Approaching mass (im)balance when using artificial DNA tracer using DNA extraction methods

Artificial tracers play an important role in hydrological studies that aim to identify subsurface flow paths. Tracers can be used to investigate water transit times but also, for example, to assess if a structure is leak-proof. Recently, artificial DNA (artDNA) has been proposed as a tracer alongside traditional tracers such as salt. However, like traditional tracers, artDNA suffers from input tracer mass loss. This is even more pronounced in the case of artDNA. Different approaches were proposed to improve the recovery of tracer mass and thus reach the required limit of detection and quantification required for the analysis. Using column tests, a controlled experiment was designed to examine the recovery success of DNA extraction and the detachment from soil via a buffer. In each case water was spiked with artDNA, flushed through the column and subsequently the remaining molecules recovered using a magnetic bead extraction method. The ongoing experiments will show the enhancement of artDNA tracer recovery by using methods for DNA extraction from molecular biology. Further, to recover potential substrate-bound artDNA and possibly identify one source of the observed mass imbalance, a phosphate-containing buffer of high pH was used to detach artDNA from the substrate inside the column. The results will be cross-factored by comparing the recovery of tracer mass in the plain eluate vs. the DNA extracted from the eluate and by determining the substrate-bound artDNA in both cases. Insights from this experiment and the methodological advancement will be fundamental for the use of artDNA-based tracing in hydrological research.