Javed and Siddique1 presented laboratory experiments demonstrating that arsenic (As) is released from sediments when heated to 200 °C. This study agrees with earlier studies showing arsenic is released from sediments upon heating,2 and from other media containing iron-(hydr)oxides.3−7 The work applies a sequential extraction technique to show that thermally released arsenic is primarily (∼89−100%) the result of desorption from specifically bound and exchangeable fractions. Although the study provides new and interesting insights, the underlying mechanisms of arsenic desorption are only limitedly discussed. The understanding of the key biogeochemical processes is a prerequisite for predicting the degree of arsenic (im)mobilization and the spatial extent of elevated arsenic concentrations in thermally impacted aquifers. In this comment, we address these issues and make recommendations for further research.