The leachate concentrations of Se and B released from FGDG, soil and soil-FGDG mixture obtained from EPA-method 1314 is included in the data set. The non-equilibrium partitioning coefficients calculated based on the experimental data also included along with the predicted NPC values calculated using a regression model based on a power function. Long term environmental release of Se and B in agricultural field and a landfill calculated using fate and transport model simulation also included in the data set. This dataset is associated with the following publication: Koralegedara, N., S. Al-Abed , M. Arambewela, and D. Dionysiou. Impact of Leaching Conditions on Constituents Release from Flue Gas Desulfurization Gypsum (FGDG) and FGDG-Soil Mixture. Edith Rene, Robin Gerlach, Peter Galaz, Davide Zannoni and Piet Lens JOURNAL OF ENVIRONMENTAL MANAGEMENT. Elsevier Science Ltd, New York, NY, USA, 324: 83-93, (2017).