Biogenic dissolution of a soil cerium-phosphate mineral

Abstract

ABSTRACT. The productivity of many terrestrial ecosystems is

Environmental release, fate and ecotoxicological effects of manufactured ceria nanomaterials

“…There are many naturally occurring Ce containing minerals include rhabdophane, allanite, cerite, cerianite, samarskite, zircon, monazite and bastnasite. 5,6 The existence of naturally occurring ceria nanoparticles is also likely and may play a key role in controlling dissolved Ce concentrations, 6 but precisely how the properties of naturally occurring ceria nanoparticles compare to manufactured ceria (CeO2) nanomaterials (nanoceria) is unclear.…”

Coupled redox transformations of catechol and cerium at the surface of a cerium(III) phosphate mineral

“…In other words, direct inorganic reaction of catechol with dissolved oxygen cannot account for by coloration in the CePO 4 ÁH 2 O dissolution experiments due to variation in C speciation. The dark material was found after reacting CePO 4 ÁH 2 O and catechol was found to be similar in structure to humic material as evidenced firstly by infrared spectroscopy (Cervini-Silva et al, 2005), and discussed in the present work. Previous reports show that strongly-sorbed humified products formed following reaction of birnessite with catechol, suggesting that such polymerized materials may be common products of mineral surface oxidation of catechol (Machjer et al, 2000).…”

“…In young weathering profiles, field data suggest that most Ce exists as Ce 3+ , whereas in older weathered profiles Ce 3+ is oxidized to Ce 4+ (Taunton et al, 2000a,b). It has been shown previously that dissolution of phosphate minerals containing Ce 3+ is accompanied by cerium oxidation and precipitation of nanocrystalline CeO 2 (Gardner et al, 1983;Jonasson et al, 1985;Banfield et al, 1999;Taunton et al, 2000a,b;Cervini-Silva et al, 2005). These processes are believed to be responsible for the accumulation of Ce at the top of the saprolite layers of lateritic soil profiles (Braun et al, 1990) and the depletion of dissolved Ce in the oceans relative to other lanthanides (Moffett, 1990(Moffett, , 1993.…”

The coupled release of REE and Pb to the soil labile pool with time by weathering of accessory phases, Wind River Mountains, WY

“…In addition, the percent extraction of elements within the LREE increases with element mass. Since none of the primary or accessory minerals exhibit such REE patterns, this behavior is attributed solely to loss via groundwater or sequestration of LREE in secondary phases as noted previously (e.g., Banfield and Eggleton, 1989;Taunton et al, 2000a,b andCervini-Silva et al, 2005). Rhabdophane and florencite are secondary phosphate minerals which have low solubility (Jonasson et al, 1985;Firsching and Brune, 1991).…”