You have a lot of the hexadecimal named directories under "/var/log/journal". This means that you have updated the Edison firmware many times."journald" saves its journal (log) files under a directory named as 128-bit "machine ID", which changes when you update the firmware. "journald" keeps track of the disk usage to be under 10% of the filesystem capacity and under 15% of the remaining disk space of the filesystem (default setting). However, it does not check the disk usage under directories except the current "machine ID".
You can fix your problem now by following command:
# rm -rf /var/log/journal/*
# reboot
Please note you may want to use the following command to update the firmware by "reboot ota" next time.
# rm -rf /var/log/journal/*
# reboot ota
I hope this helps.
sgk