Analytical Procedures in Field Sampling For Aqueous Organic Volatile Sulfides

Abstract

<p> The sulfur cycle is perhaps one of earth's most important cycles. Biologically sulfur is the main constituent needed to form building blocks such as amino acids. Ecologically, it can devastate forests, lakes and ecosystems in one of it's many forms. Industrially (and perhaps naturally) it is the source of our acid rain problem. </p> <p> An estimation of sulfide fluxes emitted into the atmosphere is extremely variant due to the lack of efficient means of measuring these fluxes. Several simplistic measuring devices have been employed to estimate the oceanic, continental and atmospheric fluxes. Problems have arisen due to the non-uniform distribution of sulfur sources such as industries, volcanoes and marshlands. </p> <p> In the specific case estimates of fluxes have of organic volatile been deduced and not sulfides, actually measured to any great extent. The fundamental reason for this being the lack of an efficient means of recording data in the field to support the flux estimates. </p> <p> This study has attempted to secure the efficiency of adsorption tubes used to sample in situ freshwater sulfide fluxes. Optimal preparation involved using Molecular Sieve SA (60/80 mesh) contained and activated in pyrex glass tubing (6mm. o.d.). Proper activation occurred at 300C for 8 hours under a constant helium flow. </p> <p> Adsorption of sulfides was by helium induced release of gases at room/atmospheric temperatures. After 15 minutes, the adsorption tube was recapped and stored at (-8C) for no more than 7 days. At this time, the tubes were analyzed. </p> <p> Analysis was by GC/HECD in the laboratory. A custom made heat desorber (at 270C), in conjunction with liquid nitrogen and hot water sufficiently trapped the released sulfides from the adsorption tube. Calibrated data obtained in the laboratory provided for proper analytical interpretations of the flux of sulfides emitted from the sample. </p>