Put sprites in the middle of a 3d particle system, instead of in front or behind (based on sorting order)?

The problem:

1. In 3d space, I have sprites positioned within a particle system portraying clouds (composed of sprites).

2. When I use 3d objects, they behave appropriately: objects that are closer are less obscured by the cloud than objects that are farther.

3. But when I use sprite objects, they're either entirely in front of, or entirely behind the particle system, depending on their sprite sorting order, rather than their position in 3d space. (If sprites' are set to 0 in the default sorting order, they'll be behind. If they're set to 1 in the default sorting order, then they'll be in front.)