Each spring, high school students, college interns, and retirees count and weigh tiny glass eels in streams that feed into the Hudson River. They report their observations to the New York State Department of Environmental Conservation Hudson River Estuary Program and the National Estuarine Research Reserve System, who depend on volunteers, to help build a database of information about glass eels. The observations that these volunteers make would best be described as

chemical weathering

explanation:

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.

the tricuspid valve is present between right atrium and right ventricle