On-site classification of manganese forms in natural waters by membrane filtration and chelating exchange

The possibility of chemical speciation of manganese was studied to explain the behavior and fate of trace metals in the aquatic environment. An operationally defined on-site preconcentration and fractionation scheme was developed that was based on the difference in the thermodynamic and kinetic behavior of manganese species. This scheme was used to distinguish between the different manganese forms in river and karstic groundwater. According to the elaborated “in field” procedure, the water sample was pressed through a membrane filter (0.22 μm) coupled to an imino diacetic acid-ethyl cellulose (IDAEC) chelating exchanger minicolumn by means of a syringe, followed by a batch enrichment. The fractions were analyzed by graphite furnace atomic absorption spectrometry. The dissolved manganese part was in the range of 0.5-1.5 μg l−1 and the on-site spike addition resulted in a satisfactory recovery. The binding behavior of manganese in different classes was characterized by means of stability constants of the Mn-IDAEC complexes.