FIG. 3.

Epifluorescent microscopic visualization of fluorescent microspheres at increasing depths from the core surface. A permafrost sample from site Eu1 at 11.58 m was used and was representative of the other samples. Fluorescent microspheres were seen as discrete points (white triangle), whereas background fluorescence from particulates was seen as diffuse smears (gray triangle), which was confirmed by visualization with white light. (A) Section at 1 mm from exterior core surface; (B) section at 2 mm from exterior core surface; (C) section at 4 mm from exterior core surface; (D) section at 6 mm from exterior core surface. No beads were observed in sections more than 6 mm from the exterior core surface.