The decontamination symbolism in the ab-zohr is a reflection of Zoroastrian cosmogony, wherein the primeval waters (the lower half of the sky, upon which the universe rests, and from which two rivers encircle the earth) fear pollution by humankind.
The decontamination iconography within the ab-zohr mirrors Zoroastrian cosmogenesis, depicting the primordial waters (comprising the lower celestial hemisphere, underpinning the cosmos, and encompassed by two rivers encircling the planet) as being apprehensive of human contamination.