Adsorption/desorption of organic anions in Brazilian Oxisols

• Published in: Communications in soil science and plant analysis Vol. 37; no. 9-10; pp. 1367 - 1379
• Main Authors: Marchi, G, Guilherme, L.R.G, Lima, J.M, Chang, A.C, Fontes, R.L.F
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 01-01-2006; Taylor & Francis
• Subjects: A horizons; acetic acid; adsorption; Agronomy. Soil science and plant productions; anions; B horizons; Biological and medical sciences; buffering capacity; citric acid; desorption; Fundamental and applied biological sciences. Psychology; ionic strength; Isotherms; organic anions; oxalic acid; Oxisols; sodium chloride; soil pH; Soil science; soil solution; specific adsorption; tropical soils; variable-charge soils; Brazil; South America; America; Soils; Organic anion; Adsorption; Isotherms; Isotherm; variable-charge soils; Desorption; organic anions; Oxisols; specific adsorption
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1080/00103620600626841

Organic anions affect solute mobility in soils. This study evaluated citrate and oxalate adsorption (0 to 4 mmol L(-1), soil-solution 1:100, pH 5.5, ionic strength 30 mmol L(-1) as NaCl, 72-h reaction) and desorption (pH 5.5, 30-mmol L(-1) NaCl, 72 h) on A- and B-horizon samples of two Brazilian Oxisols. Langmuir and Freundlich isotherms were used to assess adsorption maximum, distribution coefficients (Kf, Ku), and buffer index. Adsorption maximums (mol kg(-1)) for red Latosol-A, red Latosol-B, red-yellow Latosol-A, and red-yellow Latosol-B horizons follow: citrate 0.0318, 0.0272, 0.0289, 0.0392; oxalate 0.0641, 0.0329, 0.0538, 0.0380. Kf (mol(1-1/n) kg(-1) L(1/n)) follows: citrate 0.3550, 0.3781, 0.4211, 0.2024; oxalate 1.0916, 0.0637, 1.8228, 0.0922. Buffer index (mol kg(-1))(mol kg(-1))-1 follows: citrate 0.0841, 0.0756, 0.0738, 0.0264; oxalate 0.3787, 0.0862, 0.3233, 0.1082. Both anions showed great affinity for variable-charge soils. The distribution curves for Ku showed higher adsorption energy in B- than in A-horizons.