Extraction of low-level sulphide from groundwaters for sulphur isotope analysis

Abstract

A method is described for the preparation of sulphide precipitates for sulphur isotope analysis from sub-ppm (< 1 mg 1⁻ levels of sulphide in natural waters. Hydrogen sulphide is degassed from acidified water samples into a nitrogen stream and subsequently re-precipitated in a silver nitrate trap. Control experiments on model waters of known sulphur isotope composition show that the average fractionation of sulphide is small (0.069‰) but an uncertainty of ±0.6‰ is appropriate for this method.