**Author details**

It is clearly shown in **Figure 9** that the content of lanthanides in nitric acid extract from the most contaminated soil C1 significantly exceeds the sum of isolated fractions. In other less polluted soils, both these indices are practically equal. Terbium and cerium are out of the general trend in soil C1, and the differences in the behavior of cerium hadn't been noticed earlier and can be associated not with soil contamination by this element but its variable valency and its variation when forms are extracted from the soil. The extraction of lanthanides by nitric acid from the soil of C1 is higher than the amount of other fractions; the inflow of chemically resistant technogenic compounds of lanthanides (presumably oxides) into the soil that could

**1.** Because of different natural abundances of lanthanides, their comparative study in soils is impossible without techniques that allow eliminating this factor: the normalization of the content of elements by a standard object similar to the investigated soils in terms of composition and conditions of formation and determination of extraction degree of various forms of lanthanide compounds. Comparison of distribution diagrams of lanthanides constructed with these indicators allows deriving both qualitative and sometimes quantitative differences in the behavior of these elements and in the technogenic contamination

**2.** The soils of the investigated territory are contaminated with the lanthanides due to CSM activities. The lanthanides are characterized by a high degree of extraction of acid-soluble

**3.** A significantly increased content of praseodymium and terbium was found in soils near CSM. In these soils a less increase in the content of other light lanthanides, from lanthanum to gadolinium inclusive, was also determined. Technogenic contamination also leads to an increase in the amount and to changes in extraction degree of acid-soluble forms of

**4.** About 80–95% of the total content of lanthanides in the soils of the impact zone of CSM is concentrated in the residual fraction; thus, they are represented by extremely chemically stable compounds. The main soil components determining the background level of the lanthanides in investigated soils are aluminosilicate minerals, strongly fixing the lanthanides in their structure, and the compounds fallen into the soils as a result of the CSM

**5.** As a result of soil processes, a part of the lanthanides is bound to organic matter and Fe and Mn (hydr)oxides (5–18% and 0.1–5% of the total content correspondingly). The individual properties of the lanthanides are clearly manifested in their interaction with these soil components. The largest part of the fraction, bound to organic matter, contains medium lanthanides; the part bound to Fe and Mn (hydr)oxides contains heavy lanthanides.

not be extracted under sequential fractionation is clearly indicated.

**5. Conclusions**

80 Lanthanides

of soils with lanthanides.

lanthanides from soils.

forms (5–40% of the total content).

impact are also chemically stable.

Dmitry V. Ladonin

Address all correspondence to: ladonin@inbox.ru

Moscow State University, Moscow, Russia
