Pedogenesis and distribution of humic substances in Pyrenean soils, France

The role of trace minerals in chemical weathering in a high-elevation granitic watershed (Estibère, France): chemical and mineralogical evidence

“…1A). Soils in the Estibère watershed have been the subject of previous studies (Remaury, 1999(Remaury, , 2002.…”

“…Rocky crests are covered by heath and pine whereas depressions are more or less colonized by hydromorphic vegetation. Two types of soil develop over the granitic units: ranker type soils under grassland and podzolic type soils mainly located on slopes and rocky zones more or less colonized by open forest and ericaceae (Remaury et al, 1999(Remaury et al, , 2002. Both are thin, acid, and have a high organic matter content.…”

“…The clay fraction (Ͻ2 m) in the podzolic soils from the Estibère watershed represents 4 to 20% of the Ͻ2 mm fraction (Remaury, 1999(Remaury, , 2002. XRD analysis of the clay fraction indicated the presence of smectite (showing X-ray characteristics of a Na-smectite: occurrence of 12.5 Å peak on the air-dried pattern, a 17 Å peak on the ethylene glycoled pattern and their disappearance in the heated pattern), illite (10 Å ), mixed layer illite-smectite (intermediate peaks between 10 Å and 12.5 Å ), and chlorite, and to a lesser extent vermiculite (14 Å ) and kaolinite (7 Å ) in the clay fraction.…”

Characterization of Humic Acids from Raised Bog Peat

“…In humic substances from peat, concentrations of carboxyl groups and phenolic hydroxyl groups are lower (Table 1), than in humic substances from other sources (waters, soils, sediments) [2,5,6,29].…”

“…It has been shown, that the structure and properties of humic substances differ for humic acids of different [5,6], but in the same time, considering the great variability in natural organic matter properties, the actual relationship is far from being explained. Another open question can be related to the genesis of peat and fossil carbon deposits and development of peat.…”