Lamentations 2:10 (ESV)

10 The elders of the daughter of Zion sit on the ground in silence; they have thrown dust on their heads and put on sackcloth; the young women of Jerusalem have bowed their heads to the ground.

Young and old mourn together the fall of the city and the temple. It was the custom for people in mourning to sprinkle dust on their heads and wear a sack as clothes. The young women were probably mourning for their husbands or male friends who had been killed or deported.