An Introduction to Environmental Chemistry

4.9.3 Soils with gley horizons

Gley horizons form when the water table is present within the soil profile. Soils
with gley horizons (denoted ‘g’) are typically aquepts (gleysols), a suborder of the
inceptisols (Fig. 4.22). Gley horizons may be either Bg and/or Ag horizons,
depending on the height of the water table influence in the soil profile (Fig. 4.25).

The Chemistry of Continental Solids 117

Ah

L

Ea

Bs

C

Fulvic acids

Fe and Mn

Water complexes

Acidic leaf litter

Organic layer formed by soil macro- and

micro-flora processing litter

Formation of water-soluble fulvic acids

Spodic horizon: metal ions reprecipitate

(illuvation) due to oversaturation or

degradation of fulvic acids

Fulvic acids chelate metal ions

(e.g. Fe and Mn) enhancing their solubility

Downward percolating water transports

metal complexes (eluvation)

Fig. 4.24Schematic diagram of a spodosol (podzol) with an explanation of horizon
formation. The resulting horizons are comparable to those in Plate 4.2(b). The master
horizons are typically centimetres to tens of centimetres thick.