The masses of Earth's major fluid and ice envelopes (atmosphere, hydrosphere, and cryosphere) are standard geophysical quantities well-established in Earth sciences, making this claim common knowledge.
The claim that the combined mass of Earth's atmosphere, hydrosphere, and cryosphere can be quantified is a matter of standard scientific definition and everyday observation in the geosciences. No specific citation is strictly needed, though papers discussing global water budgets and planetary volatile reservoirs touch upon these quantifiable masses.