02 3.1e+02 9 8 2.4e+02 2.4e+02 4 4 4.8e+01 4.7e+01 18 22 2.3e+02 2.3e+02 6 6
W 1.1e+02 7.8e+01 88 29 4.2e+00 3.6e+00 47 30 9.1e-01 9.0e-01 44 35 4.3e+00 4.2e+00 21 26
Y 6.1e+01 6.3e+01 13 11 3.1e+01 3.0e+01 16 12 3.2e+01 3.1e+01 20 28 3.3e+01 3.3e+01 14 12
Yb 4.9e+00 4.9e+00 18 19 2.1e+00 2.1e+00 28 25 1.2e+00 1.1e+00 41 46 2.2e+00 2.2e+00 34 33
Zn 6.3e+04 6.3e+04 7 3 1.0e+05 1.0e+05 3 3 5.6e+04 5.5e+04 2 2 8.6e+04 8.7e+04 3 3
Zr 8.4e+01 8.0e+01 16 18 3.8e+01 4.0e+01 15 16 7.4e+00 8.1e+00 70 81 4.4e+01 4.4e+01 23 16

1.1.3 Comparison of reference values with measurement values

The preanalysed values are provided from the measurements of the reference material powder at external labs, in this case ACTLAB.

X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

Figure 1.1: X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

Figure 1.2: X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

Figure 1.3: X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

Figure 1.4: X-charts of UPDEEP_SPRY_NEED_DRY/UPDEEP_SPRY_TWIG_DRY/UPDEEP_SPRY_BARK_DRY SRMs analysed with the routine samples (dots) vs. the preanalysed SRM values (mean as solid line, 1st standard deviation as dashed line.) The lines of the predefined values are missing if the SRM values were below detection limit. See Table 1.1 for the numbers of the preanalysed SRMs and their missing values. The two laboratory batches (A20-02249, A20-02250) are distinquised by colour.

The following elements were discarded due to poor precision and repeatability when compared to the reference values: B, Ga, Ge, Nb, Pd, Th, Tm, Zr, Ca, K, P, and Na.

Of these elements, also the main elements Ca, K, P, and Na exhibited poor statistical performance. Despite this, the X-charts for these elements showed a somewhat consistent pattern. This suggests that the issues may stem from factors such as the OES measurement process or potential problems with dry weight measurements, rather than inherent issues with the elements themselves.

Given this, Ca, K, P, and Na were retained in the selection and were not discarded, as their behavior could be attributed to measurement artifacts rather than actual analytical errors.

Thus, only these elements should be discarded due to poor performance in the reference materials: B, Ga, Ge, Nb, Pd, Th, Tm, Zr.

1.2 Step 2: Drift and offset correction

Drift and offset correction was made based on the routine samples, laboratory and field replicate samples.

First, a statistical test was conducted to assess whether significant drift occurred within either batch; if detected, a linear drift correction was applied. Second, an analysis of variance (ANOVA) was performed between batches to identify significant differences, and a correction was applied to align the batches when necessary. Minor drift and batch offsets were observed between the two laboratory batches across all data subsets.

1.2.1 Before drift correction

Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.5: Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.6: Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.7: Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.8: Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.9: Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.10: Raw data concentrations of routine samples, laboratory and field replicates of presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

1.2.2 After drift correction

Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.11: Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.12: Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.13: Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.14: Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.15: Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

Figure 1.16: Drift and offset corrected concentrations of routine samples, laboratory and field replicates presented in the sequence analysed in the laboratory. The two laboratory batches (A20-02249, A20-02250) are presented with colours.

1.3 Step 3: Uncertainty modelling and laboratory precision

Uncertainty modelling was performed using laboratory replicate samples. The relative standard deviation (RSD) was calculated based on existing replicate samples. Then, an uncertainty function was fitted to the RSD and mean replicate value pairs. This model was developed by Hawkins (2014) in A Model for Assay Precision doi link and is also published in Eurachem/CITAC Guide: Quantifying Uncertainty in Analytical Measurement (Third edition), in Annex E pdf link. The laboratory precision for each sample was then calculated based on the fitted function and the sample’s concentration value.

Table of number of lab replicates per tissue.

Table 1.4: Number of laboratory replicates used for uncertainty modelling and calculation of the laboratory precision.
Tissue n
Norway spruce bark 5
Norway spruce needle 9
Scots pine bark 5
Common juniper needle 3
Norway spruce twig 7
Common juniper twig 2

Examples for the uncertainty functions:

For each sample and each element, a modelled measurement uncertainty is calculated based on these functions and expressed as RSD. As the concentration levels of various tissue types can differ widely, the uncertainty can also vary significantly between tissue types. Therefore, the elements considered potentially difficult due to high uncertainty are considered separately by tissue type.

Please note: for three elements (Be, Re, and W), the lab did not provide replicate values. Therefore, no uncertainty functions could be calculated for these three elements, and they were removed from the analysis.

Table 1.5: Median of the modelled measurement uncertainty, expressed as relative standard deviation (RSD). Elements with high median RSD (>15%) were excluded from further analysis (show as red in the table).
Tissue Ag Al As Au B Ba Bi Ca Cd Ce Co Cr Cs Cu Dy Er Eu Fe Ga Gd Ge Hf Hg Ho In K La Li Lu Mg Mn Mo Na Nb Nd Ni P Pb Pd Pr Pt Rb Sb Se Sm Sn Sr Ta Tb Te Th Ti Tl Tm U V Y Yb Zn Zr
Common juniper twig 17 8 22 42 7.3 2.2 8.1 1 2.7 4.9 2.5 14 7.2 1.9 11 16 4.8 4 22 12 74 22 4.9 17 31 2.1 8.3 16 420 1.8 1.9 12 3.9 8.7 9.5 3.3 2.1 3.6 8 8.7 21 1.9 39 33 13 110 1.3 5.2 17 49 13 11 9.6 20 20 4.3 13 17 1.9 18
Norway spruce bark 4 8 2.8 49 12 2 4.4 0.88 2.6 4.3 3.4 15 6.5 1.9 9.7 16 3.9 3.8 17 9.6 19 25 3.6 17 19 2.1 8.2 36 440 1.8 1.5 17 3.3 15 9.2 4.9 4.6 3.1 6.6 8.4 47 1.9 17 31 10 59 1.2 4.6 16 48 13 11 3.6 21 14 2.8 13 14 1.4 19
Scots pine bark 15 8 5.6 59 29 3.6 5.3 2.5 2.6 6.5 4.6 16 6.7 1.9 16 17 7.9 4.4 11 17 9.4 32 3.7 17 33 2.1 9.1 52 490 1.8 2.1 15 5.2 22 11 5.8 6.1 3.3 15 13 28 1.9 14 33 19 56 1.5 6.4 21 50 13 11 2.9 26 21 3 13 20 2.1 25
Common juniper needle 38 8 74 63 6.6 2.6 9.3 1.1 3.2 8.7 2.4 16 6.9 1.9 19 18 6 4 76 22 0 34 4.4 18 54 2.1 9.7 39 310 1.8 1.6 7.6 16 16 14 2.9 2 7.9 7.6 17 52 1.9 66 39 29 140 1.3 7.9 28 46 13 11 30 32 42 7.6 13 29 2.2 29
Norway spruce twig 3.8 8 17 32 8.1 2.1 12 2.7 2.9 5 2.9 13 5.6 1.8 11 16 4.2 4 15 12 29 22 4.9 17 51 2.1 8.5 9.5 260 1.8 1.5 13 3 7.3 9.5 3.1 2 3.6 8.9 8.8 43 1.9 42 40 14 96 1.3 6.7 16 49 13 11 2.7 22 20 4.3 13 16 1.5 17
Norway spruce needle 11 8 59 52 7.5 2.3 22 2 6.4 24 3.9 18 5.5 2.1 36 22 6 4.9 41 63 310 73 5.3 25 93 2.1 19 10 720 1.8 1.5 41 8.7 50 32 3.5 2 16 11 54 45 1.9 160 33 68 330 1.4 8.3 62 48 13 14 3 48 100 13 13 47 1.5 58

1.4 Step 4: Field precision

Field precision was assessed using replicate samples collected in the field.

Table 1.6: Number of field replicate pairs per tissue type
Tissue V1
Scots pine bark 9
Norway spruce bark 10
Norway spruce twig 10
Common juniper needle 10
Norway spruce needle 10
Common juniper twig 10

For the field replicates, the decision process focuses on the log-ratios of elements because raw concentrations can vary due to mass dilution effects. The variability of these log-ratios across different elements is considered, as it can differ at various locations. The aim is to filter out elements with high variability in their log-ratios across multiple locations.

To do this, we count how many times the relative standard deviation (RSD) of a log-ratio exceeds 20% for each location. The values range from 0 to 10, where 0 means the RSD is always less than 20% for that log-ratio, and 10 means it’s always greater than 20%.

Only elements that passed the measurement uncertainty QAQC test for the specific tissue were used for these log-ratios.

Examples for the log-ratio variability decision triangles:

To determine which elements most frequently contribute to high log-ratio variability in the field, we counted how often each element was involved in log-ratios with high variability. This count was done for both elements in the log-ratio (numerator and denominator), and then the average of these counts was calculated for each element.

1.5 Step 5: Summary of elements

Here is a summary of the elements that were carried forward to the statistical analysis.

Table 1.7: Element selection across different sample types. Elements which passed all QAQC steps are denoted by ‘+’. ‘MU’, ‘FU’ or ‘SRM’ indicates why the element had been discarded. ‘MU’ stands for Measurement Uncertainty, ‘FU’ denotes Field Uncertainty, and ‘SRM’ refers to Standard Reference Material. Note that FU analysis was only carried out for elements which passed the MU QAQC step.
Element Common.juniper.needle Common.juniper.twig Norway.spruce.bark Norway.spruce.needle Norway.spruce.twig Scots.pine.bark
Ag MU MU FU FU
MU
Al
As MU MU
MU MU
Au MU MU MU MU MU MU
B SRM SRM SRM SRM SRM MU, SRM
Ba
Be MU MU MU MU MU MU
Bi
MU FU
Ca
Cd
Ce
MU
Co
Cr MU
MU MU
MU
Cs
Cu
Dy MU
MU
MU
Er MU MU MU MU MU MU
Eu
FU FU
Fe
Ga MU, SRM MU, SRM MU, SRM SRM SRM SRM
Gd MU
MU
MU
Ge SRM SRM MU, SRM SRM SRM FU, SRM
Hf MU MU MU MU MU MU
Hg
Ho MU MU MU MU MU MU
In MU MU MU MU MU MU
K
La
MU
Li MU MU MU
MU
Lu MU MU MU MU MU MU
Mg
Mn
Mo
MU MU
MU
Na MU
Nb MU, SRM SRM MU, SRM MU, SRM FU, SRM MU, SRM
Nd
MU
Ni
P
Pb
MU
Pd SRM SRM SRM SRM SRM MU, SRM
Pr MU
MU
Pt MU MU MU MU MU MU
Rb
Re MU MU MU MU MU MU
Sb MU MU MU MU MU
Se MU MU MU MU MU MU
Sm MU
MU
MU
Sn MU MU MU MU MU MU
Sr
Ta FU
FU FU
Tb MU MU MU MU MU MU
Te MU MU MU MU MU MU
Th SRM FU, SRM FU, SRM SRM FU, SRM SRM
Ti
Tl MU FU FU FU FU FU
Tm MU, SRM MU, SRM MU, SRM MU, SRM MU, SRM MU, SRM
U MU MU
MU MU MU
V
W MU MU MU MU MU MU
Y
Yb MU MU
MU MU MU
Zn
Zr MU, SRM MU, SRM MU, SRM MU, SRM MU, SRM MU, SRM

2 Environmental variables

2.1 Field precision

The ten field replicates had the following relative standard deviations: