Final answer:
Aerosol concentration changes with altitude due to the decrease in atmospheric pressure and air density, causing lower oxygen saturation and increased risk of hypoxia and altitude sickness as altitude increases.
Step-by-step explanation:
The changes in aerosol concentration as you gain altitudes can be explained by the corresponding decrease in atmospheric pressure. Atmospheric pressure and air density both diminish as altitude increases. This decrease results in a reduction of gas molecules, including aerosols, in any given volume. The oxygen concentration, which is a part of the air's gas composition, also declines with increased altitude, leading to lower oxygen saturation in the bloodstream. At higher altitudes, the partial pressure of oxygen is reduced even though the proportion of oxygen in the atmosphere remains constant at around 21%. As such, hemoglobin saturation at high altitudes is significantly lower compared to at sea level, with implications for human health such as experiencing hypoxia and altitude sickness due to the diminished ability to take in oxygen and release carbon dioxide.