title: Reduction of orthophosphates loss in agricultural soil by nano calcium sulfate.
abstract: Nutrient loss from soil, especially phosphorous (P) from farmlands to natural water bodies via surface runoff or infiltration, have caused significant eutrophication problems. This is because dissolved orthophosphates are usually the limiting nutrient for algal blooms. Currently, available techniques to control eutrophication are surprisingly scarce. Calcium sulfate or gypsum is a common soil amendment and has a strong complexation to orthophosphates. The results showed that calcium sulfate reduced the amount of water extractable P (WEP) through soil incubation tests, suggesting less P loss from farmlands. A greater decrease in WEP occurred with a greater dosage of calcium sulfate. Compared to conventional coarse calcium sulfate, nano calcium sulfate further reduced WEP by providing a much greater specific surface area, higher solubility, better contact with the fertilizer and the soil particles, and superior dispersibility. The enhancement of the nano calcium sulfate for WEP reduction is more apparent for a pellet- than a powdered- fertilizer. At the dosage of Ca/P weight ratio of 2.8, the WEP decreased by 31±5% with the nano calcium sulfate compared to 20±5% decrease with the coarse calcium sulfate when the pellet fertilizer was used. Computation of the chemical equilibrium speciation shows that calcium hydroxyapatite has the lowest solubility. However, other mineral phases such as hydroxydicalcium phosphate, dicalcium phosphate dihydrate, octacalcium phosphate, and tricalcium phosphate might form preceding to calcium hydroxyapatite. Since calcium sulfate is the major product of the flue gas desulfurization (FGD) process, this study demonstrates a potential beneficial reuse and reduction of the solid FGD waste.
authors.affiliation: Department of Civil and Mechanical Engineering, Indiana University - Purdue University, 2101 E Coliseum Blvd, Fort Wayne, IN 46805, USA. Electronic address: chend@ipfw.edu.
authors.forename: Dong
authors.initials: D
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Indiana University - Purdue University, 2101 E Coliseum Blvd, Fort Wayne, IN 46805, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Szostak
authors.affiliation: Department of Civil, Environmental and Geodetic Engineering, The Ohio State University, 470 Hitchcock Hall, 2070 Neil Avenue, Columbus, OH 43210, USA.
authors.forename: Zongsu
authors.initials: Z
authors.lastname: Wei
authors.affiliation: Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China; Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China.
authors.forename: Ruiyang
authors.initials: R
authors.lastname: Xiao
mesh_terms: D000383:Agriculture / Q000379:methods*; D002133:Calcium Sulfate / Q000737:chemistry*; D005068:Eutrophication; D005308:Fertilizers; D010710:Phosphates / Q000032:analysis* / Q000737:chemistry; D012987:Soil / Q000737:chemistry*
chemical_list: D005308:Fertilizers; D010710:Phosphates; D012987:Soil; D002133:Calcium Sulfate
keywords: Eutrophication; Gypsum; Nano calcium sulfate; Nutrient; Orthophosphate; Phosphorus