A rapid and sensitive ion chromatographic technique for the determination of sulfate and sulfate reduction rates in freshwater lake sediments

Abstract

Newly developed low capacity columns were used in suppressed ion chromatography for rapid and highly reproducible determination of SO42− in porewater samples from freshwater sediments without preconcentration of samples. With a 50 μl injection the detection limit for SO42− was ca. 50 pmol (= 1 μM) with a precision of 1–3% at the 10–200 μM level and <1% at concentrations above 200 μM. SO42− could be measured in 4–5 min with the routinely used eluent (3.0 mM NaHCO3/0.8 mM Na2CO3). When the strength of the eluent was increased to 3.0 mM NaHCO3/2.0 mM Na2CO3, sulfate analysis was possible in less than 3 min, provided that samples were nitrate-free. Under these conditions S2O32− could also be sensitively determined in about 6 min. Examples of application of the method are given for measurements of sulfate reduction rates in freshwater sediment samples from Lake Constance.