Mikko Sillanpää

Hivenaineet suoprofiilissa

Sillanpää M. Hivenaineet suoprofiilissa.

Tiivistelmä

Total contents of various trace elements in Finnish soil types are presented. The tendency for the trace element content to decrease with increasing particle size in mineral soil is discussed. It is believed to be associated with the geological origin of the soil matrix and especially with the relative resistance to weathering of the minerals from which the trace elements are derived. Fine textured soils are likely to have been derived from more easily weatherable rocks and minerals than coarse soils, in which resistant minerals like quartz are known to be the main constituents. On the other hand, those minerals containing the trace elements in question are among the most easily weatherable, while quartz is likely to contain none of these elements. The characteristic distribution of 13 trace elements in two peat profiles X', as well as the low content of most elements in peats as compared with those in mineral soils are explained as a result of the transport of elements by plants from lower strata: The trace elements can be considered as originating from the mineral soil underlying the peat. Plants which grow and then decay, first on the mineral soil and later on the peat, obtain the trace elements from the subsoil and, when dying, cause these elements to accumulate on the surface layer. When the peat layer becomes thicker contact between the plant roots and the mineral subsoil is gradually reduced until finally the bulk of the roots are no longer in contact with the mineral soil. Subsequendy, the plants lift up elements from the lower peaty layers of the profile, thus decreasing the element content of the lower parts of the peat. For this reason, the trace element content in the peat profile decreases as the peat thickness increases; extreme cases of this development are the "raised bogs" of Sphagnum peat which are known to have a very low content of all the nutrients. The relatively high concentration at the immediate surface is obviously a result of the elements lifting activity of the most recent generations of plants; the elements have been lifted to the surface and are awaiting removal by future generations of plants. x) Orig. pubi.: Sillanpää, M. 1972. Distribution of trace elements in peat profiles. Proc. 4th Intern. Peat Congr. I-IV: 185-191.

Vastaanotettu 31.10.2017 Julkaistu 1.1.1975

Katselukerrat 2073

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