In which zone do the pore spaces contain both water and air?

The correct answer is the unsaturated zone, where the pore spaces contain both water and air. This zone, also known as the vadose zone, exists above the groundwater table and below the land surface. In this area, the soil or rock formations are not fully saturated with water; instead, there are pockets of air in the void spaces between soil particles or rock fractures.

The presence of both water and air is significant for various environmental processes, such as plant growth and the movement of gases. As water infiltrates from the surface, it moves through the unsaturated zone, replenishing moisture and interacting with the air in the pore spaces, which supports biological activity and processes like evaporation. This zone plays a vital role in the hydrological cycle by allowing water to percolate downwards into the saturated zone, where groundwater resides, and contributing to the overall health of ecosystems.

In contrast, the saturated zone, groundwater zone, and water table refer to areas where the pore spaces are fully or predominantly filled with water.