Field-based measurements of sulfur gas emissions from an agricultural coastal acid sulfate soil, eastern Australia

The emissions of biogenic hydrogen sulfide (Hâ‚‚S) and sulfur dioxide (SOâ‚‚) play important roles in the global atmospheric sulfur (S) cycle. Field-based investigations using ultraviolet fluorescence spectroscopy show that drained acid sulfate soils (ASS) are a potentially unaccounted source of biogenic Hâ‚‚S and SOâ‚‚. Significant diurnal variations were evident in SOâ‚‚ fluxes, with average daytime measurements 9.3-16.5-fold greater than night-time emissions. Similar diurnal patterns in Hâ‚‚S fluxes were observed but proved statistically insignificant. The results from simultaneously collected micrometeorological measurements suggest that emissions of SOâ‚‚ and Hâ‚‚S are most likely occurring via different processes. The SOâ‚‚ fluxes are closely linked to surface soil temperature and moisture content, whereas Hâ‚‚S is constantly emitted from the land surface at the two study sites. Drained ASS are most likely mapped as agricultural lands rather than drained backswamps. Therefore, these areas are likely to be assigned Hâ‚‚S and SOâ‚‚ flux values of zero in greenhouse gas species inventories. These findings suggest a need to expand these measurements to other drained ASS areas to refine regional (and possibly global) atmospheric S budgets. Further research is necessary to elucidate the sources of measured S compounds, and specifically whether they are limited to individual agricultural drainage patterns in ASS.