Case Study of the Relationship between Aqua Regia and Real Total Contents of Harmful Trace Elements in Some European Soils
Table 5
Summary of consecutive stages of stepwise polynomial regression.
El.
ST
Eliminated points
0
1
2
Min
Max
2
As
S0
None
0.3632
1.1429
1.10
25.0
0.9933
S1
910
1.3257
−0.01417
1.10
15.1
0.9959
0.9321
Ba
S0
None
182
1.1243
7.95
368
0.7662
S1
909
172
1.3042
7.95
229
0.7078
0.8962
Be
S0
None
0.2167
1.4473
0.072
2.03
0.9864
S1
910
0.2118
1.4581
0.072
1.53
0.9779
0.9995
S2
910, 872
0.1907
1.5144
0.072
1.33
0.9822
0.9643
Cd
S0
None
0.0123
1.0068
0.066
12.8
0.9993
S1
995
1.0290
0.066
0.768
0.9781
0.9995
S2
995, 992
1.0436
0.066
0.768
0.9859
0.7751
Co
S0
None
0.0628
1.1422
0.58
15.7
0.9961
S1
910
1.1397
0.58
15.1
0.9962
0.9976
Cr
S0
None
−1.6570
2.3694
−0.01041
5.58
117
0.7456
S1
986, 995
1.7540
24.8
78.2
0.6822
−1.2020
Cu
S0
None
0.186
1.1291
−0.00180
4.66
64.7
0.9981
S1
995
0.829
1.0475
4.66
45.4
0.9977
0.9956
S2
995, 889
0.915
1.0376
4.66
45.4
0.9987
0.9895
Hg
S0
None
4.710
0.8848
0.00073
22.1
265
0.8963
S1
995
1.0078
22.1
116
0.9806
0.9894
Mn
S0
None
32.86
1.0340
32.1
1462
0.9988
S1
872
29.66
1.0438
32.1
1005
0.9985
0.9995
Mo
S0
None
0.1601
1.0277
0.16
4.42
0.9967
S1
867
0.1612
1.0264
0.16
2.37
0.9903
1.0000
S2
867, 910
0.1457
1.0315
0.16
2.37
0.9965
−155.6
Ni
S0
None
−0.0031
1.1213
1.50
75.0
0.9910
S1
872
1.1248
1.50
44.5
0.9821
0.9998
S2
872, 910
1.1076
1.50
39.3
0.9838
0.9805
Pb
S0
None
1.9085
1.1593
6.81
71.0
0.9632
S1
995, 910
2.9985
1.1011
6.81
33.4
0.9790
0.9739
S2
995, 910, 865
3.2856
1.0959
6.81
33.4
0.9912
0.4736
Sb
S0
None
0.3399
0.7841
0.5071
0.12
2.19
0.5253
S1
910
0.2321
1.3008
0.12
1.04
0.8837
0.8547
S2
910, 889
0.1604
1.5092
0.12
0.65
0.8825
0.8354
Sn
S0
None
0.6464
1.3820
−0.0206
0.53
15.9
0.9943
S1
995
0.7000
1.3090
0.53
2.86
0.8716
0.9230
S2
995, 881
0.5606
1.4285
0.53
2.51
0.9055
0.4721
V
S0
None
−3.88
1.7815
7.66
88.2
0.9119
S1
910
1.6942
7.66
71.0
0.8715
0.9986
S2
910, 909
1.6190
7.66
63.7
0.8669
0.8873
Zn
S0
None
3.1815
1.0472
8.11
214
0.9940
S1
995, 910
1.1685
−0.0008
8.11
187
0.9954
0.9863
S2
995, 910, 961, 909
1.1044
8.11
187
0.9985
0.7843
El.: chemical element, ST: stage of stepwise polynomial regression = 0+ 1 * + 2* (S0: preliminary which S1 and S2: main stages), 0, 1, 2: coefficients, significant are given in bold. Min and Max: lower and upper boundary of the interval of aqua regia contents (Hg: g/kg, for all other elements: mg/kg), where the equation was obtained. 2: cross-validation parameter and : external validation parameter.
