Charakterisierung der Submicron-Partikel in einem umweltrelevanten Wasser: Stauwasser in einer Kommunalmülldeponie über einem Schlammteich (Tailing) der Uranerzaufbereitung in Freital/Sachsen

Characterization of Submicron Particles in an Environmentally-Relevant Water: Backwater From a Sanitary Landfill on a Uranium Mine Tailing at Freital, Saxony. A strategy for characterizing submicron particles in environmental waters based on filtration, centrifugation and photon correlation spectroscopy (PCS) is proposed. Filtration and centrifugation are not used here as methods for particle characterization but serve merely as techniques of a rough separation of the sample. They are applied as cautiously and non-invasively as possible and are only aimed at separating the sample sufficiently for measurements by primarily PCS. The separation should unmask small particles
that scatter little light and divide the sample into populations of particles that have monomodal or bimodal size distributions. In this way, the strategy optimizes subsequent particle-size determinations by PCS and minimizes the influence of sample preparation on the samples. A further essential feature of this strategy is the parallel application of complementary methods for both sample preparation and particle characterization (filtration/centrifugation, PCS/SEM, gravimetry/ICP-MS etc.). This facilitates the validation of results and increases the probability for recognizing artifacts. Based on our experimental experience, a guideline for PCS measurements on low-concentration colloids with the BI 90/Correlator BI 9000 AT system from Brookhaven Instruments Corp. was developed. This guideline is aimed at obtaining autocorrelation functions of sufficiently good photon counting statistics which is crucial in PCS on colloidal solutions poor in particles. A measuring campaign on an environmentally-relevant water (backwater from a sanitary landfill on a uranium mine tailing at Freital, Saxony) showed the presence of about 1 to 2 mg/l of submicron particles having a particle size of 30 to 300 nm and of about 5 mg/l of suspended matter (>1000 nm).