Find in the text above English equivalents for the following words and expressions and memorize them.

1) напочвенный покров

2) лесная подстилка (поверхность почвы в лесу)

3) первичные продуценты

4) высшие растения

5) неоднородная (гетерогенная) смесь

6) аморфные соединения

7) растительные и животные остатки

8) разъединять (диссоциировать)

9) ёмкость катионного обмена (ЕКО)

10) углубления

11) останки и фекалии

12) водяные животные

13) пыльца (пыльцевые зерна)

14) устойчивый – неустойчивый (лабильный)

15) разлагаемые растения

16) быть подверженным чему-л.

17) стремиться/приближаться к равновесию/ балансу

18) садовый торф

19) компосты

20) мульчирование

TEXT 2.

Soil Minerology

Mineralogical Composition of Rocks

Most elements of the earth's crust have combined with one or more other elements to form the minerals. The minerals generally exist in mixtures to form rocks, such as the igneous rocks, granite and basalt. The mineralogical composition of igneous rocks, and the sedimentary rocks, shale and sandstone, are given in Table 10.1. Limestone is also an important sedimentary rock, which is composed largely of calcium and magnesium carbonates, with varying amounts of other minerals as impurities. The dominant minerals in these rocks are feldspars, amphiboles, pyroxenes, quartz, mica, apatite, clay, iron oxides (goethite), and carbonate minerals.

The kaolinite, even though very resistant to further weathering, may be decomposed and disappear from the soil. The reaction:

The decomposition of kaolinite resulted in the formation of gibbsite, a mineral more resistant to weathering than the kaolinite. Both kaolinite and gibbsite are clay minerals that have distinctly different properties. Thus, as weathering proceeds and the mineralogical composition of the soil changes, the chemical and physical properties also change. The loss of silicic acid by leaching results in the progressive loss of silicon. There is a progressive increase in the accumulation of aluminum, because the aluminum tends to be incorporated into resistant secondary minerals that accumulate in the soil. For this reason, an indicator of weathering intensity is the silica: alumina ratio (Si0 ² /A1 ²03). As silicon is lost from the soil by leaching and aluminum accumulates, the silica: alumina ratio decreases. The Si0 ² /A1 ²03 ratio decreases from 3:1 for albite to 1:1 for kaolinite. Other weathering reactions include oxidation, dissolution, hydration, reduction, and carbonation.

SUMMARY

In an acid soil environment, weathering of minerals is stimulated. Minerals weather at different rates, depending on their resistance to weathering. In general, primary minerals weather and secondary minerals are formed. Over time, the mineralogical composition of the soil changes and, consequently, soil properties change. Weathering releases ions to the soil solution. Many of these ions are plant nutrients. Some ions precipitate to form secondary minerals and some ions are leached from the soil. Minimally and moderately weathered soils tend to be rich in primary minerals and to be fertile with high cation exchange capacity. Intensively weathered soils are depleted of primary minerals. Few nutrient ions are released and soils are infertile. The clay minerals in intensively weathered soils have low cation exchange capacity. Nutrient ions adsorbed to the surfaces of clay particles represent a reservoir of nutrients that is exchangeable and available to plants. Ultimately, soils become "weathered out" and have almost no capacity to support plants. Such soils may be mined for ore. Clay edge Al-OH protonate in acid soils and form sites of anion exchange capacity and deprotonate in alkaline soils and form sites of cation exchange capacity.

(H.D. Foth, Fundamentals of Soil Science)

Find in the text above English equivalents for the following words and expressions and memorize them.

1) земная кора

2) магматические горные породы

3) гранит

4) базальт

5) осадочные горные породы

6) глинистый сланец

7) примеси

8) шпат

9) слюда

10) гётит