A RAPID AND SENSITIVE ION CHROMATOGRAPHIC TECHNIQUE FOR THE DETERMINATION OF SULFATE AND SULFATE REDUCTION RATES IN FRESH-WATER LAKE-SEDIMENTS

Newly developed low capacity columns were used in suppressed ion chromatography for rapid and highly reproducible determination of SO4(2-) in porewater samples from freshwater sediments without preconcentration of samples. With a 50-mu-l injection the detection limit for SO4(2-) was ca. 50 pmol ( = 1-mu-M) with a precision of 1-3% at the 10-200-mu-M level and < 1% at concentrations above 200-mu-M. SO4(2-) 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 S2O3(2-) 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.