BioGeoChemistry of Tidal Flats


A. M. Al-Raei, M. E. Böttcher, D. de Beer, T. Ferdelman

Application of a liquid-ion-exchange microsensor for in situ measurement of sulfate in freshwater and marine sediments

Precise high-resolution sulfate measurements are fundamental for the evaluation of consumption and production of sulfate in dynamic surface sediments such as intertidal flats. Especially sediments with high near-surface activities of sulfate-reducing bacteria and in sulfate-limited fresh-water sediments, steep sulfate gradients may develop. We have adapted a potentiometric sulfate microsensor for in situ measurements that has a membrane containing an ionophore with a high selectivity for sulfate1. Our sulfate microelectrodes exhibit a Nernstian response to sulfate in the concentration range from 10-6 to 10-2 M and work well in fresh water. We have modified the electrode to minimize chloride interference for use in marine sediments; results from Wadden Sea Sediments appear promising. Examples will be presented from different fresh water sediments as well as coastal marine intertidal sediments.
(1) Nishizawa, S.; Buhlmann, P.; Xiao, K. P.; Umezawa, Y. Analytica Chimica Acta 1998, 358, 35-44.