In honour of the work of Joy Bear and Richard Thomas, who coined the word petrichor in 1964 to describe the aroma earth emits when rain falls*, I offer potamichor.

ποτάμι Potámi ~ greek ~ river.

Ichor ~ The sacred blood of the Greek Gods.

Potamichor ~ a familiar odour of rivers.

Dimethyl sulfide**, along with other elements and biochemicals, offer the familar and pungent sulphurous odour of sea spray, an important moment of the sulphur/sulfur cycle that aids protein, vitamin and hormone building – I’ll call the smell thalassicor (sea/blood of the gods).

And in the same vein, estuaries and saltmarshes create ekvolichor (estuary/blood of the gods); lakes give off limnichor; ponds – limnoulichor: swamps and bog – telmichor.

Potamichor is complex, with varying cocktails of minerals, biochemicals and olifactory matter bound to be unique to the continuums of river-place given geological, meteorological, climatic, symbiological, microbial (including respiration), ecological and anthropological (extrinsic/intrinsic impacts).

With complexity in matter and directionality, and in a constant state of flux, salmonids, lampreys, twait shad and sturgeon know more than we ever could about potamichor. They smell their particular birth-streams miles out to sea, and without the use of material and energy-greedy tools. Perhaps migratory birds use these cues to navigate too, high up in the atmosphere. And more? Imagine.

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• * Bear, I., Thomas, R. Nature of Argillaceous Odour. Nature 201, 993–995 (1964). https://doi.org/10.1038/201993a0 – geosmins produced by Streptomyces, etc.
• ** Shemi, A., Alcolombri, U., Schatz, D. et al. Dimethyl sulfide mediates microbial predator–prey interactions between zooplankton and algae in the ocean. Nat Microbiol 6, 1357–1366 (2021). https://doi.org/10.1038/s41564-021-00971-3