Higher Molecular Mass Organic Matter Molecules Compete with Orthophosphate for Adsorption to Iron (Oxy)hydroxide

Abstract

13The competition between orthophosphate and water-extractable organic matter 14 (WEOM) for adsorption to iron (oxy)hydroxide mineral surfaces is an important factor in 15 determining the plant bioavailability of P in soils. Chemical force spectroscopy was used to 16 determine the binding force between orthophosphate and iron (oxy)hydroxide that was coated 17 onto atomic force microscopy (AFM) tips and adsorbed with WEOM. The force measurements 18 were conducted at pH 4.65 and 0.02 M ionic strength which are representative of typical acid 19 soil solutions. The chemical composition of the WEOM was determined by ultrahigh resolution 20 electrospray ionization Fourier transform ion cyclotron mass spectrometry. The results indicate 21 a correlation between aromatic WEOM molecules that are greater than 600 Daltons and the 22 reduced binding force of orthophosphate to WEOM-adsorbed iron (oxy)hydroxide AFM tips 23 suggesting that the molecular mass of aromatic WEOM molecules plays a critical role in 24 regulating the WEOM-P interactions with surface functional groups of minerals. Based on the 25 results of this study, we show the importance of obtaining a detailed, molecular-scale 26understanding of soil processes that can help develop better management strategies to reduce 27 waste of limited P resources and adverse environmental impacts. Specifically, soil amendments 28 with greater content of high molecular mass aromatic components may positively affect 29 dissolved P use efficiency in soils by maintaining P is soil solution.

Selective Adsorption of Terrestrial Dissolved Organic Matter to Inorganic Surfaces Along a Boreal Inland Water Continuum

“…In the PLS analysis, both cations and anions were identified as negative predictors of percentage DOC adsorbed. We attribute this largely to the inherent covariation between cations and anions, although SO 4 2− and PO 4 3− tend to compete with DOM for adsorption sites (Chassé & Ohno, ; Gobran & Nilsson, ; Gu et al, ) and thereby lower the potential for DOM to adsorb, while others suggest that at least SO 4 2− is easily replaced with DOM (Tipping, ).…”

Variation in the Molecular Structure and Radiocarbon Abundance of Mineral-Associated Organic Matter across a Lithosequence of Forest Soils

“…The preferential binding of N-bearing moieties on Fe-rich mineral surfaces at circum-neutral pH has been illustrated in both laboratory settings and natural soils [52][53][54][55][56]. Recently, atomic force microscopy was used to illustrate the strong binding of N to goethite, where ammonia bonds were on averageIn addition to illustrating competitive sorption behavior, bonding to Fe surfaces seems to confer greater stability to the bound organics.…”

Bioavailability of Phosphorus on Iron (Oxy)hydroxide Not Affected by Soil Amendment–Derived Organic Matter

“…The reason for the inability of DOM to affect P uptake (Fig. 3) in this study despite this 1.5 to 11.9% range in DOM aromatic molecule content is likely due to the fact that only the content of aromatic molecules with molecular mass >600 was significantly negatively correlated to phosphate binding force as determined by atomic force microscopy (Chassé and Ohno, 2016). Food compost DOM, which had an aromatic content of 11.9%, had only 0.6% of its aromatic molecules above the 600 Da threshold (Fig.…”

“…The P concentration of the solution was determined using the ascorbic acid method (Murphy and Riley, 1962) The chemical composition of the DOM was characterized using negative ion mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry using a 12 T Bruker instrument. The details of the analysis can be found in Chassé and Ohno (2016). The post-processing of the mass spectra data are described in Ohno and Ohno (2013).…”

“…reduced the binding force of orthophosphate to iron (oxy) hydroxide (FeOOH) minerals (Chassé and Ohno, 2016). In the current study, we used a bioassay to directly determine the bioavailability of P adsorbed onto FeOOH minerals that were pre-reacted with DOM from C-rich amendments (crop residues, animal manures, and compost) and P to mimic likely field soil components.…”