your fart and the other fart that's coming in July
An ecologist studies pollution
A mineralogist studies minerals.
A scientist who studies water (H2O) would be a hydrologist or a water chemist.
The kind of scientist who studies Urology would be a Biologist, since Urology concerns a biological function (urination). If you mean the kind of doctor who studies Urology, that would be a Urologist.
meteoroligists
Audiologist
An Ichthyologist.
A zoologist.
Botanist
seismologist
a biologist
cosmologists