Use of GEOCHEM-PC to predict rare earth element (REE) species in nutrient solutions

Abstract

The interpretation of results of some experiments examining effects of rare earth elements (REE) on plant growth may have been complicated by rare earth phosphate precipitation. Simulations were undertaken using the computer model GEOCHEM-PC to define REE solubility limits and predict REE species in low and high ionic strength nutrient solutions. In low ionic strength solutions containing 5 ~tM P, lanthanum phosphate (LaPO~) precipitation is predicted to occur at solution pH>4.0, reaching a maximum (>95% of total) at pH 5.5. In high ionic strength solutions (1000 ~tM P) over 95% of the La is predicted to precipitate as phosphate at pH>4.0. The predicted behaviour of cerium (Ce) was closely similar to that for La. At pH 5.5, the concentration of REE species in solution can be increased only after virtually all the P has been precipitated. Consequently, it is important to consider REE-P interactions in nutrient solutions when investigating REE effects on plant growth.

Cerium negatively impacts the nutritional status in rapeseed

“…In a natural environment Ce bioavailability will be enhanced by low pH, and it is likely that it will be complexed with dissolved organic carbon (Tyler and Olsson, 2002). Instead, Ce bioavailability will decrease in soils with high phosphate, which can precipitate Ce as non-soluble CePO 4 (Diatloff et al, 1993;Diatloff et al, 1996). An approximation of Ce solubility in soil would be its concentration in soil solution, which had a range of 0.01-0.51 μM in unamended Australian soils (Diatloff et al, 1996) and of 0.005-0.19 μM in Swedish non-fertilized forest (Tyler and Olsson, 2002).…”

Effect of substrate properties and phosphorus supply on facilitating the uptake of rare earth elements (REE) in mixed culture cropping systems of Hordeum vulgare, Lupinus albus and Lupinus angustifolius

“…In soils, REEs share many chemical similarities with essential plant nutrients, especially calcium (Brioschi et al 2013 ; Censi et al 2014 , 2017 ; Martinez et al 2018 ; Wyttenbach et al 1998 ). Thus, nutrient-bearing soil phases such as phosphates, organic matter and Fe oxyhydroxides are important hosts for these elements (Diatloff et al 1993 ; Zhimang et al 2000 ; Cao et al 2001 ; Wiche and Heilmeier 2016 ; Wiche et al 2016b ). Accordingly, in the soil used for the field experiment, REEs were mostly present in fractions 3–5 and with slight enrichment in fraction 3 of substrate B (Table 2 ).…”

“…Accordingly, in the soil used for the field experiment, REEs were mostly present in fractions 3–5 and with slight enrichment in fraction 3 of substrate B (Table 2 ). Low soil pH and the presence of dissolved organic matter strongly impact the mobility and plant availability of REEs (Diatloff et al 1993 ; Zhimang et al 2000 ; Cao et al 2001 ; Tyler and Olsson 2001 ; Pourret et al 2007 ; Kovaříková et al 2019 ). As such, the higher concentrations (Table 6 ) and accumulation (Fig.…”

“…More specifically, the REEs comprise a group of 17 elements from the lanthanide series including lanthanum, yttrium (Y) and scandium (Sc) that are abundant in the Earth’s crust with concentrations that vary from 66 µg g −1 (Ce), 30 µg g −1 (La) and 28 µg g −1 (Nd) to 0.3 µg g −1 (Lu) (McLennan 2001 ; Kabata-Pendias 2010 ; Davranche et al 2017 ). As a special feature in this group, all 16 REEs exhibit ionic radii similar to Ca 2+ ; however, under most pedological relevant conditions, REEs form + 3 ions (Wyttenbach et al 1998 ) which strongly interact with phosphate and other negatively charged soil constituents (Diatloff et al 1993 ; Zhimang et al 2000 ; Cao et al 2001 ; Li et al 2014 ). As an exception in this group, Eu and Ce may also occur in the divalent or tetravalent state (Davranche et al 2017 ).…”

Novel composite materials as P-adsorption agents and their potential application as fertilizers

“…The solubility product (Ksp) of the La-phosphate complex is particularly low (24.76 and 27.92) in both aqueous and seawater solutions, making it the least soluble of the rare earth-phosphate complexes. The complex is known to be so insoluble in low La and phosphate concentrations and low pH conditions (Diatloff et al, 1993).…”