Separation

well.. dust does several things at once. First, it evokes the traditional christian funeral rites. The death of love as a corporeal entity, and the death of the body and soul as a result of lost love. Then it also alludes to the desert -- which works somewhat well with the car speeding off leaving behind a contrail. Creating, i hope, a more powerful image of abandonment. Dust also offers up that general idea of body dissipating - as most dust in a house is made up of human skin. 

 The bitterness offers 2 things that i want to hold, first is the image of breathing in the dead love. That taste of love gone bad. That taste of separation. Also, it reinforces the idea of desert and works off the stereotypes. 

I will ponder them more though. Thanks Sin.