Silica Particles with Encapsulated DNA and Magnetite as Hydrological Tracer

Magnetic Concentration and Proof-of-Concept

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DNA has a number of characteristics which make it very promising as a hydrological tracer. It is detectable in extremely low quantities and can provide a virtually unlimited amount of unique tracers. The DNA tracer method has been further developed towards a multipurpose tracer combining a DNA tag, a paramagnetic core and a protective coating into complex microcarriers adding non-degrading, identical transport properties and magnetic concentration to the list of advantages. In this research an attempt is made to utilise the full potential of such a microcarrier. We introduced a new microcarrier, Silica Particles with Encapsulated DNA and Magnetite (SPEDaM), to three hydrological environments and examined practical issues surrounding magnetic concentration. SPEDaM containing samples were magnetically concentrated, taking the loss of DNA mass into account, 500 times. A breakthrough curve was constructed from an injection in sewer water showing the protective capabilities. Consistent adsorption properties were found during ground column tests. However, for turbid waters fine particulates were concentrated together with the DNA during magnetic concentration into an inseparable goo which often prevented DNA detection. This remains an issue which needs to be solved before large scale surface water applications can be tried.