IngentaConnect Apparent Cation - Exchange Equilibria and Aluminium Solubility in...

Abstract:

Apparent cation–exchange equilibria and solubility of aluminium were analysed in two acidic forest soils: a Cambisol and a Cambic Podzol. Soil solution was obtained by a centrifuge drainage method from fresh soil samples and with suction lysimeters. The total positive charge of the measured cations as well as the concentrations of the cations were generally much larger in the centrifugates than in the lysimeter solutions, which implies that total charge of soil solution is larger in small pores than in large pores. Hydrogen ion in particular was concentrated in some of the centrifugates, the ratio centrifugate:lysimeter solution being over 10. The total positive charge of the measured cations decreased with increasing depth with both methods. The apparent cation–exchange coefficients K_H-Ca, K_Al-Ca, and K_K-Ca had different values in the methods, and the variation in the cation exchange coefficients was larger in the lysimeter method than in the centrifuging method. The coefficient K_Mg-Ca had similar values in both methods. The results imply that mobile solution could not have cation–exchange equilibria with bulk exchangeable cations in the soils, although solution in small pores seemed to have equilibria. Solubility of Al did not follow the solubility of an Al(OH)_3 phase in the centrifugates, and the centrifugates with a H^+ activity larger than 60 mol were undersaturated with respect to the gibbsite. Solubility of Al was between gibbsite and amorphous Al(OH)_3 in the lysimeter solutions. Differences between the centrifugates and the lysimeter solutions in the ion concentrations and in the apparent chemical equilibria were similar for both soils studied.

Keywords: acidification model; aluminium; cation–exchange; centrifuging; lysimeter

Language: English

Document Type: Regular paper

Affiliations: 1: Department of Forest Ecology, P.O.Box 24, 00014 University of Helsinki, Finland (e-mail: ari.nissinen@helsinki.fi) 2: Department of Forest Ecology, P.O.Box 24, 00014 University of Helsinki, Finland

The full text electronic article is available for purchase. You will be able to download the full text electronic article after payment.

$47.00 plus tax Refund Policy

Apparent Cation – Exchange Equilibria and Aluminium Solubility in Solutions Obtained from Two Acidic Forest Soils by Centrifuge Drainage Method and Suction Lysimeters