**3. Objects and methods**

We've studied the content of lanthanides in the soils of the impact zone of the Cherepovets steel mill. CSM is one of the most powerful sources of technogenic impact on the European territory of Russia. Pollution with heavy metals on the investigated territory has been monitored since 1955 [26, 27]. We selected soil samples from five soil profiles at different distances from the CSM. Profile C1 is located near the CSM boundary, and profiles C2–C5 are at a distance of 2, 5, 12, and 30 km to the north from it.

The soil of profile C1 is represented by an industrizem—strongly technogenic-transformed soil. The top layer of this soil contains a large number of fallout particles, containing heavy metals, which adhere the soil mass, making it difficult to take samples from deeper layers (only one sample from 0 to 20 cm layer was selected).

The sequential fractionation of the lanthanides in soils was carried out by using the McLaren and Crawford scheme [29]. The following fractions were separated: exchangeable cations, fraction of specifically sorbed ions, fraction bound to organic matter, fraction bound to (hydr) oxides of iron and manganese, and residual (strongly bound to aluminosilicates) fraction.

<sup>O</sup> **Total organic carbon, % Sum of exchangeable** 

**cations, cmolec**

Lanthanides in Soils of the Cherepovets Steel Mill http://dx.doi.org/10.5772/intechopen.80294

**/kg**

71

The quantitative determination of the lanthanides in the obtained extracts was carried out by the inductively coupled plasma mass spectrometry on 7500a ICP-MS (Agilent Technologies), according to [28]. The lower determination limit of measured concentrations of the lanthanides does not exceed 0.001 mg/L, which corresponds to a total metal content equal to 0.05 mg/kg or forms of compound content of 0.01 mg/kg. The relative error of determination did

The analysis of the results shows that changes in total content of the lanthanides are observed in profiles C1 and C2 located in close vicinity to the pollution source. We observe either a significant increase or some decrease in the total content of the lanthanides (primarily Pr and Tb)

not exceed 20%.

**4. Results and discussion**

**4.1. Total content of the lanthanides**

**Profile Horizon, depth, cm pH**<sup>H</sup>**<sup>2</sup>**

C1 U, 0–20 7.60 Not determined

C2 A, 0–20 7.14 2.65 18.79

C3 A, 0–23 6.89 3.17 21.10

C4 A, 0–21 6.77 2.95 19.21

C5 A, 0–23 6.85 2.86 20.36

**Table 1.** Some chemical properties of soils in the CSM impact zone.

B, 20–35 7.05 0.68 15.05 C, 35–65 7.25 0.15 12.31

B, 23–41 6.92 0.51 16.32 C, 41–70 7.12 0.12 13.58

B, 21–38 6.89 0.57 14.39 C, 38–70 7.10 0.14 11.06

B, 23–45 6.93 0.49 16.54 C, 45–75 7.14 0.17 11.88

Total content of the lanthanides in soils is given in **Table 2**.

compared to soils, located at a considerable distance from the CSM.

The soils in other profiles are represented by soddy-carbonate leached (Rendzic Leptosols) also formed on light cover loam and underlain by carbonate calcareous moraine. The profiles of these soils include humus-accumulative A horizons with thickness from 10 to 25 cm, gray color, of medium granular structure, transitional B horizons from 15 to 30 cm, and calcareous C horizons of parent rock. Samples for chemical analysis have been taken from these horizons.

According to their chemical properties (**Table 1**), the investigated soils are quite typical representatives of soddy-carbonate leached soils.

The upper humus-accumulative horizon is characterized by a rather high content of organic carbon (in comparison with the underlying horizons) and weakly acid reaction, which becomes weakly alkaline down the profile. Near the source of pollution, weakly alkaline reaction is observed throughout the profile because of the input of a large number of technogenic compounds on the soil surface. The content of exchangeable cations is typical for light loamy soils.

To determine the total content of the lanthanides, soil samples were treated with a mixture of hydrofluoric, hydrochloric, and nitric acids in medium-pressure autoclaves in the laboratory microwave Ethos One (Milestone) according to [28].

Acid-soluble forms of the lanthanides were extracted from soils by the treatment with 1M HNO<sup>3</sup> with a ratio of soil:solution equal to 1:10 [29].


**Table 1.** Some chemical properties of soils in the CSM impact zone.

The sequential fractionation of the lanthanides in soils was carried out by using the McLaren and Crawford scheme [29]. The following fractions were separated: exchangeable cations, fraction of specifically sorbed ions, fraction bound to organic matter, fraction bound to (hydr) oxides of iron and manganese, and residual (strongly bound to aluminosilicates) fraction.

The quantitative determination of the lanthanides in the obtained extracts was carried out by the inductively coupled plasma mass spectrometry on 7500a ICP-MS (Agilent Technologies), according to [28]. The lower determination limit of measured concentrations of the lanthanides does not exceed 0.001 mg/L, which corresponds to a total metal content equal to 0.05 mg/kg or forms of compound content of 0.01 mg/kg. The relative error of determination did not exceed 20%.
