A COMPARISON OF SULFUR-FREE AND AMBIENT AIR ENCLOSURE TECHNIQUES FOR MEASURING THE EXCHANGE OF REDUCED SULFUR GASES BETWEEN SOILS AND THE ATMOSPHERE

The exchange of reduced sulfur gases between the atmosphere and forest soils in the Shaver Hollow watershed (Shenandoah National Park, Virginia) were measured with sulfur-free and ambient air enclosures at least twice a month from March through November 1989. Soils within sulfur-free enclosures were sources of carbonyl sulfide (COS) and carbon disulfide (CS2). Atmospheric fluxes of COS and CS2 ranged from 0.77 to 13.03 ng COS-S/m2-min and from 2.04 to 15.74 ng CS2-S/m2-min. In contrast, soils within ambient air enclosures were sinks for COS and CS2. Uptake rates of COS and CS2 ranged from 2.78 to 16.20 ng COS-S/m2-min and from 3.42 to 26.62 ng CS2-S/m2-min. The discrepancy in the direction of these fluxes was caused by the flux measurement techniques.