Agricultural soils generally require the use of fertilizers and soil conditioners for optimal production. Phosphate fertilizers produced from igneous phosphate rock often contain small amounts of natural radionuclides (most notably 23U and 232Th), while the byproduct phosphogypsum (dihydrated calcium sulfate) is enriched in 226Ra and 210Pb. Our study focused on the long-term (200 year) subsurface fate of 226Ra when phosphogypsurn (PG) is applied annually for 27 years as an amendment to a typical Brazilian Cerrado soil profile, after which PG applications ceased but agriculture continued. Expected water flow and solute transport processes were estimated first using the standard HYDRUS- 1 D software package assuming linear equilibrium transport, followed by simulations using the HP 1 module of HYDRUS-l D. Analyses with HPI considered a range of geochemical and physical parameters affecting Ra transport in the vadose zone, especially the effects of varying calcium concentrations resulting from the PG applications. Several aspects related to the modeling approach, such using daily versus monthly averaged weather data and assuming long-term steady-state flow conditions, are discussed also.
|Title of host publication||Proceedings of the 4 International Conference HYDRUS Software Applications to Subsurface Flow and Contaminant Transport Problems|
|Place of Publication||Prague, Czech Republic|
|State||Published - Jul 2013|
|Event||4th International Conference HYDRUS Software Applications to Subsurface Flow and Contaminant Transport Problems - Czech University of Life Sciences, Prague|
Duration: 21 Mar 2013 → 22 Mar 2013
|Conference||4th International Conference HYDRUS Software Applications to Subsurface Flow and Contaminant Transport Problems|
|Period||2013-03-21 → 2013-03-22|