Oxidation chemistry of acid-volatile sulfide during analysis

The susceptibility of some components of sediment acid-volatile sulfide (AVS) to chemical oxidation is a critical factor impacting accurate measurement of AVS in sediment samples. This well-documented susceptibility to oxidation led to the requirement for oxygen-free conditions in the analytical method developed for AVS. In light of this acute potential to oxidize, the serendipitous finding that air can be used in the analysis of sediment AVS is counterintuitive and unexpected. To demonstrate and investigate this interesting observation, extraction experiments were performed using aqueous and solid-phase sulfide species. Experiments using air as the carrier gas showed a mean percentage recovery of sulfide matching that of traditional (nitrogen gas) analysis (i.e., >91%) and a time to completion of less than 30 min for aqueous sulfide and less than 60 min for sediment samples. These results are consistent with those of sulfide oxidation studies reported in the literature. Using air as the analytical carrier gas can provide an interesting alternative for developing an analytical method to determine AVS parameters in the field.