the bulk of the world's phosphate reserves is located in sedimentary horizons that contain appreciable amounts of carbonate. during beneficiation of phosphate rocks, huge amounts of oversize phosphate rocks are rejected from crushers. this reject also mostly contains low tricalcium phosphate and high carbonate content. in this study, experiments have been carried out to reduce/eliminate carbona...

Phosphate rocks are a vital resource for world food supply and security. They the primary raw material phosphoric acid fertilizers used in agriculture, increasingly considered to be potential source of rare earth elements. occur either as sedimentary deposits or igneous ores associated with alkaline rocks. In both cases, genesis high-grade phosphate results from complex concentration mechanisms...

The stable oxygen isotope compositions of soil phosphate (δ(18)O(p)) were suggested recently to be a tracer of phosphorus cycling in soils and plants. Here we present a survey of bioavailable (resin-extractable or resin-P) inorganic phosphate δ(18)O(p) across natural and experimental rainfall gradients, and across soil formed on sedimentary and igneous bedrock. In addition, we analyzed the soil...

Our previous studies on the phosphate sorption on sediments in Florida Bay at 25 °C in salinity 36 seawater revealed that the sorption capacity varies considerably within the bay but can be attributed to the content of sedimentary P and Fe. It is known that both temperature and salinity influence the sorption process and their natural variations are the greatest in estuaries. To provide useful ...

Phosphate and environmental samples were collected from Abu Tartor phosphate mine and the surrounding region. The activity concentration of 226Ra (238U) series, 232Th series and 40K were measured using a gamma-ray spectrometer. The activities of uranium isotopes (238U, 235U and 234U) and 210Pb were measured using an alpha spectrometer and a low-background proportional gas counting system, respe...

[1] Below its sill depth, the Santa Barbara Basin (SBB) is commonly suboxic ([O2] 3 mM), with only brief periods of ventilation. Associated with development of suboxia, the concentration of nitrate decreases with depth into the basin without an associated decrease in phosphate, indicating that a substantial fraction of the nitrate supplied to the basin is removed by denitrification. Coincident ...

Biomineralization marks one of the most significant evolutionary milestones among the Eukarya, but its roots in the fossil record remain obscure. We report crystallographic and geochemical evidence for controlled eukaryotic biomineralization in Neoproterozoic scale microfossils from the Fifteenmile Group of Yukon, Canada. High-resolution transmission electron microscopy reveals that the microfo...