Volume 6 (2010): Article 6

Chemical properties of surface peat on forest land in Estonia.

by R. Kõlli, E. Asi, V. Apuhtin, K. Kauer and L.W. Szajdak

Published online: 31.10.2010

Summary

The chemical properties of surface peat cover (SPC) were studied in the context of Estonian pedoecological conditions. SPC comprises the superficial layers of fens (Group 1) and transitional bogs (Group 2), together with slightly acid peaty mull / strongly acid peaty moder (Group 3) and very strongly acid peaty mor (Group 4) layers overlying mineral soils. Thus, it spans organic soils, namely Histosols (Groups 1 and 2); together with Histic Gleysols (Group 3) and Histic Podzols (Group 4), which are developmentally intermediate between organic and mineral soils. Moderately acid eutrophic (Group 1) and very strongly acid mesotrophic (Group 2) peats (forest litter layers excluded) were uniformly characterised up to 40 cm depth; whereas for Groups 3 and 4 we examined the full thickness of available peat layers, which ranged from 10 to 30 cm. The results show that Al, K and heavy metal contents are significantly higher and organic carbon content is lower in Histic Soils (3, 4) than in Histosols (1, 2). The amounts of Ca, Mg, Mn and Fe are significantly higher and C:N ratio, exchangeable acidity and content of free H⁺ lower in less acidic (1, 3) than in more acidic (2, 4) soil types. The total concentration of elements (excluding heavy metals) extracted by nitro-hydrochloric acid (aqua regia) is considerably higher in less acidic soils, at 28–45 g kg^-1 (1, 3) versus 10–12 g kg^-1 (2, 4); and mean contents of individual elements decrease in the order Ca(51%) > Fe(20%) > S(10%) ? Al(10%) > Mg(3%) ? P(3%) > K(2%) > Mn(1%) > Na(<1%). The most abundant heavy metals are Pb (12–33 mg kg^-1), Zn (7–41 mg kg^-1), Cu (3–12 mg kg^-1), Cr (2–23 mg kg^-1) and Ni (2–8 mg kg^-1); Cd and Hg contents are very low, ranging from 0.2 to 0.5 mg kg^-1. The dominant exchangeable basic cations are Ca²⁺ (78–93%) and Mg²⁺ (7–15%), and the peat contains much smaller amounts of K⁺ (1–6%) and Na⁺ (<2%). The total exchangeable acidic cations (1–14 cmol kg^-1) are dominated by H⁺ (51–83%) and Al³⁺(15–47%), whereas Mn and Fe (2–4%) cations are modestly represented.

Citation

Kõlli, R., Asi, E., Apuhtin, V., Kauer, K. & Szajdak, L.W. (2010): Chemical properties of surface peat on forest land in Estonia. Mires and Peat 6: Art. 6. (Online: http://www.mires-and-peat.net/pages/volumes/map06/map0606.php)

Reviewers

IMCG and IPS acknowledge the work of the reviewers.