Effects of Dissolved Organic Carbon on Phosphate Retention on Two Calcareous Soils

Abstract

To evaluate the effects of dissolved organic carbon (DOC) on phosphate retention (including both sorption and/or precipitation reactions) on soils, experiments were performed by using two typical calcareous soils from southeastern Spain (Calcic Regosol and Luvic Xerosol) and two different types of DOC: (1) extracts from a commercial peat (DOC-PE) and (2) high-purity tannic acid (DOC-TA). The experiments were carried out from a 0.01 M CaCl2 aqueous medium at 25 degrees C. The results obtained show that the presence of both DOC-PE and DOC-TA, over a concentration range of 15 (DOC-15) to 100 (DOC-100) mg L(-1), produces in all cases a decreasing amount of phosphate retained in the soils studied, the decrease observed being higher when DOC-PE is used as source of DOC. The values of the decrease observed when DOC-PE was added ranged between 19.9% (DOC-15) and 15.6% (DOC-100) for the Calcic Regosol and between 17.3% (DOC-70, DOC-100) and 14.6% (DOC-15) for the Luvic Xerosol. The variation observed when DOC-TA was added ranged between 8.5% (DOC-100) and 0.5% (DOC-35) for the Calcic Regosol and between 7.0% (DOC-100) and 1.0% (DOC-15) for the Luvic Xerosol.

Effect of phosphate on phenanthrene sorption in soils

“…At the same time, the presence of phosphate can definitely affect the characteristics of environmental microinterfaces through non-biological reactions. For example, it has been demonstrated that phosphate can be specifically adsorbed by soil minerals [15], strongly competing with dissolved organic carbon (DOC) for sorption sites [7,16] and effectively changing the composition and aggregation of dissolved humic acid on mineral surfaces [5]. On the other hand, due to its colloidal properties, DOC can enhance the apparent solubility of HOC and reduce their sorption to solid matrixes in environmental interfaces [3,[17][18][19].…”

Root and arbuscular mycorrhizal effects on soil nutrient loss are modulated by soil texture

“…This can be explained by the contribution of root exudation (Nowack et al 2008;Boddy et al 2007) and rhizosphere microbial activity (by using non-sterilised soil substrate) (GoEdde et al 1996) that would increase soil DOC. Also, DOC can interact with many soil chemicals, affecting their fate in soil (Fernández-Pérez et al 2005). The presence of the DOC may decrease P absorption (Kang et al 2011) because of the competition of organic anions with P for sorption sites (Bhatti et al 1998;Iyamuremye et al 1996) or increase of negative charge on soil surface that can inhibit P adsorption (Barrow 1989;Jiao et al 2007).…”