Fig. 3.

FE-SEM images (a–c) and EDX spot spectrum (a1–c2) of (a) pristine MB filter fibers and fragments, (b) collected MB filter fibers and fragments from springtail test soil 28 days after exposure and (c) collected MB filter fibers and fragments from earthworm casts 21 days after exposure. Orange arrows (b1 and c1) indicate fragmented nano-sized fibers on the surface of MB filter microfibers. White symbol of element in the inner box of a1–c2 indicates meaningfully detected elements. Green arrows (b2–b3 and c2) indicate what we interpret as soil particles exhibiting Si signals. White chemical element symbols in (a1–c2) show significant signals detected by EDX. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)