The data include chemical composition of Pb contaminated soils by adding FGDG as an amendment. The data shows the changes in Pb speciation to sulfur based minerals. This dataset is associated with the following publication: Koralegedara, N., S. Al-Abed, S. Rodrigo, R. Karna, K. Scheckel, and D. Dionysiou. Alterations of lead speciation by sulfate from addition of flue gas desulfurization gypsum (FGDG) in two contaminated soils. D. Barcelo SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 575: 1522-1529, (2017).