The DNA concern is particularly acute because DNA is not simply a passive molecule embedded in a fixed structure.

When organisms die and their tissues decompose, the DNA they contained is released into the surrounding environment.

In soil and sediment, this environmental DNA — sometimes called eDNA — can persist for varying periods depending on temperature, pH, and the presence of protective mineral surfaces that can shield DNA molecules from enzymatic degradation.

Environmental DNA in sediment can be transported by percolating water.

As rainwater or snowmelt moves downward through a sediment profile, it carries dissolved and suspended organic material — including DNA fragments — with it.