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Abstract "Heft 8"


Freiburger Bodenkundliche Abhandlungen

Schriftenreihe des
Institut für Bodenkunde und Waldernährungslehre
der Albert-Ludwigs-Universität Freiburg i.Br.
Schriftleitung: F. Hädrich


Heft 8


Karl Keilen


Spurenelementverteilung und Bodenentwicklung im Bärhaldegranit
(Südschwarzwald)


Freiburg im Breisgau 1978

ISSN 0344-2691

Summary:

Soil development and trace element (Be, Cd, Co, Cu, Pb, V, Zn) distribution were studied in the Baerhalde granite area in the southern Black Forest near Neuglashuetten, Feldberg (1000 - 1300 m a.s.l.). The climate is perhumid (P = 2000 m p.a.) and cool (T  = 4°C), the actual vegetation is predominantly spruce forest.
Parent material is base-poor Baerhalde granite and associated rocks. The Baerhalde ridges carry relic periglacial scree and patterned ground, the upper slopes mostly gelifluction deposits. Soils on the lower slope and on the valley bottom are developed from glacial till and periglacial, partly fluviatile sediments.
Dominant soil types are on the ridge and upper slope brown forest soils and podzols, on the lower slopes and on the valley bottom stagno-gley, forest bog and ochreous earth. The soils are moderately weathered. The mineral content of the profiles reflect still the parent material fairly closely.
The brown earth corresponds to the "sols brun ocreux", the podzols to the "podzols modals" of SOUCHIER (1971). Lateral water movement in the stagno-gley and bog removes Fe, Mn and Al finally into the ochreous earth. The soils are very acid and the base saturation is low.
Balances showed considerable losses in Na, P, K, Ca, Mg and Mn. Al and Fe are mostly redeposited within the area; Zr, Ti and Si are largely immobile, and consequently relatively accumulated.
The Baerhalde granite is comparatively poor in trace elements, except for Be. The studied trace elements are chiefly bound in biotite, less in muscovite and orthoclase. As a result of physical weathering especially the fine fractions are enriched with Be, Cd, Co, Cu, V and Zn, the coarser fraction with Pb.
High levels of Pb and Cd in the humus originate mainly from far-distant immission, less from natural cycling, while Co, Cu, V and Zn are to a noticably larger degree absorbed in plants. Be apparently is hardly included in the cycling.
Cd and Co are very mobile, depending on pH and Eh. Cd is accumulated in the peats of the bogs, Co in the sesqui-oxide accumulation horizons of the ochreous earth. Be also moves along pH gradients and is absorbed in podzols, by sesqui-oxides in the ochreous earth, and by crystalline muscovite-illite of the silt fraction in the hydromorphic soils. Cu and Zn are strongly bound by organic matter and sesqui-oxides. V and Pb are relatively immobile, but Pb is redeposited within the organic complexes.
The pedochemical characteristics of Be are similar to Al, those of Cd, Co and Zn to Mn, those of Cu and V to Fe. The Pb depth functions correspond to those of humus.
Cd is most likely to cause harm to man if immissions would increase, as a result of its high toxidity and mobility. Pb would be largely immobilized. Be would be increasingly more redeposited and removed. Co, Cu, Zn (and V) are in short supply as nutrients and increased immission would initially improve supply.



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