Hi Omega,
I spoke to the Android dev about this, and here was his advice:
A 2048x2048 alpha texture in ETC1 will be stored uncompressed and will take 16MB. Lower the resolution; I doubt it needs to be that high for an Android device for particles.
Other alternative is to split the rgb and alpha components into separate textures so they can be compressed and modify the material to sample from the two textures with same UVs.
Hope this helps!