Soil processes and chemical transport
- Univ. of Alberta, Edmonton (Canada)
Phosphogypsum (PG) is an acidic by-product of the phosphate fertilizer industry, and is produced in large quantities by the wet phosphoric acid process. Most PG is sluiced out to repositories, forming large stockpiles. Phosphogypsum is composed mainly of gypsum (Ca-SO{sub 4}{center_dot}2H{sub 2}O), but contains impurities of environmental concern such as F{sup -}, acids, trace elements, and naturally occurring radionuclides, which originate from the phosphate rock used in processing. Possible movement of these impurities into groundwater is an issue. {sup 226}Radium is the major source of radioactivity in PG produced from sedimentary phosphate rock. Few studies have addressed the leachability of {sup 226}Ra because solid solutions of Ra, Ba, and Sr are very insoluble. The objective of this study was to investigate the concentrations of {sup 226}Ra, Ba and Sr in leachate generated from PG produced from Togo phosphate rock. Phosphogypsum was extracted 30 times with deionized distilled (d.d.) H{sub 2}O over 30 d. Extractable {sup 226}Ra was maximal (0.55 Bq L{sup -1}) and Day 30 Minimum extractable {sup 226}RA (0.23 Bq L{sup -1}) occurred on the Day 30 extraction but still exceeded the current U.S. drinking water standard. Solid phase {sup 226}Ra increased between Day 0 (850 Bq kg{sup -1}) and DAy 30 (1120 Bq kg{sup -1}). The {sup 226}Ra/Ba ratios in the solid phase and in the extractable liquid phase very nearly equal over the last half of the extraction period. If this relationship holds for other PGs, then solution {sup 226}Ra activities can be estimated if solid-phase {sup 226}Ra/Ba ratios are known and Ba solution concentrations are known or estimated. 38 refs., 3 figs., 3 tabs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 258796
- Journal Information:
- Journal of Environmental Quality, Vol. 24, Issue 2; Other Information: PBD: Mar-Apr 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Radium-226 and calcium uptake by crops grown in mixtures of sand and cay tailings from phosphate mining
Crop response to soil applications of phosphogypsum